Manganese Oxide Catalysts Supported on TiO2, Al2O3, and SiO2

臭氧催化氧化脱除低浓度甲醛的新方法朱斌;李小松;孙鹏;刘景林;马晓媛;朱晓兵;朱爱民【期刊名称】《催化学报》【年(卷),期】2017(038)010【摘要】甲醛作为一种典型的室内挥发性有机污染物,对人体健康危害很大.目前,在可用于室内甲醛脱除的诸多方法之中,臭氧催化氧化法因可于室温下使用廉价的金属氧化物催化剂实现对甲醛的高效脱除,从而受到了科研工作者的广泛关注.然而,考虑到室内甲醛的浓度极低,且存在着长期缓慢释放的特点,传统的臭氧催化氧化法应用于实际的室内甲醛脱除不仅会造成能量的浪费,而且还易因未完全分解臭氧的连续释放带来二次污染问题.为了提高臭氧催化氧化脱除甲醛过程的臭氧利用率,降低能耗,并有效缓解未分解臭氧引起的二次污染,本文将一种循环的甲醛存储-臭氧催化氧化新方法应用于室内低浓度甲醛的脱除.该新方法包含甲醛存储与臭氧催化氧化两个过程,在存储阶段低浓度甲醛吸附存储于催化剂表面,而在臭氧催化氧化阶段臭氧将存储的甲醛氧化为CO2与H2O,并重新释放催化剂表面的吸附位.因负载型氧化锰具有优良的臭氧分解能力,本研究以Al2O3负载的MnOx为催化剂,通过研究前驱体及担载量对甲醛脱除反应的影响,筛选出了最优的MnOx/Al2O3催化剂,并对相对湿度的影响规律进行了考察,最后通过低浓度甲醛存储-臭氧催化氧化循环实验验证了该甲醛臭氧催化氧化新过程的可靠性.我们采用传统的等体积浸渍法,基于不同的前驱体制备MnOx/Al2O3催化剂.XRD表征结果表明,乙酸锰为前驱体制得的MA/Al2O3催化剂中MnOx相主要为Mn3O4(粒径约为6.0 nm);而硝酸锰前驱体所得MN/Al2O3催化剂中则含有MnO2与Mn2O3相,且其MnOx颗粒粒径较大,约为9.5 nm.XPS测试结果表明,MA/Al2O3催化剂含有Mn2+,Mn3+及Mn4+,其中Mn3+与Mn4+的含量分别为75%与12%;而MN/Al2O3催化剂则仅含有Mn3+与Mn4+,含量分别为35%与65%.上述XRD与XPS结果相一致,说明以乙酸锰为前驱体所得催化剂的分散度较高且易形成低氧化态的Mn.甲醛存储-臭氧催化氧化实验结果表明,与Al2O3及MN/Al2O3相比,MA/Al2O3催化剂具有更高的甲醛存储与催化氧化脱除性能.基于MA/Al2O3催化剂,不同Mn负载量下的甲醛存储与臭氧催化氧化实验结果表明,Mn负载量为10 wt%时MA/Al2O3的性能最佳.因而,进一步的实验中我们均选用最优的10 wt%MA/Al2O3为催化剂,其在50%相对湿度下的甲醛存储量为26.9μmol/mL,臭氧催化氧化阶段碳平衡为92%,CO2选择性为100%.相对湿度的影响结果(23℃)则表明,由于水分子与甲醛分子间存在着竞争吸附作用,甲醛存储容量随相对湿度的增加而降低;但因相对湿度增加可建立利于甲醛氧化的新途径,故臭氧催化氧化性能随相对湿度增加而增强.综合考虑,10 wt%MA/Al2O3上甲醛存储-臭氧催化氧化的最优相对湿度为50%.为验证所提出新方法的实用性,我们基于10 wt%MA/Al2O3开展了甲醛存储-臭氧催化氧化的4次循环实验.4次循环实验中的甲醛存储以及臭氧催化氧化处理的规律可基本保持一致.50%相对湿度下,低浓度甲醛(15×10-6)在空速为27000 h-1时的穿透时间为110 min,而在臭氧催化氧化阶段(150×10-6臭氧,空速15000 h-1)仅需约50 min即可实现对存储甲醛的氧化脱除(碳平衡大于92%,CO2选择性100%),表明该新方法较传统的臭氧催化氧化方法臭氧用量可节省60%.%To reduce energy costs, minimize secondary pollution from undecomposed ozone, and improve the efficiency of ozone use, a novel process of cycled storage-ozone catalytic oxidation (OZCO) was employed to remove formaldehyde (HCHO) at low concentrations in air. We applied Al2O3-supported manganese oxide (MnOx) catalysts to this process, and examined the HCHO ad-sorption capacity and OZCO performance over theMnOx catalysts. Owing to the high dispersion of MnOx and low oxidation state of manganese, the MnOx/Al2O3 catalysts with a manganese acetate precursor and 10%-Mn loading showed good performance in both storage and OZCO stages. The presence of H2O led to a decrease of the HCHO adsorption capacity owing to competitive adsorption between moisture and HCHO at the storage stage; however, high relative humidity (RH) favored complete conversion of stored HCHO to CO2 at the OZCO stage and contributed to an excellent car-bon balance. Four low concentration HCHO storage-OZCO cycles with a long HCHO storage period and relatively short OZCO period were successfully performed over the selected MnOx/Al2O3 cata-lyst at room temperature and a RH of 50%, demonstrating that the proposed storage-OZCO process is an economical, reliable, and promising technique for indoor air purification.【总页数】11页(P1759-1769)【作者】朱斌;李小松;孙鹏;刘景林;马晓媛;朱晓兵;朱爱民【作者单位】大连海事大学船舶防污染测控技术协同创新中心, 辽宁大连116026;大连理工大学等离子体物理化学实验室, 辽宁大连116024;大连理工大学氢能与环境催化研究中心, 辽宁大连116024;大连理工大学等离子体物理化学实验室, 辽宁大连116024;大连理工大学氢能与环境催化研究中心, 辽宁大连116024;大连理工大学等离子体物理化学实验室, 辽宁大连116024;大连理工大学氢能与环境催化研究中心, 辽宁大连116024;大连理工大学等离子体物理化学实验室, 辽宁大连116024;大连理工大学氢能与环境催化研究中心, 辽宁大连116024;大连理工大学等离子体物理化学实验室, 辽宁大连116024;大连理工大学氢能与环境催化研究中心, 辽宁大连116024;大连理工大学等离子体物理化学实验室, 辽宁大连116024;大连理工大学氢能与环境催化研究中心, 辽宁大连116024;大连理工大学等离子体物理化学实验室, 辽宁大连116024;大连理工大学氢能与环境催化研究中心, 辽宁大连116024【正文语种】中文【相关文献】1.微波辐照褐煤半焦脱除低浓度 NO 的研究 [J], 朱政;王光华;李文兵;李进;朱亦男;刘贝;胡帅2.湿式电除尘器对低浓度污染物脱除效率的研究 [J], 易玉萍;周道斌;李小龙;赵洋3.改性活性炭脱除低浓度H2S研究进展 [J], 王治红;马梦彧4.织构可控多孔炭纳米纤维的制备及其室温脱除低浓度氮氧化物（英文） [J], 王明玺;郭泽宇;黄正宏;康飞宇5.非均相臭氧催化氧化处理低浓度VOCs的研究现状 [J], 魏玉滨;袁厚伟;路琳;朱建因版权原因，仅展示原文概要，查看原文内容请购买。

