CATALYTIC DEHYDROGENATION OF ETHANOL IN A METAL-MODIFIED ALUMINA MEMBRANE REACTOR

Alumina membranes modified by metals (Pd, Pt, Cu, Ni) were prepared by the sol-gel method, and characterized by adsorption of N-2, scanning electron microscopy, X-ray diffraction and hydrogen-oxygen titration. The average pore diameters of the membranes were 4-7 nm, which is larger than for a pure alumina membrane, but still within the range of a Knudsen process. For the membranes modified by copper, nickel, the separation factor of H-2/Ar was close to that of pure Al2O3 membrane, but for the membranes modified by palladium, platinum, the separation factor of H-2/Ar was not only better than the pure Al2O3 membrane, but also than the Knudsen value. This suggested that the increase of the selectivity for hydrogen permeation through the membranes was caused by adsorption of hydrogen to palladium or platinum. The catalytic dehydrogenation of ethanol to acetaldehyde was performed in these membrane reactors. For the palladium, platinum modified membrane reactor, the yield of acetaldehyde was higher than that in the pure Al2O3 membrane reactor, and increased with the flow-rate of sweeping argon.