Unit V Green Chemistry PDF

Unit V Green Chemistry Engineering Chemistry DCH002A By Dr Anita Nehra Department of Chemistry, JECRC university, Jaipur 2024-25  What is green chemistry? Is ‘Environmental Chemistry’ same as ‘...

Unit V Green Chemistry Engineering Chemistry DCH002A By Dr Anita Nehra Department of Chemistry, JECRC university, Jaipur 2024-25  What is green chemistry? Is ‘Environmental Chemistry’ same as ‘Green Chemistry’? No Environmental Chemistry is ‘CHEMISTRY OF THE ENVIRONMENT’, that explains nature and the impact of man on the nature. While, Green Chemistry is ‘CHEMISTRY FOR THE ENVIRONMENT’ i.e. a more environmentally friendly chemistry.  Definition "the utilization 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." -Anastas and Warner, Green Chemistry Theory and Practice, Oxford University Press, 1998. About Green Chemistry Pro-active approach to addressing pollution and hazards in the design phase of a product life cycle. Empowers chemists to use the skills impart sustainability into their practice. The 12 Principles of Green Chemistry serve as guidelines for practicing chemists to implement best practices. It is related to each sub-discipline of chemistry to placing the chemist at the centre of solving sustainability challenges. Upstream approach: Tremendous opportunity to minimize impacts and maximize efficiencies. Industry perspective: A growing demand with green chemistry training as the green chemicals market continues to grow. Projected growth in green chemistry jobs and companies: aiming to achieve their sustainability goals through chemistry research and development. Integrating green chemistry into global education systems is essential in preparing the next generation of scientists and citizens who are ready to design, select, and support sustainable chemistry.  THE NEED FOR GREEN CHEMISTRY Union Carbide, 1984 Poison gas leaked from a Union Carbide factory (Bhopal, India) killing thousands instantly and injuring many more (many of who died later of exposure). Up to 20,000 people have died as a result of exposure (3-8,000 instantly). More than 120,000 still suffer from ailments caused by exposure. How did this happen? Methyl isocyanate - used to make pesticides - was being stored in large quantities on-site at the plant. Methyl isocyanate is highly reactive, exothermic molecule. Most safety systems either failed or were inoperative. Water was released into the tank holding the methyl isocyanate. The reaction occurred and the methyl isocyanate rapidly boiled, producing large quantities of toxic gas. Real world cases in Green Chemistry by Cann and Connelly, 2000 Union Carbide, 1984 What is left of the abandoned The flare tower where toxic methyl isocyanate Union Carbide plant. gas was released into the air. https://www.theatlantic.com/photo/2014/12/bhopal-the- worlds-worst-industrial-disaster-30-years-later/100864/ Aftermath of Infrastructure Damage What do you see? …What do you think happened? https://www.theatlantic.com/photo/2014/12/bhopal- the-worlds-worst-industrial-disaster-30-years- later/100864/ Cuyahoga River – Cleveland Ohio 1969 There were many things being dumped in the river such as: gasoline, oil, paint, and metals. The river was called "a rainbow of many different colors". Although fires had erupted on the river several times, the Cuyahoga River didn’t receive national attention until August 1969, when Time Magazine gave a report on a river fire that occurred on June 22, 1969. Image source: https://commons.wikimedia.org/wiki/File:Downt own_Cleveland,_Ohio,_in_winter,_from_the_air,_ 12-1937_-_NARA_-_512842.jpg/ Cuyahoga River – Cleveland Ohio 1969 Some river! Chocolate-brown, oily, bubbling with subsurface gases, it oozes rather than flows. "Anyone who falls into the Cuyahoga does not drown," Cleveland’s citizens joke grimly. "He decays.” -Time Magazine, August 1969 Image Source: https://commons.wikimedia.org/wiki/File:DISCOLORED_WATER_IN_FOREGRO UND_IS_FROM_SEWAGE_DISCHARGED_INTO_THE_CUYAHOGA_RIVER_BY_TH E_CITY_PUMP_STATION_-_NARA_-_550214.jpg Cuyahoga River – Cleveland Ohio 1969 Images Courtesy of The Cleveland Press Collection, Cleveland State University Library; Author: Fred Bottomer, and James Thomas  Port of Tianjin, 2015 In August 2015, a warehouse in the port of Tianjin in northern China experienced two major explosions. According to the China Earthquake Networks Centre, the first explosion was as powerful as if three tons of TNT had detonated, and the second was equivalent to 21 tons detonating. A series of explosions killed 173 people and injured hundreds of others at a container storage station. The first two explosions occurred within 30 seconds of each other at the facility. The second explosion was far larger and involved the detonation of about 800 tons of ammonium nitrate. Fires caused by