The reduction and oxidation behaviour of manganese oxidesE.R.Stobbe *,B.A.de Boer,J.W.GeusDepartment of Inorganic Chemistry,Debye Institute,Utrecht University,Sorbonnelaan 16,3584CA Utrecht,NetherlandsAbstractThe reduction of manganese oxides with methane was studied to investigate the suitability of manganese as an oxygen storage compound.Manganese oxides are reduced by CH 4to a lower-valent manganese oxide,producing CO 2and water.Once the manganese oxide is reduced,it can be regenerated,i.e.reoxidised.By integrating this exothermic oxidation cycle with endothermic methane reforming,a new setup for exothermic,small scale syngas production is obtained.Manganese oxides can be reduced to manganese(II)oxide with methane at temperatures higher than 723K.Reoxidation of MnO at 823K leads to the formation of Mn 2O 3at 823K.At 1073K reoxidation of MnO gives Mn 3O 4,which corresponds to a lower Mn-valency than expected thermodynamically.Subsequent oxidation±reduction cycles lead to an increase in reduction temperature,probably due to a higher crystallinity.#1999Elsevier Science B.V .All rights reserved.Keywords:Manganese oxide (MnO x );Methane;Oxidation1.IntroductionCurrent processes for syngas production have sev-eral drawbacks.The most widely used process for syngas production,methane-steam reforming,has the disadvantage of NO x formation,which is caused by burners used for this highly endothermic process.Moreover,expensive multitubular,high-temperature resistant reactors are used [1,2].On the other hand,the partial oxidation of methane to synthesis gas is slightly exothermic.Unfortunately,direct catalytic partial oxi-dation is often thought to proceed through a two-step mechanism:Methane is oxidised exothermally to carbon dioxide and water,after which carbon mon-oxide and hydrogen are formed in subsequent endothermic reforming reactions [3,4].The high tem-perature gradients,the risk of explosions and the needfor pure oxygen are major drawbacks of this process.A novel two-step process for the production of syngas out of methane and air has been proposed by Van Looij [3].In this process methane is oxidised in the absence of gas-phase oxygen by a metal oxide,that acts as an oxygen storage compound (OSC).Once the storage capacity has been used,i.e.the metal oxide is reduced,the lower-valent oxide or metal is regen-erated,i.e.re-oxidised,by air.By using two parallel reactors,one in which the OSC oxidises methane,and one in which the regeneration of the OSC proceeds,a continuous oxidation process can be obtained.Both heat and products,viz.CO 2and H 2O,can be used for the subsequent endothermic production of syngas.Schematically the overall process is shown in Fig.1.This novel setup for the partial oxidation of methane to syngas,the integration of oxidation of methane by an OSC with a reforming reactor,has the advantage of being slightly exothermic,and of the absence of explosion risks,because gaseousoxidantCatalysis Today 47(1999)161±167*Corresponding author.E-mail:e.r.stobbe@chem.uu.nl0920-5861/99/$±see front matter #1999Elsevier Science B.V .All rights reserved.P I I :S 0920-5861(98)00296-Xand fuel are separated.Moreover,air can be used instead of pure oxygen,which brings about consider-able cost saving.Due to the relatively low operating temperature and the absence of burners,NO x form-ation is prevented [3].However,most transition metal oxides are not suitable for the oxidation of methane in the absence of oxygen.For instance,iron,cobalt and nickel,formed in the reduction,show the formation of car-bides and carbon whiskers in the presence of methane [3,5].Copper does not show carbon deposition,but shows a very high volatility [6].Manganese oxides,however,are expected to exhibit a relatively low volatility.The reduction to a metallic phase,which is favourable for both sintering and carbide formation,is highly unlikely for manganese.We think that,among the transition metal oxides,manganese oxide is unique in this behaviour.Manganese oxides are known to be active catalysts in several oxidation or reduction reactions.Manganese oxides can be used as catalysts for the oxidation of methane and carbon monoxide [7],or the selective reduction of nitrobenzene [8,9].Moreover,the appli-cation of manganese oxides as an oxygen storage component (OSC)for a three-way catalyst has been proposed.Recently Chang and McCarty [10]showed oxygen absorption and desorption behaviour of man-ganese oxide to be superior to that of cerium oxide.In all of these applications the redox properties of manganese oxide play a key role.The catalytic oxida-tion of methane over manganese oxide is supposed to proceed through a Mars and van Krevelen mechanism [7].In the oxidation of methane lattice oxygen isconsumed.Therefore,in principle,manganese oxide should be able to oxidise methane in the absence of gas-phase oxygen.Of the manganese oxides which are known,the most important phases and their transition temperatures in air are given in Fig.2.The reoxidation of manganese oxides is reversible up to Mn 2O 3,reoxidation to MnO 2in pure oxygen only proceeds at pressures higher than 3000bar.Van de Kleut [7]has shown that (supported)manganese catalysts can be reduced with methane at temperatures above 2508C.This temperature is far below the oper-ating temperature of the oxidation of methane with the OSC,which will proceed at temperatures higher than the reformer unit,which usually operates at tempera-tures of about 1100K.The aim of this investigation is to get insight into the reduction behaviour of unsupported manganese oxi-des in the presence of methane.Also the reoxidation behaviour of manganese oxides is investigated.On the basis of both reduction and reoxidation an evaluation of the suitability of manganese oxides as an OSC for the cyclic oxidation of methane will be made.Only unsupported manganese oxides are involved in order to rule out support effects.2.Experimental 2.1.MaterialsFor the preparation of the samples,mostly proce-dures according to Van de Kleut [7]were used.MnO 2was prepared by calcining Mn(NO 3)2Á4H 2O(MerckFig.1.A novel process for the production of syngas:(OSC O reoxidised/fresh,OSC ÀOreduced/exhausted).Fig.2.The most common manganese oxide phases in air at different temperatures.162 E.R.Stobbe et al./Catalysis Today 47(1999)161±167p.a.)in air for 13h at 1458C.Mn 2O 3was prepared by heating MnCO 3Áx H 2O in air consecutively for 3h at 1208C,8h at 2408C,and ®nally 8h at 5508C.Mn 3O 4was prepared by two different methods.A ``high''surface area Mn 3O 4was prepared by precipitation from a manganese nitrate solution with ammonia in a nitrogen atmosphere,and subsequent drying of the manganese hydroxide precipitate in air at 1308C for 72h.A low surface area Mn 3O 4was prepared by calcining MnCO 3at 10008C in air for 8h.2.2.CharacterisationThe oxides were characterised at room temperature by X-ray diffraction on a Nonius PDS 120powder diffractometer system,equipped with a position sen-sitive detector of 12082q .The radiation used was CuK 1,! 1.5406AÊ.The oxidation state of the samples,or manganese±oxygen ratio,was determined by temperature-pro-grammed reduction with hydrogen on a conventional TPR ¯ow apparatus equipped with a HWD.Samples of 30mg were heated from room temperature to 1050K in a mixture of 10%H 2in Ar (50ml/min),with a heating rate of 5K/min.A cold trap was used for the removal of water.For the determination of the oxidation state of the samples,reduction not further than to MnO was assumed.Copper(II)oxide was used as a calibration compound.The speci®c surface area of the samples was deter-mined by the BET method using nitrogen adsorption±desorption isotherms (Micromeritics ASAP2400).2.3.Temperature-programmed experimentsTemperature-programmed experiments were per-formed in an automated ¯ow apparatus.Reductions were carried out in a mixture of 1%methane in argon.Methane consumption was always lower than 20%.The samples were (re-)oxidised in a mixture of 5%oxygen in Ar (100ml/min).An amount of 80mg sieve fraction (0.15±0.50mm)of oxide was heated in 1%methane in argon from room temperature to 1100K with a heating rate of 5K/min.After 2h of isothermal reduction at 1100K,the sample was cooled down to 823K in argon after which reoxidation in 5%oxygen in argon was performed isothermally for 2h.Subse-quently the sample was cooled down in 5%oxygen inargon to 473K.After purging with argon a next reduction±reoxidation cycle was performed.Products were analysed by an on-line gas chroma-tograph (Chrompack CP9001)equipped with two columns and two detectors.A permapure dryer was used for the removal of water.A Porapak column was used to separate carbon containing products,which were detected by a ¯ame ionisation detector after methanising.Hydrogen and oxygen were separated on a Molsieve 5A column and detected by a thermal conductivity detector.An on-line quadrupole mass spectrometer (Balzers)was used for short-time ana-lysis of reactants and products.3.Results and discussion 3.1.CharacterisationX-ray diffraction was used to determine the bulk crystalline phases in the samples.The diffraction patterns of the various manganese samples are shown in Fig.3.The diffraction patterns indicate that no other bulk crystalline phases than the predicted phases were present in the samples.The diffraction patterns of MnO 2and Mn 2O 3corresponded with -MnO 2(pyrolusite)and -Mn 2O 3,respectively.The Mn 3O 4samples showed both similar diffraction patterns,representing the diffraction pattern of -Mn 3O 4,haus-Fig.3.XRD patterns of (a)MnO 2,(b)Mn 2O 3,(c)Mn 3O a 4and (d)Mn 3O b4.E.R.Stobbe et al./Catalysis Today 47(1999)161±167163mannite.The manganese oxide particles were too large to determine particle size by XRD.BET mea-surements,results of which are summarised in Table 1,showed a higher surface area for Mn 3O 4,which suggests a lower crystallinity.According to BET results,MnO 2is the most crystalline phase,whereas Mn 2O 3is the least crystallinic.3.2.Temperature-programmed reduction with H 2The oxygen-to-manganese ratios were determined by temperature-programmed reduction with hydrogen (Fig.4).From the peak area,that was calibrated with the reduction of copper(II)oxide,the oxidation state of the manganese oxide samples was determined.The oxidation states of the samples were very close to the theoretical oxidation states.The oxidation states of the samples are shown in Table 1.MnO 2showed almost a one-step reduction,whereas Mn 2O 3showed a clear two-step reduction.The peakareas of the latter correspond to subsequent reduction of Mn 2O 3to Mn 3O 4and MnO.The reduction of Mn 3O 4in hydrogen is in¯uenced by the preparation procedure.The more crystalline Mn 3O b 4reduces at higher temperatures and the nature of the oxygen is more uniform,which is indicated by the relatively narrow reduction peak.The small reduction peak at low temperature for the high surface Mn 3O a 4has been reported earlier [7].Although found at somewhat higher temperature Weimin et al.[9]attributed this low temperature peak to the reduction of Mn(III)in tetrahedral sites.The reduction pro®les show that there is no direct correlation between the onset of reduction and the oxidation state of the samples.Mn 2O 3exhibited the highest surface area and the lowest reduction temperature,whereas the low surface manganese oxides,MnO 2and Mn 3O b 4,exhibited the highest reduction temperatures.From this we can conclude that not the oxidation state,but the crystallinity or defect concentration determine the reducibility by hydrogen.3.3.Temperature-programmed reduction with CH 4The manganese oxide samples were reduced withmethane to determine the oxygen storage capacity in the cyclic oxidation of methane.During the reduction of manganese oxide with methane,carbon dioxide and water were the main products.Carbon monoxide,hydrogen and higher hydrocarbons,viz.ethane and ethene,were produced only with insigni®cant yields (<1%).The reduction pro®les are shown in Fig.5.All the samples showed quantitative reduction to MnO.After reduction with methane,the MnO x stoichiometry was checked by TPR with H 2.TPR revealed a stoichio-metry of MnO 1.00Æ0.01for the samples.The formationTable 1Characteristics of prepared manganese oxide samples Sample XRDMnO x ex TPR-H 2Mn valency ex TPR-H 2BET SA (m 2/g)MnO 2 -MnO 2pyrolusiteMnO 1.96Æ0.03 3.920.3Mn 2O 3 -Mn 2O 3MnO 1.48Æ0.03 2.9626Mn 3O a 4 -Mn 3O 4hausmannite MnO 1.31Æ0.03 2.628Mn 3O b 4-Mn 3O 4hausmanniteMnO 1.33Æ0.032.661Fig.4.Temperature-programmed reduction with hydrogen of (a)MnO 2,(b)Mn 2O 3,(c)Mn 3O a 4and (d)Mn 3O b4.164 E.R.Stobbe et al./Catalysis Today 47(1999)161±167of MnO 1.00was con®rmed by the green colour of the samples,which is typical for MnO.MnO 2showed a somewhat different behaviour than the other samples.The reduction of MnO 2with methane,which is accompanied by the production of carbon dioxide and water,takes place simulta-neously with the decomposition of MnO 2into the lower-valent Mn 2O 3.The evolution of molecular oxy-gen,accompanying this decomposition,accounts for more than 75%of the reduction of MnO 2to Mn 2O 3.This indicates that the desorption of oxygen is much faster than the oxidation of methane.Heating of MnO 2in inert,i.e.argon,results in a decomposition to Mn 2O 3at the same temperature as reduction in CH 4.The further reduction of MnO 2with methane proceeded at relatively high temperatures.Although not shown in Fig.5,full reduction of MnO 2to MnO could be accomplished at 1123K.As in the reduction with hydrogen,Mn 2O 3showed a two-step reduction by methane to MnO via Mn 3O 4.Determination of the manganese valency by TPR (H 2)between the two reduction steps revealed a stoichiometry of MnO 1.33,which corresponds to Mn 3O 4.In general it can be concluded that the trends in reducibility of manganese oxides with methane and hydrogen are the same.The oxide with the lowest crystallinity or the highest defect concentration is the easiest to reduce.3.4.Reoxidation and multiple reduction±reoxidation cyclesIn view of the utilisation of manganese oxide as an oxygen storage compound for the cyclic oxidation of methane,also its reoxidation behaviour is of great importance.Therefore we have investigated the in¯u-ence of the reoxidation temperature and the in¯uence of subsequent reduction±reoxidation cycles on the reduction behaviour.Reoxidation of the reduced sam-ples was usually performed at 823K,a temperature at which Mn 2O 3is thermodynamically the most stable phase.For all reduced samples,reoxidation for 2h at 823K led to a manganese±oxygen stoichiometry of MnO 1.48Æ0.03,which corresponds to the expected for-mation of Mn 2O 3.Reoxidation at lower temperatures,viz.673K,was very slow.After 2h of reoxidation at 673K,formation of MnO to MnO 1.33,corresponding with Mn 3O 4,had been effectuated,whereas after 10h MnO 1.50,corresponding with Mn 2O 3,had been formed.Obviously,Mn 2O 3corresponds to the highest obtainable manganese valency,because further oxida-tion to MnO 2can only be effectuated under extremely high oxygen pressures.Reoxidation at higher temperatures,1073K,sur-prisingly,did not lead to a fast formation of the thermodynamically most stable Mn 2O 3.Even after 2h,only the presence of Mn 3O 4could be established.A reoxidation temperature of 1073K is close to the thermodynamical transition temperature of Mn 2O 3to Mn 3O 4.Apparently,the thermodynamical driving force for oxidation to a higher manganese valency,which decreases at higher temperatures,is too small.In the cyclic reoxidation of methane,which will proceed at about 1100K,apparently Mn 3O 4will be formed in the regenerator unit,independent of the manganese valency of the fresh sample.Increasing the oxygen pressure or lowering the temperature of reoxidation could however result in the formation of Mn 2O 3.The in¯uence of the number of subsequent reduc-tion±reoxidation cycles on the reducibility Mn 3O a 4is shown in Fig.6.Subsequent temperature-pro-grammed reduction with methane (up to 1123K)and reoxidation (823K)led to an increase in reduction temperature.The oxygen content of the regenerated samples remained constant (Mn 2O 3).The higher reduction temperatures must be due to a higher crys-tallinity,and this conclusion is supported by thefactFig.5.Temperature-programmed reduction with methane of (a)MnO 2,(b)Mn 2O 3,(c)Mn 3O a 4and (d)Mn 3O b4.((ÐÐÐ)CO 2;(---)O 2production).E.R.Stobbe et al./Catalysis Today 47(1999)161±167165that some sintering of the sieve fraction was observed.This ageing effect is not only important in the cyclic oxidation of methane,but could also be important for the application of manganese oxide as an oxygen storage compound for three-way catalysts.Possibly,this recrystallisation process and sintering can be prevented by using supported manganese oxides.The use of a thermostable support might in¯uence the manganese oxide particle size and crystallinity,resulting in a decrease of the reduction temperature.On the other hand,a support could stabilise the manganese oxide,resulting in an increase in reduci-bility.3.5.Carbon depositionCarbon deposition during the reduction of manga-nese oxide with methane is highly undesired.There-fore we have investigated the carbon deposition activity of Mn 2O 3and Mn 3O b 4.The samples were reduced in a ¯ow of 1%methane at 1100K and kept at this temperature in methane for 20h.After cooling down rapidly,temperature-programmed gasi®cation of the carbon with oxygen revealed a total carbon deposition of 0.1wt%on the low surface Mn 3O b 4,and 0.2wt%on the high surface Mn 2O 3sample.These experiments show that only negligible carbon deposi-tion had occurred.However,carbon deposition might be more pro-nounced on high surface manganese oxides.Thegasi®cation results were con®rmed by transmission electron microscopy (Philips CM200and Philips EM420).With TEM analysis no graphitic or whis-ker-like carbon or any other form of carbon deposition was observed.Moreover,we found that carbon deposition during reduction with methane at 1100K can be prevented completely on all samples by adding 3%water to the feed (1%CH 4balance Ar).Therefore the use of steam is two-fold;besides the use of steam for the heat integration of the process (Fig.1),it will also be used to prevent carbon deposition.4.ConclusionsManganese oxides are capable of oxidising methane in the absence of gas-phase oxygen at temperatures higher than 723K.The reduction rate of the manga-nese oxides is mainly determined by their crystallinity and not by their valency.This crystallinity is enhanced upon subsequent reduction and oxidation cycles,which results in a slower reduction of the manganese oxides by methane.This effect is not only important in the cyclic oxidation of methane,it is also important for it is an oxygen storage compound for three-way catalysts.The reoxidation of MnO,which remains after the oxidation of methane,results in rapid formation of Mn 3O 4.At 1100K no further oxidation of Mn 3O 4takes place.At lower temperature further reoxidation to Mn 2O 3can proceed.Under the expected process conditions,i.e.about 1200K,of cyclic oxidation of methane as thermal energy source (and feed)for the methane reforming reactions,the following cycle will take place.Mn 3O 4will oxidise methane under the formation of water,carbon dioxide and MnO.Subsequently MnO will be regenerated,with air to Mn 3O 4.Only negli-gible carbon deposition was observed.This carbon laydown can be prevented completely by adding small amounts of water to the feed.AcknowledgementsThe authors would like to thank Gastec N.V .for the ®nancial support to thisresearch.Fig.6.The influence of subsequent reduction±reoxidation cycles on the reduction of Mn 3O a 4with methane reoxidation at 823K.166 E.R.Stobbe et al./Catalysis Today 47(1999)161±167References[1]J.R.Rostrup-Nielsen,Catal.Today18(1993)305.[2]I.Dybkjñr,Fuel Process.Tech.42(1995)85.[3]F.Van Looij,Ph.D.Thesis,Utrecht University,1994.[4]F.Van Looij,J.C.Van Giezen,E.R.Stobbe,J.W.Geus,Catal.Today21(1994)495.[5]M.S.Hoogenraad,Ph.D.Thesis,Utrecht University,1995.[6]P.H.Bolt,Ph.D.Thesis,Utrecht University,1994.[7]D.Van de Kleut,Ph.D.Thesis,Utrecht University,1994.[8]E.Grootendorst,Y.Verbeek,V.Ponec,J.Catal.157(1995)706.[9]W.Weimin,Y.Yongnian,Z.Jiayu,Appl.Catal.A133(1995)81.[10]Y.F.Chang,J.G.McCarty,Catal.Today30(1996)163.E.R.Stobbe et al./Catalysis Today47(1999)161±167167。

低温SCR脱硝催化剂综述高翔;卢徐节;胡明华【摘要】目前氮氧化物（NOx）的污染越来越严重，低温选择性催化还原法（SCR）脱硝催化技术作为新型的、具有潜力的烟气脱硝技术，备受人们关注。

综述了低温SCR脱硝催化剂的的研究现状，着重介绍了锰基催化剂、钒基催化剂以及其他金属氧化物催化剂的研究进展，阐述了不同种类的催化剂制备方法、载体，以及使用不同种类的金属氧化物活性组分对催化剂活性和脱硝效率的影响，探讨了低温SCR催化剂的脱硝机理，同时介绍了烟气中水蒸气和SO2对催化过程的影响。

%Nowadays,NOx pollution becomes more and more serious ,low temperature SCR denitra-tion technology,as a kind of new and potential denitration technology,has attract people′s attention. Gives a summary and commentary on the research status of low temperature SCR denitration catalysts and mainly introduces the scientific research status of manganese catalysts,vanadium cata-lysts and other metal oxide catalysts. Indicates the different types of catalyst preparation methods, carriers,and the use of different kinds of metal oxides may all have influence on the catalyst activity and the efficiency of denitrification. Meanwhile,the denitration mechanism of low-temperature SCR catalysts is introduced. At last ,elaborates the effects of water vapor and SO2 in fuel gas on catalytic process.【期刊名称】《江汉大学学报（自然科学版）》【年(卷),期】2014(000)002【总页数】7页(P12-18)【关键词】氮氧化物(NOx);低温SCR脱硝催化剂;脱硝机理;金属氧化物【作者】高翔;卢徐节;胡明华【作者单位】工业烟尘污染控制湖北省重点实验室(江汉大学)，江汉大学化学与环境工程学院，湖北武汉430056;工业烟尘污染控制湖北省重点实验室(江汉大学)，江汉大学化学与环境工程学院，湖北武汉 430056;工业烟尘污染控制湖北省重点实验室(江汉大学)，江汉大学化学与环境工程学院，湖北武汉 430056【正文语种】中文【中图分类】X701.70 引言近年来，我国经济发展迅速，能源的消耗量越来越大。

