Temperature-programmed desorption studies of alcohol decomposition on zinc oxide. Propan-2-ol

Abstract

Temperature-programmed desorption (t.p.d.) has been used to investigate the nature of the interaction of propan-2-ol with the zinc oxide surface. Adsorption at pressures of 10 Torr resulted in an averaged saturation coverage of 2 × 10¹⁴ molecule cm^–2 at 310 K. Temperature programming resulted in the desorption of propan-2-ol itself just above the adsorption temperature and a more strongly adsorbed intermediate species (an alkoxyl) decomposed at ca. 480 K to yield products of acetone, propene and hydrogen. It is proposed that these products derive from a sequential reaction scheme; first α-hydrogen elimination occurs, which yields acetone into the gas phase and an extremely reactive surface hydride. The latter then attacks remaining alkoxyl groups at a β-H position, the resulting transition state then decomposes to yield the alkene and hydrogen into the gas phase and shows a small temperature lag in the t.p.d. experiments.