the initial explosions continued to burn uncontrolled throughout the weekend, causing eight additional secondary explosions. The facility stored large quantities of sodium cyanide and calcium carbide, as well as 800 tons of ammonium nitrate, which is principally used in manufacturing fertilizer. In total, 304 buildings, 12,428 cars, and 7,533 intermodal containers were damaged. The cost of damage was estimated at $9 billion. Port of Tianjin, 2015 https://sploid.gizmodo.com/photos-from-the-devastating aftermath-of-the-tianjin-ex-1723899654 The Cost of Using Hazardous Materials Storage Transportation Treatment Disposal Regulatory Costs Liability Worker Health and Safety Corporate Reputation Community Relations New Employee Recruitment Image Sources: Wikipedia Commons, Public Domain Pictures  Although the pesticide DDT was effective in controlling insect pests that carried deadly diseases and has saved many human lives, it also caused a precipitous decline in the bald eagle population and is a suspected carcinogen What is generally done? command and control legislation. Risk management by controlling exposure to a substance: FAILED DDT (dichloro-diphenyl-trichloroethane Green chemistry, however, addresses hazard; a benign substance poses no risk to an organism regardless of exposure. Green chemistry represents a fundamental shift away from the command and control model and toward a pollution prevention paradigm. A set of principles serves as a blueprint for implementing green chemistry Green Chemistry is about… In addition to unintended human and environmental consequences… Shifting roles Changing education of chemists Understanding Intrinsic Hazard Design Increasing Efficiency Reducing Costs Enhancing Performance Innovation Paul Anastas and John C. Warner co-authored the groundbreaking book, Green Chemistry: Theory and Practice in 1998. Fathers of Green Chemistry The 12 Principles of Green Chemistry outlined within this work declared a philosophy that motivated academic and industrial scientists at the time and continues to guide the green chemistry movement. Paul Anastas John C. Warner Green Chemistry Across Industrial Sectors Defense and aerospace Automotive Household cleaners Adhesives Solvents Surfactants Coatings Polymers Fragrances Corrosion, Fuels Dyes inhibitors Electronics Agriculture Cosmetics Solder Pesticides Builders Housings Fungicides Chelating agents Displays Fertilizers Dyes Pharmaceuticals 12 Principles of Green Chemistry 1. Waste Prevention 2. Atom Economy 3. Less Hazardous Chemical Synthesis. 4. Designing Safer Chemicals. 5. Safer Solvents and Auxiliaries. 6. Design for Energy Efficiency. 7. Use of Renewable Feedstocks. 8. Reduce Derivatives. 9. Catalysis. 10. Design for Degradation. 11. Real-time Analysis for Pollution Prevention. 12. Inherently Safer Chemistry for Accident Prevention. Anastas, P. T.; Warner, J.C. Green Chemistry: Theory and Practice, Oxford University Press,1998 The principles address: Toxicity - Reducing the hazard Feedstocks - Use of renewable resources Designing safer products - Non toxic products by design Biodegradability - Enhancing breaking down at the end of life Energy - Reducing the energy needs Accidents - Eliminating accidents Efficiency - Shorter processes and synthesis Anastas, P. T.; Warner, J.C. Green Chemistry: Theory and Practice, Oxford University Press,1998  Waste Prevention It is better to prevent waste than to treat or clean up waste after it is formed. Overall production cost increases: if treatment and disposal costs are added If A and B conversion is not complete A+B P+W Ways to prevent waste? 1.Avoid the generation of W. 2.Find alternatives to A & B to improved overall efficiency of a reaction. 3.Incorporate better catalysts to push the reaction to full completion “An ounce of prevention is worth a pound of cure”  Environmental Factor (E-Factor) Roger A Sheldon derived environmental factor (E-factor) The E-factor of a process is the ratio of the mass of waste per mass of product: Sheldon, R. Green Chem., 2007,9, 1273-1283 Annual Waste produced Industry sector E-factor "ca." is short for "circa" which production (t) (t) means approximately. Oil refining 106-108 Ca. 0.1 105 – 107 Bulk chemicals 104-106 5000 mg/kg Duck: LD50>5000 mg/kg Produced by bacteria Saccharopolyspora spinosa. Fish: LC50-96h=30.0 mg/L Isolated from Caribbean soil samples (sugar mill). Bee: LD50=0.0025 mg/bee It selectively targets nervous system of insects. Demonstrates high selectivity, low mammalian toxicity, and a good environmental profile. Saccharopolyspora spinosa Dow AgroSciences  Principle 5: Safer Solvents and Auxiliaries The use of auxiliary substances (solvents, separation agents, etc.) should be made unnecessary whenever possible and, when used, innocuous. Solvents account for the majority of mass wasted in synthesis and processes. Moreover, many conventional solvents are toxic, flammable, and/or corrosive. Solvents volatility and solubility have contributed to air, water and land pollution, have increased the risk of worker exposure, and have led to serious accidents. Recovery and reuse, when possible, is often associated with energy-intensive distillation and sometimes cross contamination. In an effort to address all those shortcomings, chemists have started to search for safer solutions.  