Two-step adsorption process for deep

Ind. Eng. Chem. Res.,45 (14), 5059 -5065, 2006. 10.1021/ie060002dS0888-5885(06)00002-9Web Release Date: June 6, 2006Copyright © 2006 American Chemical SocietyBiosorption Process for Treatment of Electroplating Wastewater Containing Cr(VI): Laboratory-Scale Feasibility TestDonghee Park,Yeoung-Sang Yun,Ji Hye Jo, and Jong Moon Park*Advanced Environmental Biotechnology Research Center, Department of Chemical Engineering, School of Environmental Science and Engineering, Pohang University of Science and Technology, San 31, Hyoja-dong, Pohang 790-784, South Korea, and Division of Environmental and Chemical Engineering, Research Institute of Industrial Technology, Chonbuk National University, 664-14ga, Duckjin-dong, Chonju 561-756, South KoreaReceived for review January 2, 2006Revised manuscript received May 2, 2006Accepted May 8, 2006Abstract:Brown seaweed Ecklonia biomass was used for the treatment of electroplating wastewater that contains chromium and zinc ions. Batch experiments showed that Cr(VI) was removed from the wastewater through reduction to Cr(III) by contact with the biomass, whereas Cr(III) and Zn(II) were removed through adsorption to the binding sites of the biomass. Among various parameters, the solution pH most significantly affected the biosorptive capacity of the biomass. As the solution pH increased, the removal efficiency of Cr(VI) decreased, whereas that of Cr(III) and Zn(II) increased, for pH <5. This divergence of efficiency, because of the removal mechanisms of chromium and zinc ions, necessitated a two-stage biosorption process for the complete removal of both ions from the wastewater. The first stage comprises the removal of Cr(VI) by reduction into Cr(III) and of total chromium by partial adsorption at a low pH (1.5-2.5), and the second stage the removal of residual total chromium and Zn(II) by adsorption at elevated pH (4-5). A series of two columns that contain the Ecklonia biomass with a pH adjustment step between column operations was successfully used as a feasibility test of the proposed process. In conclusion, the abundant and inexpensive Ecklonia biomass can be used in the two-stage biosorption process for the treatment ofelectroplating wastewater that contains Cr(VI) and other metal ions, because it shows the promise of being environmentally friendlier than any existing chemical treatment process.Thursday, 16 November 2006 - 4:50 PM572eHeavy Metals Removal from Wastewater by MagneticField-Magnetotactic Bacteria TechnologyHuiping Song1, Xingang LI2, Jinsheng Sun2, and Yanhong Wang2. (1) School of Chemical Engineering and Technology, Tianjin University, No.92 Weijin Road, Nankai district, Tianjin, 300072, China, (2) School of Chemical Engineering and Technology, National Engineering Research Center for Distillation Technology, Tianjin University,P.R. China, Tianjin, ChinaPlating, electron devices and other industries frequently generates large quantity of wastewater containing high levels of toxic heavy metal ions, such as copper, cadmium, nickel and lead, which are drastically harmful to aquatic and terrestrial life. Although traditional removal methods, such as chemical precipitation, solvent extraction andion-exchange from wastewater, have been helpful to relief the water shortage, yet they become less effective under the metal ion concentration of 100 mg l-1, which involve high capital and operational costs as well as the generation of secondary wastes. Recent studies suggest that many algae, yeasts, bacteria and fungi are capable of concentrating metal species from dilute aqueous solutions and accumulating them within their cell structure. Compared with the conventional methods, this biosorption process is more economical, efficient and environmentally friendly. However, the biosorption technology needs a bridge to connect the idea and the practical difficulty to separate the microorganisms loading metal ions from the aqueous solution. Newly-developed immobilization cell technology seems theoretically a good option. Nevertheless the float, expand, conglutination of the immobilized cells and the high mass transfer resistance of the oxygen and substrate severely restricted its mass application.The magnetotactic bacteria (MTB), discovered by Blakemore in 1975, becomes a feasible alternative. MTB can synthesize unique intracellular structures called magnetosomes (MS) by uptaking iron (III) ions from culture medium. This characteristic makes them possible to navigate along geomagnetic or applied magnetic field lines. Previous literatures are limited on the biosorption conditions of heavy metal ions on MTB and the efficiency of separation the MTB adsorbing metal ions, which will be crucially helpful to develop a practical process design for removal and recovery metals using MTB as sorbents.In this paper, the effect of performance parameters, such as the initial pH, temperature, biomass concentration and adsorption duration, are investigated in the biosorption Cu (II)ions by MTB firstly. The "real sorbent" experiment shows that there is no significant sorption when MTB is absent in the solution, indicating that MTB is the only sorbent in our experiments. Each experiment above is repeated three times and the following data are given as average. The concentration of Cu (II) in solution is determined using HITACHI 180-80 Atomic Absorption Spectrophotometer. The experimental results indicate that pH value and concentration of biomass exerted important influence on the sorption process, and the optimum scope were 1~9 and 2.0~5.0 g l-1, respectively. No significant effect of temperature has been observed in the discussed range, and the adsorption could be finished within 5 min.It is important for design purposes to get the fundamental knowledge of adsorption equilibrium and adsorption kinetics. The Langmuir, Freundlich equilibrium models and the pseudo second-order kinetic model are chosen as candidates for isothermal and kinetic adsorption behavior of Cu (II) ions, and then the model parameters are fixed. The adsorption equilibrium data of Cu (II) ions in optimum conditions fit well to both the Langmuir and Freundlich models with high correlation coefficient of 0.9996 and 0.9428. And the second-order kinetic model is very suitable for the experimental kinetic data with a high correlation coefficient of 1.0 at optimum conditions. The maximum biosorption capacity of MTB is determined as 24.3013 mg g-1 (wet-weight basis), and the rate constant 0.9549 g mg-1 min-1.Then, separation of metal-loaded MTB from the solution is studied using separators with strings by applying a high gradient magnetic field, and the focusing is the intensity of magnetic field and the place of wire casing. The separation efficiency is very good when magnetic field intensity is 100 Gauss, and no distinct improvement with higher magnetic field intensity. Moreover, the separation efficiency is better when metal wires are vertical than parallel with magnetic force line. The experiment result shows that Cu (II) ions concentration decrease from 100 mg l-1 initially to less than 5 µg l-1 at optimum conditions. At the same time, the wires loading MTB are observed by Scanning Electron Microscope (SEM). The diameter of wires after loading MTB increases from 67 to 73 µm.This "magnetic field-magnetotactic bacteria technology" shows great application potential in the area of wastewater treatment for many advantages, such as high efficiency, low power, low cost and no secondary pollution, and so on.The investigation of lead removal by biosorption: An application at storage battery industry wastewatersTolga Bahadir a, 1, , Gulfem Bakan a, , , Levent Altas b, 2, and Hanife Buyukgungor a, 1,a Environmental Engineering Department, Faculty of Engineering, Ondokuz Mayis University, Samsun, Turkeyb Environmental Engineering Department, Faculty of Engineering, Aksaray University, Aksaray, TurkeyReceived 12 September 2006; revised 1 December 2006; accepted 12 December 2006. Available online 17 December 2006.AbstractLead is present in different types of industrial effluents, being responsible for environmental pollution. Biosorption has attracted the attention in recent years as an alternative to conventional methods for heavy metal removal from water and wastewater. The biosorption of Pb(II) ions present in the storage battery industry wastewaters intensively, by Rhizopus arrhizus has been investigated in this study. This microorganism has been preferred since its biosorption feature was well known. A detailed study was conducted for the removal of Pb(II) ions which was very toxic even in low quantities to the receiving environment, from storage battery industry wastewater by biosorption system as advanced treatment technique, and to investigate the effects of the several parameters on its removal. The average Pb(II) ions concentration in the storage battery industry wastewater found 3.0 mg/L and reducing this value below 0.5 mg/L was aimed. In this study, the effects of the media conditions (pH, temperature, biomass concentration) on the biosorption of Pb(II) ions to R. arrhizus have been investigated in a batch reactor. Optimum biosorption conditions have been found of initial pH 4.5, temperature 30 °C and biomass concentration 1.0 g/L. The maximum biosorption capacity was obtained as 2.643 mg Pb(II)/g microorganism.。

化工装置常用英语词汇对照化工装置常用英语词汇对照一、概论 introduction方案(建议书) proposal可行性研究 feasibility study方案设计 concept design工艺设计 process design基础设计 basic design详细设计 detail design开工会议 kick-off meeting审核会议 review meeting外商投资 foreign investment中外合资 joint venture中外合营 joint venture补偿贸易 compensation trade合同 合同附件 contract卖方 vendor买方 buyer顾客 client承包商 contractor工程公司 company供应范围 scope of supply生产范围 production scope生产能力 production capacity项目 project界区 battery limit装置 plant公用工程 utilities工艺流程图 process flow diagram工艺流程方块图 process block diagram管道及仪表流程图 piping and instrument drawing物料及热量平衡图 mass & heat balance diagram蒸汽及冷凝水平衡图 steam & condensate balance diagram 设备布置图 equipment layout设备表 equipment list成品(产品) product(final product)副产品 by-product原料 raw-material设计基础数据 basic data for design技术数据 technical data数据表 data sheet设计文件 design document设计规定 design regulation现场服务 site service项目变更 project change用户变更 client change消耗定额 consumption quota技术转让 technical transfer技术知识 technical know-howtechnical knowledge技术保证 technical guarantee咨询服务 consultative services技术服务 technical services工作地点 location施工现场 construction field报价 quotation标书 bidding book公司利润 company profit固定价合同 fixed price contract固定单价合同 fixed unit price contract成本加酬金合同 cost plus award fee contract 定金 mobilization银行保证书 bank guarantee letter保留金 retention所得税 income taxes特别承包人税 special contractor's taxes城市和市政税 city and municipal taxes工作手册 work manual工作流程图 work flow diagram质量保证程序 QA/QC procedures采购计划 procurement plan施工计划 construction plan施工进度 construction schedule项目实施计划 project execution plan项目协调程序 project coordination procedure 项目总进度计划 project master schedule设计网络计划 engineering network logic项目质量保证 project quality assurance项目质量控制 project quality control采购 procurement采购周期 procurement period会签 the squad check计算书 calculation sheets询价 inquiry检验 inspection运输 transportation开车 start up / commission验收 inspection & acceptance校核 check审核 review审定 approve版次 version部门 department专业 specialty项目号 project number图号 drawing number目录 contents序言 foreword章 chapter节 section项 itemMR material requisitionSPEC engineering specificationDATA SHEET（技术表） technical data sheetTBA(技术评标） technical bid analysisPDP preliminary design packagePM (项目经理) project managerLDE(专业负责人) lead discipline engineerMRQ(材料询价单) Material requisition for quotationMRP(材料采购单) material requisition for purchase BEP(基础工程设计包) basic engineering packageP&ID(管道及仪表流程图) piping and instrument drawing(diagram)PFD process flow diagramNNF normally no flowFO failure openFC failure closeC/S/A civil/structure/architectureDDP（详细设计阶段） detail design phase二. 