IDENTIFICATION OF THE ACTIVE-SITES IN THE SELECTIVE HYDROGENATION OF ACETIC-ACID TO ACETALDEHYDE ON IRON-OXIDE CATALYSTS

Iron-based catalysts appeared to he very active and selective in the h ydrogenation of acetic acid to acetaldehyde. The active and selective catalyst consists of a metallic and an oxidic phase. Probably, the met al is needed to activate hydrogen, and the oxide is needed to provide the reaction site for the selective hydrogenation. Catalyst pretreatme nt and reaction conditions must be carefully controlled: the catalyst must be prereduced and the hydrogen/acid ratio must be higher than fou r Only then are both iron-containing phases formed and kept stable dur ing the reaction. The function of hydrogen is twofold: it must keep th e catalyst in its active, partly reduced, form and it acts as reactant in the hydrogenation of acetic acid. (C) 1998 Academic Press.