green chemistry ppt.pptxpp.pptxll3pptx

1. always think and act green 1 26/07/2021 AMBO UNIVERSITY COLLEGE OF NATURAL AND COPUTATIONAL SCIENCE DEPARTMENT OF CHEMISTRY Green chemistry ( Chem. 4029} By Abdisa Gebisa .(assistant professor)

2. 2 26/07/2021 always think and act green LEARNING OUTCOMES: After completing the course the learner will: A functional understanding of the field of green chemistry. A working understanding of the 12 principles of green chemistry. An understanding of several real world examples where organizations used green chemistry to improve the sustainability performance of their products. Realize the Benefits of Green Chemistry An appreciation of how the practice of green chemistry enhances competitiveness, innovation and faster time to market.

3. 3 26/07/2021 What is Green Chemistry? always think and act green Basic question to be answered at the end.  What does a chemist do? •  What is “green chemistry”? •  What are some chemical products? •  What is environmental science? •  Do you think our world has environmental problems? What problems? •  How do you think we will go about solving those problems?

4. 4 26/07/2021 always think and act green What is Green Chemistry? What does a chemist do? • Chemists make things such as: – Medicines – Materials: plastics, metals – Coatings: paint, lacquers – Electronics: cell phones and computers • Chemists investigate! – To understand things in the world around them • Global problems: The ozone layer in the atmosphere • Natural processes: What is in a flower that makes it‟s petals a particular color.

5. always think and act green 5 26/07/2021 What is Green Chemistry?  Green Chemistry is the design of chemical products and processes that reduce or eliminate the use and/or generation of hazardous substances. (Paul Anastas and John Warner)  The concept of green chemistry was formally established at the ENVIRONMENTAL PROTECTION AGENCY in response to the Pollution Prevention Act of 1990.  Anastas and Warner formulated the twelve principles of green chemistry in 1998.  These serve as guidelines for chemists seeking to lower the ecological footprint of the chemicals they produce and the processes by which such chemicals are made Green chemistry can also be described as  Sustainable chemistry..  Pollution prevention at the molecular level.

6. always think and act green GREEN CHEMISTRY SUPPORTS SUSTAINABILITY BY: Making chemicals safe for our health & environment, Using industrial processes that reduce or eliminate hazardous chemicals, & Designing more efficient processes that minimize waste

7. 7 26/07/2021 always think and act green Green Chemistry Is About… . Waste Materials Hazard Risk Energy Reduction of

8. 8 26/07/2021 always think and act green Why do we need Green Chemistry ? Chemistry is unquestionably 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. 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. .

9. 9 26/07/2021 always think and act green Why do we need Green Chemistry ? Green chemistry provides an intellectual and technological framework that advances both trans materialization and dematerialization strategies within the chemical enterprise. Green chemistry leads to the search for new processes and technologies which from the very beginning are aimed to prevent or cut short environmental pollution by reducing the volumes of chemical wastes and their toxicity, using harmless materials or materials safer than those currently used, as the starting materials.

10. 10 26/07/2021 always think and act green Cont.. The Green Chemistry program supports the invention of more environmentally friendly chemical processes which reduce or even eliminate the generation of hazardous substances. Green chemistry is different from environmental chemistry because environmental chemistry identifies source, elucidates mechanism and quantifies problems in the earth environment while green chemistry seeks these environmental problems by creating alternative and safe technology. This program works very closely with the twelve principles of Green Chemistry

11. 11 26/07/2021 always think and act green 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 non-renewable 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. 6. To develop products that degrade more rapidly in the environment than the current products.

12. 12 26/07/2021 always think and act green Cont… 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.

