Impregnating photo-stable gold precursor onto uncalcined TS-1 to boost catalytic hydro-oxidation of propane

Immobilizing highly dispersed Au nanoparticles onto titanium silicalite-1 (TS-1) by a simple impregnation method under light is still a challenging task. In this work, a high photostable Au precursor protected by thiol ligands was firstly synthesized, and the as-prepared Au precursor displayed excellent stability under light for over 30 days, while the Au precursor without thiol ligands formed precipitates after just 2 h under light. Subsequently, the Au precursor protected by thiol ligands was immobilized on the external surface of uncalcined TS-1 (i.e., TS-1-B) by the incipient wetness impregnation method (IWI method) to prepare Au/TS-1-B catalyst. The activity of as-prepared Au/TS-1-B catalyst in the hydro-oxidation of propane to acetone was 1.4 times higher than that of the catalyst prepared by the deposition-precipitation urea method (DPU method). The structures of the Au/TS-1-B catalysts prepared by different methods were analyzed by multiple characterizations. Compared to the Au/TS-1-B catalyst prepared by the DPU method, the Au/TS-1-B catalyst synthesized by the IWI method exhibited a narrower size distribution of Au nanoparticles and had more small Au particles (<2 nm), which is the main reason for its superior activity. Additionally, the effects of gold loadings, reaction temperature and Si/Ti molar ratio on the catalytic performance of the Au/TS-1-B catalyst prepared by the IWI method were also investigated. In addition, the Au/TS-1-B catalyst prepared by the IWI method also exhibited excellent stability for over 140 h.