(50a) Evaluating CeO2-Supported Ni Catalysts in the Dry Reforming of Methane at High Space Velocities

CeO₂ is an excellent catalyst support for Dry reforming of methane (DRM) due to its low oxygen vacancy formation energy, reducibility, and high basicity. In this study, traditional wet impregnation synthesis (WIS) was compared with solution combustion synthesis (SCS) and sol-gel synthesis (SGS) to produce CeO₂-supported Ni catalysts for DRM. γ-Al₂O₃-supported Ni was also prepared as a reference. The Ni content of the catalyst was between 8-11 wt%, and the catalyst crystallite sizes were 23-25 nm. X-ray photoelectron spectroscopy (XPS) confirmed the presence of Ce³⁺ in the oxide, which can be correlated with oxygen vacancy formation. XPS analysis confirmed that catalyst nanoparticles had greater metal-support interaction (MSI) with CeO₂ than γ-Al₂O₃. The catalysts were tested at a high space velocity (180,000 ml/g_cat.hr), 700°C, 1:1 feed ratio, and atmospheric pressure. The catalysts showed stable DRM performance for 45 h. Ni/CeO₂-WIS and Ni/γ-Al₂O₃-WIS showed the highest average apparent CH₄ reaction rate of 96 ± 17 mmol/g_Ni.min, and in the order Ni/CeO₂-WIS, Ni/γ-Al₂O₃-WIS > Ni/CeO₂-SCS > Ni/CeO₂-SGS. The highest average apparent CO₂ reaction rate was observed for Ni/CeO₂-SGS at 669 ± 27 mmol/g_Ni.min, and the others were in the order Ni/CeO₂-SGS > Ni/CeO₂-SGS > Ni/CeO₂-WIS > Ni/γ-Al₂O₃-WIS. CeO₂-supported catalysts had an H₂/CO ratio of 0.4-0.55 while γ-Al₂O₃-supported catalyst was 0.6. The degree of graphitization of the deposited coke, as revealed by the G- to D-band ratio in their Raman spectra, was highest in Ni/CeO₂-SGS at 1.1, while the others were in the range of 0.8-0.9. The carbon deposition rate was lower in CeO₂-supported catalysts (12 - 27 µg/g_cat.min) compared to Ni/γ-Al₂O₃-WIS (116.6 µg/g_cat.min). This study reveals that at high space velocities, reverse water gas shift is more severe in CeO₂-supported Ni catalysts leading to lower H₂/CO ratios. Also, coke oxidation is superior in CeO₂-supported Ni catalysts due to the higher CO₂ activation rate.