Actual reliance of catalytic activities tuned oxygen vacancies on VOx/Ce1-xZrxO2 catalyst for selective oxydehydrogenation of methanol to dimethoxymethane

Abstract

Metal oxide catalysts like ceria-supported vanadia (VO_x/Ce_1-xZr_xO₂) with different Zr contents were prepared by coupling ceria-zirconia solid solution and vanadia. Characterization revealed that the insertion of zirconia into ceria significantly improved catalytic activity due to the generation of more oxygen vacancies and distortion of the composite structure. The oxygen vacancy concentration initially increased with the increase of Zr (x= wt%) and peaked at x=0.7 and then decreased. The reliance of oxygen vacancy concentration in VO_x/Ce_1-xZr_xO₂ catalyst on their catalytic activity in methanol oxydehydrogenation was further investigated. Results indicated that oxygen vacancies not only activated oxygen species but also cleaved C–H bonds alongside V⁵⁺ active site contained terminal oxygen atoms for cleaving O–H and C–H bonds within the adsorbed methanol. The VO_x/Ce_0.3Zr_0.7O₂ exhibited the best catalytic activity with the methanol conversion of 76 % and the dimethoxymethane selectivity of 96 % at 200 ℃ and atmospheric pressure in a fixed-bed reactor.