Selective Reduction of Acetic Acid to Acetaldehyde on Iron Oxides

Article abstract of DOI:10.1006/jcat.1994.1207

The selective reduction of acetic acid to acetaldehyde on iron oxides has been studied in various pressure ranges.A good selectivity towards acetaldehyde could be achieved with molecular hydrogen continously present in the gas phase and on a prereduced catalyst containing both a metal phase (zero-valent metal) and an oxidic phase.The pressure of acetic acid appears to influence the formation and the kind of by-products.At low pressure of acetic acid (0.015 mbar) ketene (CH2=C=O) is the most important (by-)product, while at high pressures (25 mbar) ketene has never been observed and acetone is the main (by-) product.Reaction mechanisms have been proposed for the selective reduction to acetaldehyde and for the formation of the (by-)products.Presumably the reduction to acetaldehyde occurs on the vacancy-rich oxidic layer, while hydrogen is dissociated on the zero-valent metal sites.The by-products are most likely formed via a common ketene-like intermedite.