Workup Chromatography Re-crystallization Workup Green Chem., 2016,18, 5769-5772 Re-crystallization Even if non-hazardous Materials of mobile and stationary phases: Waste Consumption of energy https://youtu.be/04HWovMzkAk?si=e8Oh0abt5vJs6f8D  trichloromethane perchloroethylene Carbon tetrachloride VOCs: Volatile organic compounds: SMOG! Respiratory problems Compounds that evaporate at room temperature  First in 1914 by Problematic organic solvents Paul Walden Greener alternatives ethylammonium nitrate Avoidance Easily separable, safe and selective Zero Environmentally No Solvent Volatility benign and safe Supercritical Ionic Water solvent Molten state fluids liquids reactions Most innocuous Cross between liquid Reagent serve solvent and gas a salt in the liquid state as a solvent Cost of separation at ambient conditions, Dense phase CO2 Feedstock as melting point below of products and by- Tunable properties 100 oC a solvent products with temperature and Reactions on Non-hazardous pressure nonvolatile, non- clays effluents flammable, and air and water stable IONIC LIQUIDS  Medical Chemistry solvent Selection Guide Preferred Usable Undesirable Water Cyclohexane Pentane Acetone Heptane Hexane(s) Ethanol Toluene Di-isopropyl ether 2-Propanol Methylcyclohexane Diethyl ether 1-Propanol TBME Dichloromethane Ethyl Acetate Isooctane Dichloroethane Isopropyl acetate Acetonitrile Chloroform Methanol 2-MeTHF NMP MEK THF DMF 1-Butanol Xylenes Pyridine t-Butanol DMSO DMAc Acetic Acid Dioxane Ethylene Glycol Dimethoxyethane Benzene Carbon tetrachloride  Case study: Coffee decaffeination Conventional method of coffee decaffeination: Coffee decaffeination was performed in a chlorinated organic solvent, dichloromethane (DCM), exposure to which can lead to headaches, mental confusion, nausea, vomiting, dizziness and fatigue. Coffee beans were heated with steam and then exposed to DCM for decaffeination. Use of scCO : Supercritical CO 2 2 Alternative method for coffee decaffeination: Soaking green coffee beans in water doubles their size, allowing the caffeine to dissolve into water inside the bean. Caffeine removal occurs in an extraction vessel (70 feet high,10 feet in diameter), suffused with carbon dioxide at roughly 90 °C and 250 atm. Caffeine diffuses into this scCO2. The beans enter at the top of the chamber and move toward the bottom over 5 hours. Decaffeinated beans at the bottom of the vessel are removed, dried and roasted. Recovery of dissolved caffeine occurs in an absorption chamber. A shower of water droplets leaches the caffeine out of the supercritical carbon dioxide. The caffeine in this aqueous extract is then often sold to soft-drink manufacturers and drug companies. The purified carbon dioxide is recirculated for further use. scCO2: Supercritical CO2 Zosel, K. Practical Applications of Material Separation with Supercritical Gases. Angew. Chem., Int. Ed. 1978, 17, 702-709  Design for Energy Efficiency Energy requirements should be recognized for their environmental and economic impacts and should be minimized. Synthetic methods should be conducted at ambient temperature and pressure. Heating/Reflux To accelerate rate of reaction To control reaction rate by cooling Purification and separation Most energy is used for heating, cooling, separations and pumping. Ideally, all reactions are performed at ‘ambient’ conditions – room temperature and atmospheric pressure – in order to minimize energy usage.  Sono-, microwave-, and photo-assisted chemistry are known to save energy, improve reaction time, and catalytic activity. Sonochemistry: Microwave: Photo-assisted: Uses of high frequency (20- Uses a high-frequency Naturally occurring, such as 100 kHz) sound waves to electric field to heat or cool using the sun as a catalyst. promote chemical reaction. the local environment with Used in photo-driven acylation for The collapse of bubbles electrical charges. the production of valuable formed in a solution Avoids unnecessarily synthetic intermediates and generates a very high prolonged residence time at commercial fragrances in bulk. temperature and a higher a given temperature. Used by BASF to develop pressure than conventional automotive primer coating, a heating. precursor readily able to be Used in the production of crosslinked under photo triglycerides from methyl irradiation, as opposed to its transesterification. conventional energy-intensive thermally driven variation.  