A new gas-liquid-solid reactor is presented whose concept is based on the coupling of liquid imbibition, evaporation, and an exothermic gas-phase reaction within a non-perm selective catalytic porous membrane. Because of enhanced thermal conductivity of the sintered metal catalyst support and liquid flow re-circulation, it is possible to eliminate hot spots and runaways and to maintain high productivity of the reactor. When vapor conversion in the membrane is high, the problem of separation of the product from the gas phase reduces to common condensation. The preliminary experiments on the alpha-methylstyrene (AMS) hydrogenation on the 10% (0.9% Pd/gamma-Al2O3) + 90% (80% Ni, 20% Al) membrane sintered on the tube wall are very promising, however, further investigations are required. (C) 2003 Elsevier Science B.V. All rights reserved.