Catalysis-spillover-membrane-2 - The rate enhancement of methanol steam reforming reaction in a membrane catalytic reactor

Steam reforming reaction of methanol was carried out with commercial G66B catalyst (CuOZnO) and with two modified catalysts, 1 % Pd/G66B and 1% La2O3/G66B at a temperature of 270, 310 and 350 degreesC under a pressure of 0.1, 0.4 and 0.9 MPa absolute pressure. The space velocity ranges from 427 to 460 h(-1) to allow the conversion level small between 3 and 17 mol%. Similar reactions rate studies were carried out with the catalytic reactor inserted with a palladium membrane tube at 310 degreesC and 0.9 MPa absolute pressure. It was found that the reaction rates in the catalytic membrane rector (CMR) were 50-100% faster than the corresponding reaction without the Pd-membrane in the reactor. Likewise, rate enhancement was also observed in the steam reforming reactions of n-hexane at 500 degreesC under an absolute reaction pressure of 0.9 MPa. The rate enhancement by the use of Pd-membrane is attributed to the reverse hydrogen spillover from the catalyst sites to the palladium surface of membrane; this hydrogen spillover enables the hydrogen occupancy on the catalyst sites to be shortened and become more efficient for catalytic turning over. Since the observed rate enhancement takes place in the forward reaction, it is proposed that the general phenomena of higher reaction conversion by the use of catalytic membrane reactor is a result of speed up forward reaction rate not the reduced backward reaction rate as generally proposed in the literature. (C) 2004 Published by Elsevier B.V.