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Homogeneous Catalysis HMC-11- 2010 Dr. K.R.Krishnamurthy National Centre for Catalysis Research Indian Institute of Technology,Madras Chennai-600036
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Bi-phasic catalysis
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Homogeneous Catalysis-Features
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Origin of Biphasic Catalysis To retain specific advantages ( milder conditions, higher selectivity) of homogeneous catalysis Easy recovery and recycling of precious metal catalysts Move towards economically viable as well as sustainable processes
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Biphasic Catalysis- Illustration
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Biphasic Catalysis- Process Flow Scheme Biphasic Catalysis Liquid-Liquid Systems Water- Organic- Aqueous biphasic catalysis Organic-Organic
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Polar ligands- for water soluble complexes
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Telomerization of Butadiene Hydrocyanation of butadiene
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Aqueous biphasic catalysis- Applications Synthesis of Phenyl acetic acid Conventional process Benzyl chloride → Benzyl cyanide → PAA + 1400 kg of salt/kg PAA Novel route via biphasic carbonylation - 60% reduction in salt - Lower cost of raw material – HCN Vs CO Ring Opening polymerization (1.4$/kg Vs 0.2$)
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Water as solvent-Demerits Lower reaction rates in aqueous phase Lower solubility of organic substrates Mass transfer limitations across the interphase Sensitivity of substrates/catalysts towards water
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Non-aqueous biphasic catalysis Thermo regulated phase transfer catalysis (TRPTC) Use of fluorocarbons as solvents Special mixtures of organic solvents Super critical CO 2 Ionic liquids
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Thermo regulated biphasic catalysis (TRPTC) Basis Solubility Vs Temp patterns PEG substituted Tri Phenyl Phosphine OctylPolyglycol- Phenylene-Phosphite
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TGME-Triethylene glycol mono methyl ether
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Montedison process for Phenyl acetic acid Phases- Di-phenyl ether & aqueous alkali Pre-catalyst –Co(CO) 8 forms [Co(CO) 4 ] - in alkali phase P-T Catalyst- (R4 + NX - ) PTC solubilizes [Co(CO)4] - in organic medium Nucleophillic attack by [Co(CO)4] - on Benzyl chloride CO insertion follows PTC transfers (OH) - to DPE Hydrolysis follows PAA released in aq, phase as Na /Quad..Amm.salt
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Ibuprofen- Old & New Processes Ibuprofen, 2-4-iso-butyl phenyl propionic acid
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Celanese process for Ibuprofen Isobutylation of benzene Acylation & hydrogenation to alcohol Carbonylation to yield Ibuprofen Replaces the old process with six steps
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PdCl 2 (PPh 3 ) 2 –Pre-catalyst 130C, 50 bar CO pressure Org.solvent & HCl medium Oxidative addition of Ar-Cl CO insertion Reductive elimination of ArCOCl Acid chloride on hydrolysis gives Ibuprofen Catalytic cycle for Ibuprofen by Hoechst-Celanase process
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Ibuprofen from 4-Isobutyl stryrene OPGPP- OctylPolygly- Col-Phenylene-Phosphite TRL- Temperature regulated ligand
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Thermo regulated biphasic catalysis Phase separation of Water-THF system – With CO2 dissolved under pressure OTAS-Organic –Aqueous Tunable Solvent
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pH dependent solubility of ligand is exploited
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Biphasic reactions with Supercritical CO 2
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Fluorous phase Catalysis Fluorous Solvents- Temperature dependent solubility for hydrocarbons Perfluorohexane Perfluorooctane Perfluoromethylcyclohexane
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Ionic liquids Ionic liquids can immobilize metal complexes and help in separation
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Methanol Synthesis CH 3 OH + HI→ CH 3 I +H 2 O CH3I + CO → CH 3 COI CH3COI + H 2 O → CH 3 COOH + HI CH3OH + HI→ CH3I +H2O Acetic anhydride synthesis CH3COI + CH3COOH → CH 3 CO CH 3 CO CH 3 COO CH 3 + HI → CH 3 COOH + CH 3 I O +HI Acetic anhydride by Carbonylation of methyl acetate
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Processes for manufacture of Methyl Methacrylic Acid -MMA Old process New process by Shell- Based on Reppe Chemistry
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Carbonylation of Propyene in methanol to MMA
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