Homogeneous Catalysis HMC Dr. K.R.Krishnamurthy National Centre for Catalysis Research Indian Institute of Technology,Madras Chennai

Bi-phasic catalysis

Homogeneous Catalysis-Features

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

Biphasic Catalysis- Illustration

Biphasic Catalysis- Process Flow Scheme Biphasic Catalysis Liquid-Liquid Systems Water- Organic- Aqueous biphasic catalysis Organic-Organic

Polar ligands- for water soluble complexes

Telomerization of Butadiene Hydrocyanation of butadiene

Aqueous biphasic catalysis- Applications Synthesis of Phenyl acetic acid Conventional process Benzyl chloride → Benzyl cyanide → PAA 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$/kg Vs 0.2$)

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

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

Thermo regulated biphasic catalysis (TRPTC) Basis Solubility Vs Temp patterns PEG substituted Tri Phenyl Phosphine OctylPolyglycol- Phenylene-Phosphite

TGME-Triethylene glycol mono methyl ether

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

Ibuprofen- Old & New Processes Ibuprofen, 2-4-iso-butyl phenyl propionic acid

Celanese process for Ibuprofen  Isobutylation of benzene  Acylation & hydrogenation to alcohol  Carbonylation to yield Ibuprofen  Replaces the old process with six steps

 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

Ibuprofen from 4-Isobutyl stryrene OPGPP- OctylPolygly- Col-Phenylene-Phosphite TRL- Temperature regulated ligand

Thermo regulated biphasic catalysis Phase separation of Water-THF system – With CO2 dissolved under pressure OTAS-Organic –Aqueous Tunable Solvent

pH dependent solubility of ligand is exploited

Biphasic reactions with Supercritical CO 2

Fluorous phase Catalysis Fluorous Solvents- Temperature dependent solubility for hydrocarbons Perfluorohexane Perfluorooctane Perfluoromethylcyclohexane

Ionic liquids Ionic liquids can immobilize metal complexes and help in separation

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

Processes for manufacture of Methyl Methacrylic Acid -MMA Old process New process by Shell- Based on Reppe Chemistry

Carbonylation of Propyene in methanol to MMA