第61卷 第3期吉林大学学报(理学版)V o l .61 N o .32023年5月J o u r n a l o f J i l i nU n i v e r s i t y (S c i e n c eE d i t i o n )M a y2023d o i :10.13413/j .c n k i .jd x b l x b .2022304水热法制备M n O 2活化过硫酸盐降解水中的四环素杜蕊含1,尚 丹1,蒋 欣1,王 洋2,康春莉1(1.吉林大学新能源与环境学院,长春130012;2.中国科学院东北地理与农业生态研究所湿地生态与环境重点实验室,长春130102)摘要:基于过硫酸盐的高级氧化技术在抗生素污染治理方面重要的应用价值,分别以M n S O 4,M n C l 2和M n (N O 3)2为原料,采用水热法制备3种M n O 2,并利用X 射线衍射仪(X R D )㊁扫描电子显微镜(S E M )和X 射线光电子能谱(X P S )对制备的M n O 2进行表征,对比分析3种M n O 2催化过氧单硫酸盐(p e r o x y m o n o s u l f a t e ,P M S )去除四环素的效果,通过猝灭实验研究催化作用的机理.结果表明:以M n S O 4制备的M n O 2具有纳米棒结构,对P M S 表现出最佳催化效果,60m i n 内对50m g/L 四环素去除率为56.8%;催化过程中存在M n (Ⅳ)/M n (Ⅲ)循环,S O -4∙,∙O H 和1O 2对去除四环素均有贡献;M n O 2/P M S 体系的pH>7时对四环素具有较高的去除率,10mm o l /L N O -3和C l -对四环素降解效率基本无影响,10mm o l /L H C O -3可促进四环素降解;该方法对3种四环素类抗生素去除的大小顺序为金霉素>四环素>土霉素,可用于抗生素污染的治理.关键词:二氧化锰;过氧单硫酸盐;高级氧化;四环素中图分类号:X 131 文献标志码:A 文章编号:1671-5489(2023)03-0707-10P r e p a r a t i o no fM n O 2A c t i v a t e dP e r s u l f a t e b y H yd r o t he r m a l M e t h o df o rD eg r a d a t i o no fT e t r a c yc l i n e i n W a t e r D U R u i h a n 1,S H A N G D a n 1,J I A N G X i n 1,WA N G Y a n g 2,K A N GC h u n l i 1(1.C o l l e g e o f N e w E n e r g y a n dE n v i r o n m e n t ,J i l i nU n i v e r s i t y ,C h a n gc h u n 130012,C h i n a ;2.K e y L a b o r a t o r y o f W e t l a n dE c o l o g y a n dE n v i r o n m e n t ,N o r t h e a s t I n s t i t u t e o f G e o g r a p h y a n dA g r o e c o l o g y ,C h i n e s eA c a d e m y o f S c i e n c e s ,C h a n gc h u n 130102,C h i n a )收稿日期:2022-07-11.第一作者简介:杜蕊含(1998 ),女,汉族,博士研究生,从事环境化学的研究,E -m a i l :1791994130@q q.c o m.通信作者简介:王 洋(1970 ),男,汉族,博士,研究员,博士生导师,从事环境生态与生物地球化学的研究,E -m a i l :w a n g y a n g w@i g a .a c .c n ;康春莉(1963 ),女,汉族,博士,教授,博士生导师,从事环境化学的研究,E -m a i l :k a n g c l @jl u .e d u .c n .基金项目:中国科学院战略性先导科技专项(A 类)基金(批准号:X D A 23070502).A b s t r a c t :A d v a n c e d o x i d a t i o n t e c h n o l o g y b a s e d o n p e r s u l f a t e h a d i m p o r t a n t p o t e n t i a l v a l u e i n t r e a t i n ga n t ib i o t ic p o l l u t i o n .W eu s ed M n S O 4,M n C l 2a n d M n (N O 3)2a s r a w m a te r i a l s t o p r e p a r e t h r e ek i n d s o fM n O 2b y h y d r o t h e r m a lm e t h o d .T h e p r e p a r e d M n O 2wa s c h a r a c t e r i z e db y a nX -r a y d i f f r ac t o m e t e r (X R D ),s c a n n i n g e l e c t r o n m i c r o s c o p e (S E M )a nd X -r a yp h o t oe l e c t r o ns p e c t r o s c o p y (X P S ).T h e e f f e c t s o f t h r e ek i n d so fM n O 2ca t a l y s t so nt h e r e m o v a l o f t e t r a c y c l i n e (T C )b yp e r o x y m o n o s u l f a t e (P M S )w e r ec o m p a r ed a n d a n a l y ze d ,a n d t h e c a t a l y t i c m e c h a n i s m w a s s t u d i e d b y q u e n c h i n g e x p e r i m e n t s .T h e r e s u l t s s h o wt h a t t h e M n O 2p r e p a r e db y M n S O 4ha san a n o r o ds t r u c t u r ea n dt h eb e s tc a t a l y t i c e f f e c t o nP M S .T h e r e m o v a l r a t e o f 50m g/LT C i s 56.8%w i t h i n60m i n .T h e r e i s a n M n (Ⅳ)/M n (Ⅲ)c y c l e i nt h ec a t a l y t i c p r o c e s s ,a n dS O -4∙,∙O H ,a n d 1O 2al l c o n t r i b u t et ot h e Copyright ©博看网. All Rights Reserved.807吉林大学学报(理学版)第61卷r e m o v a l o fT C.T h e M n O2/P M Ss y s t e m h a sah i g hr e m o v a lr a t ef o rt e t r a c y c l i n e w h e n p H>7,10mm o l/LN O-3a n dC l-h a v en o a f f e c t o n t h e d e g r a d a t i o n e f f i c i e n c y o fT C,a n d10mm o l/L H C O-3 c a n p r o m o t et h ed e g r a d a t i o no fT C.T h eo r d e ro fr e m o v a lo f t h r e et e t r a c y c l i n ea n t i b i o t i c sb y t h i s m e t h o d i s c h l o r t e t r a c y c l i n e>T C>o x y t e t r a c y c l i n e,w h i c hc a nb eu s e d f o r t h e t r e a t m e n t o f a n t i b i o t i c p o l l u t i o n.K e y w o r d s:m a n g a n e s eb i o x i d e;p e r o x y m o n o s u l f a t e;a d v a n c e do x i d a t i o n;t e t r a c y c l i n e四环素类抗生素(t e t r a c y c l i n e a n t i b i o t i c s,T C s)是一类广谱抗生素,生产和使用量均较大[1].常见的T C s包括四环素(t e t r a c y c l i n e s,T C)㊁土霉素(o x y t e t r a c y c l i n e,O T C)和金霉素(c h l o r t e t r a c y c l i n e, C T C).人体和动物摄入的T C s只有部分被吸收利用,剩余部分会以代谢物的形式排放到环境中,导致环境污染,因此,有效处理T C s是当前急需解决的环境问题.高级氧化技术(a d v a n c e do x i d a t i o n p r o c e s s e s,A O P s)依靠反应中产生的强氧化自由基快速有效地降解有机污染物,是一种有效的废水处理方法[2],目前利用F e n t o n氧化和电化学氧化等技术处理T C s废水已取得了较好的效果[3-5].基于硫酸根自由基的高级氧化工艺(s u l f a t er a d i c a lb a s e d-a d v a n c e d o x i d a t i o n p r o c e s s e s, S R-A O P s)在降解水中有机污染物方面已引起人们广泛关注[6-8].S R-A O P s技术中使用的氧化剂过氧单硫酸盐(p e r o x y m o n o s u l f a t e,P M S)和过氧二硫酸盐(p e r o x y d i s u l f a t e,P S)需经活化才能充分发挥其氧化能力,二者经催化剂活化可生成不同种类的活性氧化基团(r e a c t i v eo x y g e ns p e c i e s,R O S),如硫酸根自由基(S O-4∙)㊁羟基自由基(∙O H)㊁单线态氧(1O2)和超氧自由基(O-2∙)[9].活化方法主要有热活化[10-11]㊁紫外(U V)活化[12]㊁碱活化[13]和过渡金属活化[14-15]等.相对于其他过硫酸盐的非均相活化剂,锰基材料具有在地壳中含量丰富㊁价格便宜㊁环境友好和低毒性等优势.L i a n g等[16]首次将锰基材料(M n O2)用于过硫酸盐的活化,并发现其具有良好的活化性能.之后,越来越多的锰氧化物(M n O x)被用作过硫酸盐的活性剂.M n O x是废水处理中传统且经济有效的吸附剂和氧化剂[17],在活化P M S/P S方面表现出极大的潜力[18].其中,M n O2具有较强的氧化性,能够活化P M S/P S,高效去除有机污染物[18-19].M n O x表面的M n(Ⅱ)㊁M n(Ⅲ)和M n(Ⅳ)之间的转化是P M S激活的主要因素[18-20].由于不同的电子和几何排布,因此不同晶相结构M n O2的催化活性也有差异.H u a n g等[18]合成了不同结构的M n O2(隧道结构的α-,β-,γ-M n O2和层状结构δ-M n O2),发现不同相结构M n O2对P M S降解污染物的活化顺序不同.此外,对不同形貌和晶相M n O2活化P M S 的能力进行了对比,发现M n O2的结晶度是影响催化反应活性的主要因素[21-22].水热法是合成M n O2的经典方法,通常采用无机锰(Ⅱ)盐与其他无机盐反应制备,包括M n(A C)2[18],M n C O3[23],M n C l2[24]和M n S O4[25]等.但无机锰(Ⅱ)盐的种类对制备出的M n O2活化P M S的影响尚不清楚.M n O2在活化P M S/P S高效去除有机污染物的应用较多,但关于M n O2活化P M S降解T C s的研究目前尚未见文献报道.基于此,本文以常见的四环素类抗生素(T C,O T C和C T C)为目标污染物,采用M n S O4,M n C l2和M n(N O3)23种无机锰(Ⅱ)盐作为原材料,通过水热反应制备M n O2,并对其活化P M S降解不同种类的T C s效果进行研究.分析无机锰(Ⅱ)盐种类对所制备M n O2活化能力的影响机理,考察污染物初始质量浓度㊁催化剂投加量㊁P M S浓度㊁溶液p H值以及共存阴离子对T C s降解的影响,提出M n O2活化P M S降解T C s的作用机理,为S R-A O P s处理T C s的实际应用提供理论依据.1材料与方法1.1试剂高锰酸钾(KM n O4)购自天津新通精细化工有限公司,硝酸锰(M n(N O3)2)和无水乙醇(C H3C H2O H)购自北京化工厂,一水合硫酸锰(M n S O4∙H2O)㊁氯化亚锰(M n C l2∙4H2O)和叔丁醇(C4H10O)购自国药集团,甲醇(C H3O H)购自费希尔化学品公司,迭氮钠(N a N3)购自天津风船化学试剂有限公司,盐酸四环素(C22H24N2O8∙H C l)㊁盐酸土霉素(C22H24N2O9∙H C l)和盐酸金霉素Copyright©博看网. All Rights Reserved.(C 22H 23C l N 2O 8∙HC l )购自美国A l a d d i n 公司.所有试剂均为分析纯试剂,实验用水为自制超纯水(ȡ18.2MΩ∙c m ).1.2 M n O 2的制备与表征M n O 2制备方法参考文献[26].将0.0024m o l M n S O 4/M n C l 2/M n (N O 3)2与0.0016m o l KM n O 4溶解于15m L 自制蒸馏水中,磁力搅拌0.5h ,倒入反应釜中,密封,于150ħ反应6h ,待反应结束后,冷却至室温,固体产物分别用蒸馏水和无水乙醇洗涤,在6000r /m i n 下用高速离心机离心5m i n ,固体于70ħ干燥得到最终产物M n O 2.1.3 M n O 2的表征用X 射线衍射仪(X R D ,D 8A D V A N C E 型,德国B r u k e r 公司)分析产物的晶型结构㊁晶型参数和衍射面等信息.用扫描电子显微镜(S E M ,X L -30E S E M F E G 型,美国F e i 公司)观察材料的表面形貌.用X 射线光电子能谱(X P S ,T h e r m oE S C A L A B250型,美国赛默飞世尔科技公司)分析元素的价态.1.4 T C s 降解实验在锥形瓶中加入100m L 的50m g /LT C (或O T C 或C T C )溶液和0.1g /L 的M n O 2催化剂,充分搅拌均匀后,加入P M S 溶液使其浓度为0.15mm o l /L 并开始计时.分别在5,10,20,30,45,60m i n 时准确移取1m L 反应液,加入1m L 的1m o l /L 甲醇终止反应,用0.22μm 滤头过滤,以待测试.1.5 分析方法用高效液相色谱仪(H P L C ,L C -20A 型,日本岛津实验器材有限公司)测量T C s 的浓度.色谱柱为I n e r t S u s t a i nC 18柱(4.6mmˑ150mm ,5μm ),流动相中的水相和有机相为0.01m o l /L V (草酸)ʒV (乙腈)=3ʒ1,流速为1.0m L /m i n ,进样量为20μL ,柱温为25ħ.T C ,O T C 和C T C 的检测波长分别为355,355,365n m.2 结果与讨论2.1 M n O 2的XR D 和S E M 表征将KM n O 4分别与M n S O 4,M n C l 2和M n (N O 3)2为原材料制备的M n O 2命名为M n O 2(1),图1 样品M n O 2的X R D 谱F i g .1 X R D p a t t e r n s o f s a m pl eM n O 2M n O 2(2)和M n O 2(3),图1为3种M n O 2的XR D 谱.由图1可见,3种M n O 2的X R D 谱中衍射峰明显且尖锐,表明制备的M n O 2的结晶度和纯度均较高.由曲线a 可见,在2θ=12.7ʎ,18.0ʎ,25.5ʎ,28.7ʎ,36.6ʎ,37.5ʎ,41.9ʎ,49.8ʎ,52.7ʎ,56.1ʎ,60.1ʎ,65.3ʎ,69.4ʎ,72.9ʎ处出现了明显的衍射峰,通过M D IJ a d e5软件进行对比分析,这些峰与M n O 2的PD F44-0141标准卡片吻合,分别对应(110),(200),(220),(310),(400),(211),(301),(411),(440),(600),(521),(002),(541)和(312)晶面,为α-M n O 2[19].曲线b 和曲线c 的出峰位置较一致,且峰强度相当.曲线a 中存在的衍射峰在曲线b ,c 上均存在,但峰强度减弱,而曲线b ,c 在22.1ʎ处明显多出一个峰.比对证明该峰属于γ-M n O 2的峰(P D F 44-0142),因此M n O 2(2)和M n O 2(3)除了含有α-M n O 2外,还含有一定数量的γ-M n O 2.研究表明,不同原料和合成条件制备的M n O 2在晶相和结晶度方面均具有明显差异[21,24],5种晶型的M n O 2均有可能生成.图2为3种M n O 2的S E M 照片.由图2(A ),(D )可见,M n O 2(1)由直径约为50n m ㊁长短不同的纳米棒构成.由图2(B ),(E )和图2(C ),(F )可见,M n O 2(2)和M n O 2(3)的形貌较相似,主要由纳米棒状结构组成,但在纳米棒上出现了一些小的纳米片.结合X R D 谱,出现片状结构可能是由于生成了907 第3期 杜蕊含,等:水热法制备M n O 2活化过硫酸盐降解水中的四环素Copyright ©博看网. All Rights Reserved.017吉林大学学报(理学版)第61卷一部分γ-M n O2所致.图2样品的S E M照片F i g.2S E Mi m a g e s o f s a m p l e s2.2M n O2催化性能的对比3种M n O2的催化效果如图3所示.由图3可见:60m i n内M n O2对T C的去除率较低,小于5%;单独的P M S对T C有较好的去除能力,去除率为38.2%,这是因为P M S本身具有一定的氧化能力,可氧化去除污染物;加入M n O2催化剂后,体系对T C的去除效果明显提升,3种M n O2催化P M S去除T C s的最高去除率分别为56.8%(M n O2(1)),47.1%(M n O2(2))和51.9%(M n O2(3)).显著性差异分析表明,M n O2(1),M n O2(2)和M n O2(3)活化P M S降解T C的3组数据间具有显著性差异,P值均小于0.05.以KM n O4和M n S O4为原材料制备的M n O2(1)略好于M n O2(2)和M n O2(3)的催化效果.由表征分析结果可知,M n O2(1)的结晶性为α-M n O2,而M n O2(2)和M n O2(3)除含有α-M n O2外,还含有一定数量的γ-M n O2.M n O2的P M S活化能力取决于它的价态㊁形貌和晶相[27],结晶较多的M n O2更具反应性,不同晶型的M n O2活化P M S的顺序为:α-M n O2>γ-M n O2>β-M n O2>δ-M n O2[18],所以M n O2(1)具有最好的降解效果.由于M n O2(2)和M n O2(3)的结构组成与形貌相近,因此其催化效果也相近.在后续实验中,以催化效果最佳的M n O2(1)为催化剂进一步开展研究. 2.3M n O2催化P M S去除T C的机理2.3.1活性氧基团的作用研究表明,过硫酸盐体系反应中可生成多种R O S,如羟基自由基(∙O H)㊁硫酸根自由基(S O-4∙)和单线态氧(1O2)[4].为验证所研究体系中产生的活性氧基团,分别选用叔丁醇(T B A)㊁甲醇(M e O H)和迭氮钠(N a N3)进行猝灭实验.由于T B A猝灭∙O H(k(∙O H)=3.8~7.6ˑ108(m o l/L)-1∙s-1)的速率远高于对S O-4∙(k(S O-4∙)=4.0~9.1ˑ105(m o l/L)-1∙s-1)的猝灭速率[28],因此选择T B A作为∙O H的猝灭剂.M e O H作为∙O H和S O-4∙共同的猝灭剂(k(∙O H)=1.2~2.8ˑ109(m o l/L)-1∙s-1,k(S O-4∙) =1.6~7.7ˑ107(m o l/L)-1∙s-1)[29-30],N a N3作为1O2的猝灭剂(k(1O2)=1.2ˑ108(m o l/L)-1∙s-1)[31].选择大过量的猝灭剂添加浓度以保证猝灭效果[32-33].3种猝灭剂的浓度分别为:c(T B A)=c(M e O H)= 0.5m o l/L,c(N a N3)=15mm o l/L,猝灭实验结果如图4所示.加入M e O H和T B A后,T C的去除率分别下降10.4%和3.9%,表明M n O2/P M S体系中S O-4∙和∙O H均对T C的降解具有重要作用.加入N a N3后,T C的去除率下降22.1%,远大于S O-4∙和∙O H的作用,表明1O2是T C降解的主要活性物质.因此T C的降解过程包括自由基途径(S O-4∙和∙O H)和非自由基途径(1O2),且以后者为主.在P M S/P S降解磺胺甲恶唑[34-35]和环丙沙星[36]的过程中也存在类似的机理.Copyright©博看网. All Rights Reserved.图3 不同体系降解效果的对比F i g .3 C o m p a r i s o no f d e gr a d a t i o n e f f e c t s o f d i f f e r e n t s ys t e ms 图4 不同猝灭剂对T C 降解的影响F i g .4 E f f e c t s o f d i f f e r e n t q u e n c h i n g a ge n t s o nd e gr a d a t i o no fT C 2.3.2 反应前后X P S 对比为进一步研究M n O 2的催化机理,利用X P S 分析反应前后M n O 2中Mn 元素的变化,结果如图5所示.由图5(A )可见,催化剂中主要含有M n ,O ,C 元素,C 的出现可归因于制备时引入了杂质.反应前后M n2p 的X P S 如图5(B ),(C )所示.由图5(B )可见,M n2p 轨道可分裂为M n2p3/2和M n2p 1/2,结合能为653.9e V 的特征峰对应M n2p 1/2,归因于M n O 2中的M n (Ⅳ)[20].M n2p 3/2可分出结合能为641.9,643e V 的2个峰,分别对应M n (Ⅲ)和M n (Ⅳ)[37].通过比较峰面积发现,M n2p 中Mn (Ⅲ)占19.0%,表明制备的M n O 2以M n (Ⅳ)为主,并存在一定量的M n (Ⅲ)[18].反应前后体系中都只存在M n (Ⅳ)和M n (Ⅲ)的特征峰,且反应后M n (Ⅲ)百分数升高(图5(C )),从19.0%增加至31.4%,表明在M n O 2活化PM S 降解T C s 的过程中,M n (Ⅳ)向M n (Ⅲ)转化.M n (Ⅳ)和H S O -5的反应式为H S O -5+M n (Ⅳң)S O -5∙+M n (Ⅲ)+H+(1)是体系中M n (Ⅲ)百分数增加的主要原因.猝灭实验已证明反应过程中S O -4∙起重要作用,M n (Ⅲ)和P M S 的反应式为H S O -5+M n (Ⅲң)S O -4∙+M n (Ⅳ)+OH-(2)该反应导致M n (Ⅲ)被进一步氧化成M n (Ⅳ).据此推测反应过程中存在M n (I V )/M n (Ⅲ)的氧化还原循环[1],M n (Ⅳ)/M n (Ⅲ)的氧化还原循环有利于电荷流动,促进生成S O -4∙,从而促进了T C 的降解.图5 样品的X P S F i g .5 X P S o f s a m pl e s 2.3.3 催化机理分析综合猝灭实验和反应前后X P S 比较的结果,推测M n O 2催化PM S 去除T C 的机理如下:P M S 与M n (Ⅳ)反应生成S O -5∙和M n (Ⅲ),P M S 与M n (Ⅲ)反应生成S O -4∙和M n (Ⅳ),形成了M n (Ⅳ)/M n (Ⅲ)循环(式(1),(2));生成的S O -4∙与体系中H 2O 的反应式为H 2O +S O -4ң∙SO 2-4+∙OH +H +(3)生成的S O -5∙与H 2O 的反应式为117 第3期 杜蕊含,等:水热法制备M n O 2活化过硫酸盐降解水中的四环素Copyright ©博看网. All Rights Reserved.217吉林大学学报(理学版)第61卷∙2H S O-4+321O2+H2O(4)2H2O+2S O-5ң反应生成了1O2[38];∙O H通过自反应生成1O2[39]的反应式为2∙ңOH H2O+121O2(5)通过产生的S O-4∙,∙O H和1O2有效去除了T C.2.4M n O2催化去除T C的影响因素2.4.1 M n O2投加量、P M S浓度和T C初始质量浓度的影响催化剂投加量㊁P M S浓度和T C初始质量浓度对T C去除效果的影响如图6所示.随着催化剂用量由0.05g/L增加到0.20g/L,50m g/LT C的去除率从49.3%增加到60.4%(图6(A)).M n O2催化P M S去除T C的反应主要发生在M n O2的表面,P M S被吸附到M n O2表面,活化产生的R O S进一步与迁移到催化剂表面的污染物发生反应.增加M n O2催化剂投加量可提供更多的活性位点,使P M S 活化更充分,也可使T C与M n O2的接触几率增大,从而提高T C的去除率.由图6(B)可见,当P M S 的浓度从0.05mm o l/L增加到0.20mm o l/L时,50m g/L T C的去除率从25.9%增加到60.8%. P M S增加会产生更多的活性物质,从而提高溶液中T C的去除率.当P M S浓度从0.15mm o l/L增到0.20mm o l/L时,去除率提升的效果减缓,仅提升约6%,这可能是过量的P M S与体系产生的S O-4∙和∙O H发生反应,生成了氧化能力较差的S O-5∙,使去除率提升减缓,而且过量的S O-4∙和S O-5∙也会发生自反应,进一步消耗自由基[40],其反应式为∙S O2-4+S O-5∙+H+(6)H S O-5+S O-4ңH S O-5+∙ңOH H2O+S O-5∙(7)2S O-4ң∙S2O2-8(8)2S O-5ң∙O2+S2O2-8(9)综上,选择0.15mm o l/L的P M S和0.10g/L的M n O2作为最佳试剂用量.在P M S和M n O2用量一定的条件下,当T C初始质量浓度从25m g/L增加到100m g/L时,60m i n内降解率从79.5%下降到40%(图6(C)),为方便对比分析,后续实验中T C的质量浓度均为50m g/L .图6不同实验参数对T C降解的影响F i g.6E f f e c t s o f d i f f e r e n t e x p e r i m e n t a l p a r a m e t e r s o nd e g r a d a t i o no fT C2.4.2p H值的影响图7为初始p H值对T C降解率的影响.由图7可见,随着p H值由3增加到7,T C的去除率逐渐降低.这是由于在酸性至中性条件下,随着p H值的增大,体系中形成的S O-4∙易于和H2O形成氧化性较弱的∙O H(式(3)),S O-4∙和∙OH的反应式[36]为2∙OH+2S O-4ң∙O2+2H S O-4,(10)导致自由基自消耗,进而影响与T C的反应.当初始p H=9时,体系的T C去除效果最佳,为63.4%.自由基猝灭实验结果表明,1O2是该体系降解T C的主要活性物质,在碱性条件下反应过程中会产生更多的1O2[39],从而提高了去除效果.Copyright©博看网. All Rights Reserved.2.4.3 共存离子的影响天然水以及各种污水中含有多种无机阴离子,主要包括C l -,N O -3和H C O -3等,废水中这几种离子的浓度一般为几毫摩每升[41-43].在实际污水处理中,共存离子会影响污染物的去除效率[42],参考文献[44-45],本文选择共存阴离子的浓度为10mm o l /L .H C O -3,C l -和N O -3对T C 降解的影响如图8所示.由图8可见,当N O -3和C l -与T C 共存时,T C 去除率未发生明显改变[37-38].当H C O -3与T C 共存时,T C 的去除率显著提升,这是由于加入H C O -3使溶液的p H 值升高所致,H C O -3+H 2ңO H 2C O 3+OH-(11)溶液为碱性可提高P M S 的催化活性,从而提高T C 的去除率.图7 初始p H 值对T C 降解的影响F i g .7 E f f e c t s o f i n i t i a l p Hv a l u e s o nd e gr a d a t i o no fT C 图8 不同离子对T C 降解的影响F i g .8 E f f e c t s o f d i f f e r e n t i o n s o nd e gr a d a t i o no fT C 2.5 催化剂的重复利用性在每次反应结束后,将分离得到的催化剂用适量蒸馏水洗涤,离心㊁干燥后,重新用于催化反应.M n O 2的重复利用性如图9所示.由图9可见,M n O 2循环使用5次后TC 去除率由55.8%降为50.9%,仅下降4.9%,表明所制备的M n O 2催化剂具有良好的重复利用性.去除率略有下降的原因可能是因为有少量锰离子溶出或有少量污染物占据了催化剂活性位点[40].2.6 M n O 2催化PM S 去除不同T C s 为检验M n O 2在实际应用中的潜力,比较M n O 2/P M S 体系对T C ,O T C 和C T C 的去除效果,结果如图10所示.虽然T C ,O T C 和C T C 的分子结构基本相同,但所含基团存在一定的差异,导致去除效果不同.由图10可见:C T C 的去除效果最佳,达到75.1%;O T C 的去除效果最差,为45.3%.这是由于C T C 的结构中比T C 多一个 C l ,降解时易脱氯,因此较活泼;而O T C 比T C 多一个 O H ,羟基间易形成缔合物使其难以吸附在催化剂的表面,从而抑制其降解[46].虽然体系对3种T C s 的去除率不同,但所制备的M n O 2能有效催化PM S 去除水中多种T C s .图9 M n O 2的循环试验F i g .9 C y c l i c e x pe r i m e n t o fM n O 2图10 不同T C s 的降解效果F i g .10 D e gr a d a t i o n e f f e c t s o f d i f f e r e n t T C s 综上所述,本文采用水热法,分别利用M n S O 4,M n C l 2和M n (N O 3)2为原料制备M n O 2,并将其用于活化P M S 降解T C s ,通过材料表征和模拟实验,分析了无机锰(Ⅱ)盐种类对所制备M n O 2活化能力的影响机理,考察了污染物初始质量浓度㊁催化剂投加量㊁P M S 浓度㊁溶液p H 值以及共存阴离子对317 第3期 杜蕊含,等:水热法制备M n O 2活化过硫酸盐降解水中的四环素Copyright ©博看网. All Rights Reserved.417吉林大学学报(理学版)第61卷T C降解的影响,提出了M n O2活化P M S降解T C s的作用机理.结果表明,以M n S O4为原料制备的M n O2为α-M n O2晶相,结晶度较高,具有最佳催化效果,在60m i n内对50m g/L T C的去除率为56.8%.催化剂和P M S投加量的增加均会促进T C降解,催化剂在碱性条件下以及有阴离子共存的溶液中具有良好的适应性.通过猝灭实验和反应前后X P S分析,发现T C的去除机理包括自由基途径和非自由基途径,1O2是主要活性物质,催化过程中M n O2通过M n(Ⅳ)/M n(Ⅲ)循环活化P M S.M n O2催化剂性能稳定,使用5次后,去除率仅下降4.9%.在最佳条件下,M n O2/P M S对C T C和O T C的去除效果分别为75.1%和45.3%,表明M n O2/P M S对T C s具有普遍的适用性.参考文献[1] WA N G X Y,J I A N GJJ,MA Y H,e ta l.T e t r a c y c l i n e H y d r o c h l o r i d eD e g r a d a t i o no v e r M a n g a n e s eC o b a l t a t e(M n C o2O4)M o d i f i e d U l t r a t h i n G r a p h i t i c C a r b o n N i t r i d e(g-C3N4)N a n o s h e e tt h r o u g ht h e H i g h l y E f f i c i e n tA c t i v a t i o no fP e r o x y m o n o s u l f a t eu n d e rV i s i b l eL i g h t I r r a d i a t i o n[J].J o u r n a lo fC o l l o i da n dI n t e r f a c eS c i e n c e,2021,600:449-462.[2] P E IX Y,P E N G X X,J I A X S,e ta l.N-D o p e d B i o c h a rf r o m S e w a g eS l u d g ef o rC a t a l y t i cP e r o x y d i s u l f a t eA c t i v a t i o n t o w a r dS u l f a d i a z i n e:E f f i c i e n c y,M e c h a n i s m,a n dS t a b i l i t y[J].J o u r n a l o fH a z a r d o u sM a t e r i a l s,2021,419:126446-1-126446-13.[3] Y A D A E IH,N OWR O O Z IM,B E Y K IM H,e t a l.S y n t h e s i s o fM a g n e t i cF e-C a r b o nN a n o h y b r i d f o rA d s o r p t i o na n dF e n t o nO x i d a t i o no fT e t r a c y c l i n e[J].D e s a l i n a t i o na n d W a t e rT r e a t m e n t,2020,173:294-312.[4] HO N GJY,HWA N GDK,S E L V A R A JR,e t a l.F a c i l e S y n t h e s i s o f B r-D o p e d g-C3N4N a n o s h e e t s v i aO n e-S t e pE x f o l i a t i o n U s i n g A mm o n i u m B r o m i d ef o r P h o t o d e g r a d a t i o n o f O x y t e t r a c y c l i n e A n t i b i o t i c s[J].J o u r n a lo fI n d u s t r i a l a n dE n g i n e e r i n g C h e m i s t r y,2019,79:473-481.[5] WA N GJB,Z H ID,Z HO U H,e t a l.E v a l u a t i n g T e t r a c y c l i n eD e g r a d a t i o nP a t h w a y a n dI n t e r m e d i a t eT o x i c i t yd u r i n g t h eE le c t r o c h e m i c a lO x i d a t i o no v e r aT i/T i4O7A n o d e[J].W a t e rR e s e a r c h,2018,137:324-334.[6]沈一君,彭明国,徐彬焜,等.紫外活化过硫酸盐降解二苯甲酮-4的动力学影响及降解机理与风险评价[J].环境科学研究,2019,32(1):174-182.(S H E N Y J,P E N G M G,X U B K,e ta l.D e g r a d a t i o no fB P4b y U V-A c t i v a t e dP e r s u l f a t eP r o c e s s:K i n e t i c,M e c h a n i s ma n dR i s k[J].R e s e a r c ho fE n v i r o n m e n t a l S c i e n c e s,2019, 32(1):174-182.)[7]许若梦,吴桐,锁瑞娟,等.基于不同自由基的高级氧化技术对水中诺氟沙星的去除效果[J].环境工程技术学报,2020,10(3):433-439.(X U R M,WU T,S U O RJ,e ta l.R e m o v a lP e r f o r m a n c eo fN o r f l o x a c i nf r o m W a t e r sb y A d v a n c e d O x i d a t i o n P r o c e s s e s B a s e d o n D i f f e r e n t F r e e R a d i c a l s[J].J o u r n a lo f E n v i r o n m e n t a lE n g i n e e r i n g T e c h n o l o g y,2020,10(3):433-439.)[8]任何军,林雯雯,鲁松,等.热活化过硫酸盐降解氧氟沙星特性及响应面优化[J].吉林大学学报(地球科学版),2021,51(3):887-897.(R E N HJ,L I N W W,L U S,e t a l.D e g r a d a t i o no fO f l o x a c i nb y T h e r m a l l y A c t i v a t e d P e r s u l f a t e a n d I t sR e s p o n s eS u r f a c eO p t i m i z a t i o n[J].J o u r n a l o f J i l i nU n i v e r s i t y(E a r t hS c i e n c eE d i t i o n),2021, 51(3):887-897.)[9] HO UJF,H EXD,Z HA N GSQ,e t a l.R e c e n tA d v a n c e s i nC o b a l t-A c t i v a t e dS u l f a t eR a d i c a l-B a s e dA d v a n c e dO x i d a t i o nP r o c e s s e sf o r W a t e r R e m e d i a t i o n:A R e v i e w[J].S c i e n c eo ft h e T o t a lE n v i r o n m e n t,2021,770: 145311-1-145311-15.[10]J IY F,D O N G C X,K O N G D Y,e ta l.H e a t-A c t i v a t e d P e r s u l f a t e O x i d a t i o no f A t r a z i n e:I m p l i c a t i o n sf o rR e m e d i a t i o no fG r o u n d-W a t e r C o n t a m i n a t e d b y H e r b i c i d e s[J].C h e m i c a l E n g i n e e r i n g J o u r n a l,2015,263:45-54.[11] Z R I N Y IN,P HAM A L T.O x i d a t i o no fB e n z o i cA c i db y H e a t a c t i v a t e dP e r s u l f a t e:E f f e c to fT e m p e r a t u r eo nT r a n s f o r m a t i o nP a t h w a y a n dP r o d u c tD i s t r i b u t i o n[J].W a t e rR e s e a r c h,2017,120:43-51.[12] F R O N T I S T I SZ,HA P E S H IE,F A T T A-K A S S I N O S D,e ta l.U l t r a v i o l e t-A c t i v a t e d P e r s u l f a t e O x i d a t i o no fM e t h y lO r a n g e:A C o m p a r i s o nb e t w e e n A r t i f i c i a lN e u r a lN e t w o r k sa n dF a c t o r i a lD e s i g nf o rP r o c e s s M o d e l l i n g [J].P h o t o c h e m i c a l&P h o t o b i o l o g i c a l S c i e n c e s,2015,14(3):528-535.[13] F U R MA N OS,T E E L A L,WA T T S RJ.M e c h a n i s m o fB a s e A c t i v a t i o no fP e r s u l f a t e[J].E n v i r o n m e n t a lS c i e n c e&T e c h n o l o g y,2010,44(16):6423-6428.Copyright©博看网. 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All Rights Reserved.。