工艺流程连续过程 continuous process间歇过程 batch process工艺叙述 process description工艺特点 process feature操作 operation反应 reaction副反应 side reaction絮凝 flocculation浮洗 flotation倾析decantation催化反应 catalytical reaction 萃取extraction中和 neutralization水解hydrolysis过滤filtration干燥drying还原 reduction氧化oxidation氢化hydrogenation分解decomposition离解dissociation合成 synthetics吸收 absorption吸附 adsorption解吸desorption结晶crystallization溶解solution调节 modulate控制 control悬浮 suspension循环circulation再生 regeneration再活化reactivation沥取leaching破碎crushing煅烧caloination沉降sedimentation沉淀precipitation气化gasification冷冻refrigeration固化、结晶 solidification 包装 package升华sublimation燃烧combustion引烧ignition蒸馏distillation碳化carbonization压缩compression三、化学物质及特性固体solid液体liquid气体gas化合物 compound混合物 mixture粉 powder片状粉未flake小粒granule结晶crystal乳化物 emulsion氧化物 oxidizing agent 还原剂reducing agent 有机物 organic material 真空vacuum母液master liquor富液rich liquor贫液lean liquor萃出物 extract萃余物 raffinate絮凝剂flocculants冷冻盐水 brine酸度 acidity浓度 concentration碱度 alkalinity溶解度 solubility凝固点 solidificalion point沸点 boiling point熔点 melting point蒸发率evaporation rate粘度 viscosity吸水的water absorbent(a)无水的anhydrous(a)外观appearance无色的colorless(a)透明的transparent(a)半透明的translucent密度 density比重specific gravity催化剂catalyst燃烧combustion引燃ignition自然点 self-ignition temperature可燃气体combustible gas可燃液体inflammable liquid易燃液体volatile liquid爆炸混合物 explosive mixture爆炸性环境 explosive atmosphere(environment) 爆炸极限explosive concentration limit废水 waste water废液waste 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mill振动筛vibrating screen回转筛rotary screen风机fan罗茨鼓风机 root's blower起重机crane桥式起重机 bridge crane电动葫芦motor hoist发电机generator电动机motor汽轮机steam turbine五、管道工程 piping engineering1阀门 valve阀杆stem内螺纹阀杆 inside screw阀座valve seat (body seat)阀座环、密封圈sealing ring阀芯(包括密封圈,杆等) trim阀盘disc阀体body阀盖bonnet手轮hand wheel手柄hand level (handle)压盖gland闸阀gate valve平行双闸板 double disc parallel seat 楔形单闸板 split wedge截止阀globe valve节流阀throttle valve针阀needle valve角阀(角式截止阀) angle valveY型阀(截止阀) Y-valve(Y-body globe valve)球阀ball valve三通球阀3-way ball valve蝶阀butterfly valve对夹式(薄片型) wafer type偏心阀板蝶阀offset disc (eccentric) butterfly valve 斜阀盘蝶阀 canted disc butterfly valve连杆式蝶阀 link butterfly valve止回式蝶阀 combined non-return butterfly valve柱塞阀piston type valve旋塞阀plug valve三通旋塞阀 three-way plug valve四通旋塞阀 four-way plug valve旋塞cock衬套旋塞sleeve cock隔膜阀diaphragm valve橡胶衬里隔膜阀rubber lined diaphragm valve直通式隔膜阀straight way diaphragm valve夹紧式胶管阀pinch valve止回阀check valve升降式止回阀lift check valve旋启式止回阀swing check valve落球式止回阀ball check valve弹簧球式止回阀spring ball check valve底阀foot valve切断式止回阀stop check valve活塞式止回阀piston check valve翻板止回阀 flap check valve蝶式止回阀 butterfly check valve安全泄气阀 safety[S V]安全泄放阀 relief valve[R V]安全泄压阀 safety relief valve杠杆重锤式 lever and weight type罐底排污阀 flush-bottom tank valve波纹管密封阀bellow sealed valve电磁阀solenoid (operated) valve电动阀electrically(electric-motor)operated valve 气动阀pneumatic operated valve低温用阀cryogenic service valve蒸汽疏水阀 steam trap机械式疏水阀mechanical trap浮桶式疏水阀open (top) bucket trap浮球式疏水阀float trap倒吊桶式疏水阀inverted bucket trap自由浮球式疏水阀 loose float trap恒温式疏水阀thermostatic trap压力平衡式恒温疏水阀balanced pressure thermostatic trap热动力式疏水阀thermodynamic trap脉冲式蒸汽疏水阀 impulse steam trap放汽阀(自动放汽阀) (automatic) air vent valve换向阀diverting (reversing) valve呼吸阀breather valve减压阀pressure reducing valve控制阀control valve执行机构actuator差压调节阀 differential pressure regulating valve切断阀block (shut-off, stop) valve调节阀regulating valve快开阀quick opening valve快闭阀quick closing valve隔断阀isolating valve三通阀three way valve夹套阀jacketed valve非旋转式阀 non-rotary valve2管子,管件,法兰管子pipe(按标准制造的配管用管)tube(不按标准规格制造的其它用管)钢管 steel pipe铸铁管 cast iron pipe衬里管 lined pipe复合管 clad pipe碳钢管 carbon steel[C.S.]pipe合金钢管 alloy steel pipe不锈钢管 stainless steel[S.S.]pipe奥氏体不锈钢管 austenitic stainless steel pipe 铁合金钢管 ferritic alloy steel pipe轧制钢管 wrought-steel pipe锻铁管 wrought-iron pipe无缝钢管 seamless[SMLS] steel pipe焊接钢管 welded steel pipe电阻焊钢管 electric-resistance-welded steel pipe 电熔(弧)焊钢板卷管 electric-fusion(arc)-welded steel-plate pipe螺旋焊接钢管 spiral welded steel pipe镀锌钢管 galvanized steel pipe排污阀blowdown valve集液排放阀 drip valve排液阀drain valve放空阀vent valve卸载阀unloading valve排出阀discharge valve吸入阀suction valve取样阀sampling valve手动阀hand operated(manually-operated) valve(水)龙头bibb;bib;faucet抽出液阀(小阀) bleed valve旁路阀by-pass valve软管阀hose valve混合阀mixing valve破真空阀vacuum breaker冲洗阀flush valve根部阀root (primary, header) valve水煤气钢管 water-gas steel pipe塑料管 plastic pipe玻璃管 glass tube橡胶管 rubber tube壁厚wall thickness[W T]壁厚系列号 schedule number[SCH.NO.]加厚的,加强的 extra heavy (strong)双倍加厚的,双倍加强的double extra heavy (strong) 弯头elbow异径弯头reducing elbow长半径弯头 long radius elbow短半径弯头 short radius elbow长半径180°弯头long radius return短半径180°弯头short radius return三通tee异径三通reducing tee等径三通straight tee带支座三通 base tee45°斜三通45°lateralY型三通 true"Y"四通cross异径管 reducer同心异径管 concentric reducer偏心异径管 eccentric reducer管接头coupling;full coupling活接头union短管 nipple预制弯管 fabricated pipe bendU型弯管 "U"bend法兰端flanged end万向接头universal joint对焊的butt welded[B W]螺纹的threaded[THD]承插焊的socket welded[S W]法兰flange[FL G]整体管法兰 integral pipe flange 钢管法兰steel pipe flange螺纹法兰threaded flange滑套法兰slip-on flange平焊法兰slip-on-welding flange 承插焊法兰 socket welding flange 松套法兰lap joint flange[L J F]对焊法兰weld neck flange[W NF]法兰盖blind flange;blind异径法兰reducing flange压力级pressure rating(class) 突面raised face[RF]凸面male face凹面female face全平面;满平面 flat face;full face[FF]3.管道特殊件 piping speciality粗滤器strainer过滤器filter临时过滤器 temporary strainer(cone type) Y型过滤器Y-type strainerT型过滤器T-type strainer永久过滤器 permanent filter洗眼器及淋浴器eye washer and shower视镜sight glass阻火器flame arrester喷咀;喷头spray nozzle喷射器ejector取样冷却器 sample cooler消音器silencer膨胀节 expansion joint波纹膨胀节 bellow补偿器compensator软管接头hose connection[HC]快速接头quick coupling金属软管 metal hose橡胶管 rubber hose挠性管 flexible tube特殊法兰special flange漏斗funnel8字盲板 spectacle (figure 8) blind 爆破板rupture disk4,其它材料碳素钢carbon steel [C.S.]不锈钢stainless steel[S.S.]铸铁cast iron[C.I.]铝 aluminum铜,紫铜copper钛 titanium抗拉强度 tensile strength非金属材料 non-metallic material塑料 plastic陶瓷ceramic搪瓷porcelain enamel玻璃glass橡胶rubber垫片gasket[G S K T]平垫片flat gasket填料 packing型钢shaped steel角钢angle steel槽钢channel steel工字钢I-beam宽缘工字钢或H钢 wide flanged beam扁钢flat bar圆钢round steel; rod钢带strap steel网络钢板checkered plate材料表 bill of material[BOM]材料统计 material take-off[MTO]散装材料 bulk material综合管道材料表 consolidated piping material summary sheet[CPMSS]汇总表 summary sheet5.设备布置及管道设计中心线center line装置边界 boundary limit[BL]区界 area limit设备布置 equipment arrangement (layout);plot plan标高,立面elevation[EL]支撑点 point of support[POS]工厂北向plant north方位orientation危险区 hazardous area classification净正吸入压头net positive suction head绝对标高absolute elevation坐标 coordinate管道研究 piping study管道布置平面piping arrangement plan[PAP]管道布置 piping assembly; layout详图 detail"X"视图 view "X""A-A"剖视 section "A-A"轴测图 isometric drawing索引图 key plan管道及仪表流程图 piping and instrument diagram[P&ID]管口表 list of nozzles地上管道 above ground piping地下管道 under ground piping管线号 line number总管 header; manifold旁路by pass常开 normally open常闭normally closed取样接口sampling connection 伴热管 tracing pipe蒸汽伴热 steam tracing热水伴热 hot-water tracing电伴热 electrical tracing 夹套管 jacketed line全夹套管 full jacketed比例scale图 figure草图 sketch图例legend符号 symbol件号 part number入口inlet; suction出口outlet;discharge排出口exhaust排液drain放空vent污水坑sump pit集水池collecting basin沟槽trough管沟piping trench地漏floor drain走道,过道 walk way; gang way 预留区 future area人孔manhole[MH]手孔handhole[HH]下水管 sewer管口nozzle管口方位nozzle orientation方向direction位置 location相交intersection垂直,正交,垂直的 perpendicular 平行,平行的p arallel管顶top of pipe [TOP]管底bottom of pipe [BOP]沟底bottom of trench底平 flat on bottom[FOB]顶平 flat on top[FOT]水平的Horizontal垂直的,立式的 vertical上升管;垂直管 riser等级分界 material specification break隔热分界 insulation break管道等级piping class管道材料规定 piping material specification公称直径nominal (pipe) size diameter[DN]公称压力 nominal pressure(pressure rating)磅/平方英寸p ounds per square inch[PSI]公斤/平方厘米 kilograms per square centimeter[kg/cm2]管道附件 piping attachment腐蚀余量 corrosion allowance管段,短管 spool piece ; spool直管 run pipe;straight pipe弯管 bend管件直连 fitting to fitting水平安装 horizontal installation垂直安装 vertical installation对称的symmetric坡度 slope管间距line spacing管道跨距line span间隙,净空clearance尺寸dimension高度 height6.管道支吊架管托shoe管卡clampU型夹(卡) clevis支耳lug预埋件 embedded part鞍座saddle裙座skirt支承架resting support滑动架sliding support固定架anchor导向架guide限位架stop吊架hanger弹簧架spring support弹簧托resting type;spring support弹簧吊架spring hanger滚动支架rolling support减振器snubber标准管架standard pipe support通用管架typical pipe support悬臂架cantilever support三角架triangular support支腿legΠ型管架Π-type supportL型管架 L-type support柱式管架pole type support墙架support-on-wall管墩,低管架s leeper特殊管架special support跨度 span伸出长度(指预埋螺栓) extrusion热应力分析 thermal stress analysis管道柔性分析piping flexibility analysis 力矩moment弯曲力矩bending moment扭矩torque荷载load反力 reaction位移displacement附加位移appendant displacement冷紧,冷拉cold spring固定点 fix point; anchor point应力 stress弯曲应力 bending stress轴向应力 axial stress安全系数 safety factor7焊接及热处理焊接welding电弧焊arc welding电熔焊electric fusion welding[EF W]氩弧焊argon-arc welding水压试验 hydraulic testing气压试验 pneumatic testing8.隔热隔音及涂漆玻璃棉glass wool岩棉rock wool聚氨脂,聚氨基甲酸脂polyurethane管壳shell棉毡blanket玻璃布 glass (fiber) cloth镀锌铁皮galvanized (sheet) iron;galvenized plain sheet隔热层insulation保温hot insulation保冷 cold insulation人身保护personal protection隔音sound insulation吸声sound-absorbing分贝decibel涂漆painting螺栓bolt自攻螺钉self tapping screw螺母nut垫圈gasket管螺纹pipe thread锥管螺纹taper pipe thread六.