AuPd Bimetallic catalyst for Lignin-derivatives alcohols valorization

Lignin moieties consist in three hydroxycinnamyl alcohol derivatives (p-coumaryl, coniferyl and sinapyl alcohols), which differ in the degree of methoxylation on the aromatic ring. Their oxidation to aldehydes is one of the major methods for their valorization. Au-Pd based catalysts effectively oxidize benzyl alcohol (BA), as Wang et al. showed that the Au:Pd ratio on the surface of the particles is a key parameter that influences the catalytic performance. On the basis of these results, here we investigated the effect of the methoxy substituent on catalytic activity of Au-Pd catalysts by studying the oxidation of 4- and 3,4-Dimethoxybenzyl alcohol (4-MBA, 3,4-DMBA) to the corresponding aldehydes. Samples at different Au/Pd ratio were synthesized by sol impregnation. The presence of the OMe group influenced the catalytic activity, depending on its position. When OMe is in para, we observed a clear difference in catalytic activity by changing the Au-Pd ratio. Contrariwise, a substantial negligible effect of the Au/Pd ratio was detected for 3,4-DMBA oxidation. A deep characterization of the NPs structure will be shown to give some insight on the reaction