Zn supported on titania-doped mesoporous silicate MCM-41 as efficient catalysts for acetylene hydration†
A highly efficient grafting method to synthesise Ti-doped MCM-41 mesoporous supports and their respective Zn catalysts was investigated. The structure and dispersion of titanium species for the as-synthesised materials and their influence on the catalytic performance of Zn catalysts in the acetylene hydration reaction were systematically studied. All of the synthesised materials were characterised by FTIR, XRD, BET, TEM, NH3-TPD, XPS, TG and solid-state UV-vis techniques. NH3-TPD and pyridine FTIR confirm that the incorporation of titanium species greatly enhanced the acid sites and total acid quantity. The XRD, TEM and UV-vis results reveal that the addition of titania in the form of Ti4+ ions having a tetrahedral coordination can facilitate the control of zinc particle sizes and enhance the dispersion of zinc species. XPS suggests that the introduction of titania enhanced the enrichment of zinc species on the surfaces of supports. In addition, the superior interaction between active Zn species and the modified support effectively inhibited the deposition of carbon and the reduction of active Zn species during the reaction. Moreover, the incorporation of titania considerably enhanced the catalytic activity and stability of Zn/MCM catalysts. The best Zn/Ti-MCM-5 catalyst exhibited a C2H2 conversion of nearly 95% and a selectivity to acetaldehyde of 90%.