Catalytic Conversion of Benzyl Alcohol to Benzaldehyde over a Cu-CeO2 Catalyst: Utilization of CO2 for Enhancement of Selectivity and Activity

CO2-assisted dehydrogenation of benzyl alcohol to benzaldehyde over Cu nanoparticles dispersed on CeO2 was reported. Cu nanoparticles with an average size of similar to 11.4 nm dispersed over CeO2 cubes were efficient in selective conversion of benzyl alcohol with a rate of formation of benzaldehyde of 250.99 mu mol s(-1) g(cat)(-1). The high rate of reaction might be due to the miscibility of BOH in CO2, which led to enhanced diffusion of BOH reactant molecules toward active sites. The controlled surface acid-base sites were responsible for the activation of benzyl alcohol, and nearby Cu nanoparticles abstracted alpha-H of benzyl alcohol to form benzaldehyde. During a time on stream study, the Cu-CeO2 catalyst experienced a gradual deactivation in the presence of N-2 as the carrier gas, while in the presence of CO2, it delivered constant activity for 24 h. In the presence of N-2, in-situ generated hydrogen was responsible for the formation of much toluene via hydrogenolysis of benzyl alcohol. CO2 acted as a soft oxidant, which minimized the in-situ generated hydrogen via the reverse water gas shift reaction; as a result, the toluene formation and deposition of carbonaceous species were minimized.