Nano-architectured CeO₂ supported Rh with remarkably enhanced catalytic activity for propylene glycol reforming reaction in microreactors

Abstract

The influence of morphology and crystalline facets of nanoshaped ceria oxide support in Rh/CeO₂ and Rh/CeO₂/Al₂O₃ catalysts have been investigated by oxidative steam reforming of propylene glycol in microreactors at 630 °C at S/C = 3.5 and O/C = 0.15. First, well−defined ceria nanorods (NRs) and nanocubes (NCs) have been successfully synthesized by a facile hydrothermal method and then they are deposited on to α−Al₂O₃. The result of transmission electron microscopy indicates that the ceria nanorods exposed (110) and (100) planes but nanocubes possess only (100) planes. The developed shape controlled ceria nanocrystals and they are mixed with alumina have been used as supports for the preparation of highly dispersed and size controlled Rh nanoparticles of Rh/CeO₂ and Rh/CeO₂/Al₂O₃ catalysts. Their performance was tested for the propylene glycol reforming reaction in microreactors, which provide high surface of the catalyst coatings, heat and mass transfer rate and controllability. The XPS and TEM results indicate that the CeO₂ morphology shows the selective exposure of different crystal planes which has a significant impact on the dispersion of Rh nanoparticles that influenced in the reforming reaction. The steam reforming reaction experiments show that the ceria nanorods supported Rh catalyst was achieved significantly better activity and stability for 100 h of time on stream than for the all other catalysts. This could be related to the better dispersion of Rh species and the higher surface oxygen vacancies associated with the exposed (100) and (110) crystal planes favor the stabilization of Rh nanoparticles against sintering and elimination of carbon deposition on active Rh nanoparticles during reforming reaction.