Mechanistic aspects for the direct oxidative esterification of aldehydes with alcohols over Pd catalyst: A computational study

The detailed transformation mechanism of methacrolein with methanol to methyl methacrylate over Pd was investigated by density functional theory (DFT) calculation as an attempt to gain more insight into the oxidative esterification reaction. The entire catalytic cycle and reaction energies are computed for various possible paths over Pd20 cluster. It is found that the hydrogen elimination of MAL following acyl group reaction with methoxyl appears to be an energetically favorable pathway in catalyst cycle. The formation of unsaturated alcohol by H addition, and that of saturated aldehyde through the CC addition by methoxyl and H are also competitive. The formation of hemiacetal intermediate is not necessary for the production of MMA.

Oxidative esterification reaction: The detailed transformation mechanism of methacrolein with methanol to methyl methacrylate over Pd was obtained by density functional theory (DFT) calculation. On the basis of the computed activation parameters the hydrogen elimination of MAL following CO reaction with methoxyl is an energetically favorable pathway. The formation of unsaturated alcohol and saturated aldehyde are also competitive.Figure optionsDownload high-quality image (205 K)Download as PowerPoint slideHighlights
► The detailed transformation mechanism of methacrolein with methanol to methyl methacrylate over Pd20 cluster was investigated by density functional theory (DFT).
► The structures and relative energies of intermediates/transition states were calculated.
► The hydrogen elimination of MAL following acyl group reaction with methoxyl appears to be an energetically favorable pathway.