Green Chemistry Ok Tk2014

GREEN CHEMISTRYDEFINITION Green Chemistry is the utilisation of a set of principles that reduces or eliminates the use or generation of hazardous substances in the design, manufacture and application of chemical products .

GREEN CHEMISTRY IS ABOUTWaste Minimisation at SourceUse of Catalysts in place of ReagentsUsing Non-Toxic ReagentsUse of Renewable ResourcesImproved Atom EfficiencyUse of Solvent Free or Recyclable Environmentally Benign Solvent systems

Green Chemistry Is About... CostWasteMaterialsHazardRisk Energy

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.A famous example is the pesticide DDT.

Why do we need Green Chemistry ?

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.

ChemicalProcessIt is better to prevent waste than to treat or clean up waste after it is formed

Human society is constantly facing such environmental issues and problems, air pollution, global climate change, soil and water pollution, acid rain, depletion of natural resources and accumulation of natural hazardous wasteGreen chemistry preventing pollution and sustaining the earth

Principles of Green ChemistryIts better to develop reactions with fewer waste products than to have to clean up the waste.i.e. high atom economyReactions that use fewer reactants, particularly ones that arent hazardous, are better.Reactants from renewable sources (e.g. plants) are preferable.

Photo credit: Lea Paterson / Science Photo Library (Ref M750/917)

Principles of Green ChemistryIts better to develop reactions with fewer waste products than to have to clean up the waste.i.e. high atom economyReactions that use fewer reactants, particularly ones that arent hazardous, are better.Reactants from renewable sources (e.g. plants are preferable).Processes should rely on renewable energy resources, rather than fossil fuels.

Photo credit: Martin Bond / Science Photo Library (Ref G350/762)

Principles of Green ChemistryIts better to develop reactions with fewer waste products than to have to clean up the waste.i.e. high atom economyReactions that use fewer reactants, particularly ones that arent hazardous, are better.Reactants from renewable sources (e.g. plants are preferable).Processes should rely on renewable energy resources, rather than fossil fuels.Solvent use should be minimised, & solvents should be benign in their impact on the environment.

Photo credit: Keith Weller / US Dept of Agriculture / Science Photo Library (Ref G350/762)

Principles of Green ChemistryIts better to develop reactions with fewer waste products than to have to clean up the waste.i.e. high atom economyReactions that use fewer reactants, particularly ones that arent hazardous, are better.Reactants from renewable sources (e.g. plants are preferable).Processes should rely on renewable energy resources, rather than fossil fuels.Solvent use should be minimised, & solvents should be benign in their impact on the environment.Materials produced by chemists should be biodegradable so they dont persist in the environment after theyve been used.

Photo credit: Robert Brook / Science Photo Library (Ref E820/268 )

Principles of Green ChemistryIts better to develop reactions with fewer waste products than to have to clean up the waste.i.e. high atom economyReactions that use fewer reactants, particularly ones that arent hazardous, are better.Reactants from renewable sources (e.g. plants are preferable).Processes should rely on renewable energy resources, rather than fossil fuels.It is desirable to find ways to use waste products in other chemical reactions.Alternatively, waste products that are non-toxic and biodegradable are favourable.Solvent use should be minimised, & solvents should be benign in their impact on the environment.Materials produced by chemists should be biodegradable so they dont persist in the environment after theyve been used.

Photo credit: David Read / University of Southampton

Principles of Green ChemistryIts better to develop reactions with fewer waste products than to have to clean up the waste.i.e. high atom economyReactions that use fewer reactants, particularly ones that arent hazardous, are better.Reactants from renewable sources (e.g. plants are preferable).Processes should rely on renewable energy resources, rather than fossil fuels.It is desirable to find ways to use waste products in other chemical reactions.Alternatively, waste products that are non-toxic and biodegradable are favourable.Solvent use should be minimised, & solvents should be benign in their impact on the environment.Materials produced by chemists should be biodegradable so they dont persist in the environment after theyve been used.For a more detailed treatment, see: Paul T. Anstas and John C. Warner Green Chemistry: Theory and Practice, New York: Oxford University Press, 1998

Yield vs Atom economyYield can be calculated as:% yield = mass (g) of product obtained x 100 theoretical yield (g)

The yield tells us how efficient a reaction is in terms of the amount of product we obtained relative to the maximum we could get from the amounts of reactants we used.But it doesnt take account of waste products!

Yield vs Atom economyAtom economy can be calculated as:

% AE = x 100

A reaction may have a high % yield but a low atom economy.RFM desired product sum of RFMs of all products

Atom economy some examplesCalculate the % atom economy of CH2Cl2:CH4 + 2Cl2 CH2Cl2 + 2HClRFM: CH2Cl2 = 85, HCl = 36.5

% AE = x 100AE = x 100 = 53.8 % 85 85 + (2 x 36.5)RFM desired product sum of RFMs of all products

Atom economy some examplesCH4 + 2Cl2 CH2Cl2 + 2HClAn atom economy of 53.8% may be considered to be quite low. How could a chemical company maximise their profits from this chemical process?The by-product is hydrogen chloride, which can be sold as a gas or made into hydrochloric acid. These can then be sold.