二氧化锰催化氧化甲醛的研究进展发布时间：2022-06-15T07:58:50.865Z 来源：《科学与技术》2022年2月4期作者：顾辉子[导读] 随着人们在室内停留时间的增加，室内甲醛污染逐渐成为一个对人体健康很重要的影响因素顾辉子浙江新火原新材料科技有限公司浙江绍兴 312030摘要：随着人们在室内停留时间的增加，室内甲醛污染逐渐成为一个对人体健康很重要的影响因素。

二氧化锰因其高催化活性、热稳定性、原材料易得、成本低、晶型丰富，引起了很大的关注。

本综述总结了近几年以二氧化锰为主的催化材料在甲醛催化氧化上的应用，特别是甲醛低温催化领域的研究进展。

介绍了二氧化锰的晶型、形貌对催化性能的影响并对甲醛催化机理进行分析。

关键词：氧化锰；催化氧化；甲醛；室内污染随着社会的发展，居民生活水平的提高，人们在室内活动时间明显增加。

城市大环境的空气污染导致部分地区室外环境也不理想，因此室内外环境的交换频率也逐渐降低。

而室内装饰、家具、人体本身，办公用品等各种生活用品，都在不断的产生各种室内空气污染物。

在这些污染物种，VOC因其特有的难闻、刺激性的气味和致癌性正受到日益广泛的关注。

其中，甲醛释放周期长，难彻底清除成为最受关注的室内大气污染物之一。

2004年，IARC将甲醛认定为致癌物质[3]。

2000年，WHO将室内甲醛浓度限定在0.1mg/m3。

因此，提高室内空气质量并发展室内甲醛处理技术是十分必要。

控制甲醛的策略主要有三方面，源头控制，通风和末端治理。

源头控制可以减少甲醛的释放，比如控制建筑板材中含醛胶水的用量。

尿醛树脂作为主要的粘结剂用在板材中，将在几个月甚至几年的时间内持续释放甲醛。

加强通风被证明是非常有效的手段，而且是必要手段。

但是如果室外环境欠佳，通风会带来PM2.5和臭氧的污染[4]。

末端治理包括吸附，光催化氧化，等离子催化，和热催化或室温催化。

物理吸附比如活性炭吸附的有效性局限于他的吸附能力。

另外，吸附饱和后的材料会脱附，引起二次污染[5]。

3.1.1. Metal-Based Catalysts For ORR .氧还原金属基催化剂。

3.1.1.1. Pt Catalysts.1 PT催化剂。

Among all of the pure metal ORR catalysts developedto date, Pt is the most wid ely us electrocatalyst for ORR.在所有的纯金属和催化剂的开发到目前为止，PT是最广泛使用的氧还原催化剂.The ORR performance of the Pt catalyst depends on itscrystallization, morphology, sh ape, and size.Pt催化剂ORR的性能取决于其结晶，形态，形状和尺寸。

found that the ORR activity on Pt(100) is much higher than thaton Pt(111) in a H2SO4 medium due to the different adsorptionrates for the sulfates to be adso rbed on these different rates for the sulfates to be adsorbed on these different f acets.发现Pt的ORR活性（100）明显高于在Pt（111）在硫酸介质中的硫酸盐率，由于不同的吸附对于被吸附在这些不同的平面上.Therefore , it is critical to control the shape and morphology of Pt nanoparticles因此，它是控制铂的形状和形态的关键纳米材料.In this context, Wang et al. synthesized monodisperse Pt nanocubes, showing aSpecific activity over 2 times as high as that of the commercial Pt catalyst.在此背景下，王等人。

三氧化二锰转化为二氧化锰标题：三氧化二锰转化为二氧化锰的化学过程与应用导语：三氧化二锰（Mn3O4）是一种常见的锰氧化物，它可以通过一系列化学反应与条件转化为二氧化锰（MnO2）。

这一转化过程及其应用在多个领域都具有重要意义。

本文将从深度和广度两方面来探讨这一主题，帮助您全面理解三氧化二锰转化为二氧化锰的化学过程以及其中的应用。

一、三氧化二锰转化为二氧化锰的化学过程1. 反应方程式三氧化二锰的转化过程可以通过以下反应方程式来描述：2 Mn3O4 + O2 → 6 MnO2该方程式表示了三氧化二锰与氧气反应，生成六个氧化锰分子。

