Abstract
Ordered CeO2 nanotubes (CeO2-T) were prepared via a hydrothermal synthesis process using the triblock copolymer polyethylene oxide-polypropylene oxide-polyethylene oxide (P123) as a morphology control agent. CeO2-T characterization demonstrated the formation of single crystal structures having lengths between 1–3 μm and diameters < 100 nm. A supported Pd catalyst (Pd/CeO2-T) was also prepared through hydrothermal means. H2-temperature reduction profile and Raman spectroscopy analyses showed that the oxygen vacancies on the CeO2 surface increased and the reduction temperature of the surface oxygen decreased after Pd loading onto CeO2-T. Pd/CeO2-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 CeO2 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.
Highlights
Diphenyl carbonate (DPC) is a signi cant green organic carbonate that is widely used to synthesize many important organic compounds and polymer materials
CeO2 nanotubes (CeO2-T) and Pd/CeO2-T morphologies were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and selected area electron diffraction (SAED)
CeO2-T with uniform tubular morphology of 1–3 mm were synthesized via a hydrothermal method using P123 as a surfactant to control morphology
Summary
Diphenyl carbonate (DPC) is a signi cant green organic carbonate that is widely used to synthesize many important organic compounds and polymer materials. As a more sustainable and green approach, phosgene-free processes have been explored and developed.[2] Among the phosgene-free routes, oxidative carbonylation of phenol is the most promising candidate, demonstrating several advantages such as readily available starting materials, high atom utilization, and water as the sole by-product.[3]. Considering Ce as a good redox co-catalyst toward the Pd-catalyzed oxidative carbonylation of phenol, CeO2 nanotubes have been studied as a support to promote this reaction. In view of the aforementioned issues, this research focused on synthesizing heterogeneous catalysts with an enhanced degree of stability compared with previously reported catalysts. Pd-supported monocrystalline CeO2 nanotube (CeO2-T) catalysts possessing well-ordered structures were prepared and their catalyst performance toward the oxidative carbonylation of phenol was investigated
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