自动控制测量 measurement测量点 measurement point反馈信号 feedback signal范围 range精确度 accuracy量程迁移span shift零点迁移zero shift信号 signal模拟信号 analog signal输出信号 output signal输入信号 input signal数字信号 digital signal变送器transmitter检测仪表 measuring instrument显示仪表 display instrument积算器integrating instrument指示仪表 indicating instrument记录仪表 recording instrument盘装仪表 panel-mounted instrument架装仪表 rack-mounted instrument分散控制仪表 distributed control system 执行器correcting unit执行机构actuator控制阀control valve座环seat ring阀芯valve plug阀座seat阀杆stem填料 packing单座single ported双座double portedG LOBE阀 globe valve口径port/bore气蚀cavitation薄膜执行机构diaphragm actuator 活塞执行机构piston actuator电动执行机构electric actuator 膜片diaphragm膜盒diaphragm capsule弹簧管 bourdontube比例作用 proportional(P)-action 积分作用 integral(I)-action微分作用 derivative(D)-action正作用 direct action反作用 reverse action回路loop系统system串级控制 cascade control前馈控制 feed forward control反馈控制 feedback control自力式控制 self-operated control开环控制 open loop control定值控制 control with fixed set point比值控制 ratio control均匀控制 average control分程控制 split range control模糊控制 fuzzy control顺序控制 sequential control硬件 hardware系统软件 system software应用软件 application software平均故障间隔时间 mean time interval between failures(MTBF)平均故障修复时间 mean time to repair(MTTR)接口interface总线bus控制室control room空调区 air conditioned area就地 local仪表盘instrument panel柜式仪表盘 panel of angle frame enclosed design框式仪表盘 panel of open angle frame design通道式仪表盘panel of angle frame enclosed with passageway就是式仪表盘local board操纵台control desk console保护箱shelter保温箱shelter with insulation危险区域hazardous area安全区域safe area爆炸性环境 explosive atmosphere防护型式type of protection本质安全型 intrinsic safety type隔爆型flameproof enclosure type防爆通风充气型purged and pressurized enclosure type 电源power supply不间断电源U ninterrupted Power Supply (U PS)气源air supply补偿导线thermocouple extension wire信号线signal wire配管 piping配线wiring电缆保护管 conduit汇线槽cable/wire duct取源部件 tap接管 connections管件 fitting三阀组three-valve manifold 分析analysis报警alarm火焰flame电导率conductivity控制 control密度 density差 differences电压voltage检测元件 detecting element流量 flow rate比 ratio视镜glass手动hand高 high电流 current指示indicate功率power扫描scan时间 time物位level灯 light低 low湿度 humidity整体integrity中 middle节流孔orifice压力 pressure真空vacuum数量 quantity积算 integrate累积totals核辐射radioactivity 记录 record打印print速度 speed频率frequency安全safety开关switch温度 temperature传送transmit振动vibration风门 damper百叶窗louver重量 weight力 force套管 well安装 installation按钮push button备用电源reserve power supply 背面back编号 number变速speed change标准图 standard drawing材料清单 material list操作程序 operation sequence 操作说明书 operating manual成套设备 complete sets of equipment出线口outlet触点 contact point单层窗single window单价 unit price单线图 single line drawing地脚螺栓foundation bolt底图 original drawing地下敷设 underground laying电缆cable电气图纸electric installation drawing 电线wire端子板terminal board防静电地板 conductive flooring分线盒junction box附件 appendix; accessories负荷load附录 appendix隔栅grille观察窗observation window管线布置 layout of pipeline桁架truss活动地板raised flooring技术参数 technical parameter接地电极earth electrode接线图 wiring diagram截面积sectional area静电static electricity聚氯乙烯绝缘电缆 polyvinyl chloride cable 铠装电缆armored cable埋深depth of embodiment脉冲pulse屏蔽电缆shielded cable索引index现场制作 site fabrication现场安装 field erection积算 integrate联锁interlock数据累积data acquisition差,微分difference数字的(信号) discrete继电器隔离输出isolated relay output薄膜执行机构diaphragm actuator执行元件符号 actuator symbols调节器regulator名称designation气动的pneumatic补偿 compensation节流孔板restriction orifice旋涡vortex超声ultrasonic文丘里管 venturi涡轮turbine阿牛巴流量计(用于大管径) annubar element 质量流量计 Coriolis meter=mass meter容积式流量计 positive displacement电磁流量计 magnetic element辅助的auxiliary分布的distributed紧急情况emergency修正modifier比率ratio测量 gauging气压计 glass进度 schedule瞬间 momentary真空vacuum事件 event辐射,放射radiation频率frequency多元变量 multivariable变量 variable多功能 multifunction振动vibration分解analysis节气阀damper强制 force继电器relay执行机构actuator七.储运工程码头dock or jetty罐区 tank area or tank farm装卸栈台loading/unloading plat form 分配站distribution station库区 warehouse area收发油站oil sending/receiving station 管理室manage room地秤房weigh bridge room(汽车)罐车 tank truck储罐storage tank气柜gas holder鹤管 loading/unloading arms固体物料堆场 solids stacking area罩棚shelter称重,包装 weighing and packing塑料袋plastic bag编织袋woven bag铁桶steel drum运输 transportation皮带运输机 belt conveyor斗式提升机 bucket elevator螺旋输送机 screw conveyor电动葫芦electric hoist桥式吊车 overhead crane(rolling bridge) 叉车升降机 fork lift电瓶车 battery truck。

www.j cc s o c .co m王 磊 等：制备条件对微波合成YAG :Ce 3+荧光粉性能的影响· 335 ·第39卷第3期两步烧结法制备纳米氧化钇稳定的四方氧化锆陶瓷陈 静，黄晓巍，覃国恒(福州大学材料科学与工程学院，福州 350108)摘 要：采用共沉淀法制备纳米氧化钇稳定的四方氧化锆(yttria stabilized tetragonal zirconia ，3Y-TZP)粉体。

利用X 射线衍射、N 2吸附–脱附等温线，透射电子显微镜对3Y-TZP 粉体的物理性能和化学性能进行表征。

研究了纳米3Y-TZP 粉体的烧结曲线，分析了3Y-TZP 素坯在烧结过程中的致密化行为和显微结构，探讨了两步烧结工艺对3Y-TZP 纳米陶瓷微观结构的影响。

结果表明：采用共沉淀法，在600 ℃煅烧2 h 后，可获得晶粒尺寸为13 nm 、晶型发育良好、团聚较少的纳米3Y-TZP 粉体；采用两步烧结法，将素坯升温至1 200 ℃保温1 min 后，再降温到1 050 ℃保温35 h ，可获得相对密度大于98%，晶粒尺寸约为100 nm 的3Y-TZP 陶瓷。

两步烧结法通过控制煅烧温度和保温时间，利用晶界扩散及其迁移动力学之间的差异，使晶粒生长受到抑制，样品烧结致密化得以维持，实现在晶粒无显著生长前提下完成致密化。

关键词：氧化钇稳定的四方氧化锆；共沉淀法；两步烧结；晶粒尺寸中图分类号：TB383 文献标志码：A 文章编号：0454–5648(2012)03–0335–05 网络出版时间：2012–02–17 14:13:39DOI ：CNKI:11-2310/TQ.20120217.1413.002网络出版地址：/kcms/detail/11.2310.TQ.20120217.1413.002.htmlTwo-Step Sintering of Nano-Yttria Stabilized Tetragonal Zirconia CeramicsCHEN Jing ，HUANG Xiaowei ，QIN Guoheng(College of Materials Science and Engineering, Fuzhou University, Fuzhou 350108, China)Abstract: A nano-sized powder of 3% (mole fraction) yttria stabilized tetragonal zirconia (3Y -TZP) was prepared by a co-precipitation method. The physical and chemical properties of 3Y -TZP powders were characterized by X-ray diffraction, N 2 adsorption–desorption iso-therms and transmission electron microscope, respectively. The sintering curve of the nano-sized powder of 3Y -TZP , the densification behav-ior and microstructure of the sintered bulk were analyzed, and the influence of two-step sintering on the microstructure of the 3Y -TZP ceram-ics was discussed. The results show that the well-developed crystal and agglomeration-free nano-sized powder with the grain size of 13 nm was obtained by co-precipitation method and the subsequent calcination at 600 for 2℃ h. The relative density of the 3Y -TZP ceramics was >98% and the grain size was 100 nm when the green body was calcined at 1 200 ℃ for 1 min and then decreased to 1 050 ℃ for 35 h using two-step sintering method. It was found that the grain growth was inhibited and the densification of the samples was achieved through controlling the calcining temperature and holding time in the two-step sintering process utilizing the different migration kinetics between the grain boundary diffusion and the grain boundary migration. Finally, the sintered body had a full density without any grain growth.Key words: yttria stabilized tetragonal zirconia; co-precipitation method; two-step sintering; grain size纳米氧化锆陶瓷具有优异的强度、韧性、耐腐蚀和超塑性[1]，其中，氧化钇稳定的四方氧化锆(Y-TZP)陶瓷作为工程结构材料受到广泛关注[2]。

二次催化溶胶-凝胶法制备多孔硅胶微球赵贝贝;许婵婵;唐涛;李彤;张维冰;王风云【摘要】Micrometer SiO2 microspheres were prepared by two-step catalytic Sol-Gel method with tetraethoxysi-lane (TEOS) as starting material and N,N-Dimethylformamide (DMF) as template. The effects of some factors on the diameter and particle size distribution of the SiO2 microspheres were discussed, such as H2O quantity and etha-nol quantity during the first catalytic process, the electrolyte concentration and stirring speed during the secondary catalytic process. SiO2 microspheres were characterized by SEM, Zetasizer, BET measurements and microscope-particle image analysis system. Results show that SiO2 microspheres are mostly regular-ball with no particle agglomeration. The mean particle size (D50) is 8.9μm, and the particle size distribution follows typical Gaussian distribution. The specific surface area is 546.67m2/g, and pore volume is 0.7142m3/g, with a narrow pore size varied from 2nm to 8nm. Also the particle size increases with water quantity, ethanol quantity and NaCl concentration in-creaing, but decreases with stirring speed acceleration.%以四乙氧基硅烷(TEOS)为原料,N,N-二甲基甲酰氨(DMF)为模板,采用二次催化的溶胶-凝胶法制得微米级多孔性硅胶微球.考察了一次催化水解缩聚过程中水量、乙醇量,二次催化反应过程中电解质浓度、搅拌速度对微球粒径的影响,并采用扫描电子显微镜(SEM)、激光粒度分布仪、比表面及孔径分析仪、显微镜-图像颗粒分析系统进行表征.结果表明,制得硅胶微球球形规则且无团聚现象,平均粒径(D50)为8.9μm,粒径呈典型高斯分布,比表面积546.67m2/g,孔体积0.7142m3/g,孔径主要分布在2～8nm之间,分布范围窄；硅胶微球粒径大小随一次催化过程中水量、乙醇量及二次催化过程中电解质浓度增加而增大,随乳状液形成过程中搅拌速度加快而减小.【期刊名称】《无机材料学报》【年(卷),期】2011(026)010【总页数】5页(P1090-1094)【关键词】硅胶微球;二次催化;溶胶-凝胶法【作者】赵贝贝;许婵婵;唐涛;李彤;张维冰;王风云【作者单位】南京理工大学工业化学研究所,南京210094;胜利石油管理局钻井工艺研究院,东营257017;南京理工大学工业化学研究所,南京210094;大连依利特分析仪器有限公司,大连116023;大连依利特分析仪器有限公司,大连116023;大连依利特分析仪器有限公司,大连116023;华东理工大学化学与分子工程学院,上海200237;南京理工大学工业化学研究所,南京210094【正文语种】中文【中图分类】TQ127硅胶是极其重要的高科技超微细无机材料之一,具有粒径小、比表面积大、表面吸附力强、表面能大, 以及优越的稳定性、补强性、增稠性、触变性等, 在众多学科及领域内独具特性, 有着不可取代的作用. 其中, 硅胶微球是开发最早、研究最深入、应用最广泛的高效液相色谱固定相基质[1]. 此外,多孔性硅胶微球还广泛应用于催化剂、化妆品和油墨添加剂等领域[2-4]. 溶胶−凝胶法是制备硅胶微球的常用方法,通常在酸性或碱性条件下使硅源水解缩聚得到硅胶微球[5]. 酸性条件下, 硅源水解速率大于其缩聚速率, 易形成多孔性结构; 而在 pH值7～9的弱碱性条件下, 硅源缩聚速率大于其水解速率, 并最终形成无孔的凝胶状结构[6]. 传统溶胶−凝胶法制得微球通常为微米级或亚微米级的无孔硅胶微球[7]. Unger等[8]首次采用二次催化的溶胶−凝胶法, 先在酸性条件下将正硅酸乙酯催化水解得到一定分子量的交联溶胶, 再在碱性条件下将溶胶凝胶、老化, 得到硅胶微球粒度范围为2～25μm. 催化过程中反应物浓度、温度、pH值以及硅源种类等条件对硅胶粒度、结构的影响, 也得到了详细的探讨[9-11]. 为研究二次催化溶胶−凝胶法制备硅胶微球的反应机理, Bernards等[12-13]将四乙氧基锗烷(TEOG)引入反应, 研究其对TEOS水解、缩聚过程的影响. 此外, 在二次催化水解过程中加入模板物质, 有助于调控硅胶孔结构, 制得粒度均匀、孔结构均一的硅胶微球[14-15]. Choi等[16]以正硅酸甲酯为硅源, 以聚环氧乙烷、聚环氧丙烷为模板, 制得孔结构规整的硅胶. Hohenesche等[17]以硅酸乙酯 40为硅源、DMF为模板, 两步水解缩聚制得平均粒径为6μm的硅胶微球, 并用作液相色谱固定相基质. 二次催化水解过程中加入模板形成乳状液后, 硅胶微球的粒径主要由乳状液中的分散液滴粒径决定. 在乳状液中加入微量电解质, 通过对乳状液的形成、分散液滴粒径的影响调整硅胶微球粒径, 而有关此方面的研究尚未有报道.本工作采用二次催化溶胶−凝胶法, 以TEOS为硅源, N,N-二甲基甲酰氨(DMF)为模板, 制备硅胶微球, 并研究了一次催化水解过程中水量、乙醇量,二次催化水解过程中电解质浓度、搅拌速度对微球粒径的影响.1 实验1.1 制备方法多孔硅胶微球的制备主要分为两步: 先在酸性条件下使 TEOS水解缩聚生成聚乙氧基硅烷(PES);再在碱性条件下使PES完全水解, 静置老化形成二氧化硅凝胶球. 在250mL三口烧甁中加入 25mL TEOS、一定量乙醇溶剂、盐酸催化剂, 不断搅拌并以 0.5mL/min的速度向三口烧甁中逐滴加入水, 滴加完毕后继续搅拌1h使反应完全, 旋蒸除去乙醇、盐酸等物质. 然后向旋蒸后PES中加入50mL水、30mL异丙醇、1.2mL DMF, 高速搅拌以形成O/W型乳状液, 加入1mL氨水催化剂引发二次水解缩聚反应, 以1700r/min搅拌反应30min, 静置24h, 将下层白色沉淀抽滤、洗涤, 150℃下烘干5h, 650℃下煅烧6h, 得到多孔硅胶微球.1.2 表征以日本GEOL公司的JSM-6380LV型扫描电子显微镜观察硅胶微球的大小及形貌, 以XSZ-HS3型显微镜−图像颗粒分析系统观察硅胶微球的大小及分散状况. 硅胶微球粒径分布采用丹东百特公司生产BT-9300H激光粒度分析仪测试. 以D50表示微球平均粒径, D90/D10表示粒径分布宽度, 统计颗粒数目不少于100个. 比表面积及孔径测试在北京金埃谱科技有限公司的V-Sorb 2800P比表面积及孔径分析仪上进行, 测试前经120℃真空干燥 2h, 液氮温度下测量样品在不同氮气分压下的氮气饱和吸附量,由BET公式计算得到样品的比表面积.2 结果与讨论2.1 微球形貌结构分析图 1(a)为硅胶微球表面形态的扫描电镜照片,微球球形规则且表面光滑, 无团聚现象, 由扫描电镜图得到微球平均粒径为5.8μm, 粒径分布宽度为2.50. 经激光粒度分析仪测试, 硅胶微球的粒径呈典型高斯分布, 如图 1(b)所示. 由此可见, 硅胶微球粒径分布宽度较窄, 单分散性较好.硅胶的吸附脱附等温线如图 2(a)所示, 吸附分支和脱附分支比较靠近, 为第四类吸附等温线, 表明孔结构为近似圆筒状结构. 基于硅胶的吸附脱附等温线计算得到硅胶的孔径分布图, 如图 2(b)所示, 孔径主要分布在2～8nm之间, 孔径分布窄. 经BET法计算得到, 硅胶微球比表面积达 546.67m2/g, 孔体积0.7142m3/g, 与部分商品化的高比表面积硅胶相关数据接近.2.2 一次催化过程对硅胶微球粒径的影响2.2.1 水量影响在一次催化水解缩聚过程中, 保持恒定的水滴加速度, 改变滴加时间, 得到硅胶微球粒径随水量变化如图3所示. 从图3可以看出, 随着水量的增加,硅胶微球平均粒径及粒径分布宽度均增大, 单分散性变差.图1 硅胶微球的扫描电镜照片(a)和粒度分布图(b)Fig. 1 SEM image (a) and particle size distribution (b) of SiO2 microspheres图2 硅胶微球的吸附脱附等温线图(a)和孔径分布图(b)Fig. 2 N2adsorption/desorption isotherms (a) and pore size distribution curve (b) of SiO2 microspheres图3 水量对硅胶微球粒径的影响Fig. 3 Influence of H2O quantity on SiO2 particle size酸性条件下, TEOS与水发生水解缩聚生成PES.首先, H+亲电进攻TEOS分子中一个−OC2H5基团使之质子化, 电子云向该−OC2H5基团偏移, 造成硅原子另一侧表面空隙加大并呈亲电性, 易于阴离子进攻, 反应速率加快. 同时, 由于位阻及中间体稳定性等原因, TEOS已有一个−OC2H5水解为−OH, 其余−OC2H5基团反应活性降低, 继续发生−OH取代的可能性减小, 水量不足时首先生成最低水解产物(C2H5OH)3Si−OH, 然后脱水缩合为(C2H5OH)3Si−O−Si(C2H5OH)3, 最后得到链状聚合物[18]. 反应式如下:由反应式可知, 1mol TEOS完全水解需要2mol水. 当n(H2O) /n(TEOS)＜2时, TEOS不能完全水解,需要初期生成的硅羟基脱水缩合产生水以继续水解,水成为水解缩聚反应的制约因素. 实验过程中发现,缩聚产物PES的粘度随水量增加而增大,说明水量增多时水解缩聚速率加快, 有更多高分子聚合物生成. Hohenesche等[17]经过多次实验, 认为成球好坏的决定性因素是 PES粘度大小. 因此, 精确控制水量是整个实验的关键. n(H2O) /n(TEOS)为 5.60时,硅胶微球平均粒径6.6μm, 粒径分布宽度为 3.00; n(H2O)/n(TEOS)为 8.20时, 硅胶微球粒径增至21.7μm, 同时粒径分布范围宽度增至 4.03; 若n(H2O)/n(TEOS)进一步增大, 聚合产物易形成三维短链交联结构的凝胶[18], 导致旋蒸时出现“果冻”现象, 不利于后续二次催化水解过程的顺利进行.2.2.2 乙醇量的影响保持其它反应条件不变, 一次催化过程中乙醇量与硅胶微球粒径的关系如图 4所示, 硅胶微球粒径随乙醇量的增加而增大. 乙醇与 TEOS摩尔比从3.38增至8.44时, 制得硅胶微球平均粒径从6.9μm增至15.0μm, 同时粒径分布宽度也有所增加. 从反应平衡角度来讲, 乙醇在水解缩聚反应中承担双重角色: 一方面, 乙醇是TEOS、PES的良好溶剂, 在反应过程中充当分散剂, 起着稀释反应物、降低反应速率的作用; 另外乙醇还是水解缩聚反应的产物,一定程度上抑制水解缩聚反应向脱醇方向进行. 另一方面, 反应体系中加入适量乙醇可以促进 TEOS溶解, 使反应更加均匀, 并且乙醇粘度比较小, 可以降低反应体系粘度, 减小传质扩散阻力, 促进反应进行. 两方面共同作用影响着硅胶微球粒径, 在本实验中, 乙醇主要起促进水解缩聚反应的作用,乙醇量增加而微球粒径增大[19].图4 乙醇量对硅胶微球粒径的影响Fig. 4 Effect of ethanol quantity on SiO2 particle size2.3 二次催化过程对硅胶微球粒径的影响2.3.1 搅拌速率的影响在加入氨水催化剂之前, 高速搅拌 PES、水、异丙醇混合物得到乳白色 O/W 型乳状液[17], 然后加入氨水以引发二次水解缩聚反应, 氨水催化剂与水分子渗透过相膜进入分散相PES液滴内, PES继续水解为硅溶胶, 并缓慢变成二氧化硅凝胶. 因此,乳状液中分散相液滴大小初步决定了硅胶微球粒径.随着搅拌速度的增加, 乳状液在大的搅拌机械力作用下分散为小液滴, 经后续二次水解缩聚反应, 最终制得小粒径硅胶微球. 经显微镜−图像颗粒分析系统测试, 乳状液形成过程中搅拌速度为1700r/min时, 微球平均粒径为5.8μm; 搅拌速度降至 1500r/min时, 微球平均粒径增大至10.2μm, 同时粒径分布宽度也有所增大.2.3.2 NaCl浓度的影响图5 NaCl浓度对硅胶微球粒径的影响Fig. 5 Effect of NaCl concentration on SiO2 particle size保持其它反应条件不变, 在乳状液形成过程中加入微量NaCl电解质, 发现NaCl有增大硅胶微球粒径的作用. 如图 5所示, NaCl浓度从 0增至5mmol/L时, 微球平均粒径从5.8μm增至11.7μm.加入少量电解质, 乳状液带电荷形成双电层而变得比较稳定. 电解质含量增大时, 由于压缩双电层亲水头变小, 不利于形成O/W型乳状液, 而有利于形成 W/O型乳状液体系. 根据乳状液稳定性理论, O/W 型乳状液中分散相液滴尺寸会随着电解质浓度增加而增大, 若体系中油相与水相体积相近, 电解质浓度进一步增加导致 O/W 体系经过双连续相后变成W/O型乳状液, 继而液滴尺寸又随着电解质浓度增加由大变小. 由于该实验水相的量占绝对优势, 这种趋向仅表现为随电解质浓度增加, 分散相液滴由小变大. 