这一反应是一个氧化还原反应，其中三氧化二锰发生氧化，而氧气则起到氧化剂的作用。

2. 形成二氧化锰的条件三氧化二锰的转化为二氧化锰的过程通常在高温下进行。

在一般情况下，反应温度通常在350度至450度之间，并通过控制温度来控制反应速率。

3. 反应机理具体的反应机理还在科学界存在着一定的争议，但目前有两种主要的理论被广泛接受。

（1）氧扩散机制：该机制认为，在高温下，氧气与三氧化二锰表面发生反应，形成氧化锰，再通过氧扩散至体相中，最终形成均一的二氧化锰产物。

（2）氧离子传导机制：该机制认为，在高温条件下，三氧化二锰晶体表面存在缺陷和空位，氧离子可以通过这些空位在晶体中传导，并与表面的三氧化二锰反应生成二氧化锰。

二、三氧化二锰转化为二氧化锰的应用1. 电化学电池二氧化锰作为一种优秀的催化剂，广泛应用于电化学电池中。

通过将三氧化二锰转化为二氧化锰，并将其作为阳极催化剂应用于电池中，可以提高电池的性能和循环寿命。

2. 化学工业二氧化锰在化学工业中有着广泛的应用。

它被用作催化剂和氧化剂，在有机合成、医药制剂生产以及有色金属提取等过程中起到关键作用。

3. 环境领域二氧化锰还被广泛应用于环境领域。

它可以作为催化剂用于净化废水和处理有机废气中的有毒有害物质，具有良好的催化降解性能。

个人观点和理解：三氧化二锰转化为二氧化锰的化学过程伴随着氧气的介入，是一种重要的氧化还原反应。

Catalysts for Production of Lower Olefins from Synthesis Gas:A ReviewHirsa M.Torres Galvis and Krijn P.de Jong*Inorganic Chemistry and Catalysis,Utrecht University,Universiteitsweg99,3584CG Utrecht,The Netherlands1000h on stream.Remarkably the high(P,T,H2/CO ratio,GHSV).A majorof carbon lay-down to enhance catalystcatalysts,ethylene,propylene1.1.Lower Olefins.Ethylene,propylene,and butylenes are key building blocks in the chemical industry.Throughout this review we refer to C2−C4olefins as lower or light olefins.These base chemicals are among the organic chemicals with the largest production volumes worldwide(Table1).Their broad spectrum of derivatives result in a very diverse end market ranging from packing materials and synthetic textiles to antifreezing agents,solvents,and coatings.Ethylene is the largest-volume petrochemical produced worldwide.It is used to produce intermediate chemicals of high importance in industry such as ethyl benzene,ethylene oxide,and ethylene dichloride,which were listed,along with ethylene,in the top30highest volume chemicals in the United States in2000.The major chemicals derived from ethyleneand their derivatives are shown in Figure1.Ethylene is mainlyused by the plastics industry.In2010,approximately61%of thetotal consumption of ethylene was for production of poly-ethylene in the Western European countries(Figure2).Ethylene is also used in the production of other plastics suchas polystyrene(PS),polyethylene terephthalate(PET),andpolyvinyl chloride(PVC),which are widely used in thepackaging,textile,and construction industries. Commercial ethylene production is mainly based on steamcracking of a broad range of hydrocarbon feedstocks.In Europeand Asia,ethylene is obtained mainly from cracking of naphtha,gas oil,and condensates,while in the U.S.,Canada,and theMiddle East ethylene is produced by cracking of ethane and propane.Naphtha cracking is the major source of ethylene worldwide;however,gas cracking has been gaining importance in recent years.Propylene is a versatile petrochemical which has even morederivatives than ethylene.However,the tremendous growth ofpolypropylene consumption over the past15years has been the main driver of the large increase of the demand of propylene.In 2010,more than55%of propylene consumption was dedicated to the production of polypropylene in the Western European countries.Approximately13%of the propylene was used in the production of propylene oxide,which is a chemical precursor for the synthesis of propylene glycol and polyols.The rest ofReceived:May13,2013Revised:July3,2013Published:July8,2013Table1.Production of Organic Chemicals in2010in Thousands of Metric Tons1 a China Europe ethylene23975182371418819968 propylene1408514295na b14758 ethylene dichloride88103222c na1323 benzene6862d1088955305107 ethyl benzene4240na na1226 cumene3478na na naethylene oxide2664845c na2619 butadiene1580e2715na2020 methanol na na15740naa Japan,South Korea,and Taiwan.b Information not available.c Japan only.d Thousands of liters.e1,3-Butadiene rubber grade.the production was used in the synthesis of cumene (about8%),acrylonitrile,isopropyl alcohol,and many otherindustrially relevant chemicals.3Traditionally,propylene is produced as a byproduct of steamcracking of naphtha for ethylene production or it is recoveredfrom re finery processes,especially from fluid catalytic cracking(FCC).During steam cracking it is possible to tune thepropylene/ethylene ratio by varying the severity of the crackingprocess.A low severity cracking process yields less ethylene andmore byproducts.Although the normal condition is moderatelyhigh severity cracking to achieve ethylene maximization,thenecessity to increase the production of high value byproducts,such as propylene,may dictate lowering the severity duringshort-term optimization.Re finery propylene is primarily derived from FCC,visbreaking/thermal cracking,and coking.For all of theseprocesses propylene is obtained as a diluted stream in propane.FCC-derived propylene accounts for approximately 30%of the global supply,and this percentage tends to increase as the steam cracking-derived propylene decreases as a result of thegrowth of ethylene production from ethane-based cracking.4InFigure 1.Ethylene and itsderivatives.Figure 2.Ethylene consumption over di fferent products in the Western Europeancountries.LDPE:low-density polyethylene.LLDPE:linear low-density polyethylene.HDPE:high-density poly-ethylene.EB:ethyl benzene.EO:ethylene oxide.EDC:ethylene dichloride.VAM:vinyl acetate monomer.Statistics of 2010.3recent years,the production of propene via dehydrogenation of propane (PDH)has grown in view of the availability of low-priced propane in shale gas.5The C 4ole fins fraction is composed of butadiene,isobutylene,and n -butenes which are used in fuel and chemical applications.Butadiene is mainly used as raw material for the production of di fferent types of synthetic rubber (SBR,polybutadiene rubber,etc.).These synthetic rubbers are in high demand all over the world,especially in Asia,for the manufacture of finished goods in the electronics and automotive sectors.Butadiene is also used for the production of ABS (acrylonitrile −butadiene −styrene),SB (styrene −butadiene)copolymer latex and block copolymers,and nitrile rubbers (NBR).One of the most important applications of butylenes is in the fuel industry,accounting for approximately 85%of butylenes ’world production.They are used for the production of gasoline alkylate,polymer gasoline,and dimersol,which are gasoline blending components.Isobutylene is a raw material for the synthesis of methyl tert -butyl ether (MTBE)and ethyl tert -butyl ether (ETBE),which are used as octane enhancers,and for the production of isooctane by dimerization and subsequent hydrogenation.n -Butenes have a smaller chemical market compared with butadiene and isobutylene.They are used as comonomers for polyethylene,for the production of sec -butyl alcohol,which is a raw material in the synthesis of MEK (methyl ethyl ketone),and for the synthesis of higher ole fins.Approximately 95%of butadiene world production is a byproduct of the steam cracking of naphtha and gas oil for the production of ethylene and propylene.Butadiene is then recovered from the C 4cracker stream by extractive distillation.Other processes for the production of butadiene involve further processing of the C 4stream,e.g.,recycle cocracking with and without selective or full dehydrogenation.1.2.Alternative Feedstocks.The constantly growing demand for lower ole fins has caused the global production capacity to double over the past 15years.During 2008and 2009,ethylene demand decreased due to the slow global economic growth;nevertheless,analysts predict that the demand will grow after 2012(Figure 3).It is expected that new steam crackers will provide su fficient ethylene to meet the growing demand.Propylene production will increase as well;however,according to experts the production capacity will be insu fficient to cover the demand.6The growth of the demand for lower ole fins will inevitably increase the demand for the feedstocks required in the petrochemical industry.With the recent high oil prices,research has been directed to the development of processes based on alternative feedstocks for the production of lower ole fins.Apart from high oil prices,there are some other drivers in the search for alternative routes and feedstocks:•Theproduction of lower ole fins via steam cracking is one of the ten most energy-consuming processes of the chemical and petrochemical industry.7•Thereis a growing awareness of the depletion of conventional oil reserves.Some analysts suggest that oil consumption will surpass the discovery of new reserves followedby the depletion of known reserves.8•The oil contained in unconventional reserves is heavy oil in the case of so-called oil sands.The extraction and upgrading of unconventional oil currently may involve higher costs and higher CO 2emissions in comparison with conventionaloil.9•There is a pressing necessity to decrease CO 2emissions.10Feedstocks such as biomass have lower net CO 2contribution.11•Many countries,among them Japan,China,and Brazil,are searching for alternatives to reduce their reliance on imported crude oil and re fined products.Several processes have been developed in an attempt to solve one or more of the challenges encountered by the lower ole fins industry.These processes are based on alternative feedstocksuch as coal,natural gas,or biomass.Although coal has long been used as a feedstock for the chemical industry,for instance,for the production of acetylenevia the carbide process and for the synthesis of ammonia,in times of abundant low-cost oil and gas,its role diminished.The rapid increase of energy demand,the high oil and gas prices,and the strategic drive of coal-rich countries to reduce their dependence on imported crude oil have led to reconsider coal as a primary feedstock for the production of chemicals.Countries with large coal reserves,such as China,are very active in the research,development,and implementation of coal-based projects such as the transformation of syngas to ole fins via methanol synthesis (MTO)or via dimethyl ether or SDTO process (syngas via dimethyl ether to ole fins).However,there are some challenges in the great potential of the coal-to-ole fins industry.Coal gasi fication generates excess CO 2that has to be removed from the synthesis gas and discharged from the plant.The environmental pressure to reduce CO 2emissions may bring about CO 2sequestration technologies that have to be implemented before coal-based processes are established worldwide.Biomass gasi fication has potential as a source for hydro-carbon products in view of feedstock flexibility and the possibilities to reduce net CO 2emissions.12−15The use of biomass for the production of lower ole fins might bene fit from low feedstock costs and tax incentives.However,the potential for cost reduction in light ole fins production is limited by the cost of collection and transportation of biomass in large-scale applications and the production of synthesis gas.The use of biomass is mainly encouraged by its carbon-neutral nature.Biomass may be transformed throughpyrolysisFigure 3.Ethylene demand in the period 2006−2011.Forecast for the period 2012−2016.Source:CMAI.to achieve high energy density and then converted to syngas.The syngas obtained from biomass is CO-rich and in general contains several impurities,as is the case for coal-based syngas.The syngas derived from these sources requires extensive puri fication to remove contaminants,such as sulfur,that are detrimental for the catalysts used in syngas transformation processes.For most conversion processes,the H 2/CO ratio needs to be adjusted by means of the water gas shift reaction (WGS).After puri fication and tuning the H 2/CO ratio,syngas can be used for the production of chemicals and fuels.With the recent discovery of large shale gas reserves in the U.S.,16,17new possibilities are open for the transformation of natural gas to ole fins.Wet shale gas can be directly fed to ethane crackers to produce ethylene,while dry shale gas can be used for the production of syngas and thus be transformed directly or indirectly to lower ole fins.The increased availability of natural gas from shale deposits has produced a major shift in the feedstocks used for the production of ethylene in U.S.,and consequently it has a ffected the propylene and butadiene markets.The use of ethane as feedstock for the crackers instead of naphtha results in a tighter supply of C 3and C 4ole fins,and it might increase the prices for those chemicals in the future.5,18These issues have also opened opportunities for alternative processes for the production of propylene and rge shale gas reserves have been found not only in U.S.but also in other countries such as China,which holds the largest technically recoverable reserves.19The exploitation of shale gas for energy purposes and for the production of lower ole fins is expected to increase dramatically in the years to come in spite of some environmental concerns related to its extraction 20and the high costs involved in the production of shale gas.21 2.PRODUCTION OF LOWER OLEFINS FROM SYNTHESIS GASSome of the alternative processes for the production of lowerole fins are dehydrogenation of lower alkanes,syngas-based processes,and speci fic processes for target products such as theproduction of ethylene via dehydration of ethanol derived from renewable sources or propylene synthesis via dehydrogenation of propane obtained as a byproduct of biodiesel production.Figure 4displays the di fferent conversion processes that use coal or biomass-based syngas as feedstock.The same scheme applies for H 2-rich syngas although,in that case,the step for the adjustment of the H2/CO ratio is not necessary.The processesfor the production of lower ole fins via syngas can be dividedinto two main groups:indirect processes,which require the synthesis of an intermediate such as methanol or dimethyl ether,and direct processes.2.1.Indirect Processes.Several indirect processes for the conversion of syngas to lower ole fins have been developed inview of the selectivity restriction posed by the Anderson −Schulz −Flory productdistribution that governs the Fischer −Tropsch synthesis.22−25The methanol-to-ole fins process (MTO)has been developed and commercialized in places where the technology has an economical advantage over naphtha cracking and other natural gas conversion processes.Mobil synthesized the ZSM-5zeolite and used it for the methanol-to-gasoline process (MTG).26Later,the MTO process was developed by UOP/Hydro to produce a mixture of C 2−C 4ole fins from methanol using a zeolite-based catalyst.The main product of MTO is ethylene when the process is performed using a SAPO-34catalyst.The MTO UOP/Hydro process produces up to 90%of light ole fins from methanol,but the SAPO-34catalyst can be rapidly deactivated (in the orderof minutes to hours)by coke formation,depending on reactionconditions and crystal size.27Figure 4.Processes for the transformation of CO-rich synthesis gas into lower ole fins.High selectivities to propylene have not been reported for the MTO process using SAPO-34.28For this reason,the methanol-to-propylene(MTP)process was developed by Lurgi to selectively produce propylene obtaining gasoline,fuel gas, and LPG as byproducts.The ZSM-5-based Lurgi process produces up to70%propylene from methanol via recycling of byproducts.29Liu et al.22reported on a pilot plant for MTO using two reactors:thefirst reactor containedγ-Al2O3to dehydrate methanol to dimethyl ether(DME),and the second one used ZSM-5for the conversion of DME to light olefins.They obtained a C2−C4olefin selectivity of85wt%(C2H4,24wt%; C3H6,40wt%)with a methanol conversion of100%.The catalyst showed a good stability during the1500h of the test. Another indirect process that has been developed is the dimethyl ether-to-olefins process(DMTO)that is also known as SDTO(syngas-via-dimethyl ether-to-olefins)or simply DTO.In principle this process could be more efficient than MTO as the synthesis of dimethyl ether(DME)from syngas has more favorable thermodynamics in comparison with methanol synthesis.The process uses two types of catalysts: in afirst reactor,the DME synthesis is carried out using a metal−acid bifunctional catalyst,and the DME conversion reaction is performed using a SAPO-34catalyst in a second reactor.Liu and co-workers22reported a C2−C4olefin selectivity of90wt%(C2H4,∼60wt%;C3H6,∼20wt%) at a DME conversion of100%,using a Cu−Zn/ZSM-5catalyst for the conversion of syngas to DME and a metal-modified SAPO-34type of molecular sieve for the conversion of DME to lower olefins.Selectivities to other products were not reported. The SAPO-type catalyst had to be regenerated by coke burnoff. The catalyst retained its performance after regeneration and only showed a small decrease in relative crystallinity in the presence of water.30It has been stated that DMTO should be closely related to MTO because of the fast conversion equilibrium that occurs among methanol,DME,and water;28 this has been observed as well by Liu et al.when they used methanol instead of DME on their modified SAPO-type catalyst obtaining similar selectivities.22Zhao et al.28investigated the synthesis of light olefins over modified H-ZSM-5catalysts using DME as feed.They obtained high C2−C4olefin selectivities(up to75%C)with preferential formation of propylene(∼45%C)using zirconia-modified H-ZSM-5.Some of other indirect processes for the production of lower olefins from synthesis gas that have been reported are as follows:1.The Texaco process.31This process consists of twostages:in thefirst step,syngas is converted intocarboxylic acid esters in a homogeneous reaction in thepresence of a ruthenium catalyst promoted withquaternary phosphonium salts.The second stage involvesthe pyrolysis of the aliphatic carboxylic acid esters toalkenes and the parent acid.Product selectivity can betailored depending on the feed to obtain ethylene or propylene selectivities up to55%.2.A process developed by Dow Chemical Company totransform syngas into a mixture of lower alcohols(C1−C5)using molybdenum sulfides.The alcohol mix can besubsequently dehydrated to produce lower olefins.3.The production of lower olefins from FT liquids.32Hydrocarbons that are produced through the Fischer−Tropsch reaction route can be transformed into C2−C4olefins through cracking and upgrading using traditionalpetrochemical processes.All indirect processes involve more than one step which generates additional costs in terms of equipment and energy consumption.However,processes with high selectivities to ethylene such as MTO or DMTO,or highly selective toward propylene like MTP,can be of great interest for the production of polyethylene or polypropylene in remote areas not linked to chemical complexes.33,342.2.Direct Processes.The direct conversion of syngas into lower olefins via the Fischer−Tropsch synthesis of the Fischer−Tropsch to olefins(FTO)process is an interesting option compared to cracking of FT liquids,MTO,or DMTO.34The idea of following a direct route for the synthesis of lower olefins from synthesis gas has been considered for more than50years, and many references can be found in the literature about catalytic systems that might be suitable for this applica-tion.24,25,35Figure5represents the output of research publications and industrial patents on the direct Fischer−Tropsch synthesis oflower olefins since1955.The increase in the number of publications in this subject was preceded by periods where oil prices reached peak values.It is also clear that oil prices are strongly dependent on geopolitical issues as depicted in Figure 5.It is interesting to observe for instance how the number of patents on the direct production of light olefins from syngas reached maximum values after the oil embargo of1973and the second oil crisis in1979.The shortage and the consequent high cost of oil for the production of light olefins via naphtha cracking increased the urge to develop alternative routes to produce these valuable commodity chemicals via syngas-based processes.After oil prices dropped to lower levels,between1987and 2003,the number of patents on the topic decreased but academic research related to the catalysts and the process was still very active.During this period the scientific publications were mostly dedicated to the influence of chemical promoters and supports on C2−C4olefins selectivity and tothe Figure5.Scientific papers and patents on the direct production of lower olefins via Fischer−Tropsch36(bars)in1955−2013in relation to the oil price37(solid line).optimization of process conditions to maximize the activity and selectivity toward the target products.After the invasion of Iraq in 2003oil prices rose steeply,renewing the interest of chemical and petrochemical companies on more e fficient catalysts and processes to produce lower ole fins using natural gas,coal,or biomass as feedstock.Once more in 2010,the oil prices increased dramatically caused by political instability in many oil-producing countries in the Middle East.Therefore countries such as China and the U.S.with large reserves of natural and shale gas or coal are taking the lead on the research and development of direct processes for the production of C 2−C 4ole fins to ensure a reliable supply of these bulk chemicals and to achieve independence from oil imports.Figure 6shows the 10countries with the highest number of research papers and patents on catalysts for the production of lower ole fins via Fischer −Tropsch.Despite of the number of publications on the direct production of lower ole fins via the Fischer −Tropsch reaction,there has been no commercial application for this process in view of the low C 2−C 4ole fins selectivity,low mechanical or chemical stability,or high methane production of some of the catalysts proposed up to now.Researchers have developed di fferent catalytic systems based on metals that exhibit CO hydrogenation activity.Among these metals only iron,cobalt,nickel,and ruthenium have been found to be su fficiently active for their application.38From the commercial standpoint only Fe and Co are used as they are more readily available and less expensive compared to ruthenium.Ni is very active as well,but it produces much more methane than Co or Fe and it forms volatile carbonyls at the reaction conditions at which FT plants operate,resulting in continuous loss of the metal.Other metals with moderate FT activity are Rh and Os.The products obtained from FT synthesis when using Rh as catalyst contain large fractions of oxygenates.Mo has also shown some FT activity in the presence of H 2S,but it was found to be less active than Fe.Cr has also been investigated as a possible FT catalyst,but its activity is even lower than Mo.It has been found that the properties of the FT active metals can be modi fied by adding chemical promoters to improve selectivity to light ole fins or to enhance catalytic activity.Improvements on the mechanical stability of the catalysts might be achieved by addition of structural promoters whereas the surface area of the active metal can be extended by dispersing it on a support or carrier material.The di fferent catalytic systems developed for the FTO process are discussed more in detail in section 3.To the best of our knowledge,there are no other direct syngas transformation routes to produce lower ole fins apart from FTO.Some researchers have designed hybrid processes that use one reactor with two di fferent catalysts such as the development reported by Arakawa et al.39In this process theupper part of the catalyst bed consisted of a Rh −Ti −Fe −Ir/SiO 2catalyst to produce ethanol and the lower part contained H-silicalite for alcohol dehydration.This process produced approximately 45%C of ethylene while propylene andbutylenes were produced in negligible amounts.Although selectivity to ethylene was high,the selectivity to methane wasnear 33% C.Another example is the composite catalyst developed by Denise et al.40where a physical mixture of amethanol catalyst (Cr2O3/ZnO)and dealuminated mordeniteproduced a mixture of light hydrocarbons (alkenes and alkanes in the C 1−C 5range).Other examples of hybrid processes involve the use of aFischer −Tropsch catalyst to produce hydrocarbons fromsyngas and further cracking of the products in a second catalyst bed containing a zeolite.41,42Park et al.41used a precipitatedFe −Cu −Al 2O 3catalyst promoted with potassium for the FT synthesis while cracking of the C5+products was performed oning this dual bed reactor they obtained a C 2−C 4ole fins selectivity of 41%C with a low methane production (10%)under high CO conversions (320°C,10bar,and H 2/CO =2).Although it could be expected that the stability of the zeolite would be compromised by the presence of water duringreaction,Lee et al.42pointed out that ZSM-5maintained its hydrothermal stability and activity at least during 100h time on stream.3.FISCHER −TROPSCH TO OLEFINS PROCESS (FTO)The Fischer −Tropsch synthesis is the reaction of CO and H 2inthe presence of an active catalyst to produce hydrocarbons and alcohols.Due to the nature of the reaction,which may beconsidered as a surface polymerization reaction,the product stream consists of a range of products instead of a single component.Although the mechanism of the Fischer −Tropsch reaction has been a matter of study for several years,it has notbeen completely elucidated yet.However,it is widely acceptedthat the reaction proceeds through a surface carbide mechanism which is shown as a simpli fied scheme in Figure7.Figure 6.Number of publications on the direct production of lower ole fins from synthesis gas from 1955to 201336(Fischer −Tropsch only,top 10countries).Figure 7.Fischer −Tropsch reaction mechanism (surface carbide mechanism).The product distribution can be predicted using the Anderson −Schulz −Flory (ASF)model that depends on the chain growth probability α.Di fferent factors have an in fluence on the alpha parameter such as process conditions,type of catalyst,and chemical promoters.43The ASF product distribution as a function of αis depicted in Figure 8.Since the Fischer −Tropsch reaction has been known for almost a century,there is a vast amount of information related to the fundamentals of the reaction,the industrial process,and the FT catalysts,which has been covered in several comprehensive reviews.38,44−48Other more speci fic reviews involve the preparation,application,and deactivation of iron,43,49,50cobalt,51−53and nickel 54catalysts in the traditional Fischer −Tropsch process for the production of fuels.For this reason,we will not discuss the general aspects of the Fischer −Tropsch reaction or traditional FT catalysts but we rather focus on the Fischer −Tropsch synthesis of lower ole fins or FTO and the catalysts for that purpose.The primary aims of FTO are to maximize lower ole fins selectivity,to reduce methane production,and to avoid the formation of excess CO 2.According to the ASF model,the maximum selectivity toward C 2−C 4ole fins is achieved with an alpha value between 0.4and 0.5.One of the most e fficient ways of shifting product selectivity to low alpha values is by increasing reaction temperature.However,a decrease on the chain growth probability results in an increase of methane selectivity as indicated by the ASF product distribution.This e ffect was long considered a major restriction for the industrial application of the direct conversion of syngas into lower ole fins via the Fischer −Tropsch synthesis.24,25Negative deviations of the ASF model for methane selectivity have been observed for iron-based catalysts.34,55Schwab et al.34proposed that Fe catalysts possess di fferent catalytic sites,some in charge of C −C coupling for the growth of the carbon chain and others responsible for methane formation.According to Schwab,these catalytic sites can be modi fied independently and controlled by addition of promoters.Torres Galvis et al.56ascribed the negative deviations of methane selectivity of Na/S-promoted iron catalysts to selective blockage of hydrogenation sites.They put forward that sulfur restricts the termination of carbon chain growth through hydrogenation thus favoring the β-hydride abstraction termination pathway.This proposal not only explains the lower methane selectivity but also the higher light ole fins selectivity observed when iron catalysts were promoted with low amounts of sulfur.The vast majority of the catalysts suggested for FTO contain iron.In comparison to cobalt,iron is less expensive,it has a lower activity,Fe Fischer −Tropsch products have a higher ole fin content,as iron is less reactive to secondary hydro-genation reactions,and it displays lower methane selectivity at the high temperatures necessary to drive alpha to lower values.In view of their high water gas shift (WGS)activity,iron catalysts are an attractive option for the conversion of CO-rich syngas derived from coal or biomass because an additional H 2/CO ratio adjustment step is not necessary.Many catalyst formulations containing iron or other FT-active metals have been proposed for the synthesis of light ole fins from synthesis gas.In this review we have divided these catalytic systems into two major groups:bulk or unsupported catalysts,including those materials with structural promoter content below 50wt %,and supported catalysts.Researchers in the field use di fferent ways to present their catalytic data.The product selectivity for iron-based catalysts is generally reported excluding CO 2.Selectivity can be expressed based on weight (wt %:g of a product ×100/g of hydrocarbons),molar-based (moles of a product ×100/total moles of hydrocarbons)or carbon-based (%C:carbon atoms in a product ×100/total carbon atoms present in hydro-carbons).The conversion of CO can be reported as total CO conversion (including CO2)or CO conversion to hydro-carbons.Some other authors prefer to mention syngas conversion (CO +H 2)instead of CO conversion.In the following sections,product selectivity and CO conversion willbe expressed as a percentage (%).The speci fic details on thechoice of the researchers to report their results can be found in the summary tables (Tables 3and 4).3.1.Bulk or Unsupported Iron Catalysts.South Africa possesses large coal deposits and limited exploitable oil reserves.For this reason,this country has done its utmost to become independent from oil imports.In view of this necessity,the South African government issued a license to start the oil-from-coal project after the Second World War.Since 1955SASOL has produced chemicals and gasoline using the so-called Synthol process.57The main aim of this process is toproduce liquid fuels although lower ole fins are also obtained depending on the operating conditions and the type of catalysts.The product selectivities obtained by SASOL with the low temperature (LTFT)and the high temperature (HTFT)processes is shown in Table 2.The catalyst used for the HTFT process in fluidized bed reactors is a fused catalyst containing iron oxide andstructural Figure 8.Anderson −Schulz −Flory (ASF)model for the prediction of product distribution.Table 2.Fischer −Tropsch Products of Iron-BasedCatalysts 38LTFTslurry reactor,T =240°C,20bar HTFT fluidized bed reactor,T =340°C,20bar %selectivities (Catom basis)methane 48C2−C 4para ffins 2.56C 2−C 4ole fins 624C5−C 6716C7+76.541water-solubleoxygenates 45α0.950.70。

