Gold Nanoparticles for Oxidation Reactions: Critical Role of Supports and Au Particle Size
Supported gold nanoparticles (Au NPs) exhibit unique catalytic properties for the oxidation of organic compounds. The catalytic activities and the selectivities of the supported Au catalysts largely depend on the kind of support and the particle size of A
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Gold Nanoparticles for Oxidation Reactions: Critical Role of Supports and Au Particle Size Tamao Ishida, Ayako Taketoshi, and Masatake Haruta
Contents 1 Introduction 2 Oxidation of Alcohols to Aldehydes and Ketones 2.1 Reducible MOx 2.2 Non-reducible MOx 2.3 Non-oxides 2.4 Inorganic-Organic Hybrids 2.5 Carbonaceous and Organic Materials 2.6 Non-supported Au 3 Oxidation of Alcohols and Aldehydes to Carboxylic Acids 4 Oxidative Esterification of Alcohols and Aldehydes 5 Dehydrogenation of Alcohols in the Absence of O2 6 Oxidation of Alkenes 7 Oxidation of Alkanes 8 Oxidative C–H Coupling Reaction 9 Conclusion References
T. Ishida (*) Department of Applied Chemistry for Environment, Graduate School of Urban Environmental Sciences, Tokyo Metropolitan University, Tokyo, Japan Research Center for Gold Chemistry, Graduate School of Urban Environmental Sciences, Tokyo Metropolitan University, Tokyo, Japan e-mail: [email protected] A. Taketoshi Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, Tokyo, Japan Research Center for Gold Chemistry, Graduate School of Urban Environmental Sciences, Tokyo Metropolitan University, Tokyo, Japan M. Haruta Research Center for Gold Chemistry, Graduate School of Urban Environmental Sciences, Tokyo Metropolitan University, Tokyo, Japan
T. Ishida et al.
Keywords Alcohol oxidation · Alkane oxidation · Alkene oxidation · Gold clusters · Gold nanoparticles · Oxidative coupling · Oxidative esterification
1 Introduction Selective oxidation is of great importance in chemical industry, because oxidation reactions occupy ca. 30% of chemical processes. In particular, aerobic oxidation using O2 or air as an oxidant is regarded as an environmentally benign reaction that can avoid use of harmful stoichiometric oxidants and minimize wastes. Thus, development of heterogeneous oxidation catalysts that have not only high catalytic activity but also high selectivity to a specific functional group in the substrates is highly desired. Since the discovery of catalysis by gold nanoparticles (Au NPs) in 1987 [1], Au has attracted growing interest in the field of catalysis [2–4]. In the early studies, reducible metal oxides (MOx) supported Au NPs were revealed to exhibit very high catalytic activity for CO oxidation below room temperature, while supported Pd and Pt catalysts generally required higher reaction temperature such as 100 C [1, 5]. Au also exhibits unique catalysis for propylene oxidation to give propylene oxide directly and selectively in the presence of H2 and O2 [6] and then O2 and H2O [7]. Reducible MOx, such as Fe2O3, Co3O4, NiO, and MnO2, are defined as that the MOx have redox properties or have semiconducting properties. The oxygen atoms in the reducible MOx are easily removed to form the oxygen vacancies on the surface. Because bare Au surface cannot dissociate O2 in contrast to Pd and Pt [8], the oxygen vacancies near the Au NPs play an important role for O2 activation in the gas-phase CO oxidation over Au catalysts. Namely, CO is adsorbed on Au
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