Use of Renewable Feedstocks A raw material or feedstock should be renewable rather than depleting whenever technically and economically practical. Biomaterials [Carbohydrates, Proteins, Lipids] Highly Functionalized Molecules Petroleum Products [Hydrocarbons] Functionalized Compounds [Olefins, Alkylchlorides] Highly Functionalized Molecules  Biomass production in nature: 180 billion metric tons/year Only about 4% utilized by humans (food, ethanol, sweeteners) Carbohydrates Lignin Fats, proteins, terpenes, etc. Nature’s richest Building blocks for a source of aromatic Converted into polymers, diverse chemical carbon. Used in lubricants, and platform. polymers, adhesives, detergents. production of phenolic chemicals.  Case study: Producing polymers from renewable resources (PHAs) Polyhydroxyalkanoates (PHAs) are a broadly useful family of natural, environmentally friendly, and high- performing, bio-based plastics. The development of microorganisms that produce polyhydroxyalkanoates (PHAs) are from renewable feedstocks such as cornstarch and cellulose hydrolysate. The microorganisms have proven to be applicable to conventional commercial equipment and can even be recycled using this same equipment. They can be used in biodegradable products, such as credit cards. They are comparable with polyolefins - which are made from petroleum feedstocks - in terms of strength, melting point, and can be manufactured with the existing equipment. Metabolix Image: Alpha Stock Images, Author: Nick Youngson  Reduce Derivatives Unnecessary derivatization (blocking group, protection/deprotection, temporary modification of physical/chemical processes) should be avoided whenever possible. Conventional approach Intermediate Substrate Intermediate B D Product Intermediate Intermediate A Intermediate E C Green Chemistry approach Substrate Product  In this example, in order to reduce the ester group in to alcohol group, the ketonic group needs to be protected. Protection is done by using ethylene glycol (II) to get the protected compound (III). The ester moiety in this protected compound can then be reduced by using LiAlH4 to yield compound (IV). This compound (IV) can then be allowed to undergo acid hydrolysis, i.e. deprotection which yields the desired product with the generation of protecting group, ethylene glycol. Such type of protection and deprotection is too common in organic chemistry. In the above procedure, the protecting group is not incorporated in to the final product, which makes a reaction less atom economical. Thus as far as possible, the use of protecting groups should be avoided.  Catalysis Catalytic reagents (as selective as possible) are superior to stoichiometric reagents. Catalysts can facilitate complex reactions by: Lowering the activation energy of the reaction. Reducing temperature necessary to achieve a reaction. Controlling the site of the reaction (selectivity enhancement). Image source: Adobe stock  Case study: Paper production Polyoxometalate (POM) catalysts - non-toxic, inorganic cluster compounds - selectively delignify wood - utilize only air and water Allows use of oxygen instead of chlorine as the whitener of paper pulp and water as the solvent Generates only CO2 and H2O, instead of chlorinated organics 1st step 2nd step 3rd step 4th step Hill, Emory University; Hill et al, Nature 2001, 414, 191–195  Design for Degradation Chemical products should be designed so that at the end of their function they do not persist in the environment and instead break down into innocuous degradation products. Early examples: Sulfonated detergents Alkylbenzene sulfonates – 1950’s & 60’s Foam in sewage plants, rivers, and streams Persistence was due to long alkyl chain Introduction of an alkene group into the chain increased degradation Chlorofluorocarbons (CFCs) Do not break down, persist in atmosphere and contribute to destruction of the ozone layer. DDT Bioaccumulate and cause thinning of egg-shells  Case study: Plasticizers Conventional plasticizers, such as DiNP, are an additive used to soften plastics: Plasticizers for plastics are additives, most commonly O phthalate esters in PVC O applications. O Almost 90% of plasticizers are O used in PVC, giving this material Diisononyl phthalate, DiNP improved flexibility and durability. DiNP exposure has been linked to liver toxicity, endocrine disruption, and carcinogenicity. The majority of PVC is used to produce films and cables. The additives persist in the environment.  Case study: Plasticizers Alternative plasticizers, such as isosorbide di-ester, can be derived from starch: HO O OH OH amylase OH OH O OH O Ra-Ni catalyst HO H 2O HO HO O OH OH H2 OH OH OH n sorbitol glucose Starch H 2O elevated temperatures O O O HO O lipase enzyme O 5 O O O OH O OH 5 caprylic acid isosorbide diester isosorbide Offers 1 to 1 substitution of DiNP in plastics. Isosorbide diester is thermally stable and biodegradable.  