绿色化学与化工导论Chapter 1 introduction

chromium (VI) as the stoichiometric oxidant
Table 1.1 ‘Atom accounts’ for a typical partial oxidation reaction using chromate
Element Fate
Atom utilisation
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.
• 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.
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.
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.
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
• The enormous populations demand western levels
• The public image of the chemical industry has badly deteriorated in the last ten years . . .
• In some of the major centres of chemicals manufacturing more people gave positive than negative views, but for many European countries the ratio of unfavourable to favourable views was alarmingly high.
• 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 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.
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.
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.
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 neutralisation)
0%
O
Product(s) + waste
<<100%
Atom Economy and environmental effects
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.
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:
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
• Pharmaceuticals products In twentieth century, World population: from 1.6 to 6 billion, Life expectancy: almost 60%↑
• Crop protection and growth enhancement chemicals
Atom economy
Atom economy: how many atoms of the starting material are converted to useful products and how many to waste.
A typical oxidation rea百度文库tion: an alcohol → a carboxylic acid
• (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;
1.1 Chemistry—Past, Present and Future
At present, the poor image of chemistry is adversely affecting demand. In the UK, the number of applicants to read chemistry at university has been falling steadily for several years The number of applicants to read chemical engineering is even more alarming (<1000 in the year 2000 in the UK)
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).
‘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 Breakdown
Materials
Treatment & Disposal Capital Depreciation Labour
Waste Labour Energy & Utilities
Materials Capital Depreciation
Figure 1.3 Production costs for speciality chemicals.