2. Green Chemistry
Paul Anastas: Father of Green Chemistry
Definition:
• Green chemistry is the design of products
and processes reducing or eliminating
hazardous substances
• Green Chemistry is a subset of Design for
Environment applying innovative scientific
solutions to product manufacturing
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3. Green Chemistry is about….
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Reducing
waste
materials
Hazard
Risk
Energy
Cost
4. Why do we need Green Chemistry
Objective Results
• Chemistry is undeniably • A famous example is the
a very prominent part of pesticide DDT.
our daily lives
. • Chemical developments
also bring new environmental
problems and harmful
unexpected side effects,
which result in the need for
‘greener’ chemical products.
.
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5. • What 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.
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6. Goals 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 nonrenewable 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.
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7. 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
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8. Principles of Green Chemistry
In 1998, Paul Anastas (who then directed the Green
Chemistry Program at the US EPA) and John C.
Warner (then of Polaroid Corporation) published a
set of principles to guide the practice of green
chemistry.
The 12 Principles of Green Chemistry
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 Economy
Atom economy (atom efficiency) describes the
conversion efficiency of a chemical process in terms
of all atoms involved (desired products produced). 8
9. 𝐴𝑡𝑜𝑚 𝐸𝑐𝑜𝑛𝑜𝑚𝑦 = 𝑀𝑜𝑙. 𝑤𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝐷𝑒𝑠𝑖𝑟𝑒𝑑 𝑝𝑟𝑜𝑑𝑢𝑐t
×1oo
𝑀𝑜𝑙. 𝑤𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑎𝑙𝑙 𝑟𝑒𝑎𝑐𝑡𝑎𝑛𝑡s
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.
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10. • 3. Minimization of hazardous products
minimization
Reduction at
sources
Recycling at
sources
Product
modification
Process
modification
Good
practices
Substitution
of materials
Technologies
changes
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11. 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
unnecessary wherever possible, and innocuous
when used”
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12. 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.
• 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.
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13. 7. Use of Renewable Feedstock
“A raw material or feedstock should be renewable
rather than depleting whenever technically and
economically practicable.”
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.
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14. • More derivatives involve
• Additional Reagents
• Generate more waste products
• More Time
• Higher Cost of Products
• Hence, it requires to reduce derivatives.
9. Catalysis
Catalytic 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
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15. 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.”
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16. 12. Safer Chemicals For Accident Prevention
“Analytical Substances and the form of a
substance used in a chemical process should be
chosen to minimize the potential for chemical
accidents, including releases, explosions, and
fires.”
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17. The major uses of GREEN CHEMISTRY
Energy
Resource Depletion
Toxics in the Environment
Feedstock
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19. Ethyl lactate – a renewable solvent
• Derived from processing corn
• Variety of lactate esters possible
• Renewable source (non-petrochemical)
• Attractive solvent properties
– Biodegradable,
– Easy to recycle,
– Non-corrosive,
– Non-carcinogenic
– Non-ozone depleting
– Good solvent for variety of processes
• Commonly used in the paint and coatings industry
– Potentially has many other applications.
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Conclusion
• Green chemistry Not a solution to all
environmental problems But the most
fundamental approach to preventing pollution.
