绿色化学与化工导论Chapter 1 introduction

1.1 Chemistry—Past, Present and Future
In the UK, a steady decline in public perception of the chemicals industries over many years is clearly evident. It is especially disturbing to analyse the survey data more closely and to note that the 16–24 year age group has the lowest opinion of the chemicals industries.
to where it is required.
• We must train the new generation of chemists to think of the environmental, social and economic factors in chemicals manufacturing.
1.2 The Costs of Waste
• In the mid-1990s in the USA, for example, only about 300 or so of the 75000 commercial substances in use were classified as hazardous.
discard all waste and spent reagent; recycle solvent where economically viable. • (6) Transport the product worldwide, often for long-term storage. • (7) Release the product into the ecosystem without proper evaluation of its long-term effects.
Atom economy
Atom economy: how many atoms of the starting material are converted to useful products and how many to waste.
A typical oxidation reaction: an alcohol → a carboxylic acid
The Costs of Waste
Figure 1.4 The costs of waste.
1.3 The Greening of Chemistry
Figure 1.5 Options for waste management within a chemical manufacturing process.
• Pharmaceuticals products In twentieth century, World population: from 1.6 to 6 billion, Life expectancy: almost 60%↑
• Crop protection and growth enhancement chemicals
C
Product(s)
Up to 100%
H
Product(s) + waste acid
<100%
Cr
Chromium waste
0%
Na
Salt waste
0%
S
Salt waste (after acid neutralisatct(s) + waste
<<100%
Atom Economy and environmental effects
• Compliance with existing environmental laws will cost new EU member states well over €10 billion; a similar amount is spent each year in the USA to treat and dispose of waste.
Where does the waste come from? Environmental factor
It is used to quantify the effects of production process to the environment Idea: All other compounds formed other than the target product are considered to be WASTE.
Figure 1.1 Trends in the favourability to the chemical industry of the general public (smoothed plots) (based on MORI Opinion Poll figures in
the period 1980–2000).
Figure 1.2 Trend in the number of applications to study chemistry in UK universities (source: UCAS Universities and Colleges Admissions Services ).
View of twentieth century chemical manufacturing
1.1 Chemistry—Past, Present and Future
Chemical products make an invaluable contribution to the quality of our lives and play a fundamental role in almost every aspect of modern society.
Hierarchy of waste management techniques
• Prevention, by far the most desirable option • Recycling, the next most favourable option • Disposal, the least desirable option • Cleaner production:
‘The continuous application of an integrated preventative environmental strategy to processes and products to reduce risks to humans and the environment. For production processes, cleaner production includes conserving raw materials, and reducing the quality and toxicity of all emissions and wastes before they leave a process.’
• Cost of waste can easily amount to 40% of the overall production costs for a typical speciality chemical product.
Production costs
Breakdown of Typical Speciality Chemical Manufacturing Cost
The recipe for the twenty-first century
• (1) Design the molecule to have minimal impact on the environment (short residence time, biodegradable).
• (2) Manufacture from a renewable feedstock (e.g. carbohydrate). • (3) Use a long-life catalyst. • (4) Use no solvent or a totally recyclable benign solvent. • (5) Use the smallest possible number of steps in the synthesis. • (6) Manufacture the product as required and as close as possible
• (1) Start with a petroleum-based feedstock. • (2) Dissolve it in a solvent. • (3) Add a reagent. • (4) React to form an intermediate chemical. • (5) Repeat (2)–(4) several times until the final product is obtained;
Chapter 1
Introduction
JAMES H. CLARK
1.1 Chemistry—Past, Present and Future 1.2 The Costs of Waste 1.3 The Greening of Chemistry
Sustainable development, Cleaner production, Atom economy, E factor, Principles of Green Chemistry, Life-cycle assessment
1.1 Chemistry—Past, Present and Future