PHASE-TRANSFER CATALYSIS - CHEMISTRY AND ENGINEERING

Phase transfer catalysis (PTC) uses catalytic amounts of phase transfe r agents which facilitate interphase transfer of species, making react ions between reagents in two immiscible phases possible. PTC is used w idely in the synthesis of various organic chemicals in both liquid-liq uid and solid-liquid systems. Existing literature on PTC is chemistry- intensive and a mere handful of recent articles constitute the entire information on engineering analysis. This article reviews the field co mprehensively by combining the existing knowledge from chemistry with insights into mechanistic and kinetic analysis and mathematical modeli ng of soluble and insoluble PTC. By its very nature, PTC involves a se ries of equilibrium and mass-transfer steps, beside the two main react ions. Neglect of mass-transfer effects can grossly overpredict the con version of a PTC mediated reaction. A practical way of using PTC, whic h enables easy separation is to immobilize the catalyst on a solid sup port. Mass-transfer limitations and higher costs, however have preclud ed its commercial use so far, requiring further analysis of mass-trans fer limitations in these complex three-phase systems. The use of PTC, combined with other rate enhancement techniques like sonochemistry, mi crowaves, electroorganic synthesis, and photochemistry, is being incre asingly explored. Applications in this area in the manufacture of orga nic intermediates and fine chemicals seem almost unlimited.