Single-site phase-transfer catalysis

Mechanism of Triphase Catalysis.. Although the activity of a supported PT catalyst is usually less than that of the corresponding soluble catalyst, it is believed (Molinari et al., 1979 Montanari et al., 1983, Anelli et al., 1984) that the mechanism of the phase-transfer cycle remains the same. However, there are certain characteristics typical of heterogeneous catalysts that make supported PTC different from soluble PTC. For example, in a triphase catalytic system, one does not consider the planar phase boundary as in a classical two-phase system. Instead, a volume element which incorporates the catalytic active sites as well as the two liquid phases has to be considered. Diffusion of both the aqueous and organic phases within the solid support is important. Various mechanisms have been proposed for triphase catalysis, some of which are touched upon here. However, it should be noted that no single mechanism has been verified completely, and it is quite possible that the true mechanism involves a combination of the various mechanisms proposed so far. 

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