PolyHipe: A new polymeric support for heterogeneous catalytic reactions: Kinetics of hydration of cyclohexene in two- and three-phase systems over a strongly acidic sulfonated PolyHipe

A novel type of highly porous polymeric monolith called PolyHipe has been applied as a support for an immobilized catalyst (sulfonic acid). Somewhat differently from a conventional packed bed where the reaction mixture flows around the porous catalytic particles, here, the reaction mixture is forced through the pores of the monolith. The kinetics of the liquid-phase hydration were measured both in a three-phase system consisting of an aqueous, an organic, and the polymer resin phase and in a two-phase system consisting of a solution of cyclohexene in aqueous sulfolane (90 mol % sulfolane) and the polymer resin phase, at a pressure of 2 MPa and temperatures between 343 and 368 K. In the three-phase system the observed conversion rates were analyzed by a three-phase reaction model with mass transfer and reaction based on the rate equation RA = k1psCA − k-1CP (with k1ps = k1*σρPH (with k1ps being the pseudo-first-order reaction rate constant of the forward reaction, k1* the idem, but applied per equivalent acid, σ the acid capacity, ρPH the apparent density of the PolyHipe, k-1 the first-order reaction rate constant of the backward reaction, and CA and CP the cyclohexene and cyclohexanol concentrations in the water phase, respectively), giving k1,aq* = 7.09 × 105 exp(−(87.01 ± 6.94) × 103/(RT)) maq3 equiv-1 s-1, where k1,aq* is the initial reaction rate constant of the reaction, R is the ideal gas constant, T is the temperature, and the subscript “aq” is the aqueous phase. In the two-phase system the observed initial rate equation could be described according to k1,s* = 4.1 × 10-4 exp(−(33.0 ± 47.9) × 103/(RT)) ms3 equiv-1 s-1, where the subscript “s” is the aqueous sulfolane phase. The value of k1,aq* agrees with the literature values of the initial rate constant measured in conventional ionic exchange beads (Amberlite XE307). k1,s* is an order of magnitude smaller than that in Amberlite XE307.