Effect of CeO₂ Morphology on Carbon Deposition Behavior and Reaction Performance in Low-Temperature Dry Reforming of Methane over NiPd Bimetallic Catalysts

This study successfully constructed a series of 4Ni0.1Pd/CeO2 catalysts by regulating the morphologies (rod, cubic, and spherical) of CeO2 supports and loading NiPd bimetallic components on them separately, and systematically investigated the effect of support morphology on the catalytic performance in low-temperature dry reforming of methane (LT-DRM). Firstly, CeO2 supports with different morphologies were synthesized via the hydrothermal method, and then the active components Ni and Pd were loaded by the impregnation method. Combined with characterization techniques including XRD, SEM, BET, H2-TPR, and CO2-TPD, this study revealed the influence of support morphology on the specific surface area and oxygen vacancy (Ov) concentration of the catalysts, as well as its effect on regulating the coke type during the LT-DRM reaction. The experimental results demonstrated that the catalyst with rod-like CeO2 as the support (4Ni0.1Pd/CeO2-R) exhibited a larger specific surface area and a higher Ov concentration. These characteristics not only enhanced the metal dispersion on the catalyst surface and improved its sintering resistance but also strengthened its CO2 adsorption capacity. Consequently, under the reaction conditions of 650 °C and a CH4/CO2 molar ratio of 1, the NiPd/CeO2-R catalyst displayed the optimal LT-DRM conversion efficiency (CH4 conversion rate of 47%, CO2 conversion rate of 60%) and stability. Particularly interestingly, the three catalysts exhibited significantly different carbon deposition behaviors. The carbon deposition on 4Ni0.1Pd/CeO2-G was predominantly composed of highly covered graphitic carbon. In contrast, 4Ni0.1Pd/CeO2-C contained a mixture of both types of carbon deposits. However, the carbon species on the surface of 4Ni0.1Pd/CeO2-R were mainly disordered carbon, which is more easily removable and present at a lower coverage.