Promotional role of Ceria in N2O assisted selective oxidative dehydrogenation of ethylbenzene over Ce–Co2AlO4 spinel catalysts

Abstract

The coupling of N2O decomposition with ethylbenzene (EB) dehydrogenation is a promising technique for greenhouse gas elimination and chemical production. The Ce–Co2AlO4 catalyst synthesized by the one-pot hydrothermal method was found to be effective for the oxidative dehydrogenation of ethylbenzene with N2O to form styrene (ST), and characterized by BET, XRD, TEM, TPR, TPD, and XPS techniques. Results showed that 0.10Ce–Co2AlO4 catalyst exhibited high EB conversion (61%) and good ST selectivity (80%), which was remarkable superior to the previously reported catalyst systems. The crystallite size of the catalyst showed a clear increasing trend with the increasing of Ce/Co molar ratio, resulting in an increased specific surface area. Among the factors determining catalytic performance, the larger number of oxygen vacancies and better reducibility of 0.10 Ce–Co2AlO4 catalyst significantly influenced the N2O adsorption and EB dehydrogenation processes. It was found that the good moderate acidic condition of 0.10Ce–Co2AlO4 catalyst was attributed to the masking of surface strong acid sites by Ce oxide, which weakened the ring-opening and dealkylation reactions during the dehydrogenation process, thus decreasing the accumulation of the deposited coke on the catalyst surface. The inter-transmission of oxygen species and N2O promotes the occupation of the oxygen vacancies and restores the redox cycle of the Co–Ce oxides, in accordance with the redox mechanism.