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4/22/2014 1 Green Chemistry Debaprasad, IIT Ropar Accidents Can Happen

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Page 1: Green Chem DM1

4/22/2014

1

Green Chemistry

Debaprasad, IIT Ropar

Accidents Can Happen

Page 2: Green Chem DM1

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Accidents Can Happen

Cyanide spill

Bhopal, India (1984)

Bhopal Gas TragedyA plant accident in Bhopal, India, released methyl

isocyanate. Nearly 4000 people died.

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Bucktail Creek

(Cobalt, Idaho)

http://www.darrp.noaa.gov/northwest/black/photo.html

Early Waste Disposal

Love Canal: Tragedy

A Legacy of Pollution

Cuyahoga River, near Cleveland 1969Cuyahoga River, 1952

On June 22, 1969, oil and debris on the surface of the Cuyahoga River in

Cleveland, Ohio, burst into flames and burned for twenty-five minutes

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We Can’t Just Ignore the Problem

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Triple Bottom Line

When economic, social and environmental benefits are

integrated and balanced, sustainability can be maintained.

Triple Bottom Line

When economic, social and environmental benefits are integrated and

balanced, sustainability can be maintained

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Green Chemistry: An Essential Component of

SustainabilityGreen Chemistry: An Essential Component of Sustainability

What is Green Chemistry?

• Chemical choices - minimizing the hazards and maximizing

efficiency

• Green chemistry is fundamentally about waste prevention at the

level of atoms and molecules

• Chemistry with respect, not disregard, for health and the

environment

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Risk is a function of hazard and exposure

Risk = f [hazard, exposure]

By reducing intrinsic hazard, risk can be minimized even in the

event of accidental exposure.

# Don’t use or produce hazardous substances, the risk is zero

Green Chemistry or Environmentally Benign Chemistry is the design of chemical

products and processes that reduce or eliminate the use or generation of hazardous

substances

Therefore, instead of limiting Risk by controlling Exposure to hazardous chemicals,

green chemistry attempts to reduce or eliminate the Hazard thus negating need to

control Exposure.

Is Green Chemistry Expensive?

Waste = Lost Profit

Is Green Chemistry Expensive?

Waste = Lost Profit

Is Green Chemistry Expensive?

Waste = Lost Profit

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Green Chemistry is About...

Cost

Waste

Materials

Hazard

Risk

Energy

Green Chemistry is the design of chemical products and processes

that reduce or eliminate the use and/or generation of hazardous

substances.

Reducing

Green Chemistry is about...

Use of Catalyst in place of Reagents

Using Non-Toxic Reagents

Waste Minimisation at Source

Use of Renewable Resources

Use of Solvent Free or Recyclable Environmentally Benign Solvent systems

Improved Atom Efficiency

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Prevent Waste

Maximize Atom Economy

Less Hazardous Chemical Syntheses

Safer Chemical and Products

Safer solvent and reaction conditions

Increase Energy Efficiency

Use renewable Feedstock

Avoid Chemical Derivatives

Use catalysts

Design chemical and products to

degrade after use

Analyze in real time to prevent

pollution

Minimize Potential for accidents

John C. Warner and Paul Anastas. Green Chemistry: Theory and Practice; Oxford University Press: New York, 1998; p 30.

12 Principles of Green Chemistry

7. Use Renewable Feedstocks

8. Reduce Derivatives

9. Catalysis

10. Design for Degradation

11. Real-Time Analysis for Pollution Prevention

12. Accident Prevention

Anastas, P.T.; Warner, J. C. Green Chemistry: Theory and Practice; Oxford University Press: New York, 1998; p 30.

John Warner and Paul Anastas

1. Prevention2. Atom Economy3. Less Hazardous Chemical Synthesis4. Design Safer Chemicals5. Safer Solvents and Auxiliaries6. Design of Energy Efficiency7. Use Renewable Feed stocks 8. Reduce Derivatives 9. Catalysis 10. Design for Degradation 11. Real-Time Analysis for Pollution Prevention 12. Accident Prevention

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1. Prevention

• It is better to prevent waste than to treat orclean up waste after it has been created.

