An experimental and theoretical investigation of a catalytic membrane reactor for the oxidative dehydrogenation of methanol

The catalytic oxidation of methanol was investigated employing a tubular wall reactor to elucidate reaction kinetics and a membrane reactor to record performance. The membrane reactor consisted of a composite multilayered ceramic tube impregnated with platinum catalyst and housed within a shell of stainless steel construction. Thermodynamic calculations and catalyst activity experiments revealed that hydrogen is a main product of reaction for mixtures rich in methanol and lean in oxygen for temperatures up to 300 degreesC and 1 bar pressure. Kinetic experiments indicated that two separate pathways yielding hydrogen were prevalent: a catalytic dehydrogenative oxidation giving H-2 and CO2 as products and complete catalytic combustion giving CO2 and H2O. Further experimental measurements using the catalytic membrane reactor showed that hydrogen as product could be partially separated from the reaction products by the action of the ceramic membrane. a comprehensive theoretical model of the membrane reactor was constructed using Maxwell-Stefan equations, the dusty gas model and differential energy balances. Results of the theoretical investigation utilising the kinetic parameters found by experiment indicated reasonably good agreement between theory and experiment. However, it was also clear that using a ceramic membrane impregnated with catalyst is not an efficient way to achieve H, separation during reaction on account of the ability of H, under the prevailing reaction conditions to diffuse in opposite directions simultaneously. (C) 2001 Elsevier Science Ltd. All rights reserved.