锰基低温催化剂的研究与发展董晓真;王虎;张捷;李倩【摘要】Nowadays, NOx pollution becomes more and more serious, selective catalytic reduction of NOx by ammoma ( NH3-SCR) is one of the widespread technologies in industrial application. Low temperature SCR denitration technology can effectively overcome the catalyst poisoningand abrasion, as a kind of new and potential denitration technology, it has attract people’s attention. The research status of supported and non-supporter low temperature SCR denitration manganesecatalysts and the denitration mechanism was summarized and discussed, and provided the basis for research and development of new low-temperature SCR catalyst.%目前氮氧化物( NOx )的污染越来越严重，以NH3为还原剂的选择性催化还原( SCR)脱硝技术成为烟气脱硝中应用最广泛的技术之一。

低温选择性催化还原( SCR)脱硝技术可以有效克服催化剂中毒及磨损的问题，其作为一种作为新型的、具有潜力的烟气脱硝技术，备受人们关注。

本文综述了负载型及非负载型锰基低温SCR脱硝催化剂的的研究现状，探讨了低温锰基SCR催化剂的脱硝机理，为研究开发新型低温SCR催化剂提供依据。

烃类晶格氧选择性氧化催化剂研究进展郭丛聪;李剑;董家丽;杨丽娜【摘要】Lattice oxygen replacing gas phase oxygen is a new technology of selective oxidation and partial oxidation of hydrocarbons. Through using the technology, high selectivity can be obtained because deep oxidation can be restrained. This new technology can increase productive power as well as decrease cost because it is limited by the explosion limit. In this paper, the reaction mechanism of oxidation with lattice oxygen was introduced. Present situation of lattice oxygen catalysts for selective oxidation of hydrocarbons was reviewed, and then the development tendency of the lattice oxygen catalysts was discussed.%用晶格氧代替气相氧，是烃类选择性氧化一种新工艺，该工艺可以避免烃类的深度氧化，提高选择性，不受爆炸极限的限制，可以提高生产能力，降低成本。

本文介绍了晶格氧氧化的反应机理，综述了不同烃类选择性氧化中的晶格氧催化剂的制备及应用现状，提出未来烃类选择性氧化的晶格氧催化剂的主要发展方向。

【期刊名称】《当代化工》【年(卷),期】2014(000)004【总页数】3页(P573-575)【关键词】烃类;晶格氧;选择性氧化;催化剂【作者】郭丛聪;李剑;董家丽;杨丽娜【作者单位】辽宁石油化工大学，辽宁抚顺 113001;辽宁石油化工大学，辽宁抚顺 113001;辽宁石油化工大学，辽宁抚顺 113001;辽宁石油化工大学，辽宁抚顺113001【正文语种】中文【中图分类】TQ426烃类选择性氧化难度很大，其选择性是各类催化剂中最低的，且反应历程复杂，难以找出普遍性规律，提高目的产物的选择性是烃类选择性氧化中最重要的问题。