Atom economy some examplesCalculate the % atom economy of ethylene oxide:

RFM: C2H4O = 44, CaCl2 = 111, H2O = 18

AE = x 100 = 37.4 % (2 x 44) (2 x 44) + 111 + (2 x 18)

Atom economy some examplesEthylene oxide A case of Green Chemistry

An atom economy of 37.4% is particularly poor, and this is a very wasteful process. Nonetheless, this was the preferred method for synthesising ethylene oxide for many years.

Atom economy some examplesEthylene oxide A case of Green Chemistry

Recently, a method of synthesising ethylene oxide from ethene and oxygen using a silver catalyst was developed.Whats the atom economy of this reaction?100 %

In this presentation the synthesis of ibuprofen by Friedel-crafts alkylation of isobutyl benzene with lactic acid and its derivatives was attmpted using various acid catalysts like Zn-Zeolite-Y, AlCl3/MCM-41, AlCl3/SiO2

IBUPROFENLactic acidIBUPROFENFirst synthezised By the Boots company in Nottingham England in 1960sIs this possible and if so how to effect this reaction catalytic?

The use of auxiliary substances (e.g. solvents, separation agents, etc.) should be made unnecessary wherever possible, and innocuous when used

Energy requirements should be recognized for their environmental impacts and should be minimized. Synthetic methods should be conducted at ambient pressure and temperature

HeatingCoolingStirringDistillationCompressionPumping SeparationEnergy Requirement(electricity)Burn fossil fuelCO2 toatmosphere

GLOBAL WARMING

Non-renewableRenewableA raw material of feedstock should be renewable rather than depleting wherever technically and economically practical

Resource DepletionRenewable resources can be made increasingly viable technologically and economically through green chemistry.

Biomass, Carbon dioxide, Nanoscience, Solar, Waste utilization

Poly lactic acid (PLA) for plastics production

Polyhydroxyalkanoates (PHAs)

The role of catalystsCatalysts have a crucial role to play in the future of Green Chemistry.They allow the development of new reactions which require fewer starting materials and produce fewer waste products.They can be recovered and re-used time and time again.They allow reactions to run at lower temperatures, cutting the amount of energy required.

Catalysts in ActionAnimation credit: Robert Raja / University of Southampton

The future of chemistryWe need to reconsider the way we go about all aspects of our lives.The planet is feeling a burden.Science has the potential to solve our problems.Green Chemistry can play a significant role in a sustainable future.Photo credit: Gusto Images / Science Photo Library (Ref: T602/318) Photo credit: NASA Earth Observatory / Science Photo Library (Ref: E050/708) Photo credit: John Cole / Science Photo Library (Ref: G350/433) Photo credit: Simon Fraser / Science Photo Library (Ref: T820/419)

The major uses of GREEN CHEMISTRYEnergyGlobal ChangeResource Depletion Food SupplyToxics in the Environment

ENERGYThe vast majority of the energy generated in the world today is from non-renewable sources that damage the environment.Carbon dioxide Depletion of Ozone layer Effects of mining, drilling, etc Toxics

ENERGYGreen Chemistry will be essential in developing the alternatives for energy generation (photo-voltaics, hydrogen, fuel cells, bio-based fuels, etc.) as well as continue the path toward energy efficiency with catalysis and product design at the forefront.

GLOBAL CHANGEConcerns for climate change, oceanic temperature, stratospheric chemistry and global distillation can be addressed through the development and implementation of green chemistry technologies

RESOURE DEPLETIONDue to the over utilization of non-renewable resources, natural resources are being depleted at an unsustainable rate. Fossil fuels are a central issue.

RESOURCE DEPLETIONRenewable resources can be made increasingly viable technologically and economically through green chemistry. Biomass Nanoscience & technology Solar Carbon dioxide Chitin Waste utilization

FOOD SUPPLYWhile current food levels are sufficient, distribution is inadequate Agricultural methods are unsustainable Future food production intensity is needed. Green chemistry can address many food supply issues

FOOD SUPPLYGreen chemistry is developing: Pesticides which only affect target organisms and degrade to innocuous by-products. Fertilizers and fertilizer adjuvants that are designed to minimize usage while maximizing effectiveness. Methods of using agricultural wastes for beneficial and profitable uses.

TOXICS IN THE ENVIRONMENTSubstances that are toxic to humans, the biosphere and all that sustains it, are currently still being released at a cost of life, health and sustainability.

One of green chemistrys greatest strengths is the ability to design for reduced hazard.

Pollution Prevention HierarchyPrevention & ReductionRecycling & ReuseTreatmentDisposal

CONCLUSIONGreen chemistry Not a solution to all environmental problems But the most fundamental approach to preventing pollution