Chemical

Process

2. Atom Economy:

Synthetic methods should be designed to maximize the incorporation of all the materials used in the process into the final product.

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Consider some common reactions like rearrangement, addition,

substitution & elimination to find out which is more atom

economical.

O

CH2

CH2

OH

Allylphenyl Ether O-Allyl Phenol

200oC

1. Rearrangement Reaction

These reactions involve rearrangement of atoms that make up a

molecule. Hence atom economy is always 100.

Butadiene Ethene Cyclohexene

CH2

CH2

CH

CH

CH2

CH2

+

CH3 CH2 C OC2H5

O

+ CH3 NH2

Ethyl propionate

Mol wt 102.13

Methyl amine

Mol wt 31.05

CH3 CH2 C NHCH3

O

N-Methyl propionate

Mol wt 87.106

+ H5C2 OH

Ethyl Alcohol

Mol wt 46.06

Atom Economy: Example

1. Reaction Yield:

The reaction should have high % of yield

% Yield = 100 × Actual Yield Theoretical

By using formula, we can calculate an atom economy

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E- Factor and Atom Efficiency

Two measures of the potential environmental acceptability of

chemical factors are:

• E- Factor defined as mass ratio of waste to desired productWaste produced as a proportion of product – the E-factor

• Atom efficiency calculated by dividing the molecular weight of the desired product by the sum of the molecular weights of all reactants in the stoichiometric reaction

Industry segment Annual production (t)

E-factor Total waste (t; approx.)

Oil refining 106 – 108 ca. 0.1 106

Bulk chemicals 104 – 106 < 1 – 5 105

Fine chemicals 102 – 104 5 –> 50 104

Pharmaceuticals 10 – 103 25 –> 100 103

% Atom Economy = 100 × Relative molecular mass desired productsRelative molecular mass desired reactants

Lecture_week1 7

Table. 3.1 Measuring the environmental efficiency of butyl acetate

synthesissynthesis

Yield 69% OK

Atom efficiency 85% Quite good

E-factor 12.2 Poor

Environmental quotient Approx. 12.2-30 Fairly good

EMY 108% Very good

Measuring the environmental efficiency of butyl acetate synthesis

5. Environmental Load Factor:

It should be minimum.

E = 100 × Total Mass of Effluents generated

Mass of desired products

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3. Less Hazardous Chemical Synthesis:

Wherever practicable, synthetic methods should be designed to use and generate substances that possess little or no toxicity to people or the environment.

• Use of Phosgene in Synthesis of Polycarbonates

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4. Designing Safer Chemicals:

Chemical products should be designed to effect their

desired function while minimising their toxicity.

Examples:

• Safer dry cleaning

– Initially gasoline and kerosene were used

– Chlorinated solvents are now used

– Supercritical/liquid carbon dioxide (CO2)

4. Designing Safer Chemicals:

Chemical products should be designed to effect their

desired function while minimising their toxicity.

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Lead Pollution has Been Decreased

• Replacing tetraethyl lead with less toxic additives (e.g.,

“lead-free” gasoline). Such as MTBE & ETBE (ethyl

tertiary butyl ether)

5. Safer Solvents & Auxiliaries:

The use of auxiliary substances (e.g., solvents or separation agents)

should be made unnecessary whenever possible and innocuous

when used.

• Water should be used as a solvent

• If water is not usable then more ecofriendly solvents like

supercritical CO2 or ionic solvents

• As far as possible synthesis is carried out without solvents

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6. Design for Energy Efficiency:

Energy 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.

This can be achieved by

• Use of proper catalyst , enzymes

• Use of micro organisms for organic synthesis

• Use of renewable materials

7. Use of Renewable Feedstock:

A raw material or feedstock should be renewable rather than

depleting whenever technically and economically practicable.