Manganese Oxides with Rod-,Wire-,Tube-,and Flower-LikeMorphologies:Highly Effective Catalysts for the Removal of TolueneFang Wang,Hongxing Dai,*Jiguang Deng,Guangmei Bai,Kemeng Ji,and Yuxi LiuLaboratory of Catalysis Chemistry and Nanoscience,Department of Chemistry and Chemical Engineering,College of Environmental and Energy Engineering,Beijing University of Technology,Beijing 100124,China*Supporting Informationconcentration and low-temperature reducibility decreased in the wire-like α-MnO 2,in good agreement with the sequence of rod-like α-MnO 2catalyst could effectively catalyze the total 90%=225°C at space velocity =20000mL/(g h)).It is nanorods might be associated with the high oxygen adspecies sure that such one-dimensional well-defined morphological elimination of air pollutants.INTRODUCTIONMost volatile organic compounds (VOCs),such as form-aldehyde,methanol,benzene,and toluene,are harmful to the atmosphere and human health.It is highly desired to control the emissions of VOCs.Up to now,a number of methods (e.g.,adsorption)have been developed for the removal of hazardous materials.1−6Among the strategies for VOCs elimination,catalytic oxidation is believed to be one of the most effective pathways because it can operate at low temperatures and no secondary pollution products are generated.7−11The key issue of such a technology is the availability of high-performance catalysts.Although supported precious metal catalysts show excellent activities for the total oxidation of toluene at low temperatures,12−14the high cost and some involved problems (e.g.,sintering and volatility)prohibit their wide applications.Cheap transition-metal oxides,such as manganese oxides,cobalt oxides,and chromia,are active at high temperatures,7,8,15but they are inferior to precious metals in catalyzing the combustion of toluene at low temperatures.Hence,it is of significance to develop a catalyst that is cheap and effective for the removal of toluene at low temperatures.In the past years,a large number of works have been focused on the controlled preparation of manganese oxides with various morphologies.Up to now,manganese oxides with rod-like,wire-like,tubular,and spherical shapes have been gener-ated.16−19For example,Zhu and co-workers prepared one-dimensional (1D)α-,β-,γ-,and δ-MnO 2nanorods using a hydrothermal method and observed good catalytic activities for CO oxidation.16Gao et al.obtained 1D α-MnO 2nanowires by hydrothermally treating the mixture of KMnO 4and NH 4Cl at 140°C for 24h.17Zheng et al.generated single-crystalline 1D β-MnO 2nanotubes (diameter 200−500nm and length several micrometers)via a poly(vinyl pyrrolidone)-assisted hydro-thermal route with MnSO 4with NaClO 3as precursor.18Without the use of a template but with CCl 4and water as medium,Yuan et al.synthesized flower-like α-and γ-MnO 2(surface area 239m 2/g),which showed a good electrochemical capacitive behavior.19It was reported that manganese oxides were catalytically active for the complete oxidation of VOCs,such as propane,n -hexane,benzene,and toluene.20−23For instance,Finocchio and Busca investigated the surface and redox properties of Mn 3O 4,Mn 2O 3,and MnO 2,and claimed that the bulk oxygen diffusion rate had an effect on the catalytic oxidation rate in the oxidation of propane.20Delmon and co-workers observed that the γ-MnO 2catalyst outperformed the 0.3wt %Pt/TiO 2catalyst in the oxidation of n -hexane.23After studying the oxidation of benzene over manganese oxideReceived:November 11,2011Revised:January 20,2012Accepted:March 11,2012octahedral molecular sieve(OMS-2)catalyst,Luo et al. believed that the excellent activity and stability of OMS-2at low temperatures were due to the hydrophobic property and the facile evolution of lattice oxygen.21Aguero et al.observed good catalytic performance over Al2O3-supproted MnO x catalyst for the combustion of ethanol and toluene,which was attributed to the high capacity for adsorbing oxygen,the existence of surface defects,and the good reducibility of the catalyst.22It has been generally accepted that catalytic activity is related to the surface area,defective structure,reducibility,and morphology of a catalyst.The particle morphology has an important impact on catalytic oxidation performance of transition metal oxides(e.g.,Co3O4).24However,up to now, rarely has work been done on the comparative investigation of manganese oxides with various well-defined morphologies. Previously,our group prepared a series of three-dimension-ally(3D)ordered or wormhole-like mesoporous transition-metal oxides(e.g.,chromia,25,26iron oxide,27manganese oxide,28and cobalt oxide28,29)by using the3D ordered mesoporous silica KIT-6-or SBA-16-nanocasting method,and investigated their physicochemical properties.We found that these3D mesoporous transition-metal oxides performed well in catalyzing the combustion of formaldehyde,acetone,methanol, and toluene.Recently,we adopted the hydrothermal method to generate a number of transition-metal oxides with well-defined morphologies.In this paper,we report the controlled preparation and catalytic properties of rod-like,wire-like,and tubular MnO2as well as flower-like Mn2O3for the combustionof toluene.■EXPERIMENTAL SECTIONCatalyst Preparation.The manganese oxide catalysts were prepared according to the hydrothermal16,30or solution method.19The detailed procedures are described in the Supporting Information.The as-prepared samples are referred to as rod-like MnO2,wire-like MnO2,tube-like MnO2,and flower-like Mn2O3.Catalyst Characterization.All of the as-prepared samples were characterized by techniques such as X-ray diffraction (XRD),N2adsorption−desorption(BET),scanning electron microscopy(SEM),transmission electron microscopy(TEM), selected-area electron diffraction(SAED),X-ray photoelectron spectroscopy(XPS),and H2temperature-programmed reduc-tion(H2-TPR).The detailed methods are stated in the Supporting Information.Catalytic Evaluation.Catalytic activity of the samples was evaluated in a continuous-flow fixed-bed quartz microreactor(i.d.4mm).To minimize the effect of hot spots,the catalyst(0.1g,40−60mesh)was diluted with0.3g of quartz sands (40−60mesh).The reactant feed(flow rate33.3mL/min)was 1000ppm toluene+O2+N2(balance),with the toluene/O2 molar ratio and space velocity(SV)being1/400and20000 mL/(g h),respectively.For the change of SV,we altered the total flow rate of the reactant feed by the mass flow controller (D0719CM,Beijing Sevenstar Electronics Co.).The outlet gases were analyzed online by a gas chromatograph(Shimadzu GC-2010)equipped with a flame ionization detector(FID)and a thermal conductivity detector(TCD),using a1/8-in. Chromosorb101column(3m long)for toluene separation and a1/8-in.Carboxen1000column(3m long)for permanent gas separation.The outlet gases were also monitored online by a mass spectrometer(HPR20,Hiden).We found that no other products were detected in addition to CO2and H2O.On the basis of the toluene consumption and CO2production,the carbon balance and the conversion of toluene were calculated. The relative errors for the gas concentration measurements were less than±1.5%.The balance of carbon throughout theinvestigation was estimated to be ca.99.5%.■RESULTS AND DISCUSSIONCrystal Phase Composition.Figure1shows the XRD patterns of the as-prepared manganese oxide samples.Bycomparing to the XRD patterns of the standardα-MnO2 (JCPDS PDF72-1982),Mn2O3(JCPDS PDF41-1442),and Mn3O4(JCPDS PDF24-0734)samples,one can realize that the hydrothermally derived rod-and tube-like manganese oxide samples were single-phaseα-MnO2and of tetragonal crystal structure;in addition to the main phase of tetragonalα-MnO2, there was a trace amount of tetragonal Mn3O4phase in the wire-like manganese oxide sample.In the CCl4-solution derived flower-like manganese oxide sample,however,there were a cubic Mn2O3phase in majority and a tetragonalα-MnO2phase in minority.All of the diffraction peaks could be well indexed, as indicated in Figure1c and d.From Figure1,one can also observe no significant difference in XRD signal intensity of the four samples,indicating that they possessed similar crystallinity, a result due to the same subsequent thermal treatments.The XRD results demonstrate that the preparation conditions had an important influence on crystal structure of the manganese oxide sample.Morphology,Surface Area,Surface Element Compo-sition,and Oxygen Species.Figure2shows the SEM images of the as-prepared manganese oxide samples.It is observed that the manganese oxide particles derived hydrothermally at140°C for12h(Figure2a and b),240°C for24h(Figure2c and d),and120°C for12h(Figure2e and f)were,respectively, rod-,wire-,and tube-like in morphology,whereas those obtained with CCl4solution displayed a flower-like spherical shape with sharp edges.It should be noted that the wire-like morphology can be differentiated from the rod-like morphology in terms of the bending or straight shape.The diameter and length of the rods in the rod-likeα-MnO2sample were ca.43 nm and2−4μm,those of the wires in the wire-likeα-MnO2 sample were ca.40nm and1−10μm,and those of the tubesin Figure1.Wide-angle XRD patterns of(a)rod-like MnO2,(b)wire-like MnO2,(c)tube-like MnO2,and(d)flower-like Mn2O3.Δ: Impurity Mn3O4phase;○:impurity MnO2phase.the tubular α-MnO 2sample were ca.65nm and 1−3μm,respectively.For the Mn 2O 3sample,the size of the flower-like spheres was in the range of 800−1000nm.Shown in Figure 3are the TEM and high-resolution TEM images as well as the SAED patterns of the manganese oxide samples.Well-grown nanorods (Figure 3a),nanowires (Figure 3c),and nanotubes (Figure 3e)of α-MnO 2could be clearly observed.The TEM images (Figure 3g and h)were recorded on the edge of a broken flower-like Mn 2O 3nanoentity.From the high-resolution TEM images (Figure 3b,d,and f),one cansee well-resolved lattice fringes.The lattice spacings (d values)of the (121)crystal plane of the rod-,wire-,and tube-like α-MnO 2samples were ca.0.239,0.238,and 0.239nm,respectively,rather close to that (0.2388nm)of the standard α-MnO 2sample (JCPDS PDF 72-1982).The d value (0.271nm)of the (222)crystal plane of the flower-like spherical Mn 2O 3sample estimated from the high-resolution TEM image (Figure 3h)was also not far away from that (0.2716nm)of the referenced Mn 2O 3sample (JCPDS PDF 41-1442).Further-more,the recording of linearly aligned brightelectronFigure 2.SEM images of (a,b)rod-like MnO 2,(c,d)wire-like MnO 2,(e,f)tube-like MnO 2,and (g,h)flower-like Mn 2O 3.Figure 3.TEM and high-resolution TEM images as well as SAED patterns (insets)of (a,b)rod-like MnO 2,(c,d)wire-like MnO 2,(e,f)tube-like MnO 2,and (g,h)flower-like Mn 2O 3.diffraction spots in the SAED patterns (insets of Figure 3b,d,and f)means that the tetragonal α-MnO 2samples with rod-like,wire-like,and tubular morphologies were single crystalline.For the flower-like spherical Mn 2O 3sample,however,the SAED pattern (inset of Figure 3h)showed multiple bright electron diffraction rings,suggesting that this cubic Mn 2O 3sample was mainly polycrystalline.As can be seen from Table 1,the BET surface areas (ca.83m 2/g)of the rod-and wire-like α-MnO 2samples were similar,and much higher than that (ca.45m 2/g)of the tubular α-MnO 2sample.However,the flower-like spherical Mn 2O 3sample possessed a surface area of ca.162m 2/g,significantly higher than those of the hydrothermally derived α-MnO 2samples.The difference in preparation method led to a big difference in surface area of the MnO x catalysts with similar crystallinity,similar phenomena also took place in the preparation of α-Fe 2O 3samples.31,32XPS is a good tool to investigate the surface element composition,element oxidation state,and adsorbed species of a material.Figure 4illustrates the Mn 2p 3/2and O 1s XPS spectra of the manganese oxide samples.As shown in Figure 4A,there was one asymmetrical signal at BE =ca.642eV for the three α-MnO 2samples and at BE =ca.641eV for the Mn 2O 3sample,in which the former could be decomposed to two components at BE =641.6and 642.8eV,whereas the latter could be decomposed to three components at BE =640.6,641.6,and 642.8eV.The components at BE =640.6,641.6,and 642.8eV were attributable to the surface Mn 2+,Mn 3+,and Mn 4+species,7,33respectively.A quantitative analysis on the Mn 2p 3/2XPS spectra of the samples gives rise to the surface Mn 3+/Mn 4+as well as Mn 2+/Mn 3+molar ratios,as summarized in Table 1.Apparently,the preparation method had an important impact on the surface Mn 3+/Mn 4+or Mn 2+/Mn 3+molar ratio ofthe product.Among the hydrothermally prepared manganese oxide samples,the rod-like α-MnO 2sample showed the highest surface Mn 3+/Mn 4+molar ratio (0.58),whereas the lowest surface Mn 3+/Mn 4+molar ratio (0.31)was achieved on the wire-like α-MnO 2sample.It is noted that there was also the copresence of Mn 2+,Mn 3+,and Mn 4+on the surface of the flower-like Mn 2O 3sample due to the formation of tetragonal Mn 2O 3and α-MnO 2phases,with the surface Mn 3+/Mn 4+and Mn 2+/Mn 3+molar ratios being 4.17and 0.38,respectively.Based on the principle of electroneutrality,we deduce that the surface oxygen vacancy density was the highest on the rod-like α-MnO 2surface,while the lowest was on the wire-like α-MnO ually,oxygen molecules are adsorbed at the oxygen vacancies of an oxide material.Therefore,we believe that the oxygen adspecies locate at the surface oxygen vacancies of α-MnO 2or Mn 2O 3.This result is in good agreement with the result of O 1s XPS investigations.The formation of surface oxygen vacancies on the α-MnO 2or Mn 2O 3sample was beneficial for the oxidation of VOCs,which provides a good interpretation for the higher catalytic activity of rod-like α-MnO 2at low temperatures (shown in Section 3.4).As can be seen from Figure 4B,the asymmetrical O 1s signal could be deconvoluted to two components:one at BE =529.0eV and the other at BE =531.7eV;the former was assigned to the surface lattice oxygen (O latt )species,whereas the latter was assigned to the surface adsorbed oxygen (O ads )species.25−27,29It is found from Table 1that the estimated surface O ads /O latt molar ratios of the samples were dependent upon the preparation method.The surface O ads /O latt molar ratio decreased in the order of rod-like α-MnO 2(1.50)>tube-like α-MnO 2(1.15)>flower-like Mn 2O 3(0.92)>wire-like α-MnO 2(0.78).The formation of oxygen adspecies was due toTable 1.Preparation Conditions,BET Surface Areas,and Surface Element Compositions of the Manganese Oxide SamplesaThe datum in parentheses is the surface Mn 2+/Mn 3+molar ratio.Figure 4.(A)Mn 2p 3/2and (B)O 1s XPS spectra of (a)rod-like MnO 2,(b)wire-like MnO 2,(c)tube-like MnO 2,and (d)flower-like Mn 2O 3.the presence of surface oxygen vacancies on α-MnO 2or Mn 2O 3,which implies that there might be the coexistence of Mn 3+and Mn 4+ions in/on the α-MnO 2samples or Mn 2+and Mn 3+ions on/in the Mn 2O 3sample.27,29Such a deduction was supported by the Mn 2p 3/2XPS results of these samples.Reducibility.Figure 5A illustrates the H 2-TPR profiles of the as-prepared manganese oxide samples.For the rod-like α-MnO 2sample,there was a main reduction band at 265°C with a shoulder at 285°C,the total H 2consumption was 11.28mmol/g (Table 2).However,only one strong reduction band centered at 275°C for the wire-like α-MnO 2sample and at 268°C for the tube-like α-MnO 2sample was recorded,with the total H 2consumption being 10.00and 10.95mmol/g (Table 2),respectively.In the case of the flower-like spherical Mn 2O 3sample,there were two weaker reduction bands at 260and 332°C,corresponding to a total H 2consumption of 5.93mmol/g (Table 2).According to the results reported previously,28,34the reduction process could be reasonably divided into two steps:(i)Mn 4+→Mn 3+and (ii)Mn 3+→Mn 2+.Theoretically,the H 2consumptions for the reduction of MnO 2to Mn 3O 4and of Mn 3O 4to MnO are 7.67and 3.83mmol/g,respectively;while a H 2consumption of 6.30mmol/g is needed if the Mn 2O 3is completely reduced to MnO.In the present studies,the totalH 2consumptions (10.00−11.28mmol/g)of the hydro-thermally derived α-MnO 2samples and that (5.93mmol/g)of the flower-like Mn 2O 3sample were quite close to their theoretical H 2consumptions (11.50and 6.30mmol/g,respectively).This result indicates that a substantial fraction of Mn 4+in α-MnO 2or Mn 3+and Mn 4+in Mn 2O 3had been reduced to Mn 2+below 400°C.To better compare the low-temperature reducibility of these samples,we calculated the initial H 2consumption rate of the first reduction band of each sample before the occurrence of phase transformation (where the initial H 2consumption of the first reduction band of the catalyst is less than 25%25−27,35,36),and the results are shown in Figure 5B.Obviously,the initial H 2consumption rate decreased in the sequence of rod-like α-MnO 2>tube-like α-MnO 2>flower-like Mn 2O 3>wire-like α-MnO 2.That is to say,the low-temperature reducibility of these manganese oxide samples followed the above order.Catalytic Performance.In the blank experiment (only quartz sands were loaded),no conversion of toluene was detected below 400°C,indicating that under the adopted reaction conditions there was no occurrence of homogeneous reactions.Figure 6shows the catalytic performance of the bulk α-MnO 2sample (surface area =ca.10m 2/g,Beijing Chemical Reagent Company,A.R.,99.9%)and the as-prepared α-MnO 2and Mn 2O 3samples for the combustion of toluene.Under the conditions of toluene concentration =1000ppm,toluene/O 2molar ratio =1/400,and SV =20000mL/(g h),toluene conversion increased with the rise in reaction temperature,and the α-MnO 2and Mn 2O 3catalysts with various morphologies performed much better than the bulk α-MnO 2catalyst.It is worth pointing out that toluene was completely oxidized to CO 2and H 2O over the as-prepared α-MnO 2and Mn 2O 3catalysts,and there was no detection of products of incomplete oxidation,as confirmed by the good carbon balance of ca.99.5%in each run.It is convenient to compare the catalytic activities of these samples by using the reaction temperatures T 10%,T 50%,and T 90%(corresponding to the toluene conversion =10,50,and 90%),as summarized in Table 2.It is clearly seen that rod-like α-MnO 2was inferior to wire-and tube-like α-MnO 2and flower-like Mn 2O 3in catalytic performance atlowerFigure 5.(A)H 2-TPR profiles and (B)initial H 2consumption rates of (a)rod-like MnO 2,(b)wire-like MnO 2,(c)tube-like MnO 2,and (d)flower-like Mn 2O 3.Table 2.Reduction Temperatures,H 2Consumptions,and Catalytic Activities of the Manganese Oxide Samples2rod-like MnO 226528511.28176210225wire-like MnO 227510.00143225245tube-like MnO 226810.95157222233flower-like Mn 2O 3260332 5.93145226238temperatures (<180°C),but the former catalyst (T 50%=210°C and T 90%=225°C)outperformed the latter three catalysts (T 50%=222−226°C and T 90%=233−245°C)at higher temperatures.Such a phenomenon might be mainly associated with the nature and distribution of the surface adsorbed oxygen (O −,O 2−,and O 22−)species on the catalysts.As we know,the oxygen adspecies can be converted from O 2−(the lowest reactivity)to O −(the highest reactivity)at elevated temper-atures.37−39Although the total amount of the surface adsorbed oxygen species on the rod-like MnO 2sample was higher than those on the wire-and tube-like MnO 2or flower-like Mn 2O 3catalyst,the O −species concentration (which is governed by the defective structure)on the rod-like MnO 2catalyst might be lower than those on the other three catalysts at lower temperatures.Hence,the rod-like MnO 2catalyst showed lower activity at low temperatures.With a rise in reactiontemperature,a larger amount of O −species might be available through the conversion of O 2−and O 22−to O −species on the rod-like MnO 2catalyst,37,39giving rise to a great enhancement in catalytic activity.The T 50%and T 90%values for the rod-like α-MnO 2catalyst were 82and 97°C lower than those for the bulk α-MnO 2catalyst,respectively.Therefore,it is concluded that in terms of T 50%and T 90%values,the catalytic performance decreased in the order of rod-like α-MnO 2>tube-like α-MnO 2>flower-like Mn 2O 3>wire-like α-MnO 2,coinciding with the sequences of oxygen adspecies concentration obtained in the XPS studies and of low-temperature reducibility revealed by the H 2-TPR investigations.25−27,29Figure 7A and B shows the effects of SV and toluene/O 2molar ratio on the catalytic activity of the rod-like α-MnO 2sample,respectively.It is observed that the catalytic activity of rod-like α-MnO 2decreased with the rise in SV value (Figure 7A)or toluene/O 2molar ratio (Figure 7B).Obviously,the rise in O 2concentration of the reactant feed favored the enhancement of toluene conversion,suggesting that the oxygen adspecies might play an important role in the total oxidation of toluene.That is to say,the oxygen nonstoichiometry relevant to structural defects might be a critical factor in determining the catalytic activity of manganese oxide.25−30To examine the catalytic stability of the rod-like α-MnO 2sample,we carried out the on-stream reaction experiment at 225°C and the result is shown in Figure S1of the Supporting Information.It is found that there was no significant decline in catalytic activity within 60h of on-stream reaction.Hence,we believe that the rod-like α-MnO 2sample was catalytically durable.In the past years,a number of materials have been used as catalysts for the oxidative removal of toluene.It was reported that under similar conditions for the combustion of toluene,the T 50%and T 90%values were 245−340and 265−375°C over the commercial Mn 3O 4,Mn 2O 3,or MnO 2catalyst at SV =15000mL/(g h),15140−200and 234−240°C over the mesoporous CrO x or MnO 2catalyst at SV =20000h −1,26,28254−279and 295−306°C over the LaMnO 3or LaCoO 3catalyst at SV =178h −1,40,41270and 300°C over the 5wt %Au/CeO 2catalyst at SV =186h −1,42and 180and 250°C over the 0.5wt %Pd/Figure 6.Toluene conversion as a function of reaction temperature over the catalysts under the conditions of toluene concentration =1000ppm,toluene/O 2molar ratio =1/400,and SV =20000mL/(g h).Figure 7.Toluene conversion versus reaction temperature over the rod-like MnO 2catalyst under the conditions of (A)toluene concentration =1000ppm,toluene/O 2molar ratio =1/400,and different SV values;and (B)toluene concentration =1000ppm,SV =20000mL/(g h),and various toluene/O 2molar ratios.LaMnO 3catalyst at SV =18000mL/(g h).43Apparently,the rod-like α-MnO 2catalyst (T 50%=210°C and T 90%=225°C at SV =20000mL/(g h))outperformed the above-mentioned commercial Mn 3O 4,Mn 2O 3,and MnO 2,mesoporous CrO x and MnO 2,LaMnO 3,LaCoO 3,5wt %Au/CeO 2,and 0.5wt %Pd/LaMnO 3catalysts for the combustion of toluene.15,26,28,40−43It is well-known that the catalytic activity of a transition metal oxide is associated with several factors,such as defect nature and density,oxygen adspecies concentration,reducibility,surface area,and morphology.For the combustion of organics,the catalyst with a higher surface area would show a better catalytic activity.15,44The surface area of the flower-like spherical Mn 2O 3sample was much higher than that of the rod-and tube-like α-MnO 2samples,but its catalytic perform-ance was inferior to the rod-and tube-like α-MnO 2samples;furthermore,the wire-like α-MnO 2sample possessed a much higher surface area than the tube-like counterpart,but the catalytic activity of the wire-like α-MnO 2sample was also poorer than that of the tube-like α-MnO 2sample.This result indicates that surface area was a minor factor influencing the catalytic performance.Although the morphology might exert an influence on the reducibility of a catalyst,45the relation between the morphology and the oxygen vacancy density is not clear.The morphology and oxygen density as well as reducibility of the as-obtained catalysts might be dependent mainly on the preparation approach in the present ually,a higher structural defect (e.g.,oxygen vacancy)density,which is beneficial for the activation of oxygen molecules to active oxygen adspecies,and a stronger reducibility render the catalyst to show better catalytic performance.22As revealed by the XPS and H 2-TPR investigations,the oxygen adspecies concentration relevant to the surface oxygen vacancy density and low-temperature reducibility were correlative with the catalytic activity of these manganese oxide samples.25−27,29Therefore,we conclude that the excellent catalytic performance of the rod-like α-MnO 2sample for toluene combustion was mainly related to the high oxygen adspecies concentration and good low-temperature reducibility.■ASSOCIATED CONTENT*Supporting Information Details of catalyst preparation procedures and characterization,and one additional figure.This material is available free of charge via the Internet at .■AUTHOR INFORMATIONCorresponding Author*Phone:+86-10-6739-6118;fax:+86-10-6739-1983;e-mail:hxdai@).NotesThe authors declare no competing financial interest.■ACKNOWLEDGMENTSFinancial support by the NSF of Beijing Municipality (grant 2102008),the NSF of China (grants 20973017and 21077007),the National High-Tech Research and Development (863)Program of China (grant 2009AA063201),the Creative Research Foundation of Beijing University Technology (grants 00500054R4003and 005000543111501),and the Funding Project for Academic Human Resources Development in Institutions of Higher Learning under the Jurisdiction ofBeijing Municipality (grants PHR201007105and PHR201107104)is gratefully acknowledged.We also thank Prof.Chak Tong Au (Department of Chemistry,Hong Kong Baptist University)and Mrs.Jianping He (State Key Laboratory of Advanced Metals and Materials,University of Science &Technology Beijing)for doing the XPS and SEM analyses,respectively.■REFERENCES(1)Gupta,V.K.;Carrott,P.J.M.;Ribeiro Carrott,M.M.;Suhas,L.Low-cost adsorbents:Growing approach to wastewater treatment −a 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柔性锂氧电池的发展现状陈建中;舒朝著;龙剑平;候志前【摘要】With the rapid development of flexible electronic devices, more and more requirements for rechargeable batteries are put forward. Flexible lithium oxygen battery with high energy density theory, have becomea hot field of battery. To develop efficient stable and high mechanical strength flexible lithium oxygen battery, flexible anode and cathode is the keyatpresent. In this paper, the development and design of flexible cathode material and lithium anode are briefly introduced, and the field is summarized and prospected.%柔性电子设备的飞速发展对可充式二次电池提出了越来越高的要求.柔性锂氧电池凭借着超高的理论能量密度,成为目前电池领域的研究热点,开发出高效、稳定、高机械强度及柔性的电池正极和负极是目前研究的关键.本文主要对柔性正极材料、锂负极的开发与设计进行简要介绍,并对该领域进行总结、展望.【期刊名称】《电子元件与材料》【年(卷),期】2018(037)001【总页数】6页(P1-6)【关键词】锂氧电池;柔性正极材料;综述;柔性锂负极;催化剂;二次电池【作者】陈建中;舒朝著;龙剑平;候志前【作者单位】成都理工大学材料与化学化工学院,四川成都 610059;成都理工大学材料与化学化工学院,四川成都 610059;成都理工大学材料与化学化工学院,四川成都 610059;成都理工大学材料与化学化工学院,四川成都 610059【正文语种】中文【中图分类】TM911.4随着现代科技的持续进步，可穿戴式电子设备越来越多地出现在人们的日常生活中，为人们带来更多的便利，如智能手表、智能运动鞋、智能衣服以及电子皮肤和可折叠可弯曲的智能手机等[1]。

