ETHANOL DEHYDROGENATION WITH A PALLADIUM MEMBRANE REACTOR - AN ALTERNATIVE TO WACKER CHEMISTRY

The use of a membrane reactor offers the possibility of shifting the e xtent of reaction beyond the normal equilibrium position by continuous ly depleting one of the products. One Such case is the dehydrogenation of ethanol to acetaldehyde. Formation of acetaldehyde is endothermic and overall unfavorable, but the secondary formation of ethyl acetate from the product and reactant is exothermic and favorable. Therefore, it is observed that the secondary product forms under catalytic reacti on conditions, thereby dropping the yield of the desired aldehyde prod uct. Herein, we show how the use of a palladium membrane to remove hyd rogen in conjunction with a catalyst leads to a shift further to the r ight in the acetaldehyde-forming step before the product can react del eteriously with ethanol, and thereby increase the yield of acetaldehyd e substantially over the conventional reactor case. With the membrane, ethanol conversion increased from 60% to nearly 90% with a commensura te rise in selectivity to acetaldehyde from 35% to 70%, moving the yie ld from 21% to 63%.