因此, 硅胶微球粒径也随着乳状液形成过程中NaCl浓度增加而变大.3 结论以TEOS为原料, 采用二次催化的溶胶−凝胶法,先在酸性条件下使TEOS水解缩聚生成PES, 再在碱性条件下将PES完全水解, 经凝胶、老化、锻烧生成多孔性硅胶微球, 最终制得硅胶微球球形规则,且粒径呈高斯分布. 考察了一次催化水解过程中水量、乙醇量, 二次催化过程中电解质浓度、搅拌速度对硅胶微球粒径的影响. 在一定范围内, 硅胶微球粒径随一次催化水解过程中水量、乙醇量, 乳状液形成过程中 NaCl浓度的增加而增大, 随乳状液形成过程中搅拌速度的增大而减小.参考文献:【相关文献】[1] Unger K K, Skudas R, Schulte M M. 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第21卷第丨期2021年1月过程工程学报The Chinese Journal of Process Engineering Vol.21 No.lJan.2021D O I : 10.12034/j .i s s n . 1009-606X.220073Direct separation of human serum albumin from Cohn fraction Vsupernatant by one-step ion exchange chromatographyJie X IA N G 1, Songping ZHANG 2, Guifeng ZHANG 2, Jian LUO 2*, Rong Y U 1*1. Department of Biopharmaceutics, West China School of Pharmacy, Key Laboratory of Drug-Targeting and Drug Delivery System ofthe Education Ministry, Sichuan Engineering Laboratory for Plant-Sourced Drug and Sichuan Research Center f o r Drug PrecisionI n d u s t r i a l Technology, West China School of Pharmacy Sichuan University, Chengdu, Sichuan 610041, China2. State Key Laboratory of Biochemical Engineering, I n s t i t u t e of Process Engineering, Chinese Academy of Sciences, Beijing 100190,ChinaAbstract: Fraction V supernatant is an effluent o f Cohnfractionation in plasma protein industry . Due to its high ethanol 0 O Cold ethanol p r e c i p i t a t i o nconcentration , further recovery of the residual protein has been •i , ii +iii ,medium to BSA in ethanol-aqueous solution was very weak , and the increase o f ethanol concentration led to the adsorption capacity approaching to 0. The cation exchange medium had a high adsorption capacity at low ethanol concentration , but decreased quickly with the increase o f the ethanol concentration . In contrast , the anion exchange medium showed the best adsorption performance , and the adsorption capacity in 40% ethanol-aqueous solution still reached 34.66 mg /mL . Further experiments showed that the adsorption of BSA on the anion exchange medium in the presence o f ethanol could be described by Langmuir isothermal adsorption equation . The anion exchange medium DEAE Sepharose Fast Flow was packed into a chromatographic column . Real purification of Cohn fraction V supernatant was performed . The Cohn fraction V supernatant , containing about 40% ethanol , was directly loaded to the anion exchange column . A two-step elution strategy was used . The first elution was pH change from 7.0 to 4.5 to obtain the target product human serum albumin , and the second elution was to increase the concentration of sodium chloride from 0 to 1 mol/L to elute glycoproteins . The purity of HSA was 96.35% by electrophoresis , and the activity of binding to the ligand warfarin was comparable to that of commercial HSA product by Cohn fractionation . The total recovery was 43 mg/L Cohn fraction V supernatant .Key words: human serum albumin ; fraction V supernatant ; ion exchange chromatography ; low-temperature ethanolprecipitation ; protein structure收稿：2020-03-05，修回：202(MM~02，网络发表：2020-05-09，Receive 山 2020-03-05, Revised: 2020~04~02, Published o n l i n e : 2020-05-09 基金项目：国家重点研发计划资助项目(编圩：2016YFD0500800;2016YFD0500809);国家自然科学基金资助项目(编号：2182丨005)作者简介：向杰(1994-)，男，重庆市云阳县人，硕士研究生，研宄方向：蛋白质分离纯化：通讯联系人，罗坚，E-man:j l U 〇@ipe.a c .c n ;余蓉，E-mail:**************.cn.引用格式：向杰，张松平，张贵锋，等•一步离子交换层析从Cohn 组分V 上清液中分离人血清白蛋白.过程工程学报，2021，21(1): 92-99.Xiang J , Zhang S P , Zhang G F , e t a l . Direct separation of human serum albumin from Cohn f r a c t i o n V supernatant by one-step ion exchangechromatography (i n Chinese). Chin. J . Process Eng., 2021, 21(1): 92-99, DOI: 10.12034/j.issn.l009-606X.220073.regarded as non -economical . In this work , a recovery o f human serum albumin (HSA ) from fraction V supernatant by ion exchange chromatography was reported , which had not been reported in the literature to our knowledge . Firstly , bovine serum albumin (BSA ) was used as model protein to compare the adsorption capacity of IV-1,IV-4, v^ Media s c r e e n i n g : BSA(0%~40% e t h a n o l )three different types of chromatographic media in different ethanol - h s aaqueous solutions . The adsorption capacity of the hydrophobicDEAE C M Octylv第1期向杰等：一步离子交换层析从Cohn组分V上清液中分离人血清白蛋白93一步离子交换层析从Cohn组分V上清液中分离人血清白蛋白向杰、张松平2，张贵锋2，罗坚2%余蓉卜1.四川大学华西药学院生物技术药物学系，靶向药物与释药系统教育部重点实验室，四川省植物来源工程实验室和四川省小分子药物精准化工程技术研宄中心，四川成都6100412.中国科学院过程工程研究所生化工程国家重点实验室，北京丨00190摘要：传统的血浆低温乙醇沉淀工艺中C o h n组分V上清液由于其乙醇浓度高(体积浓度40%),进一步回收残余蛋白困难而 被作为废弃组分。

Platinum Doped Hydrotreating Catalysts for Deep Hydrodesulfurization of Diesel FuelsSte´phanie Pessayre,†Christophe Geantet,*,†Robert Bacaud,†Michel Vrinat,†Thanh Son N’Guyen,†Yvonne Soldo,‡Jean Louis Hazemann,§and Miche`le Breysse#Institut de Recherches sur la Catalyse,UPR CNRS5401,2A V enue Albert Einstein,69626Villeurbanne Cedex,France,Laboratoire d’Electrochimie et Physico-chimie des Mate´riaux et des Interfaces,UMR CNRS,INPG-Uni V ersite´Joseph Fourier,38402St Martin d’He`res,France,Laboratoire de Cristallographie,UPRCNRS,BP166,38043Grenoble,France,and Laboratoire de Re´acti V ite´de Surfaces Paris,UMR CNRS,Uni V ersite´Pierre et Marie Curie-Paris6,75252Paris Cedex,FranceTwo-stage processes are possible solutions for reaching10ppm sulfur in gas oil without severe runningconditions.First,most of the sulfur is removed by using a CoMo conventional catalyst.Second,after H2Sremoval,the treated oil,with a remaining S content below500ppm,is again hydrotreated.In this latter case,the use of noble metal catalysts can be envisaged.In the present study dealing with this second stage reactor,we examined a catalytic system based on the addition of a low content of Pt to a commercial sulfide catalyst.An enhancement in catalytic activity can be obtained in the conversion of model molecules(tetralin anddibenzothiophene)as well as a hydrotreated straight run gas oil.The promotion effect strongly depends onthe preparation procedure which requires the impregnation of Pt on a presulfided commercial HDT catalyst.Advanced EXAFS and HRTEM characterizations were used to characterize the active phases.IntroductionThe primary goal of the recently proposed regulations by the European Community,as well as those which have appeared in United States or Japan,is to reduce the sulfur content in transportation fuels in order to minimize air pollution and prevent the poisoning of exhaust treatment catalysts.For instance,present EC or US regulation for the sulfur contents of diesel fuels is50ppm and is expected to be10ppm in2009.1 Thus,sulfur removal is still a major problem to be solved2and several approaches are proposed.3As a result of the tightening of these regulations,there has been a great interest in the research and development of refining processes and suitable catalysts.Even if the preparation of conventional hydrotreating catalysts has been improved and their reactivity enhanced by the use of P or organic additives,the severe operating conditions required to meet the objectives drastically reduces the catalyst life time.Thus,two-stage processes have been proposed and developed.4-6The objective of the first step is to reduce the sulfur content of the crude in order to decrease the H2S partial pressure in the second reactor.As a result,only organic compounds difficult to desulfurize(mostly substituted diben-zothiophenes)remain.The conversion of these sterically hindered molecules mainly proceeds via the hydrogenation route instead of the direct desulfurization route which is dominating for molecules like dibenzothiophene.2,7,8Therefore,a way to overcome the low reactivity of4,6-DMDBT would be to favor the hydrogenation pathway.Noble metal supported on silica-alumina or NiW sulfide supported on alumina catalysts were found to be promising systems for the desulfurization of a straight run gas oil containing760ppm of S.9,10Besides,by doping conventional systems with small amounts of Pt,a benefit in catalytic activity could be expected. This has been done for improving the catalytic activities of MoS2 with Pt either as a dopant11-14or as a catalyst mixture(MoS2/ Al2O3+Pt/Al2O3).15Some of these authors pointed out the importance of an impregnation of Pt on already sulfided Mo on alumina catalysts.13,14EXXON patented the preparation of a Pt doped NiMo supported on alumina catalysts,16the Pt being introduced with a S-containing precursor with ligands such as dithiocarbamates.More recently the use of mixed clusters such as[Pt(NH3)4](Mo6S8)S,x(H2O/MeOH)]was also proposed.17A favorable effect of the addition of Pt or Rh on CoMo catalysts was also reported by Vanhaeren.18The objective of the present study was to examine the effect of the addition of Pt on three industrial sulfide catalysts,i.e., CoMo,NiMo,and NiW supported on alumina,in the context of ultra-deep desulfurization,i.e.,in the presence of a low partial pressure of H2S.Hydrogenation properties and hydrodesulfur-ization properties were characterized by means of test reac-tions:tetralin hydrogenation and dibenzothiophene desulfur-ization.Moreover,the conversion of gas oils in a trickle bed reactor was also examined.The catalysts were characterized mainly by X-ray absorption spectroscopy.Experimental Sectionmercial NiMo,CoMo(14wt%MoO3,3wt %NiO or CoO),or NiW(25.7wt%WO3,3.82wt%NiO)on alumina catalysts were used.The Pt catalyst was prepared by impregnation of a250m2/g alumina with H2PtCl6(0.3wt%), then calcined for1h at773K,and reduced under pure H2during 6h at573K.Mixed PtNiW/Al2O3or PtCo(Ni)Mo/Al2O3 catalysts(0.15<Pt wt%<0.7)were obtained by deposition of H2PtCl6precursor either on the oxidic form of the commercial catalyst(so-called Pt/NiW ox,Pt/NiMo ox,or Pt/CoMo ox)or on the sulfided one(so-called Pt/NiW sulf,Pt/NiMo sulf,Pt/ CoMo sulf).In both cases,the impregnated catalysts were dried at393K.Then,the commercial samples and mixed catalysts*To whom correspondence should be addressed.Tel.:(0)47244 5336.Fax:(0)472445390.E-mail:geantet@rs.fr.†Institut de Recherches sur la Catal.‡Laboratoire d’Electrochimie et Physico-chimie des Mate´riaux et des Interfaces.§Laboratoire de Cristallographie.