Rhenium oxide-modified H3PW_(12)O_(40)/TiO2 catalysts for selective oxidation of dimethyl ether to dimethoxy dimethyl ether

摘要

An efficient rhenium oxide-modified H3PW_(12)O_(40)TiO2 catalyst is found for a new synthesis of dimethoxy dimethyl ether from dimethyl ether oxidation. The effects of Re loading, H3PW_(12)O_(40) content and different feedstocks on the performance of Re-H3PW_(12)O_(40)/TiO2 were investigated. The results showed that DMM2 selectivity was significantly improved up to 60.0%, with 15.6% of DME conversion over 5% Re-20% H3PW_(12)O_(40)/TiO2. NH3-TPD, NH3-IR, Raman spectra, H2-TPR, XPS and TEM were used to extensively characterize the structure and surface properties of the catalysts. The introduction of H3PW_(12)O_(40) significantly affected the structure and reducibility of surface rhenium oxide species, in addition to increasing the acidity of the catalyst. The increased number of Lewis acid sites and weak acid sites and the optimal ratio of Re~(4+)/Re~(7+) of Re-H3PW_(12)O_(40)TiO2 were favorable for the formation of DMM2 from DME oxidation. The possible reaction pathway of DME oxidation to DMM2 was proposed.