13. 13 26/07/2021 always think and act green Twelve Principles of Green Chemistry  1

14. always think and act green 14 26/07/2021 The 12 Principles of Green Chemistry • 1.Prevention Prevention of waste or by-products/polusion causing substance It is better to prevent waste than to treat or clean up waste after it is formed What do we do to prevent pollution? • Drive smaller, more efficient cars • Take the commuter train • Riding a bike • Recycle paper or compost leaves A chemist in a green chemistry lab is performing pollution prevention on a molecular level! always think and act green

15. 15 26/07/2021 always think and act green E-Factor E-Factor??? The E factor takes into account waste by-products, leftover reactants, solvent losses, spent catalysts and catalyst supports, and anything else that can be regarded as a waste. Its calculation depends upon what is defined as waste. Mass ratio of waste to desired product Higher e-factor – more waste and –ve environmental impact  Raw Materials-Product output product E -Factor = Total Waste (Kg) Product (Kg)

16. 16 26/07/2021 always think and act green E-factor For example, water is a significant by-product of many chemical processes and is generally harmless, so its mass is usually omitted from the total mass of waste in the calculation. However, it may be included in those processes in which it is severely contaminated and difficult to reclaim in a form pure enough to use or discharge to a publicly owned wastewater treatment facility. Leftover reactant that can be easily reclaimed and recycled to the process is not included as waste whereas reactant that cannot be salvaged is counted in the waste.

17. 17 26/07/2021 always think and act green E-factor The ideal E factor is 0 and higher E factors are relatively less desirable. E factors that can be tolerated depend upon the value of the product and the amount of product produced. For bulk chemicals manufactured in amounts of hundreds of thousands to millions of tons per year, tolerable E factors typically range from 1 to 5. In the fine chemical and specialty chemical industry where annual quantities are typically measured as a few thousand tons per year E factors up to around 500 may be acceptable if the value of the product is high enough to justify the cost of treating and disposal of wastes. In the pharmaceutical manufacturing industry where annual quantities generated typically are measured in tens to several hundred tons per year, acceptable E factors may be up to about 4000.

18. 18 26/07/2021 always think and act green What is the problem faced if by product is huge? The cost involved in the treatment and disposal of waste adds to the overall production cost. Even the unreacted starting materials (which mayor may not be hazardous) form part of the waste. The waste (or by-products) if discharged (or disposed off) in the atmosphere, sea or land not only causes pollution but also requires expenditure for cleaning-up.

19. Pollution Prevention Hierarchy Prevention & Reduction Recycling & Reuse Treatment Disposal

20. always think and act green 20 26/07/2021 2. Atom economy Synthetic methods should be designed to maximize the incorporation of all materials used in the process into the final product. A synthesis is Perfectly Efficient or Atom Economical if it generates significant amount of waste which is not visible in percentage yield calculation. ?????? ????? ??????????? ????? × ??? Percent yield: % Yield= Atom economy (atom efficiency) describes the conversion efficiency of a chemical process in terms of all atoms involved (desired products produced) %atom economy = ????????? ?????? ?? ??????? ??????? ????????? ?????? ?? ??? ???????? x100

21. 21 26/07/2021 always think and act green Atomic economy example1

22. 22 26/07/2021 2. Atom economy .e.g.. always think and act green

23. 23 26/07/2021 always think and act green Cont… Rearrangement and Addition reactions are 100% atom economical reactions since all the reactants are incorporated into products. While Substitution and Elimination reactions are less atom economical. • Eg1‟ H3C-CH=CH2 + H2 H3C-CH2-CH3 propene to propane the reaction takes place in presence of Nickel. • Here 64.8% reactants are incorporated into product. Hence this is an atom economical reaction. • 2. CH3 (CH2 )4CH2OH +SOCl2 SO2 + CH3 (CH2 )4CH2Cl this reaction is less atom economical as the % atom economy is 36.5%

24. 24 26/07/2021 always think and act green Example1

25. 25 26/07/2021 always think and act green Exrcice

26. 26 26/07/2021 always think and act green 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. Substances 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 chemistry’s greatest strengths is the ability to design for reduced hazard.

27. 27 26/07/2021 always think and act green Less Hazardous Chemical Synthesis Polycarbonate Synthesis: Phosgene Process O O NaOH + OH H O O O * * n Cl Cl  Disadvantages  phosgene is highly toxic, corrosive  requires large amount of CH2Cl2  polycarbonate contaminated with Cl impurities

28. 28 26/07/2021 always think and act green Less Hazardous Chemical Synthesis Polycarbonate Synthesis: Solid-State Process OH H O O + O O * * n O O O  Advantages  diphenylcarbonate synthesized without phosgene  eliminates use of CH2Cl2  higher-quality polycarbonates Komiya et al., Asahi Chemical Industry Co.

