Elucidation of the reaction mechanism of catalytic reaction coupling of ethylbenzene dehydrogenation with nitrobenzene hydrogenation over MoO3/TiO2 catalysts

Catalytic coupling of ethylbenzene (EB) dehydrogenation with nitrobenzene (NB) hydrogenation offers potential economical and energetic benefits. However, several studies in the literature have shown that NB conversion could be higher than that of EB, violating the law of mass conversion. This work provides a new understanding of this reaction coupling scheme over MoO3/TiO2 catalysts to elucidate this scientific mystery. Our results suggest that EB and NB have different adsorption rates on the TiO2 surfaces, resulting in higher NB conversion. In addition, three distinct reaction schemes, each follows a different EB to NB stoichiometric ratio, were identified on the MoO3 surfaces. The occurrence of the reactions is dependent on catalyst pretreatment by hydrogen reduction and the amount of oxygen vacancies on the surfaces. Our work explains why mass conservation was not satisfied in some previous studies due to the incorrect reaction stoichiometry used for analyzing the reactant conversions.