11. REAL TIME ANALYSIS Real-time analysis for pollution prevention: Analytical technologies need to be further developed to allow for real time in process monitoring and control prior to the formation of toxic substances. The Role of Analytical Chemistry Analytical chemistry has been at the heart of the environmental movement since its inception. It’s been used in: Identification Monitoring Measurement Characterization Knowing when your product is “done” can save a lot of waste, time, and energy.  Real-time Analysis for Pollution Prevention Case study: Real-time analysis in cooling systems Conventional Cooling Systems: They consume large amounts of water. Microbial growth and mineral scale decrease the efficiency and increase energy consumption of heat- exchange. However, high levels of biocide to prevent microbial growth increases the risk of leaks in the system. Biocide and metal-byproducts from corrosion are then released into the environment with the waste water. https://www.epa.gov/greenchemistry/presidential-green-chemistry-challenge-2008-greener-reaction-conditions-award Image: Wikimedia Commons, Cooling tower and cooling water discharge at a Philippsburg nuclear power plant, Author: Michael Kauffmann Real-time Analysis for Pollution Prevention Case study: Real-time analysis in cooling systems In 2008 Naclo Company won the EPA Greener Reaction Conditions Award for their innovative 3D TRASAR® Technology. Alternative Cooling System with 3D TRASAR® Technology: The 3D TRASAR® System allows for the real-time monitoring of mineral scale buildup. This system can also utilize poor-quality water. 3D Scale Control prevents mineral scale formation to increase efficiency. 3D Bio-control performs a real-time check for planktonic and sessile bacteria. This reduces the amount of biocide used since biocides are then added only when necessary, rather than on a set schedule. The 3D TRASAR® System greatly reduces the amount of wastewater discharged from cooling systems. https://www.epa.gov/greenchemistry/presidential-green-chemistry-challenge-2008-greener-reaction-conditions-award Image: Wikipedia, A lavender-colored nonpotable water pipeline in Mountain View, California, Author: 12. Inherently Safer Chemistry for Accident Prevention Substance and the form of a substance used in a chemical process should be chosen so as to minimize the potential for chemical accidents, including releases, explosions, and fires. Inherently Safer Chemistry for Accident Prevention Accidents can be avoided by minimizing hazards Approaches to design safer chemistry can include the use of solids or low vapor pressure substances in place of volatile liquids. Other approaches include avoiding the use of molecular halogens in large quantities. Continuous flow processes can help to minimize chemical hazards.  Case study: Designing safer polymers for use in airplanes Polyhydroxyamide (PHA): Can be molded into seats, bins, and wall panels. It is synthesized under mild conditions. It decomposes into fire-resistant polybenzoxazole (PBO) and water upon heating. Westmoreland, UMass Amherst Image Source: https://videohive.net/item/plane-interior-flying-in-the-clouds/989512  Case study: Production of gasoline alkylate with AlkyClean® Technology In 2016 Albemarle and CB&I won the EPA green chemistry award for their inherently safer AlkyClean® process technology. Conventional alkylate production: AlkyClean® Technology: The AlkyClean® solid acid alkylation process Alkylate is typically produced from produces high quality alkylate without using the reaction of isobutane and light liquid acid catalysts. olefins. The solid acid alkylation process is safer for This requires the use of liquid acid both people working directly in production catalyzed processes, such as and for people in the area surrounding the production facility. hydrofluoric acid. There are also environmental and economic Hydrofluoric acid is extremely toxic. benefits since neither acid-soluble oils nor When released it forms clouds that spent acids are produced. can be lethal for up to five miles. Summary: 12 Principles of Green Chemistry 1. Waste Prevention 2. Atom Economy 3. Less Hazardous Chemical Synthesis. 4. Designing Safer Chemicals. 5. Safer Solvents and Auxiliaries. 6. Design for Energy Efficiency. 7. Use of Renewable Feedstocks. 8. Reduce Derivatives. 9. Catalysis. 10. Design for Degradation. 11. Real-time Analysis for Pollution Prevention. 12. Inherently Safer Chemistry for Accident Prevention. Anastas, P. T.; Warner, J.C. Green Chemistry: Theory and Practice, Oxford University Press,1998 Green Chem., 2018, 20, 1929-1961