CHEM F337: Green Chemistry & Catalysis Lecture 08 PDF

CHEM F337: Green Chemistry & Catalysis Lecture 08 Green Chemistry: Case Studies II BITSPilani, Pilani Campus Case studies - Green Chemical Products Styrene production Traditional route: Two-step method starting with benzen...

CHEM F337: Green Chemistry & Catalysis Lecture 08 Green Chemistry: Case Studies II BITSPilani, Pilani Campus Case studies - Green Chemical Products Styrene production Traditional route: Two-step method starting with benzene (carcinogenic) and ethylene to form ethylbenzene, followed by dehydrogenation to obtain styrene Step II: Fe-oxide catalyst, K2CO3 promoter Step II: Conversion per pass = 65% ~95-97 % selectivity to styrene Green Route to styrene  Use of Xylene as starting material (less toxic than benzene)  Toluene reacts with methanol at >400 °C forming styrene – Exelus Inc. process: Overall selectivity to styrene ~ 60 % using a proprietary zeolite based catalyst Reaction at 1 atm pressure Cheapest route BITSPilani, Pilani Campus Case studies - Green Chemical Products Allyl alcohol production Traditional route: Alkaline hydrolysis of allyl chloride, which generates the product and hydrochloric acid as a by-product Shell Process: used NaOH forming huge amount of NaCl Green Route to Allyl alcohol  Avoid chlorine: Two-step using propylene (CH2=CHCH3), acetic acid (CH3COOH) and oxygen (O2) STEP I: Acetoxylation of Propylene CH2=CHCH3 + ½ O2 + CH3COOH CH2=CHCH2OCOCH3 + H2O STEP II: Hydrolysis of the acetate gives allylalcohol The acetic acid produced in the Step II can be recovered and used again.  Alternative route: From Glycerol via reaction with formic acid or oxalic acids BITSPilani, Pilani Campus Case studies - Green Chemical Products Thermal Polyaspartate as alternative to polyacrylates Polyacrylates are important class of plastics in regular applications in several commodities  Acrylic paints Transparency  Acrylate fibres Break resistance  Acrylic resins Elasticity  Synthetic acrylic rubbers Heat & Oil resistance  Plexiglas  Absorbents  Super-glues  Cosmetics Degradability is the greatest concern Green Alternatives to Polyacrylates Donlar Inc. introduced polyaspartates as greener biodegradable alternatives to polyacrylates Polyaspartate is a biopolymer synthesized from L-aspartic acid, a natural amino acid – No waste products formed Has similar properties to the polyacrylates and so it can be used as a dispersant, or an antiscalant, or a superabsorber. Polyaspartate is biodegradeable BITSPilani, Pilani Campus Case studies - Green Chemical Products Synthesis of polyaspartate H H O  N C C O H  OH heat H C H H H O  C N + 2 H2O N C C O OH H OH  H C H O n C O OH Aspartic Acid NaOH The Donlar Corporation received the O 1st Presidential Green Chemistry  H  Challenge Award in the small NH  N business category in 1996.  O O O O- m O- In April 1997, Donlar opened the world's n largest manufacturing facility for 30 % -linkage 70 % -linkage polyaspartates in Peru, Illinois. Polyaspartate BITSPilani, Pilani Campus Case studies - Green Reaction conditions Process for Ibuprofen Boots process (1960s) involved 6 steps involving stoichiometric reactions yielding unwanted chemical waste, Less efficiency, high costs Step 1 Step 2 BITSPilani, Pilani Campus Case studies - Green Reaction conditions Process for Ibuprofen Boots process (1960s) involved 6 steps involving stoichiometric reactions yielding unwanted chemical waste, Less efficiency, high costs Step 3 Step 4 BITSPilani, Pilani Campus  Case studies - Green Reaction conditions Process for Ibuprofen Boots process (1960s) involved 6 steps involving stoichiometric reactions yielding unwanted chemical waste, Less efficiency, high costs Step 5 Step 6 Boots won Queens Award for Technical Achievement in 1987 BITSPilani, Pilani Campus Case studies - Green Reaction conditions Process for Ibuprofen Hoechst-Celanese process was based on green chemistry used catalytic steps (ONLY 3 Steps) for the synthesis of ibuprofen BITSPilani, Pilani Campus Case studies - Green Reaction conditions Process for Ibuprofen 100% Atom efficient step The HC process won the Kirkpatrick Award in 1991 for using catalytic process in place of the stoichiometric pathway BITSPilani, Pilani Campus Case studies - Green Modes of Activation The high-temperature water reaction range (100–200 C) is especially well suited for microwave processing in sealed vessels with standard instruments While pure water is difficult to heat above 130 C due to a reduced absorbance of microwave irradiation at increasing temperature. in most ‘real’ cases the starting material, the reagent, the catalyst or the base are polar enough (or ionic) to enable microwave heating to 200 C. “Passive MW elements” and additives, such as salts may be used to enhance the effect not only for large-scale production, but also in the pilot- or small-scale research laboratory BITSPilani, Pilani Campus Case studies - Green Modes of Activation MW assisted C-C coupling reactions Suzuki coupling reactions in water Stille coupling reactions Heck Couplings BITSPilani, Pilani Campus Case studies - Green Modes of Activation MW assisted coupling reactions Aminocarbonylation reactions Sonogashira Reactions (TM-free) BITSPilani, Pilani Campus