Modulating surface properties of Al2O3 based on AACH for stable Ni-based dry reforming of methane catalysts

Abstract

Dry reforming of methane (DRM) is gaining attention as an effective means of reducing greenhouse gases (CH4 and CO2). While Ni/Al2O3 catalysts are typically used for DRM, catalyst deactivation due to Ni sintering and coke deposition remains a challenge. In this work, we studied how tailoring the surface properties of Al2O3 based on ammonium aluminum carbonate hydroxide (AACH) affects its interaction with the active Ni phase and enhances the DRM catalytic performance. We prepared two delta-Al2O3 by calcination at 900 degrees C from different Al2O3 precursors of AACH and boehmite (AlOOH). Ethanol-temperature programmed desorption, NH3-TPD, pyridine-infrared spectroscopy, and CO2-TPD revealed that AACH-based Al2O3 (A900) possessed fewer Lewis acid sites and basic sites than boehmite-based Al2O3 (P900). Surface properties of A900 led to smaller Ni particles, as confirmed by X-ray diffraction and transmission electron microscopy, and higher reducibility of Ni, as evidenced by H-2-temperature programmed reduction, compared to P900. DRM reaction was performed at 700 degrees C. Interestingly, Ni/A900 exhibited significantly improved catalytic activity and stability, along with H-2/CO ratios closer to theoretical value of 1 than Ni/P900. Specifically, 20Ni/A900 achieved CH4 and CO2 conversions of 78 % and 85 %, respectively, outperforming the 20Ni/P900 (69 % CH4 and 78 % CO2 conversion) after 24 h. The superior catalytic performance of Ni/A900 originates from a higher number of available Ni sites with less Ni sintering, and lower coke deposition (similar to 28 wt% less at 20Ni/Al2O3) compared to Ni/P900 due to fewer residual Lewis acid sites. Overall, modulating the surface properties of Al2O3 supports based on AACH without additives suggests a novel approach for designing stable DRM catalysts.