Synthesis of Ni-Ce loaded on CaO-Ca9Al6O18/Ca12Al14O33 sorbent-catalyst bifunctional materials for enhancing hydrogen production from biomass gasification

Abstract

Ni–Ce/CaO–Ca₁₂Al₁₄O₃₃ (Ni–Ce/C₁₂A₇) and Ni–Ce/CaO–Ca₉Al₆O₁₈ (Ni–Ce/C₉A₃) catalysts were synthesized from different calcium–aluminum precursors and evaluated for H₂ production via catalytic reforming of pine sawdust. At a Ni/Ce molar ratio of 1.5, Ni–Ce/C₉A₃(AN–CF)—prepared using Al(NO₃)₃·9H₂O (AN) and Ca(CHO₂)₂ (CF)—exhibited the best performance, achieving a peak H₂ concentration of 90.97 vol% and an H₂ yield of 294.31 mL/g, compared with 85.51 vol% and 228.19 mL/g for Ni–Ce/C₁₂A₇(AN–CA). The superior performance was attributed to the uniform, mesh-like pore network of Ni–Ce/C₉A₃(AN–CF) and to the stability of its average pore diameter during catalytic process. In cyclic tests, Ni–Ce/C₉A₃(AN–CF) maintained stable performance for the first four cycles but underwent rapid deactivation from cycle 5 and was nearly deactivated by cycle 10. Ni–Ce/C₁₂A₇(AN–CA) exhibited a more gradual performance decline. The observed deactivation was primarily ascribed to the phase transformation of Ca₉Al₆O₁₈ to Ca₁₂Al₁₄O₃₃ under H₂O–CO₂ atmospheres, which caused pore collapse and sintering of Ni–Ce active species. Although Ca₉Al₆O₁₈ exhibited greater resistance to CaO-particle sintering than Ca₁₂Al₁₄O₃₃, its thermodynamic instability under reaction conditions limited long-term cyclic performance.