#Laboratoire de Re´activite´de Surfaces Paris.3877Ind.Eng.Chem.Res.2007,46,3877-388310.1021/ie060932x CCC:$37.00©2007American Chemical SocietyPublished on Web12/16/2006were sulfided using gas flows of 5vol %H 2S in H 2at 673K for 4h (heating rate 10K/min).After cooling down to room temperature under the same sulfiding mixture and flushing with nitrogen for 30min,the catalysts were transferred under argon and kept in sealed vessels.Catalytic Activity.The catalysts were tested by means of three reactions:the hydrogenation of tetralin,the hydrode-sulfurization of dibenzothiophene (DBT),and the straight run (SR)gas oil conversion.Experiments on model molecules were carried out in a microreactor running in the dynamic mode,in the vapor phase.The operating conditions were the following for tetralin hydrogenation:reaction temperature,573K;total pressure,43×105Pa;tetralin partial pressure,8886Pa;H 2S partial pressure,550ppm or 0(to check the stability of the catalysts).For DBT conversion,the reaction temperature was kept at 523K with a total pressure of 34×105Pa,a DBT partial pressure of 480Pa,and no H 2S addition.According to the model of the integral reactor,the rate constant k of a reaction can be expressed as follows:x )conversion,m )mass of catalyst (g),F 0)molar flow of reactant (mol/s),C 0)concentration of reactant (mol/L).When the conversion is less than 15%,the above formula can be simplified,giving the following reaction rate:The rates were measured when the steady state of the catalyst was reached after 15h on-stream.The accuracy is within (5%.Catalytic rates were also measured in a trickle bed reactor described in references 19and 20using hydrotreated gas oils as feeds.The reactions were performed at 613K,with a 2<LHSV <10h -1(LHSV:liquid hourly space velocity),and a total pressure of 3Mpa (catalyst weight 0.5<m <1g).The ground catalysts were placed between two layers of alumina in an up-flow tubular reactor (2cm 3).The composition of the starting gas oil feeds is given in Table 1.A periodic sampling of the liquid effluent was performed,and the total sulfur content was determined by X-ray fluores-cence (HORIBA SLFA-1800H analyzer),careful attention being paid on matrix effects.21Kinetic orders n were obtained from the fitting of f (n ))1/LHSV according to the following expression (for n *1):with S i and S o corresponding to S concentration at the entrance and at the exit of the reactor,respectively.Then,rate constants k app were calculated according to the expression above.Catalyst Characterization.Chemical analysis was used to control the metal contents of the catalysts.The dispersion of the catalysts was determined by TEM performed on a JEOLTable position and Physical Properties of Straight Run Hydrotreated Gas Oil Feeds (A and B)gas oil Agas oil B density (288K)g/L 846852sulfur content (ppm)515142aromatics (wt %)3630Table 2.Catalytic Activities in Gas Oil Conversion of Conventional Alumina Supported Sulfides acatalystCoMo NiMo NiW gas oil 515ppm Sk app (103g 1,9mmol -1,9h -1)13.214.614.2gas oil 142ppm Sk app (106g 2,8mmol -2,8h -1)1616.315.4aInitial wt %S content:(a)515ppm S and (b)142ppmS.Figure 1.Stability in the conversion of tetralin of NiMo and NiW sulfide catalysts under reducing conditions.Figure 2.Catalytic activities in tetralin hydrogenation at 45KPa (500ppm H 2S)of (a)NiW,(b)CoMo,and (c)NiMo on alumina,Pt on alumina,and mixed catalysts prepared by impregnation of Pt on the sulfided form (sulf)or oxidic form (ox).1n -1((1S o)(n -1)-(1S i)(n -1)))k app LHSVk )F 0mC 0ln(1-x )(L s -1g -1)r )F 0mx (mol s -1g -1)3878Ind.Eng.Chem.Res.,Vol.46,No.12,20072010-FEG instrument equipped with a Link-Isis EDS detector.Catalyst grains were dispersed in pure ethanol,the suspension stirred in an ultrasonic bath,and one drop deposited on a carbon coated copper grid.X-ray absorption spectroscopy (XAS)measurements were performed using BM32beam line at the ESRF (French Collaborative Research Group).The storage ring operated at 6GeV in the multi-bunch mode (2/3filling)with a 200mA current.Experiments were performed at Pt L III edge in the fluorescence detection mode performed with a 30-element solid-state detector (Canberra).The sulfidation procedure was carried out in a dedicated in situ furnace adapted for fluorescence detection from the cell described in reference 22.This activation process was carried out in a way similar to the laboratory procedure under an H 2/H 2S (5%)flow from room temperature up to 673K (rising temperature 4K/min,gas flow 50mL/min).Standard analysis of the EXAFS spectra (normalization,background removal,Fourier transformation,and curve fitting)were carried out usingTable 3.Catalytic Activities in DBT Conversion and Gas Oil Conversion a of NiW on Alumina,Pt on Alumina,and Mixed PtNiW on Alumina CatalystscatalystPt(0.3)/Al 2O 3NiW/Al 2O 3Pt(0.3)NiW sulfPt(0.3)NiW oxDBTk (10-3L g -1s -1)0.8 2.5 3.50.7gas oilk app (106g 2,8mmol -2,8h -1)1310199aInitial wt %S content:142ppm.Figure 3.Effect of Pt loading on the catalytic activities (or conversion)of PtNiW on alumina catalysts in tetralin conversion (HYD)and gas oil conversion.Figure 4.HRTEM image of a Pt(0.3)NiW on alumina catalysts prepared from impregnation of Pt on the sulfided catalyst.Ind.Eng.Chem.Res.,Vol.46,No.12,20073879the SEDEM software 23with FEFF624theoretical phase and amplitude functions.The curve fitting procedure was performed in R -space.Fourier transformation of the normalized k 3-weighted EXAFS signal was performed over the 2.5-15Å-1k -range with Kaiser window functions.Coordination numbers (N ),interatomic distances (R ),Debye -Waller parameters (σ2),and energy shifts(∆E 0)were used as variables in the fitting procedure.Scale factors S 02were fixed at 0.8.ResultsCatalytic Properties of Conventional Catalysts.Conven-tional industrial sulfide catalysts were investigated in the conversion of the two SR gas oil hydrotreated feeds containing,respectively,515and 142ppm of S.By varying the LHSV,we determined for each reacting oil the kinetic order with respect to S and found it respectively equal to 2.9and 3.8.These kinetic orders express the wide reactivity scale of the various refractory S compounds remaining in the desulfurized oil.25It can be seen in Table 2that the three catalysts present almost the same activity.However,the stability of the sulfided catalyst is also an important factor and depends on the partial pressure of H 2S.It is known that CoMo catalysts segregate under reducing condi-tions (pure H 2)26and therefore are less stable than in the presence of H 2S.The stability of the other industrial catalysts,i.e.,NiW and NiMo,was checked in the conversion of tetralin.After stabilization of the activity under 500ppm of H 2S,the addition of this gas was suppressed and the evolution of the conversion was measured as illustrated in Figure 1.It can be seen that the NiW system is the most stable catalyst in the absence or with low partial pressure of H 2S in agreement with previous reported in the literature.27Catalytic Properties of Pt Based Systems.In order to improve the catalytic performance of conventional industrial catalytic systems and favor the hydrogenation pathway of the desulfurization scheme,these catalysts were doped with a small amount of Pt.The activity of Pt on alumina,NiW,NiMo,and CoMo on alumina catalysts alone or doped with 0.3wt %of Pt were measured in tetralin conversion (Figure 2).Among commercial catalysts,NiW is the most active one.In all cases,an improvement in the catalytic hydrogenation activity is observed when Pt is added after the sulfidation of the com-mercial catalyst.In that case,the catalytic properties seem to correspond to the addition of the properties of each component.On the contrary,when Pt is impregnated on the oxidic form of the catalyst a sharp decrease in the activity is observed.The NiW system was then studied in the conversion of DBT (see Table 3).Figure 5.Normalized absorption spectra at Pt L III edge of the catalysts after impregnation of H 2PtCl 6and drying on (a)oxidic CoMo and (b)sulfided CoMo catalysts.Figure 6.Magnitude of the Fourier transformed k 3-weighted data on (a)oxidic CoMo and (b)sulfided CoMo catalysts (top)and after sulfidation with a 5vol %H 2S in H 2gas mixture.3880Ind.Eng.Chem.Res.,Vol.46,No.12,2007A similar trend,i.e.,addition of the properties of each component,is observed when Pt is added on a presulfided NiW on alumina catalysts.Thus,we can expect that the conversion of a real feed can be increased by the use of such a mixed system.Table3gives the rate constants in the conversion of gas oil B.Again,we notice an enhancement of the rate for the mixed catalysts as compared to the unpromoted one.As compared to tetralin hydrogenation,Pt on alumina catalyst exhibits a much higher activity with respect to NiW catalyst. This effect can be ascribed to a weaker inhibiting effect of H2S due to the lower sulfur content of the feed.Under these specific conditions,Pt is less inhibited by H2S and the feed is composed of refractory alkyl DBT which are mainly converted by the hydrogenation route.2The variations of the catalytic properties with the amount of Pt added to the NiW catalyst were studied in both tetralin and gas oil conversion reactions(see Figure3).Although these variations are not exactly similar,it appears that a loading of 0.25-0.3wt%of Pt gives the best improvement in the catalytic activity.Nanoscale Characterization of the Catalysts.Character-ization by HRTEM.Both types of catalysts were characterized after sulfidation by HRTEM.For sulfided Pt(0.3)/NiW sulf, HRTEM pictures show NiW sulfide slabs and small particles with an average size of0.8nm(see Figure4)composed of Pt as revealed by1nm probe analysis with EDS.Due to the background emission of neighboring(Ni)WS2particles and the radiolytic effect of the small electron probe,the presence of S on these particles(and the stoichiometry)cannot be determined. Nevertheless,it can be concluded from these examinations that sulfide NiW slabs and Pt containing particles are separated systems.The sizes of the WS2slabs,i.e.,average length3.1 nm,and average number of layers,i.e.,2,are not very different from those reported previously for NiW catalysts,28,29but a slight decrease in the length can be noticed.The dispersion of the reference catalyst composed by0.3wt%of Pt on alumina was also determined by HRTEM,the average size of the particles being close to1.5nm by comparison to0.8nm for the mixed catalyst.This means that both phases“NiWS”and Pt are highly dispersed.By contrast,Pt cannot be observed by HRTEM in sulfided Pt(0.3)/NiW ox catalyst,which can be due either to the small size of the Pt containing particles(less than the resolution limit of the TEM,i.e.,0.8nm)or to their close vicinity to dense WS2particles.The morphology of this last phase (length and stacking)is similar to that of sulfided Pt(0.3)/ NiW sulf.XAS Characterization of the Precursor and Sulfided States of the Catalysts.Further information on the chemical nature of the noble metal nanoparticles as well as on the role of the preparation procedure was obtained by means of XAS performed before and after sulfidation under in situ conditions (5vol%H2S in H2at673K,for30min,heating rate5K/min). In order to avoid the overlap of adsorption edges(Pt L III:11564 eV and W L II:11544eV),the CoMo sulfide system was chosen instead of the NiW one.The XANES spectra of the Pt(0.3)/ CoMo ox catalyst and Pt(0.3)/CoMo sulf after impregnation by hexachloroplatinic acid and drying at393K are presented in Figure5.For Pt(0.3)/CoMo ox,some Pt-O bonds are formed as already reported for Pt/Al2O3catalysts.30,31The presence of these Pt-O bonds gives rise to a strong white line.By contrast, the Pt(0.3)/CoMo sulf sample presents a different electronic configuration indicating another nature of the Pt-neighboring atoms bonds as compared to the previous sample.The XANES spectra is similar to the one obtained on the sulfided catalyst (either Pt(0.3)/CoMo ox or sulf)suggesting that the electronic configuration of Pt is close the one obtained after in-situ sulfidation.The Fourier transforms at Pt L III edge are presented in Figure 6(top)and the results deduced from the EXAFS fitting summarized in Table4.After impregnation and drying,the Pt neighborhood for Pt(0.3)/CoMo ox sample consists of O and Cl atoms.For the Pt(0.3)/CoMo sulf sample,there is no O shell contribution but XAS is not able to distinguish between Cl or S neighboring atoms.Thus,either the platinum chloride precursor remains unmodified at the surface of alumina or,more probably,interacts with S surface atoms(SH entities)and a partial substitution of Cl by