Post on 29-Apr-2017
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Green Chemistry
Debaprasad, IIT Ropar
Accidents Can Happen
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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