The surface construction of Mo–O–Bi coordination for high catalytic performance in gas-phase epoxidation of propylene with O2

Abstract

To solve the issue of facile aggregation of active components and limited synergetic catalysis of MoO₃/Bi_xSi_1–xO₂ catalysts, we highlight an efficient strategy to achieve Mo–O–Bi coordination to fix MoO₃ strongly on a surface and improve its dispersion. Incorporating the characterization methods of XRD, N₂ adsorption/desorption, ICP, NH₃-TPD, Raman spectroscopy, TEM and XPS, the surface chemical and structure properties of Bi_xSi_1–xO₂ supports with and without modification and the supported Mo catalyst were systematically investigated. Both the dispersion of Mo and the synergetic catalysis of Bi/Mo were restrained by the self-passivated layer of the Bi_xSi_1–xO₂ support, which led to limited catalytic performance. Mo–O–Bi coordination was achieved by modification of the support in which MoO₃ was anchored on the support and monodispersed homogeneous MoO₃ was obtained. Based on this approach, the epoxidation activity of the MoO₃/Bi_xSi_1–xO₂ catalyst was obviously enhanced; C₃H₆ conversion increased from 13.2% to 20.4%, and the selectivity of propylene oxide (PO) reached 73.2%. As such, this strategy may be useful for the preparation of other high performance supported catalysts.