S atoms occurs in the neighboring shell of Pt atoms(both cases are presented in Table4).These Pt-S bonds are rather stable,and they are not expected to be strongly oxidized by the drying procedure.32After sulfidation, the Pt local structure is schematized in Figure6(bottom)by the magnitude of the Fourier transform,as a function of real space separation R.For both samples,only one main contribu-tion is visible,and data fitting indicates that Pt is surrounded by four sulfur atoms like in the PtS structure.However,we were not able to introduce a second Pt-M shell.This is indicative of the high dispersion of PtS particles as observed in the case of sulfided Pt(0.3)/CoMo sulf sample by HRTEM.Due to the high disorder of the Pt phase,it has not been possible either to characterize any interaction with WS2for sulfided Pt-(0.3)CoMo ox as proposed above for explaining the HRTEM data.DiscussionThe calcined state of CoMo,NiMo,and NiW supported on alumina catalysts has been studied by many techniques.33It was proposed by several authors that at this precursor stage an interaction between the promoter,Co or Ni,and the polymo-lybdate or polytungstate phase already exists.This interaction would prevent the formation of MoO3or WO3at high Mo or W loading and would lead to a high dispersion of the promoter.Table4.Structural Parameters Obtained from EXAFS Fitting for Impregnated and in Situ Sulfided PtCoMo Catalysts Prepared from the Oxidic or Sulfidic Statesample M neighbor K min(Å-1)K max(Å-1)R Pt-M N Pt-M E0(eV)σ2(Å2)Impregnated StatePtCoMo ox O313.7 2.064120.008 PtCoMo sulf Cl a313.7 2.33 1.5160.002 PtCoMo sulf Cl313.7 2.31 3.69.20.005 PtCoMo sulf S a 2.3348.30.0049Sulfided StatePtCoMo ox S313.5 2.3448.20.005 PtComo sulf S313.5 2.3347.80.005a S or Cl cannot be distinguished by XAS.Ind.Eng.Chem.Res.,Vol.46,No.12,20073881The interaction of Pt with molybdenum or a tungsten oxidic phase has also been addressed previously.In a comprehensive study of PtW catalysts,De Penguilly observed several kinds of interaction between both components depending on W concen-tration.34At high W loadings,Pt can be either grafted on the free alumina space left after polytungstates formation or linked to the tungstate phase by hydrogen bonding.Such a kind of interaction between Pt and W would explain HRTEM results since it has not been possible to detect distinct Pt particles in sulf Pt(0.3)NiW ox,probably because they are in close vicinity of the dense WS2sulfide phase either in a kind of decoration or between alumina and WS2slabs.In accordance with EXAFS data,the Pt phase is very well dispersed.However,whatever the nature of the mixed catalysts, CoMo or NiW,a large decrease in the catalytic properties was observed when Pt was added on the oxide form of the catalyst precursor.The close neighboring of Pt and WS2may prevent the formation of some highly active so-called“CoMoS”(or “NiWS”)entities.In the case of sulfided Pt(0.3)/NiW sulf catalyst,the isolated PtS particles independently contribute to the catalytic activity providing an additive effect.The benefit of the sulfidation for the formation of“CoMoS”is kept even after impregnation of the Pt,indicating that the negative effect originates from oxidic interactions.However in order to keep the additive effect,only a small content of Pt(0.2<wt%Pt<0.4)must be added. We can suggest that a higher Pt content gives rise to larger and less active particles.ConclusionIn order to achieve ultra-deep desulfurization,improved catalysts are needed.In the framework of a two-stage process, a tentative solution is provided by the addition of a small amount of noble metal to a conventional catalyst.This allows a20%to 40%increase in the activity as compared to the unpromoted sulfide catalyst.The benefit originates from the addition of the catalytic properties of each individual system.However,such an effect requires the impregnation of Pt on a sulfided NiW on alumina catalyst otherwise,if Pt addition is performed on the oxidic catalyst,detrimental interactions between Pt and“NiWS”or“CoMos”occur.AcknowledgmentThis work received support from TotalFina,ELF,IFP, Procatalyse,and CNRS-Ecodev.We thank the French-CRG committee for providing machine-time.F.Bourgain and M. Cattenot are gratefully acknowledged for the realization of the in situ cell.We thank also mbert for fruitful discussion on the Pt-W system.Literature Cited(1)European Union,EU directive98/70/EC,1998.EPA,Control of air pollution from new motor vehicles amendment to the tier-2/gasoline sulfur regulations,U.S.Environmental Protection Agency,April13,2001.(2)Breysse,M.;Djega-Mariadassou,G.;Pessayre,S.;Geantet,C.; Vrinat,M.;Perot,G.;Lemaire,M.Deep desulfurization:reactions,catalysts and technological challenges,Catal.Today2003,84,129-138.(3)Song,C.An overview of new approaches to deep desulfurization for ultra-clean gasoline,diesel fuel and jet fuel.Catal.Today2003,86, 211-263.(4)Sie,S.T.Reaction order and role of hydrogen sulfide in deep hydrodesulfurization of gas oils:consequences for industrial reactor configuration.Fuel Process.Technol.1999,6,149-171.(5)Stork,W.H.J.Molecules,catalysts and reactors in hydroprocessing of oil fractions.Stud.Surf.Sci.Catal.1997,106,41-67.(6)Bej,S.K.Revamping of diesel hydrodesulfurizers:options available and future research needs.Fuel Process.Technol.2004,85,1503-1517.(7)Whitehurst,D.D.;Isoda,T.;Mochida,I.Present state of the art and future challenges in the hydrodesulfurization of polyaromatic sulfur compounds.Ad V.Catal.1998,42,345-471.(8)Bataille,F.;Lemberton,J.L.;Michaud,P.;Pe´rot,G.;Vrinat,M.; Lemaire,M.;Schulz,E.;Breysse,M.;Kasztelan,S.Alkyldibenzothiophenes hydrodesulfurization:promoter effect,reactivity and reaction mechanism. 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Nanoconfinement effects on the reversibility of hydrogen storage in ammonia borane: A first-principles studyKiseok Chang, Eunja Kim, Philippe F. Weck, and David TománekCitation: The Journal of Chemical Physics 134, 214501 (2011); doi: 10.1063/1.3594115View online: /10.1063/1.3594115View Table of Contents: /content/aip/journal/jcp/134/21?ver=pdfcovPublished by the AIP PublishingArticles you may be interested inMechanism of ammonia decomposition and oxidation on Ir(110): A first-principles studyJ. Chem. Phys. 138, 144703 (2013); 10.1063/1.4798970First-principles study of hydrogenated carbon nanotubes: A promising route for bilayer graphene nanoribbons Appl. Phys. Lett. 101, 033105 (2012); 10.1063/1.4737427First-principles study of hydrogen adsorption in metal-doped COF-10J. Chem. Phys. 133, 154706 (2010); 10.1063/1.3503654Strain effects on hydrogen storage capability of metal-decorated graphene: A first-principles studyAppl. Phys. 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Phys. 130, 024507 (2009); 10.1063/1.3042270THE JOURNAL OF CHEMICAL PHYSICS134,214501(2011) Nanoconfinement effects on the reversibility of hydrogen storage in ammonia borane:Afirst-principles studyKiseok Chang,1Eunja Kim,2Philippe F.Weck,3and David T ománek1,a)1Physics and Astronomy Department,Michigan State University,East Lansing,Michigan48824-2320,USA2Department of Physics and Astronomy,University of Nevada Las Vegas,4505Maryland Parkway,Las Vegas, Nevada89154,USA3Department of Chemistry,University of Nevada Las Vegas,4505Maryland Parkway,Las Vegas,Nevada89154,USA(Received9March2011;accepted5May2011;published online1June2011)We investigate atomistic mechanisms governing hydrogen release and uptake processes in ammonia borane(AB)within the framework of the density functional theory.In order to determine the most favorable pathways for the thermal inter-conversion between AB and polyaminoborane plus H2, we calculate potential energy surfaces for the corresponding reactions.We explore the possibility of enclosing AB in narrow carbon nanotubes to limit the formation of undesirable side-products such as the cyclic compound borazine,which hinder subsequent rehydrogenation of the system.We also explore the effects of nanoconfinement on the possible rehydrogenation pathways of AB and suggest the use of photoexcitation as a means to achieve dehydrogenation of AB at low temperatures.©2011American Institute of Physics.[doi:10.1063/1.3594115]I.INTRODUCTIONHydrogen is widely regarded as a cost-effective,re-newable,and clean energy alternative to fossil fuels for transportation applications.1From the research effort con-ducted in solid-state materials capable of storing hydrogen, the NH3BH3compound called ammonia borane(AB),with an ideal storage capacity of19.5wt.%H2and a reported release,2,3of up to≈13wt.%H2below200◦C,has emerged as one of the most promising candidate materials to meet the2015volumetric( 82g H2l−1)and gravimetric( 90 g H2kg−1)density targets specified by the U.S.Department of Energy for on-board hydrogen storage.4At room temperature,AB crystallizes in a stable plastic phase with the tetragonal I4mm structure.5Upon thermally induced decomposition,AB releases H2in a two-step exothermic process.2,3,6–8The initial dehydropolymerization step occurs between343K and385K,yielding≈1mol H2and polyaminoborane(PAB)products,[BH2NH2]n ( H=−1.57kcal mol−1).9PAB further decomposes in the temperature range of383−473K,releasing hy-drogen and polyiminoborane(PIB)products,[BHNH]n ( H≈−9.5kcal mol−1).9The ultimate decomposition step leading to the formation of planar BN at≈1500K is not con-sidered practical for storage purposes.Several species,such as borazine(c-B3N3H6),cycloborazanes,or diammoniate of diborane(DADB,NH3BH2NH3+BH4),have been observed concurrently to the formation of PAB and PIB,depending on the decomposition conditions of AB.3,6–8,10,11Some mechanistic and thermodynamical aspects of these decomposition processes have been investigated in recent computational studies.9,12–15Still,the microscopic pathway of the AB dehydrogenation process has not been understood a)Electronic mail:tomanek@.in full detail yet.Also,optimum conditions have yet to be found for AB rehydrogenation and suppression of volatile by-products such as borazine,which can poison the catalyst material of proton exchange membrane fuel cells.Recent ap-proaches to remedy these problems have focused on tuning thermodynamic properties and controlling reaction pathways using catalysts,15–17modified AB materials,18,19ionic liquid solvents,10or encapsulating AB in mesoporous materials.20–23 Even though significant experimental advances have been achieved,fundamental understanding of these processes is still missing.In this manuscript,we study the governing mecha-nisms associated with hydrogenation and dehydrogenation processes of ammonia borane.Our objective is to better utilize this unique material by examining the energy profiles associated with the conversion of the AB molecular solid to polymeric molecules and hydrogen.Wefirst investigate the two-step dehydrogenation process and then explore encapsu-lation of AB molecules inside nanopores and nanotubes as a potentially viable pathway for AB rehydrogenation.Details of our computational approach are given in Sec.II,followed by a discussion of our results in Sec.III.A summary of ourfindings and conclusions is given in Sec.IV.PUTATIONAL METHODFirst-principles total-energy calculations based on density functional theory(DFT)were carried out using the SIESTA code24to determine the optimum