Ethanol dehydrogenation with a palladium membrane reactor : An alternative to Wacker chemistry

The use of a membrane reactor offers the possibility of shifting the extent of reaction beyond the normal equilibrium position by continuously 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 reaction conditions, thereby dropping the yield of the desired aldehyde product. Herein, we show how the use of a palladium membrane to remove hydrogen in conjunction with a catalyst leads to a shift further to the right in the acetaldehyde-forming step before the product can react deleteriously with ethanol, and thereby increase the yield of acetaldehyde substantially over the conventional reactor case. With the membrane, ethanol conversion increased from 60% to nearly 90% with a commensurate rise in selectivity to acetaldehyde f...