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 = k(1)(ps)C(A) - k(-1)C(P) (with k(1)(ps) = k(1)*sigma rho(PH) (with k(ps) being the pseudo-first-order reaction rate constant of the forward reaction, k(1)* the idem, but applied per equivalent acid, sigma the acid capacity, rho(PH) 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 k(1.aq)* = 7.09 x 10(5) exp(-(87.01 +/- 6.94) x 10(3)/(RT)) m(aq)(3) 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 x 10(-4) exp(-(33.0 +/- 47.9) x 10(3)/(RT)) m(s)(3) 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.