geometry of AB in the solid phase and to examine energetically preferred pathways for the dehydrogenation and rehy-drogenation processes.We used the standard Kohn-Sham self-consistent method within the local density approxi-mation with the Perdew-Zunger25parametrization of the0021-9606/2011/134(21)/214501/7/$30.00©2011American Institute of Physics134,214501-1214501-2Chang et al.J.Chem.Phys.134,214501(2011) exchange-correlation functional in the uniform electron gas.Since the weak inter-molecular interactions in our system are dominated by electrostatic and weak covalent interactions causing band dispersion,this energy functional should pro-vide an adequate description of the equilibrium structure and elastic properties.26We furthermore used a general andflex-ible linear combination of numerical atomic orbital basis and norm-conserving Troullier-Martins pseudopotentials27in the nonlocal Kleinman-Bylander form.28Our basis consisted of pseudo-atomic-orbitals(PAOs)generated by the split-valence scheme for a double-ζpolarization basis set.All calculations were performed using periodic boundary conditions in supercell geometry.Depending on the context of a particular calculation,we used supercells containing two or more AB molecules.We sampled the reciprocal space by k−point grids with comparable densities in all our calculations,with the minimum number of6k points in the smallest Brillouin zone. We limited the energy shift due to the spatial confinement of the PAO basis functions29,30to less than30meV.The charge density and pseudopotentials have been determined on a real space grid with a very high mesh cutoff energy of 200Ry,which is sufficient to converge the total energy to within1meV/atom.We used the conjugate gradient method for geometry optimization.A structure was considered opti-mized when none of the residual forces exceeded0.01eV/Å. Complementary microcanonical molecular dynamics(MD) simulations were performed at the same level of theory to investigate the thermodynamical properties and the mi-croscopic pathways for the dehydrogenation processes.A time-step of1fs was used in all simulations with a maximum simulation time of2ps.The temperature range of our MD simulations extended up to1500K.III.RESULTS AND DISCUSSIONWe have studied the structure and energetics of AB and related compounds in order tofind the most efficient microscopic reaction pathways for the dehydrogenation and rehydrogenation processes and investigated new possible methods for efficient rehydrogenation of AB under mild conditions.We have focused our studies on identifying the different crystal structures of AB,the equilibrium structure of DADB and its formation energetics,and the microscopic pathway of AB dehydrogenation processes.We have then ex-plored possible ways to improve the de-and rehydrogenation process of AB by using photoexcitations and by confining BN-based molecules in narrow carbon nanotubes(CNTs). A.Crystal structures of AB and the role of the dihydrogen bondBoraneamines in the condensed phase show a propensity to form N−Hδ+···δ−H−B close contacts as a result of the inter-molecular interaction between the NH proton and the adjacent HB bond,as seen in Fig.1(a).For this peculiar type of hydrogen bond,commonly referred to as the dihy-drogen bond,the H···H distance is typically in the range of 1.7−2.2Å,thus significantly shorter than the sum of the van der Waals radii of two hydrogen atoms,2.4Å.The hydrogen(a)(b)(e)zy(c)(d)zy(f)zyHBNchargeFIG.1.Optimized geometry of orthorhombic and tetragonal crystals of AB and DADB-AB.(a)Local geometry of AB molecules,withθdenoting the an-gle between neighboring molecules in the orthorhombic crystal.(b)Charge difference plot depicting two AB rger lobes,highlighted in blue,indicate the region with excess positive charge and smaller lobes,high-lighted in red,the region with excess negative charge,establishing a per-manent dipole.The dipole-dipole interaction stabilizes the dihydrogen-bond network moment in the crystal.(c)Optimized structure of the orthorhombic crystal withθ=22◦(θexpt=20.4◦).(d)Optimized structure of the tetrag-onal crystal with all AB molecules aligned along the same direction.Opti-mized structure of two AB molecules(e)and DADB(f)in the AB tetragonal crystal.The region,where the2AB→DADB transformation takes place,is shaded in(e)and(f).The backbones of AB and DADB involved in this reac-tion are highlighted by the white dotted lines in(e)and(f).B and N atoms in DADB are distinguished by shading in(f).atom connected to nitrogen carries a partial positive charge (Hδ+)and the hydrogen atom connected to boron a partial negative charge(Hδ−),as seen in Fig.1(b).Along with the covalent N−H···σbonds,the weaker N−Hδ+···δ−H−B dihydrogen interactions with a bond strength of≈0.3eV, stabilized by the Coulomb attraction between hydrogen atoms carrying opposite charges,largely contribute to stabilizing the molecular crystal at room temperature.At this point,it is useful to remember that ethane,the homonuclear equivalent to AB with no dihydrogen bonds,is not a solid,but rather forms a gas at room temperature.Our calculations show that the lowest-energy crystal structures of AB are orthorhombic and tetragonal molecu-lar crystals,depicted in Figs.1(c)and1(d).According to experiment,the low-temperature orthorhombic structure of AB undergoes a phase transition to the high-temperature tetragonal phase31–33at225K.The optimized structure of the Pnm21orthorhombic lattice is characterized by the lat-tice constants a=5.142Å,b=4.588Å,c=4.772Å,and the angleθ=20◦between neighboring AB molecules.This structure,shown in Fig.1(a),agrees rather well with exper-imental data.32,34The small difference between thefinite-temperature experimental valueθexpt=20.4◦and the theo-retical valueθtheo=22◦obtained at T=0may be attributed to anharmonicities in the interactions that are explored in the molecular crystal at nonzero temperatures.214501-3Nanoconfinement effects on the reversibility J.Chem.Phys.134,214501(2011)At T=0,wefind the orthorhombic Pnm21crystal to be energetically more stable than the tetragonal I4mm crystal by 49meV per AB molecule.At higher temperatures,changes in the vibrational entropy difference between the phases may overcome this small energy difference,causing a phase tran-sition.Wefind support for this generalfinding in our MD calculations,which indicate a stability reversal between the tetragonal and orthorhombic phase in terms of free energy differences between200and300K,which is very close to the experimental value of225K.B.Energetics and structural changes during the DADB formationFormation of diammoniate of diborane within the AB crystal is governed by changes in the dihydrogen bond net-work,which we study in a suitable supercell geometry.Ac-cording to our calculations,the DADB molecule possesses a large dipole moment comparable to that of the AB molecule. Also,the potential energy of DADB in the AB crystal is com-parable to that of AB in crystalline phase.To study the coex-istence of DADB with AB,we substituted DADB for two AB molecules in the tetragonal molecular crystal,as shown in the brown shaded region of Fig.1(e)(optimized AB crystal ge-ometry)and Fig.1(f)(optimized DADB geometry in the AB crystal).The large dipole moment of DADB further stabilizes the dihydrogen bond network,since the potential energy of the DADB tetragonal crystal is lower than that of the perfect AB tetragonal crystal by34meV per AB molecule.In terms of potential energy at T=0,the perfect defect-free orthorhombic AB crystal is the most stable structure, followed by the DADB tetragonal crystal,andfinally the perfect defect-free AB tetragonal crystal as the least stable of the three.Considering the fact that the tetragonal and orthorhombic AB crystal structures coexist at room tem-perature,formation of DADB in AB crystals is to be ex-pected on energy grounds,with supporting experimental evidence.33The geometry of NH3BH2NH3in DADB is simi-lar to that of polyaminoborane,the product of thefirst stage of dehydrogenation.C.Microscopic pathway of the dehydrogenation processInspection of our microcanonical molecular dynamics simulations at an average effective temperature of≈1500K reveals that hydrogen atoms attached to nitrogen and boron in ammonia borane are released and associate to a hydrogen molecule for a20fs time period.This process can be under-stood by studying reactions involving chains of AB molecules with one AB molecule per unit cell,as seen in the inset of Fig.2(a).In this particular study,we artificially increased the inter-chain separation to suppress the influence of neighbor-ing AB chains.To get detailed understanding of the optimum transition path independent of temperature and particular tra-jectories used in MD runs,we explore the potential energy surface of the system by performing constrained geometry op-timizations and show the results in Fig.2(a).In thefirst dehy-drogenation scenario NH3BH3→NH2BH2+H2,we consider pairs of distances(d N−H,d B−H)within the unit cell as indi-cated in the inset of Fig.2(a).Since the dehydrogenation pro-cess occurring in nature can be characterized by a sequence of (d N−H,d B−H)distance pairs,we use it as a prejudice-free reac-tion coordinate to characterize the reaction pathway.The po-tential energy surface E(d N−H,d B−H),presented in Fig.2(a), is the result of few hundred structure optimization studies, each of which considered specific values for the d N−H,d B−H distances that were keptfixed along with the unit cell size.The optimum trajectory from the initial geometry M1,represent-ing the equilibrium structure of AB in the crystal,over the bar-rier B to thefinal state M2containing an H2molecule per unit cell,is shown by the dashed line in Fig.2(a).The correspond-ing energy profile and structural snap shots along this trajec-tory,which corresponds to the reaction coordinate,is depicted in Fig.2(c).The reaction NH3BH3→NH2BH2+H2requires crossing the activation barrier of1.14eV per AB molecule. The net process is endothermic,requiring a0.75eV energy investment to occur,which is the reason for the short20fs time period during which a hydrogen molecule was formed as a result of temperaturefluctuations in our microcanonical MD simulation.Since dehydrogenation occurs as an activated exothermic process in nature,thefinal product should be more stable than isolated NH2BH2molecules.A possiblefinal product of the dehydrogenation of AB,which satisfies this condition, is polyaminoborane[BH2NH2]n.The second scenario of the dehydrogenation reaction that involves AB polymerization, n NH3BH3→[NH2BH2]n+n H2,is described in Figs.2(b) and2(d)and is indeed mildly exothermic.In analogy to thefirst dehydrogenation scenario,we considered pairs of distances(d x,A z),shown in the inset of Fig.2(b),useful to identify a prejudice-free reaction coordinate with focus on the polymerization.Also in this case,we artificially increased the size of the unit cell normal to the z axis to suppress the in-fluence of AB molecules away from the z-axis.The potential energy surface E(d x,A z),presented in Fig.2(b),is the result of few hundred structure optimization studies,each of which considered specific values for d x and A z.In our calculation, we consider two AB molecules per unit cell and keep their axes along the BN bond parallel to each other separated by d x.We expect the AB polymerization process to be initiated by reducing d x,accompanied by changes in the unit cell size A z in the axial direction.The most efficient pathway for this process,depicted by the white dashed line in Fig.2(b),indeed follows our expectations.Separation of the H2molecule from [NH2BH2]n is a necessary side-effect in thefinal state of the polymerization.Even though the net process is exothermic,it involves rather high activation barriers,as seen in Fig.2(d). The activation barrier values of4.29eV and3.35eV in the second scenario are much larger than the value of2×1.14eV in thefirst scenario with two AB molecules per unit cell.The origin of these high activation energy values is the strong inter-molecular repulsion and the reduced stability of the NH2BH3+H and NH3BH2+H complexes associated with the transition states.Even though these high activation energy values are expected to decrease,when artificial constraints such as relative axis orientation are relaxed,this reaction is unlikely to occur under experimental conditions.214501-4Chang et al.J.Chem.Phys.134,214501(2011)(a)d N -H (Å)d B-H (Å)0.00.51.0M 1M 2d B-Hd N-HB (c)(d)E (e V )B A C0.00.51.0 1.14eVM 1M 2Reaction coordinateE (e V )0.01.02.03.04.05.0A z (Å)1.01.52.02.5E(eV)M 1AB M 2C M 30.0DEd (Å)0.5d xA zE(eV)(b)d xd N-H d B-HHB NFIG.2.Microscopic pathways of the dehydrogenation process.