Titania-supported molybdenum oxide combined with Au nanoparticles as a hydrogen-driven deoxydehydration catalyst of diol compounds

Abstract

A heterogenous catalyst for the deoxydehydration (DODH) reaction was developed using less expensive Mo than Re as the active center. The combination of Mo with anatase-rich TiO₂ and Au as the support and promoter for H₂ activation, respectively, can selectively convert 1,4-anhydroerythritol to 2,5-dihydrofuran, which is a typical DODH model reaction, with H₂ as a reducing agent. Loading of Au on TiO₂ by the deposition–precipitation method gave the more active MoO_x–Au/TiO₂ catalyst (MoO_x–^dpAu/TiO₂) than that obtained by the impregnation method (MoO_x–^impAu/TiO₂), and the activity difference is derived from the smaller size of Au particles in MoO_x–^dpAu/TiO₂ (3–5 nm) than that in MoO_x–^impAu/TiO₂ (>25 nm). The MoO_x–^dpAu/TiO₂ catalyst could be applied to the DODH reaction of linear alkyl vicinal diols and cis-1,2-cyclohexanediol. The characterization with XRD, STEM, H₂-TPR, XAFS and XPS revealed that the Mo^IV oxide cluster species on the surface of anatase TiO₂ particles are responsible for the DODH reaction.