Efficient aerobic oxidative desulfurization over Co–Mo–O bimetallic oxide catalysts

Abstract

In this work, CoMo bimetallic oxides were prepared and proposed as catalysts for aerobic oxidative desulfurization (AODS) of fuels with oxygen in air as the oxidant. The bimetallic oxides could efficiently catalyze the oxidation of a series of thiophenic compounds at 80–120 °C and atmospheric pressure, while the neat Co or Mo oxide didn't show any catalytic ability, which directly proved the synergistic effect of Co and Mo. In the bimetallic system, the Co(II) sites could exhibit the capability to activate oxygen, while the Mo(IV) sites were suspected to directly participate in the oxidation of sulfides by forming reactive species. As is clearly evidenced by the characterization and experimental results, with the variation of Co/Mo proportion (2 : 1, 1 : 1 and 1 : 2), the bimetallic oxides possessed different electronic structures and surface compositions, which further led to their distinct catalytic performances. When the Co/Mo ratio was 2 : 1, the best performance was obtained, and some important reaction parameters were investigated. Furthermore, the catalyst could be reused for at least five cycles without changes in catalytic performance and chemical structure. Based on these results, it is expected that the CoMo bimetallic oxides may serve as an efficient, separable and recyclable catalyst for AODS of fuels.