29. 29 26/07/2021 always think and act green 4. Designing Safer Chemicals: Chemical products should be designed to effect their desired function while minimising their toxicity. Instead of using Synthetic chemicals use natural one which can be extracted from Natural Resources .

30. 30 26/07/2021 always think and act green 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. Pure extract from citrus. Highest grade solvent for mixing and cleaning oil based paints. Use for diluting our oil based Wood Finishes.  3 times stronger than Mineral Spirits, naturally

31. 31 26/07/2021 always think and act green Features and Benefits of our Greener Solvent Alternatives Solvents possess many useful properties, and also can exhibit toxic, flammable and polluting characteristics if not handled properly. greener solvents show improvements of certain characteristics over the alternative solvents commonly used for a given application. These products may be safer with reduced hazard or lower volatility, or may contribute to reduced environmental impacts by increased biodegradability.

32. 32 26/07/2021 always think and act green greener solvent alternatives offer the following features and benefits: Less toxic and less hazardous (acc. to CLP regulation) Higher biodegradability (acc. OECD) Easy to recycle, and reduced waste stream Higher boiling point compared to conventional solvents Less volatility Reduction of solvent loss and energy savings

33. 33 26/07/2021 always think and act green Ionic Liquids as Solvents Ionic Liquids as Solvents for Organic Synthesis and Catalysis Ionic liquids have the ability to dissolve various compounds and mixtures, both organic and inorganic. This property, together with non-flammability, neglible vapour pressure, chemical and thermal stability and variable miscibility with other solvents They allow treatment of the material, that was not possible before due to lack of solubility in common solvents. In addition to merely solubilizing the compounds of interest, they have other roles they can take, as for example stabilization of solutes, catalysis of chemical transformations etc. the most of ionic liquids (ILs) are clear, colourless, low melting, viscous liquid ,high electrical conductivity, high thermal stability, low nucleophilicity and capability of providing weekly coordinating or non-coordinating environment, very good solvents properties for an extensive diversity of organic, inorganic, organometallic and polymeric compounds.

34. 34 26/07/2021 always think and act green Solvent Selection Preferred Useable Undesirable Water Cyclohexane Pentane Acetone Heptane Hexane(s) Ethanol Toluene Di-isopropyl ether 2-Propanol Methylcyclohexane Diethyl ether 1-Propanol Methyl t-butyl ether Dichloromethane Ethyl acetate Isooctane Dichloroethane Isopropyl acetate Acetonitrile Chloroform Methanol 2-MethylTHF Dimethyl formamide Methyl ethyl ketone Tetrahydrofuran N-Methylpyrrolidinone 1-Butanol Xylenes Pyridine t-Butanol Dimethyl sulfoxide Dimethyl acetate Acetic acid Dioxane Ethylene glycol Dimethoxyethane Benzene Carbon tetrachloride “Green chemistry tools to influence a medicinal chemistry and research chemistry based organization” Dunn and Perry, et. al., Green Chem., 2008, 10, 31-36

35. 35 26/07/2021 always think and act green Water Water is a polar, protic solvent it has the ability to dissolve a large variety of substances. This is the reason why it is regarded as a good solvent. Furthermore, water is often referred to as the “universal solvent” because it is known to dissolve more substances than all other liquid solvents. Water is crucial to every living organism on the planet Earth. As water travels across the water cycle, through the ground and through the bodies of living organisms, it transports several valuable minerals and nutrients with it. Advantages and disadvantages of using water as a solvent exothermic reactions can be more safely controlled. Advantages  Non-toxic and Inexpensive  Opportunity for replacing VOCs  Naturally occurring and Non- flammable  High specific heat capacity- Disadvantages  Distillation is energy intensive  Contaminated waste streams may be difficult to treat  High specific heat capacity-difficult to heat or cool rapidly

36. 36 26/07/2021 always think and act green Ethanol Ethanol is considered by many to be a very versatile solvent. This organic compound forms miscible mixtures with water and several other organic solvents such as benzene, acetone, ethylene glycol, chloroform, toluene, glycerol, nitromethane, carbon tetrachloride, pyridine and diethyl ether. This compound is also miscible with many light aliphatic hydrocarbons. Some examples include pentane and hexane. Aliphatic chlorides such as tetrachloroethylene are also miscible with ethanol. Methanol Methanol /methyl alcohol is an organic compound with the chemical formula CH3-OH. mainly used as an industrial solvent to help in the manufacture of resins, inks, colours and adhesives. This compound is also used in the processing of essential pharmaceutical ingredients and products such as cholesterol, vitamins, streptomycin and hormones as a solvent.