干法脱硫催化剂原理引言干法脱硫是一种常见的工业污染控制技术，主要用于去除含硫化合物的废气中的硫化物。

干法脱硫催化剂是在脱硫过程中起到催化作用的物质。

本文将深入探讨干法脱硫催化剂的原理，包括其作用机制、影响因素以及常用的催化剂种类等。

作用机制干法脱硫催化剂的作用机制主要基于催化反应，其原理如下：1.氧化反应：干法脱硫催化剂能够将SO2氧化为SO3。

这是脱硫过程的关键步骤，因为只有SO3才能与其他物质反应形成易于分离的硫酸盐。

2.吸收反应：经过氧化反应后的SO3会与催化剂表面的活性位点发生吸附作用，形成SO3-催化剂复合物。

这种吸附作用能够促进SO3进一步与其他物质反应。

3.硫酸盐生成反应：在吸附作用的影响下，SO3与水蒸气、碱性物质等反应生成硫酸盐。

这种反应相对较快且可控，是干法脱硫过程中的目标之一。

通过以上作用机制，干法脱硫催化剂能够有效地降低废气中的硫化物含量，达到脱硫的目的。

影响因素干法脱硫催化剂效果的好坏取决于多个因素的综合作用，以下是几个重要的影响因素：1.温度：催化反应通常与温度密切相关，干法脱硫催化剂也不例外。

一般来说，较高的温度会有助于催化反应的进行，但过高的温度可能导致催化剂失活。

2.催化剂种类：不同的催化剂对应不同的反应机制和反应条件。

常见的干法脱硫催化剂有金属氧化物、过渡金属化合物等。

选择合适的催化剂种类对脱硫效果至关重要。

3.催化剂负载物：催化剂负载物可提高催化剂的稳定性和催化活性，常见的负载物有活性炭、氧化铝等。

不同的负载物对反应速率以及反应产物的选择性都有影响。

4.反应气体成分：干法脱硫催化剂一般用于处理含有SO2的废气，其他气体成分（如NOx、CO2等）会对催化反应产生一定的干扰作用。

因此，反应气体的成分也是影响催化剂效果的重要因素。

通过调节上述影响因素，可以使干法脱硫催化剂达到最佳效果。

常用的催化剂种类干法脱硫催化剂的种类繁多，下面介绍几种常用的催化剂：1.氧化铁催化剂：氧化铁是最早用于干法脱硫的催化剂之一，具有较高的催化活性和稳定性。

催化氧化法英文Catalytic Oxidation ProcessIntroductionCatalytic oxidation is a chemical process that involves the use of a catalyst to initiate the oxidation of a substance. It is widely used in various industrial processes to convert harmful pollutants into less harmful or inert substances. In this article, we will explore the principles, applications, and advantages of catalytic oxidation, as well as the different types of catalysts used in this process.Principles of Catalytic OxidationCatalytic oxidation involves the use of a catalyst, which is a substance that increases the rate of a chemical reaction without being consumed in the process. The catalyst works by lowering the activation energy required for the reaction to occur, thereby increasing the reaction rate. In the case ofoxidation reactions, the catalyst facilitates the transfer of electrons from the substance being oxidized to the oxidizing agent, promoting the formation of products.In the context of environmental pollution control, catalytic oxidation is used to convert volatile organic compounds (VOCs) and other hazardous pollutants into harmless substances such as carbon dioxide and water. The process typically involves the use of a catalyst to promote the oxidation of the pollutants at relatively low temperatures, reducing energy consumption and minimizing the formation of harmful by-products.Applications of Catalytic OxidationCatalytic oxidation has a wide range of applications in various industries, including:1. Air Pollution Control: Catalytic oxidation is commonly used in the treatment of industrial emissions and exhaust gases to remove VOCs, carbon monoxide, and other pollutants.It is an effective method for controlling air pollution in facilities such as chemical plants, refineries, and automotive manufacturing plants.2. Wastewater Treatment: The process is also utilized in the treatment of wastewater to remove organic contaminants and odor-causing compounds. Catalytic oxidation can help to improve the quality of treated water before it is discharged into natural water bodies or reused for industrial purposes.3. Chemical Synthesis: Catalytic oxidation is an important tool in the synthesis of various organic compounds, such as alcohols, ketones, and carboxylic acids. It is used to facilitate the conversion of primary alcohols to aldehydes and carboxylic acids, as well as the oxidation of aromatic compounds to produce valuable intermediates for the pharmaceutical and fine chemicals industries.Types of CatalystsSeveral types of catalysts are used in catalyticoxidation processes, each with its own specific propertiesand applications. Some of the most common catalysts include:1. Metal Catalysts: Transition metals such as platinum, palladium, and rhodium are widely used as catalysts for the oxidation of organic compounds. These metals exhibit high catalytic activity and selectivity, making them suitable fora variety of oxidation reactions.2. Metal Oxide Catalysts: Metal oxide catalysts, such as manganese dioxide and vanadium pentoxide, are effective forthe oxidation of inorganic compounds and certain organic pollutants. These catalysts are often used in combinationwith metal catalysts to enhance their performance.3. Heterogeneous Catalysts: Heterogeneous catalysts are solid materials that are used in the form of a powder, pellet, or structured catalyst bed. Examples of heterogeneouscatalysts include supported metal catalysts, zeolites, and metal oxides supported on inert substrates.Advantages of Catalytic OxidationCatalytic oxidation offers several advantages over other methods of pollutant abatement, including:1. Energy Efficiency: Catalytic oxidation can be carried out at relatively low temperatures compared to thermal oxidation, reducing energy consumption and operating costs.2. Selectivity: Catalysts can be designed to selectively promote the oxidation of specific pollutants while minimizing the formation of unwanted by-products.3. Environmental Compatibility: The use of catalysts allows for the conversion of harmful pollutants into less harmful or inert substances, reducing the overall environmental impact of the process.4. Process Intensification: Catalytic oxidation can be easily integrated into existing industrial processes, making it a cost-effective and efficient pollution control solution.ConclusionCatalytic oxidation is a versatile and effective process for the treatment of air and water pollutants, as well as the synthesis of valuable chemical products. By harnessing the power of catalysts, this technology offers significant benefits in terms of energy efficiency, selectivity, and environmental compatibility. As the demand for sustainable solutions to environmental challenges continues to grow, catalytic oxidation is expected to play an increasingly important role in pollution control and chemical synthesis.。

第35卷 第12期 无 机 材 料 学 报Vol. 35No. 122020年12月Journal of Inorganic Materials Dec., 2020收稿日期: 2020-03-02; 收到修改稿日期: 2020-05-07基金项目: 国家自然科学基金(61775131, 61376009); 上海高校特聘教授(东方学者)岗位计划(2013-70)National Natural Science Foundation of China (61775131, 61376009); The Program for Professor of Special Ap-pointment (Eastern Scholar) at Shanghai Institutions of Higher Learning (2013-70)作者简介: 王金敏(1975–), 男, 教授.E-mail:*******************.cn文章编号: 1000-324X(2020)12-1307-08 DOI: 10.15541/jim20200105纳米二氧化锰的制备及其应用研究进展王金敏, 于红玉, 马董云(上海第二工业大学 工学部, 环境与材料工程学院, 上海 201209)摘 要: 二氧化锰作为一种重要的过渡金属氧化物, 因其储量丰富、晶型多样、性能优异而备受关注。

将二氧化锰纳米化后, 其颗粒尺寸变小、比表面积变大、材料性能优化、应用领域得以拓宽。

本文在引言部分从介绍二氧化锰的应用着手, 指出纳米化和晶型多变对二氧化锰的结构和性能有着重要的影响。

正文部分主要从纳米二氧化锰的制备方法和纳米二氧化锰的应用两个方面对近年来的研究进展进行了总结和评述。

(1)介绍了水热法、溶胶-凝胶法、化学沉淀法、固相合成法等纳米二氧化锰的制备方法, 对各种制备方法的优点与缺点以及所制备纳米二氧化锰的形貌与性能进行了总结。

锰氧化物的英文Manganese oxides come in various forms, each with unique chemical properties and applications.These compounds are integral to the production of batteries, catalysts, and pigments, showcasing their versatility in the chemical industry.In nature, manganese oxides can be found as minerals, playing a role in geological processes and contributing to the Earth's mineral diversity.Understanding the different types of manganese oxides, such as MnO, MnO2, and Mn3O4, is crucial for their effective use in various scientific and industrial applications.Their reactivity with other elements makes them valuable in chemical reactions, often serving as oxidizing agents in laboratory settings.Manganese oxides' ability to catalyze reactions has made them indispensable in the petrochemical industry, where they help to speed up processes and improve efficiency.Their presence in the environment, though often in trace amounts, is significant for understanding natural processes and the role of manganese in ecosystems.In the field of energy storage, manganese oxides are key components in the development of rechargeable batteries, highlighting their importance in sustainable technology.The study of manganese oxides is a fascinating journey into the world of chemistry, where each discovery unveils new possibilities for their use and understanding.。

铜锰氧化物催化剂制备方法研究进展郭薇;张华【摘要】The transition metals are an important type of the catalysts, which have been widely applied in the catalysis field. Their catalytic performance is more excellent after the transition metals are oxidized. It is foreseeable that the transition metal oxides will become the important development direction of the catalysts. The research progress in copper manganese metal oxide catalysts in recent years were reviewed. The catalyst preparation methods, such as dipping method, hydrothermal synthesis, coprecipitation method, solidstate reaction and sol-gel method were discussed and the characteristics of the various methods were reviewed and summarized. Their development prospects were also outlined.%过渡金属是一类重要的催化剂,在催化领域已得到广泛应用,将过渡金属氧化后,其催化性能更加优良,可以预见过渡金属氧化物将是催化剂发展的重要方向.综述了近年来国内外铜锰金属氧化物催化剂的研究进展,讨论了铜锰金属氧化物催化剂的各种制备方法,如浸渍法、水热合成法、共沉淀法、固相法和溶胶-凝胶法等,对各种制备方法的特点进行总结和归纳,并展望铜锰氧化物催化剂的发展前景.【期刊名称】《工业催化》【年(卷),期】2012(020)012【总页数】6页(P15-20)【关键词】催化剂工程;过渡金属;铜锰氧化物催化剂【作者】郭薇;张华【作者单位】天津工业大学改性与功能纤维天津市重点实验室,天津300387;天津工业大学改性与功能纤维天津市重点实验室,天津300387【正文语种】中文【中图分类】TQ426.6;O643.3贵金属催化剂具有氧化活性高、不易中毒和氧化温度低等特点，在催化领域应用广泛，但因贵金属资源缺乏和价格昂贵，一直在寻找新的高效催化剂取代贵金属催化剂［1-2］。