Chapter 8 - Green Chemistry.pdf

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1. Green Chemistry
Books Ref:
1.Environmental Chemistry with Green
Chemistry, Asim K. Das
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Course No- 424
8
th
Chapter
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2. Definition
Greenchemistry,alsocalledsustainablechemistry,isanareaof
chemistryandchemicalengineeringfocusedonthedesigningof
productsandprocessesthatminimizeoreliminatetheuseand
generation of hazardous substances.
Whileenvironmentalchemistryfocusesontheeffectsofpolluting
chemicalsonnature,greenchemistryfocusesontheenvironmental
impactofchemistry,includingreducingconsumptionofnonrenewable
resources and technological approaches for preventing pollution.
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3. Principle
The twelve principles of green chemistry are:
1.Prevention.Preventingwasteisbetterthantreatingorcleaningup
waste after it is created.
2.Atomeconomy.Syntheticmethodsshouldtrytomaximizethe
incorporationofallmaterialsusedintheprocessintothefinalproduct.This
means that less waste will be generated as a result.
3.Lesshazardouschemicalsyntheses.Syntheticmethodsshouldavoid
using or generating substances toxic to humans and/or the environment.
4.Designingsaferchemicals.Chemicalproductsshouldbedesignedto
achieve their desired function while being as non-toxic as possible.
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4. Principle
5.Safersolventsandauxiliaries.Auxiliarysubstancesshouldbe
avoidedwhereverpossible,andasnon-hazardousaspossiblewhenthey
must be used.
6.Designforenergyefficiency.Energyrequirementsshouldbe
minimized,andprocessesshouldbeconductedatambienttemperature
and pressure whenever possible.
7.Useofrenewablefeedstock's.Wheneveritispracticaltodoso,
renewablefeedstock'sorrawmaterialsarepreferabletonon-renewable
ones.
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5. Principle
8.Reducederivatives.Unnecessarygenerationofderivatives—suchas
theuseofprotectinggroups—shouldbeminimizedoravoidedifpossible;
such steps require additional reagents and may generate additional waste.
9.Catalysis.Catalyticreagentsthatcanbeusedinsmallquantitiesto
repeatareactionaresuperiortostoichiometricreagents(onesthatare
consumed in a reaction).
10.Designfordegradation.Chemicalproductsshouldbedesignedso
thattheydonotpollutetheenvironment;whentheirfunctioniscomplete,
they should break down into non-harmful products.
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6. Principle
11.Real-timeanalysisforpollutionprevention.Analytical
methodologiesneedtobefurtherdevelopedtopermitreal-time,in-
process monitoring and control before hazardous substances form.
12.Inherentlysaferchemistryforaccidentprevention.Whenever
possible,thesubstancesinaprocess,andtheformsofthose
substances,shouldbechosentominimizeriskssuchasexplosions,
fires, and accidental releases.
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