A simple discrimination of the promoter effect in alcohol oxidation and dehydrogenation over platinum and palladium

Transfer Dehydrogenation of 1-Phenylethanol Over Pd/C Under Mild Conditions: Effect of Reaction Conditions and Optimization of Catalytic Performance

“…As shown in Table 2, the mean particle size calcu-lated from TEM images for the thermally treated samples remain almost constant (~3 nm) when increasing the calci-nation temperature from 110 to 200 °C, while the palladium (0) to Pd(II) at relatively high temperature. This decrease in Pd(0) content in the catalyst is associated with a decrease in the catalytic performance, the higher content of Pd(0) on the catalyst, the higher catalytic performance in the liquid phase transfer dehydrogenation of 1-phenylethanol, which is in agreement with previous observations [12,23,27,28]. As a result of increasing the Pd(II) content in the samples calcined at 150 and 200 °C, an induction period occurred during the first period of the reaction.…”

“…This induction period is directly proportional to the percentage of Pd(II) in the catalyst, the higher Pd(II) content, the longer induction period was observed. The observed catalytic data during the induction period, can be explained based on the fact that the amount of Pd (0) increased during the induction period due to the chemical reduction of Pd(II) to Pd(0) via the dehydrogenation of alcohol and the formation of hydrogen that can act as a reducing agent [24,[26][27][28][29]. Con-sequently, a continuous increase in Pd(0)/Pd(II) ratio will take place within the induction period until reaching the required Pd(0)/Pd(II) to initiate the transfer dehydrogena-tion reaction of 1-phenylethanol.…”

“…In another study, the transfer dehydrogenation of benzyl alcohol in anaerobic conditions was investigated, and the results revealed compared to the selectivity values obtained in aerobic conditions of oxidation, a decrease in selectivity towards benzaldehyde formation. The authors pointed out that in anaerobic conditions, the results indicated that other by-products could be detected which formed by saturation of the aromatic ring or hydrogenolysis of the C-O, while the presence of oxy-gen inhibits the formation of these by-products resulting in increasing the selectivity toward benzaldehyde forma-tion [28]. Shen et al [3,30] investigated the catalytic performance of Cu catalyst in the transfer dehydrogenation of primary aliphatic alcohols.…”

Catalysing Sustainable Fuel and Chemical Synthesis

“…Typical promoters such as Ag, Bi, Pb and Sn [157,[193][194][195][196], enhance oxidation performance towards challenging substrates such as propylene glycol [197] as well as allylic and benzylic alcohols. Wenkin et al [194] reported glucose oxidation to gluconates was increased by a factor of 20 over Pd-Bi/C catalysts (Bi/Pd s = 0.1) versus Pd/C counterparts.…”

Recent advances in the heterogeneously catalysed aerobic selective oxidation of alcohols

“…121,127 Bismuth is also proposed to promoters supported Pt and Pd selox catalysts by (i) accelerating H abstraction during oxidative dehydrogenation (ii) and soaking up chemisorbed oxygen to replenish active metal sites for further reaction. 128 It is important to recognise that the nature of the active species in PGM catalysed selox, whether surface metal or oxide, remains hotly debated, however, there is unequivocal evidence that atomically-dispersed Pd 2+ sites can selectively oxidise allylic alcohols with very high rates, 15 hence surface oxides undoubtedly play an important role in driving the catalytic cycle. Since XAS is an averaging and not surface-sensitive technique, it should only be used in conjunction with careful XPS or surface IR methods to elucidate the nature of active sites.…”