37. 37 26/07/2021 always think and act green Acetone Due to its ability to dissolve both polar and nonpolar compounds, acetone is considered by many to be a very good solvent (most other solvents can only dissolve either polar or non-polar compounds). Furthermore, acetone is a strong solvent because it is a miscible material. This means that it has the potential to mix in certain amounts with water. Acetone is used in a number of important organic reactions (such as nucleophilic substitution reactions) as a polar, aprotic solvent. The use of acetone solvent is also vital in the Jones oxidation reaction (an important named reaction for the conversion of secondary alcohols into ketones).  It is important to note that this compound does not form an azeotrope with water

38. 38 26/07/2021 always think and act green Flash point (° °C) Red Solvent Reason Pentane -49 Very low flash point, good alternative available. Hexane(s) -23 More toxic than the alternative heptane, classified as a HAP in the US. Di-isopropyl ether -12 Very powerful peroxide former, good alternative ethers available. Diethyl ether -40 Very low flash point, good alternative ethers available. Dichloromethane n/a High volume use, regulated by EU solvent directive, classified as HAP in US. Dichloroethane 15 Carcinogen, classified as a HAP in the US. Chloroform n/a Carcinogen, classified as a HAP in the US. Dimethyl formamide 57 Toxicity, strongly regulated by EU Solvent Directive, classified as HAP in the US. N-Methylpyrrolidinone 86 Toxicity, strongly regulated by EU Solvent Directive. Pyridine 20 Carcinogenic/mutagenic/reprotoxic (CMR) category 3 carcinogen, toxicity, very low threshold limit value (TLV) for worker exposures. Dimethyl acetate 70 Toxicity, strongly regulated by EU Solvent Directive. Dioxane 12 CMR category 3 carcinogen, classified as HAP in US. Dimethoxyethane 0 CMR category 2 carcinogen, toxicity. Benzene -11 Avoid use: CMR category 1 carcinogen, toxic to humans and environment, very low TLV (0.5 ppm), strongly regulated in EU and the US (HAP). Carbon tetrachloride n/a Avoid use: CMR category 3 carcinogen, toxic, ozone depletor, banned under the Montreal protocol, not available for large-scale use, strongly regulated in the EU and the US (HAP). “Green chemistry tools to influence a medicinal chemistry and research chemistry based organization” Dunn and Perry, et. al., Green Chem., 2008, 10, 31-36

39. 39 26/07/2021 always think and act green Solvent replacement table Undesirable Solvent Alternative Pentane Heptane Hexane(s) Heptane Di-isopropyl ether or diethyl ether 2-MeTHF or tert-butyl methyl ether Dioxane or dimethoxyethane 2-MeTHF or tert-butyl methyl ether Chloroform, dichloroethane or carbon tetrachloride Dichloromethane Dimethyl formamide, dimethyl acetamide or N-methylpyrrolidinone Acetonitrile Pyridine Et3N (if pyridine is used as a base) EtOAc, MTBE, toluene, 2-MeTHF Dichloromethane (extractions) Dichloromethane (chromatography) EtOAc/heptane Benzene Toluene “Green chemistry tools to influence a medicinal chemistry and research chemistry based organization” Dunn and Perry, et. al., Green Chem., 2008, 10, 31-36

40. 40 26/07/2021 always think and act green Environmentally Benign Solutions  Organic Solvents And Volatile Organic Compounds Organic solvents have played a key role in the development of many useful products.  They are used, for example, to produce pharmaceuticals of the required purity, to ensure the easy flow and good finish of gloss paints, to formulate inks that dry successfully, and in aerosol applications.  In chemical manufacture, organic solvents are widely used in a variety of unit operations including extraction, recrystallization and the dissolution of solids for ease of handling.  One of the key roles organic solvents play in the chemical industry, however, is that of reactant solvent allowing the homogenization of a reactant mixture, speeding up reactions through improved mixing, and in addition reducing energy consumption. Solvents also contribute to safety by acting as a heat sink for exothermic reactions.

