Methanol oxidation on Au(332): methyl formate selectivity and surface deactivation under isothermal conditions

Abstract

Surface deactivation for partial methanol oxidation to methyl formate on Au(332) under oxygen-deficient conditions at low temperatures suggests a small number of highly active sites for methyl formate formation.

Heterogeneity of oxygen reactivity: key for selectivity of partial methanol oxidation on gold surfaces

“…S2, ESI †). It should be noted that no methyl formate formation is detected under the applied conditions for temperatures above 270 K, 20,21 as formaldehyde desorption competes effectively at high temperatures with the coupling reaction under single collision conditions, similar to short contact times in np-Au catalysts. 11 Detection of small amounts of formaldehyde is, however, hampered by large (fragmentation) signals due to methanol.…”

“…3 Schematic representation of reactions of oxygen on Au(332) with methanol and methyl formate. 18,20,21 O lc denoting oxygen on lowcoordinated sites, O lc,sp the subset of O lc active in the methyl formate oxidation, O all other types of oxygen species on the Au(332) surface and P denoting other products. Double-crossed reaction arrows indicate that the respective reaction does not occur at a significant rate.…”

Nanoporous Gold: From Structure Evolution to Functional Properties in Catalysis and Electrochemistry

“…In accord, dropping selectivities were indeed observed in isothermal molecular beam experiments upon raising the temperature. 451 A further aspect that may limit the comparability of such model studies with catalytic results is related to the fact that, in the former case, the product methyl formate may desorb after its formation and thus escape further potential conversion steps. On the contrary, the chance for secondary reactions, possibly leading to total oxidation, in a catalyst bed or in a larger monolithic NPG catalyst is high due to the likelihood of multiple collisions with the catalytic surface.…”

“…In the case of partial methanol oxidation, for example, formaldehyde desorption taking place before the molecule can undergo the subsequent coupling reaction to the ester will obviously result in a lower selectivity. In accord, dropping selectivities were indeed observed in isothermal molecular beam experiments upon raising the temperature …”

Catalytic activity of 1D chains of gold oxide on a stepped gold surface from density functional theory

“…The nature of the reactive O species on a stepped gold surface has been at the heart of intensive research in heterogeneous catalysis. We expect that linear (''onedimensional'') O chains may be formed on the stepped gold surface when there is a sufficient supply of O atoms, 39 whereas two-dimensional O chains are likely to form in an abundant supply of O atoms (as for example, on Au surfaces with preadsorbed O 23,[45][46][47][48] or in molecular beam experiments 49,50 ). O atoms in such 1D and 2D oxide structures are expected to be less reactive compared to individual O atoms, and, therefore, formation and growth of O chains may also occur during ambient oxidation catalysis on Au-based catalysts, such as nanoporous gold.…”