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 R_A = k₁^psC_A - k_-1C_p (with k₁^ps = k₁^*σρ_PH (with k₁^ps being the pseudo-first-order reaction rate constant of the forward reaction, k₁^* the idem, but applied per equivalent acid, σ the acid capacity, ρ_PH the apparent density of the PolyHipe, k_-1 the first-order reaction rate constant of the backward reaction, and C_A and C_P the cyclohexene and cyclohexanol concentrations in the water phase, respectively), giving k_1,aq^* = 7.09 × 10⁵ exp(-(87.01 ± 6.94) × 10³/(RT)) m_aq³ equiv^-1 s^-1, where k_1,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 k_1,s^* = 4.1 × 10^-4 exp(-(33.0 ± 47.9) × 10³/(RT)) m_s³ equiv^-1 s^-1, where the subscript 's' is the aqueous sulfolane phase. The value of k_1,aq^* agrees with the literature values of the initial rate constant measured in conventional ionic exchange beads (Amberlite XE307). k_1,s^* is an order of magnitude smaller than that in Amberlite XE307.