Traditional Feedstock in Synthesis of Adipic Acid

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Alternative Feedstock in Synthesis of Adipic Acid

Poly lactic acid (PLA) for plastics production

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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.

Industrial Synthesis of Ibuprofen

Classic Route

Hoechst Route to Ibuprofen

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9. Catalysis:

Catalytic reagents (as selective as possible) are superior to

stoichiometric reagents.

Catalysts make the

reaction faster

decrease the energy requirement

can produced single desired product

minimize waste.

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.

Examples:

Polyethylene, polystyrene are not biodegradable but biodegradable

polymer like polyhydroxybutyrate-hydroxyvalarate ( PHBV )

Synthetic insecticides remains in the food grains & vegetables &

do not get degraded but natural insecticides (chilli, neem etc.) get

easily degraded after killing the insect.

10. Designing of Degrading

Products:

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Polyhydroxyalkanoates (PHA’s)

11. New Analytical Methods: or Real Time Analysis for

Population Prevention:

Analytical methodologies need to be further developed to allow

for real-time, in-process monitoring and control prior to the

formation of hazardous substances.

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12. Safer Chemicals for Accidents Prevention:

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.

The reagents & reaction should be risk free, in the chemical process,

to minimize the chemical accidents, explosion, fires & gas release.

Presidential Green Chemistry Challenge

1998: Professor Barry M. Trost, Stanford University

The Development of the Concept of Atom Economy

Innovation and Benefits: Concept of atom economy: chemical reactions that do not waste atoms. Prof. Trost's concept of atom economy includes reducing the use of nonrenewable resources, minimizing the amount of waste, and reducing the number of steps used to synthesize chemicals. Atom economy is one of the fundamental cornerstones of green chemistry. This concept is widely used by those who are working to improve the efficiency of chemical reactions.

1997: Professor Joseph M. DeSimone, Univ. of NC

Design and Application of Surfactants for Carbon Dioxide

1996: Professor Mark Holtzapple, Texas A&M University

Conversion of Waste Biomass to Animal Feed, Chemicals, and Fuels

Innovation and Benefits: developed new detergents that allow carbon dioxide (CO2), a nontoxic gas, to be used as a solvent in many industrial applications. Using CO2 as a solvent to replace traditional hazardous solvents

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Saving Energy

Minimum Global Changes

Minimize the Depletion of Resources

Food Supply

Releasing Non-Toxic in the Environment

Major uses of GREEN CHEMISTRY

1.Saving Energy

Green Chemistry will be essential in Developingthe alternatives for energy generation (photovoltaic's,hydrogen, fuel cells, biogases fuels, etc.)

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WHAT IS HYDROGEN ECONOMY ?

The hydrogen economy describes a system in

which our energy needs are predominantly

met by hydrogen, rather than fossil fuels.

In a hydrogen economy, vehicles like cars and airplanes use

hydrogen fuel cells for power, rather than petroleum distillates.

This type of economy would rely on

renewable resources in the form of hydrogen

gas and water, drastically changing pollution,

electricity sources, infrastructure, engines,

and international trade, without impacting

our quality of life.

USES OF HYDROGEN

Hydrogen is a very useful gas.

1) It is used as a fuel

2) It makes ammonia, NH4

3) It is used to make plastic (PV)

4) It also turns liquid vegetable oils

into margarine (vegetable ghee)

Hydrogen Gas filling in Car

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ADVANTAGES OF HYDROGEN

• Waste product of burning H2 is water.

• Elimination of fossil fuel pollution.

• Elimination of greenhouse gases.

• Elimination of economic dependence.

• Distributed production.

2. Resource Depletion

Due to the over utilization of non-renewable resources, natural

resources are being depleted at an unsustainable rate.

Fossil fuels are a central issue.

Minimize the Depletion of Resources

Renewable resources can be made increasingly viable

technologically and economically through green chemistry.

Biomass

Nano science & technology

Solar Energy

Carbon dioxide

Waste utilization

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3. Minimum Global Changes

Concerns for climate change, oceanic temperature, stratospheric

chemistry and global distillation can be addressed through the

development and implementation of green chemistry technologies.

