Oxidation Catalysis of Au Nano-Particles Immobilized on Titanium(IV)- and Alkylthiol-Functionalized SBA-15 Type Mesoporous Silicate Supports

Abstract

Novel Au nano-particle catalysts immobilized on both titanium(IV)- and alkylthiol-functionalized SBA-15 type ordered mesoporous silicate supports were developed. The bi-functionalized SBA-15 type support could be synthesized by a one-pot method. To the synthesized supports, Au was immobilized by the reaction of the alkylthiol groups on the supports with AuCl4−, following reduction with NaBH4. The immobilized amount and the formed structures and the electronic property of the Au species depended on the loading of alkylthiol. The moderate size (2–3 nm) nano particulate Au sites formed on Ti(0.5)-SBASH(0.5) were negatively charged. The aerobic alcohol oxidation activity of the catalysts depended on the loading of alkylthiol and the structure of the Au nano-particles. The non-thiol-functionalized catalyst (Au/Ti(0.5)-SBASH(0)) composed of the large (5–30 nm) and the higher thiol-loaded catalyst (Au/Ti(0.5)-SBASH(8)) composed of the small cationic Au species were almost inactive. The most active catalyst was Au/Ti(0.5)-SBASH(0.5) composed of the electron-rich Au nano-particles formed by the electron donation from the highly dispersed thiol groups. Styrene oxidation activity in the presence of 1-phenylethanol with O2 depended on the loadings of titanium(IV) on the Au/Ti(x)-SBASH(0.5). The titanium(IV) sites trapped the H2O2 generated through the alcohol oxidation reaction, and also contributed to the alkene oxidation by activating the trapped H2O2.

Advanced Oxidation Process: Applications and Prospects

“…Navidpour et al [21] present a review of the photocatalytic processes and the mechanisms, reaction kinetics, and optical and electrical properties of semiconductors, and the unique characteristics of titanium as the most widely used photocatalyst; and compare the photocatalytic activity between different titania phases (anatase, rutile, and brookite) and between colorful and white TiO 2 nanoparticles. Haketa et al [22] designed novel Au nano-particle catalysts immobilized on both titanium(IV)-and alkylthiol-functionalized SBA-15 type mesoporous silicates. The combination of Au nano-particle catalysts and other species that activate H 2 O 2 served as an aerobic oxidation catalyst applicable to various substrates, including alkenes and alkanes.…”