Rhenium oxide-modified H3PW12O40/TiO2 catalysts for selective oxidation of dimethyl ether to dimethoxy dimethyl ether

Abstract

An efficient rhenium oxide-modified H₃PW₁₂O₄₀/TiO₂ catalyst is found for a new synthesis of dimethoxy dimethyl ether from dimethyl ether oxidation. The effects of Re loading, H₃PW₁₂O₄₀ content and different feedstocks on the performance of Re–H₃PW₁₂O₄₀/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% H₃PW₁₂O₄₀/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 H₃PW₁₂O₄₀ 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 Re⁴⁺/Re⁷⁺ of Re–H₃PW₁₂O₄₀/TiO₂ were favorable for the formation of DMM₂ from DME oxidation. The possible reaction pathway of DME oxidation to DMM₂ was proposed.