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 + 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
Water as solvent-Demerits
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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
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Thermo regulated phase transfer catalysis
Use of fluorocarbons as solvents
Special mixtures of organic solvents
Super critical CO2
Ionic liquids
Thermo regulated biphasic catalysis
Basis
Solubility Vs Temp patterns
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 CO2
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