Pd catalyst supported on CeO nanotubes with enhanced structural stability toward oxidative carbonylation of phenol.

Ordered CeO nanotubes (CeO-T) were prepared a hydrothermal synthesis process using the triblock copolymer polyethylene oxide-polypropylene oxide-polyethylene oxide (P123) as a morphology control agent. CeO-T characterization demonstrated the formation of single crystal structures having lengths between 1-3 μm and diameters < 100 nm. A supported Pd catalyst (Pd/CeO-T) was also prepared through hydrothermal means. H-temperature reduction profile and Raman spectroscopy analyses showed that the oxygen vacancies on the CeO surface increased and the reduction temperature of the surface oxygen decreased after Pd loading onto CeO-T. Pd/CeO-T was employed as a catalyst toward the oxidative carbonylation of phenol and the reaction conditions were optimized. Phenol conversion was 53.2% with 96.7% selectivity to diphenyl carbonate under optimal conditions. The integrity of the tubular CeO structure was maintained after the catalyst was recycled, however, both activity and selectivity significantly decreased, which was mainly attributed to the Pd active component significantly leaching during the reaction.