(a)Contour plot of the potential energy surface as a function of d B −H and d N −H in the first dehydrogenation scenario,NH 3BH 3→NH 2BH 2+H 2,with d B −H and d N −H defined in the inset.The optimum dehydrogenation pathway is indicated by the dashed line.(b)Contour plot of the potential energy surface as a function of d x and A z in the second dehydrogenation scenario,n NH 3BH 3→[NH 2BH 2]n +n H 2.(c)Potential energy profile along the reaction coordinate for the first scenario.The selected structures (M 1,B ,M 2),are the snapshots in the process.M 1and M 2are the globally relaxed geometries of A and C ,respectively.B is the saddle point geometry on the potential energy surface.The dashed rectangle is the unit cell used in the calculation.(d)Potential energy profile along the reaction coordinate for the second scenario.Local minimum (M 1,M 2,M 3)and intermediate structures (B ,D )are shown below.Another possible scenario of dehydrogenation involves intermediate structures such as NH 3BH 2NH 3+BH 4(DADB)in the process.The formation of DADB in the dihydrogen bond network is energetically favorable due to its high polar-ity.Moreover,from a structural viewpoint,DADB is reminis-cent of a polymer.To check on the viability of this process,we calculate the potential energy surface of the DADB for-mation.In our model calculation we consider the formation of DADB from two isolated AB molecules.We find that a likely reaction may start with an initial dissociation of one of the AB molecules into NH 3and BH 3.Association of the ammonia and AB molecules would lead to the formation of NH 3BH 2NH 3,accompanied by the release of hydrogen from the BH 2site.Even though this reaction is weakly exothermic,in agreement with experimental observations,2the activation barrier of 3.59eV for this process appears too high,possibly due to the low stability of intermediate structures in our iso-lated system.Thus,we conclude that this reaction is unlikely to take place.In view of the fact that the observed thermolysis of AB is weakly exothermic and occurs under mild conditions,2we must conclude that this process is likely much more complex than described here.We can only speculate about more fa-vorable ways to form DADB in the AB molecular crystal,including autocatalytic reactions assisted by diffusing hydro-gen atoms in the matrix,since presence of hydrogen may reduce the activation barrier for the formation of DADB.Once NH 3BH 2NH 3forms in the crystal,its presence can pro-mote exothermic polymerization of AB by dehydrogenation.It is fair to assume that at any given point,we may find PAB segments of different length and possibly even branched polymers among the dehydrogenation products.We observe nonvanishing net charges only at the extremities of these products.Since the dihydrogen bonds,which are responsible for the formation of the molecular crystal,are stabilized by Coulomb attraction between charged extremities,the mixture of different dehydrogenated polymers will likely form a dis-ordered dihydrogen-bonded network that bears little resem-blance with the ordered AB crystal.D.Photo-assisted dehydrogenationAchieving dehydrogenation under mild conditions is an-other challenge if AB is to become a practical hydrogen storage medium.Most research effort in this area has fo-cused on the use of chemical catalysts to reduce the activa-tion barrier for dehydrogenation in order to lower the reaction214501-5Nanoconfinement effects on the reversibility J.Chem.Phys.134,214501(2011)temperature.Here,we explore an alternative way to accel-erate dehydrogenation by modifying the interatomic interac-tions in the photo-excited state.To study deviations from dy-namics in the ground state with electrons at T el=0,we re-populate the electronic levels according to the Fermi-Diracdistribution at T el>0,which modifies the charge distribution and thus the potential energy ing k B T el=2eV for the effective electronic temperature,which may be achieved by laser irradiation,35wefind that the activation barrier for NH3BH3→NH2BH2+H2is0.61eV per AB molecule, which corresponds to nearly a50%reduction from the pre-viously stated ground-state value1.14eV.This result indi-cates that changes in the potential energy surface associated with electronic excitations can be significant.This reduction of the activation barrier is partly caused by changing the pop-ulation of molecular orbitals that modifies the forcefield.Ad-ditional contributions to the free energy come from electronic entropy and also depend on geometry.In the present case,the electronic entropy contribution at the global minimum geom-etry is S e=6.16k B,whereas the contribution at the saddle point corresponding to the transition state is S e=6.60k B.At nonzero temperatures,this effect reduces the free energy acti-vation barrier and thus speeds up the reaction.E.Energetics of B–N based molecules inside a carbon nanotubeEven though AB is one of the best candidates for hydro-gen storage,it is not clear how to rehydrogenate products of the decomposition reaction in an efficient and cost-effective way.Here we explore the possibility to utilize narrow CNTs as a generic AB storage medium that may facilitate the re-hydrogenation process,ignoring for the moment the fact that adding nanotubes would increase the weight and thus reduce the storage capacity.The objective is to form ordered AB ar-rays within the narrow space inside the CNTs in order to con-trol the polymerization pathway during dehydrogenation and thus to facilitate rehydrogenation.We investigated the energetics of AB and B–N based molecules such as the AB monomer and dimer,AB poly-mer,cyclotriborazane,and borazine inside narrow CNTs us-ing DFT calculations.We found that all of these are energet-ically more stable inside the hollow(6,6)CNT than in the vacuum.AB molecules favor the space inside a(6,6)CNT, where they form an ordered chain,since they gain nearly0.3 eV with respect to the crystalline environment.We distin-guish two components of the energy gain that originate from either the intermolecular interaction or from the molecule-CNT interaction.Since the main purpose of introducing the CNT as a container is the narrow cylindrical cavity inside, we represented the CNT surrounding B–N based molecules by a soft potential well with cylindrical symmetry.The ra-dial part of the potential well is determined by DFT calcu-lations of the angularly and axially averaged interaction be-tween the enclosed molecule and the graphitic nanotube wall. This approach correctly reproduces the interaction between B–N based molecules and the CNT wall,which–depending on the molecule–varies between−0.7eV and−0.5eV,while ignoring the discreteness of the carbon lattice.In absence of the AB-CNT interaction,AB molecules forming chains inthis cylindrical potential are less stable by0.21eV than ABmolecules in the molecular crystal.Taking the AB-CNT at-traction into account,the AB molecule inside the CNT be-comes more stable by0.3eV inside the CNT than in the crys-tal.Thus,AB molecules favor entering a narrow nanotube toform linear arrangements.The imposed geometry constraintsmay suppress formation of unwanted side products of the de-hydrogenation reaction.F.Rehydrogenation of PAB inside a carbon nanotubeAs mentioned above,the most severe drawback in utiliz-ing AB is the lack of any practical way to regenerate the initialAB system from its dehydrogenation products.As a workinghypothesis,we assume that the reported benefits of enclosingAB in mesoporous media20–23are associated with constrain-ing the degrees of freedom of AB and thus suppressing un-desirable structural changes.Considering a narrow CNT asa generic enclosure for AB and its dehydrogenation products,we study in the following the rehydrogenation process of PABin this environment and present our results in Fig.3.The calculated potential energy surface associated withthe rehydrogenation process of PAB is shown in Fig.3(a).We consider pairs of distances(d N−H,d B−H)within the unit cell as a useful way to determine a prejudice-free reaction co-ordinate,with the quantities defined in the inset of Fig.3(b).Each point in the potential energy surface E(d N−H,d B−H), presented in Fig.3(a),represents a structure that has been individually optimized by keeping only d N−H,d B−H and the unit cell sizefixed.The schematic geometry of PAB inside a(6,6)CNT,which is represented by the previously defined potential well in our calculations,is shown in Fig.3(c).Since the potential energy surface in Fig.3(a)is based only on structural optima,the dashed line connecting the open circles represents the energetically most favorable pathway from state E,corresponding to H2far away from PAB,across a potential energy barrier to state A,representing two AB molecules as the desired end-product of rehydrogenation. The corresponding energy profile along this pathway is depicted in Fig.3(b)by the dashed line connecting the open circles.Snap shots of atomic arrangements and the charge density for selected intermediate structures are depicted in Fig.3(d).Taking the system labeled M1,representing the optimum structure of PAB and H2before hydrogenation,as a reference,the rehydrogenation step should require crossing an energy barrier of3.5eV.The abrupt energy change near the saddle point refers to an abrupt geometry change at that point,caused by a strong repulsion between PAB and H2.We consider this an artifact and modify our optimization proce-dure by introducing the distance d B−N,shown in the inset of Fig.3(b),as an additional constraint to be optimized along the way in order to minimize the energy.This approach yields a rather smooth energy profile,represented by the solid line connecting the solid data points in Fig.3(b).This smoother trajectory indicates that rehydrogenation of PAB,which involves simultaneous breaking of H2and B–N bonds while H–B and H–N bonds are forming,occurs with a lower energy。