Abstract
The epoxidation of propene without forming a substantial amount of byproducts is one of the holy grails of catalysis. Supported Cu, Ag and Au catalysts are studied for this reaction and the activity of the supported metals is generally well understood. On the contrary, limited information is available on the influence of the support on the epoxide selectivity. The reaction of propene with equal amounts of hydrogen and oxygen was tested over gold nanoparticles deposited onto CeO2, TiO2, WO3, γ-Al2O3, SiO2, TiO2-SiO2 and titanosilicate-1. Several metal oxide supports caused further conversion of the synthesized propene oxide. Strongly acidic supports, such as WO3 and titanosilicate-1, catalyzed the isomerization of propene oxide towards propanal and acetone. Key factors for achieving high PO selectivity are having inert or neutralized surface sites, a low specific surface and/or a low density of surface -OH groups. This work provides insights and practical guidelines to which metal oxide support properties lead to which products in the reaction of propene in the presence of oxygen and hydrogen over supported gold catalysts.
Highlights
Propene oxide (PO) is a chemical intermediate that is widely used in the production of a variety of derivates, including polyether polyols and propene glycol [1,2]
Gold nanoparticles were deposited on metal oxide supports by two different methods: deposition precipitation-urea was performed for the synthesis of Au/TiO2 and Au/CeO2, while the other catalysts were prepared using cation adsorption of Au(en)2 Cl3 [15,51–53]
This study for the first time gives an overview of the role of metal oxide supports in the Au catalyzed propene epoxidation reaction in the presence of H2
Summary
Propene oxide (PO) is a chemical intermediate that is widely used in the production of a variety of derivates, including polyether polyols and propene glycol [1,2]. To gold particle size and charge, the surface prop often redox active, which is essential for catalysis of oxidation reactions that follow a based supports such as reducibility and acidity/basicity. Other metal epoxidations, oxides with Lewis acid reported activate H2 Opropen a similar fashion, but2are studied in liquid phase reactions. Metal oxides with Lewis acid sites are proposed to activate H2O2, which studied using a variety of supports, including α-Al2 O3 , SiO2 , WO3 and CaCO3 [32,38–41]. In this study the reactivity of PO over a series of frequently used catalyst supports was examined in the gold-catalyzed propene epoxidation in the presence of H2 and O2. We focus on how physicochemical properties of metal oxides affect the selectivity during propene epoxidation
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