Green chemistry

transcript

Green Chemistry

2Paul Anastas: Father of Green Chemistry

3Green Chemistry is about reducing

• Waste• Materials• Hazards• Risks• Energy• Cost

4Why do we need Green Chemistry

Objective• Chemistry is undeniably a

very prominent part of our daily lives.

• Chemical developments also bring new environmental problems and harmful unexpected side effects, which result in the need for ‘greener’ chemical products.

Results• A famous example is the

pesticide DDT.

5What it looks for . . . . .

• Green chemistry looks at pollution prevention on the molecular scale and is an extremely important area of Chemistry due to the importance of Chemistry in our world today and the implications it can show on our environment.

• The Green Chemistry program supports the invention of more environmentally friendly chemical processes which reduce or even eliminate the generation of hazardous substances.

• This program works very closely with the twelve principles of Green Chemistry.

6Goals of Green Chemistry

1. To reduce adverse environmental impact, try appropriate and innovative choice of material & their chemical transformation.

2. To develop processes based on renewable rather than non-renewable raw materials.

3. To develop processes that are less prone to obnoxious chemical release, fires & explosion.

4. To minimize by-products in chemical transformation by redesign of reactions & reaction sequences.

5. To develop products that are less toxic.

7Goals of Green Chemistry

6. To develop products that degrade more rapidly in the environment than the current products.

7. To reduce the requirements for hazardous persistent solvents & extractants in chemical processes.

8. To improve energy efficiency by developing low temperature & low pressure processes using new catalysts.

9. To develop efficient & reliable methods to monitor the processes for better & improved controls.

Principles of Green Chemistry

9The 12 Principles of Green Chemistry

1. Prevention of Waste or by-products

http://www.igd.com/wasteprevention

1. Prevention of Waste or by-products

“It is better to prevent waste than to treat or clean up waste after it is formed”

2. Atom EconomyAtom economy (atom efficiency) describes

the conversion efficiency of a chemical process in terms of all atoms involved (desired products produced).

3. Minimization of hazardous products Wherever practicable, synthetic methods

should be designed to use and generate substances that possess little or no toxicity to people or the environment.

3. Minimization of hazardous products

4. Designing Safer Chemicals Chemical products should be designed to

effect their desired function while minimising their toxicity.

5. Safer Solvents & Auxiliaries

“The use of auxiliary substances (e.g. solvents,separation agents, etc.) should be made

unnecessarywherever possible, and innocuous when used”

5. Safer Solvents & Auxiliaries

6. Design for Energy EfficiencyEnergy requirements of chemical processes should

be recognised for their environmental and economic impacts and should be minimised. If possible, synthetic methods should be conducted at ambient temperature and pressure.

6. Design for Energy Efficiency

Developing the alternatives for energy generation (photovoltaic, hydrogen, fuel cells, bio based fuels, etc.) as well as

Continue the path toward energy efficiency with catalysis and product design at the forefront.

7. Use of Renewable Feedstock

“A raw material or feedstock should be renewable rather than depleting whenever technically and

economically practicable.”

7. Use of Renewable Feedstock

8. Reduce Derivatives

Unnecessary derivatization (use of blocking groups, protection/de-protection, and temporary modification of physical/chemical processes) should be minimised or avoided if possible, because such steps require additional reagents and can generate waste.

8. Reduce Derivatives

More derivatives involveAdditional ReagentsGenerate more waste productsMore TimeHigher Cost of Products

• Hence, it requires to reduce derivatives.

9. CatalysisCatalytic reagents (as selective as possible) are

superior to stoichiometric reagents.e.g. Toluene can be exclusively converted into p-xylene (avoiding o-xylene & m-xylene) by shape selective zeolite catalyst.

10. Designing of degradable products

Chemical products should be designed so that at the end of their function they break down into innocuous degradation products and do not persist in the environment.

11. New Analytical Methods

“Analytical methodologies need to be further developed to allow for real-time, in-process

monitoring and control prior to the formation of hazardous substances.”

12. Safer Chemicals For Accident Prevention

“Analytical Substances and the form of a substance used in a chemical process should be chosen to minimise the potential for chemical accidents,

including releases, explosions, and fires.”

Efficiency Parameters

291. Reaction Yield

The reaction should have high percentage of yield.

302. Atom Economy

Atom economy describes the conversion efficiency of a chemical process in terms of all atoms involved (desired products produced).

For the reaction, the atom economy should be maximum.

312. Atom Economy

e.g.1. Rearrangement Reactions:

These reactions involves rearrangement of atoms that forms molecule. Hence, the atom economy of these reactions are 100%.2. Addition Reactions:

These reactions involves addition of two or more molecules without elimination that forms molecule. Hence, the atom economy of these reactions are 100%

322. Atom Economy

e.g. Consider the following reaction to find out atom economy.

CH3 CH2 C OC2H5

+ CH3 NH2

Ethyl propionate

Mol wt 102.13

Methyl amine

Mol wt 31.05

CH3 CH2 C NHCH 3

N-Methyl propionate

Mol wt 87.106

+ H5C2 OH

Ethyl Alcohol

Mol wt 46.06

333. Conversion Factor

344. Reaction Selectivity

355. Environmental Load Factor

It is represented by E and it should be minimum.

• Energy

• Global Change

• Resource Depletion

• Food Supply

• Toxics in the Environment

The major uses of GREEN CHEMISTRY

Green chemistry

Education