Green Chemistry in Day to Day Life

We need to change our mind set and applying the concept in Classrooms

laboratory manufacture and finally the surrounding environment

Disinfection of water by chlorination. Chlorine killing the

pathogens by oxidizes them, but produces harmful chlorinated

compounds. A remedy is to use another oxidant, such as

If the chemical reaction of the type

A + B P + Waste

Find alternate A or B to avoid Waste

O3 or supercritical water oxidation

Example 1:

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Dry Cleaning of Clothes

• Tetra chloroethene (C2Cl4) was earlier used as solvent for dry

cleaning but these compound contaminates the ground water and

suspected carcinogen.

• The process using this compound is now being replaced by a

process where liquefied carbon dioxide with a suitable detergent

is used .

• Replacement of halogenated solvent by liquid Carbon dioxide

(CO2) will result in less harm to ground water .

Green chemistry: Example 2

• Traditional route: Alkaline hydrolysis of allyl chloride, which generates the

product and hydrochloric acid as a by-product

• Greener route, to avoid chlorine: Two-step using propylene (CH2=CHCH3),

acetic acid (CH3COOH) and oxygen (O2)

• Added benefit: The acetic acid produced in the 2nd reaction can be recovered

and used again for the 1st reaction, leaving no unwanted by-product.

CH2=CHCH2Cl + H2O CH2=CHCH2OH + HCl

problem product

CH2=CHCH2OCOCH3 + H2O CH2=CHCH2OH + CH3COOH

CH2=CHCH3 + CH3COOH + 1/2 O2 CH2=CHCH2OCOCH3 + H2O

Production of Allyl alcohol CH2=CHCH2OH

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BLEACHING OF PAPER

Chlorine gas was used earlierfor bleaching of paper .

These days hydrogen peroxidewith suitable catalyst whichpromotes the bleaching actionof hydrogen peroxide is used .

Synthesis of Chemicals

Acetaldehyde (CH3CHO) is now commercially prepared by one step

oxidation of Ethene in the presence of ionic catalyst in aqueous

medium with a yield of 90%

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Green Chemistry: Example 3

• Production of styrene (benzene ring with CH=CH2 tail)

• Traditional route: Two-step method starting with benzene, which is

carcinogenic) and ethylene to form ethylbenzene, followed by dehydrogenation

to obtain styrene

Greener route: To avoid benzene, start with xylene (cheapest source of aromatics

and environmentally safer than benzene).

Another option, still under development, is to start with toluene.

Examples: Monsanto Acetic Acid Synthesis

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Example 2 : Cativa Process

References

http://www.epa.gov/greenchemistry/

http://www.epa.gov/greenchemistry/pubs/educat.html

http://www.epa.gov/greenchemistry/

http://www.epa.gov/greenchemistry/pubs/principles.html

http://en.wikipedia.org/wiki/Green_chemistry

http://portal.acs.org/portal/acs/corg/content?_nfpb=true&_pageLabel=PP_TRANSITIONMAIN&node_id=830&use

_sec=false&sec_url_var=region1&__uuid=76247a16-94d0-458e-9092-10de1c35f2c6

http://books.google.com/books?id=ZMjkTMwO3NkC&dq=green+chemistry&printsec=frontcover&source=bl&ots=

ZdGD63CxOJ&sig=vM94PxekSEhIX3a9yFOPpDAOXGo&hl=en&ei=mD9RSqSoDqDMjAfJg4mfBQ&sa=X&oi=b

ook_result&ct=result&resnum=8

http://books.google.com/books?id=ZMjkTMwO3NkC&dq=green+chemistry&printsec=frontcover&source=bl&ots=

ZdGD63CxOJ&sig=vM94PxekSEhIX3a9yFOPpDAOXGo&hl=en&ei=mD9RSqSoDqDMjAfJg4mfBQ&sa=X&oi=b

ook_result&ct=result&resnum=8