41. 41 26/07/2021 always think and act green Environmentally Benign Solutions  Many of the applications discussed above use volatile organic compounds (VOCs) as solvents because of their ease of removal or evaporation.  VOCs have a significant vapour pressure at room temperature and are released from many sources including process industries and most forms of transport, the latter being responsible for the majority of VOC emissions.  The main environmental issue concerned with VOCs is their ability to form low-level ozone and smog through free radical air oxidation processes.  The EPA has published a list detailing a number of adverse health effects, which are now thought to originate from the presence of VOCs in the environment,including:  conjunctival irritation ,nose and throat discomfort ,headache, allergic skin reaction, dyspnea ,declines in serum cholinesterase levels nausea fatigue dizziness

42. 42 26/07/2021 always think and act green 6. Design for Energy Efficiency: Energy We use lots of energy for  Driving our cars • Heating and cooling our houses • Cooking food • Drying our hair  Chemists also use lots of energy:for Heating • Drying • Cooling Energy is not only expensive – most of the time the power plant that creates the energy contributes to pollution.

43. 43 26/07/2021 always think and act green Cont… 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. Energy requirements should be recognized for their environmental impacts and should be minimized. Synthetic methods should be conducted at ambient pressure and temperature”

44. 44 26/07/2021 always think and act green Energy Green Chemistry will be essential in 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. Solar energy is an abundant and renewable source of power that could alleviate world energy demand. New materials technologies are rising to the challenge of replacing a silicon-dominated market with the promise of cheaper and more versatile photovoltaic's.  One of the most highly studied alternatives, the dye-sensitized solar cell (DSSC), is discussed from a historical perspective as well as recent advances in DSSC technologies.  In addition, the emerging technology of perovskite solar cells, which bear some similarity to DSSCs, is also introduced.

45. Green Ch 7.Use of Renewable Feedstock: try Principles 7 45 26/07/2021 always think and act green  Raw material or feedstock should be renewable rather than depletingwhenever technically and economically practical.  Use chemicals which are made from renewable (i.e. plant-based) sources, rather than other, equivalent chemicals originating from petroleum, coal and natural gas sources. Example: Formation of furfural from bagasse and waste biomass of wheat and rice plant etc

46. 46 26/07/2021 always think and act green Eg . Polymers from Renewable Resources: Polyhydroxyalkanoates (PHAs) • Fermentation of glucose in the presence of bacteria and propanoic acid (product contains 5-20% polyhydroxyvalerate) • Similar to polypropene and polyethene • Biodegradable (credit card) OH R O O OH O n Alcaligenes eutrophus propanoic acid HO OH R = Me, polydroxybutyrate R = Et, polyhydroxyvalerate OH

47. 47 26/07/2021 always think and act green Polymers from Renewable Resources:Poly(lactic acid) http://www.natureworksllc.com/corporate/nw_pack_home.asp

48. 48 26/07/2021 Raw Materials from Renewable Resources: The BioFine Process O Paper mill sludge HO O Agricultural residues, Waste wood Levulinic acid Green Chemistry Challenge Award 1999 Small Business Award Municipal solid wasteand waste paper

49. 49 26/07/2021 Levulinic acid as a platform chemical O OH HO butanediol OH O HO Acrylic acid OH Succinic acid O H2N O O O O HO • . MTHF THF O (fuel additive) CH3 O O HO C C H2 C H2 C OH O Diphenolic acid DALA (-amino levulinic acid) (non-toxic, biodegradable herbicide) gamma butyrolactone always think and act green

50. 50 26/07/2021 always think and act green 8. Reduce Derivatives Unnecessary derivatization (blocking group, protection/deprotection, temporary modification of physical/chemical processes) should be avoided whenever possible. A Minimise the number of steps in the reaction. void because such steps require additional reagents and can generate waste.