A Comparative Study of Size Effects in the Au‐Catalyzed Oxidative and Non‐Oxidative Dehydrogenation of Benzyl Alcohol

Abstract

A hydrotalcite-supported gold catalyst has been found to be efficient for both oxidative and non-oxidative conversions of benzyl alcohol into benzaldehyde. In both cases, the reaction rates were dependent on the size of the Au particles, but the size dependence for the non-oxidative reaction was more pronounced. Our analyses on the intrinsic rates of different sites suggested that all of the atoms on the Au surfaces participated in the oxidative reaction, whereas the edge and corner Au atoms predominantly contributed to the non-oxidative reaction, and that the terrace atoms were at least two orders of magnitude less active than the edge or corner atoms. In both cases, the rate-determining step was CH bond cleavage. The presence of oxygen significantly enhanced the reaction rate. Herein, we propose that the non-oxidative reaction proceeds through a β-H elimination step by the low-coordination-number edge and corner Au atoms, whereas the active oxygen species, which are even generated on the terrace Au atoms, might assist CH bond cleavage under oxidative conditions.

Supported rhenium nanoparticle catalysts for acceptorless dehydrogenation of alcohols: structure–activity relationship and mechanistic studies

“…To meet environmental and economical acceptability, efforts have been devoted to heterogeneous catalytic systems for acceptorless dehydrogenation of alcohols. [8][9][10][11][12][13][14][15][16][17][18][19][20] However, rational improvement of the catalytic efficiency of heterogeneous catalyst for this reaction is still difficult due to a lack of fundamental information on the structure-activity relationship and reaction mechanism. For example, controversial models are proposed on the oxidation states of transition metal catalysts for this reaction; metallic species are proposed to be effective for the supported Ag, 17 Co, 18 Ni 19 and Pt 20 catalysts, whereas Re 0 -core/ReO 2 -shell model is proposed as an active Re species of unsupported nanocrystalline catalyst.…”

Supported Cobalt Catalysts for Acceptorless Alcohol Dehydrogenation

“…Noble metal-based catalysts, i.e. Pt, [18] Pd, [19] Ru, [20,21] Re, [22] Au, [23][24][25] and Ag, [26][27][28][29][30] have been shown to be active towards acceptor-less alcohol dehydrogenation. Due to their higher abundancy and lower costs, non-noble metal catalysts have also been investigated, namely Cu, [31][32][33] Ni, [34,35] and Co [36] which proved to be also active.…”

One‐pot oxidant‐free dehydrogenation‐Knoevenagel tandem reaction catalyzed by a recyclable magnetic base‐metal bifunctional catalyst

“…In recent years, some catalysts have been developed for the dehydrogenation of alcohols without oxidants or hydrogen receptors. [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] However, most of them need to be carried out in organic solvents or in the presence of acid or alkali additives and have some unavoidable deficiencies including long reaction time, high temperature and inconvenient recovery of catalyst. Therefore, development of an efficient, atomeconomic and green method for the preparation of carbonyl compounds from the corresponding alcohols is still demanded.…”