Propan-2-ol adsorption and decomposition on zinc oxide promoted by alkali metal

Abstract

Temperature-programmed desorption has been used to investigate the adsorption and decomposition of propan-2-ol on potassium-promoted polycrystalline ZnO catalysts. The observed desorption and decomposition products were as follows: reversible adsorption yielding the parent alcohol, dehydrogenation to acetone and hydrogen, dehydration to propene and water, and an oxidative decomposition to carbon dioxide, hydrogen and methane. Three propene states were observed, but the water produced was mainly readsorbed and desorbed at high temperature. Only propene was formed in a significant amount on the Zn(0001) polar surface, while both acetone and propene were produced on the non-polar (1010) faces. Limited reaction took place on the O(0001) surface to yield a small quantity of propene. Alkali-metal promotion was found to change the reaction selectivity such that dehydration was completely suppressed on both polar surfaces and to a significant extent on the non-polar face. Dehydrogenation of propan-2-ol to acetone was enhanced by potassium promotion, as was the quantity of reversibly adsorbed propan-2-ol.