Adsorption, thermal conversion, and catalytic hydrogenation of acrolein on Cu surfaces

The adsorption, thermal chemistry, and catalytic hydrogenation of acrolein on copper model surfaces was characterized by a combination of surface-science techniques, namely, reflection–absorption infrared spectroscopy (RAIRS) and temperature program desorption (TPD), quantum mechanics (DFT) calculations, and catalytic kinetic measurements using a so-called “high-pressure cell”. Adsorption of acrolein on the Cu surface was found to involve both the carbonyl oxygen atom and the C[dbnd]C bond. Thermal activation leads to early dissociation and dehydrogenation to produce acetylene and carbon monoxide below 160 K, and later to the production of ketene (220 K) and propene (260 K). Under vacuum hydrogenation with H₂ is not possible, but upon predosing of the surface with atomic H all the possible hydrogenation products, namely, propanal, 1-propanol, and allyl alcohol, were detected in TPD experiments, at 162, 190, and 210 K, respectively. Finally, catalytic hydrogenation under atmospheric pressures is slow and only produces propanal, at turnover frequencies below 0.2 s⁻¹.