Regenerable oxygen-deficient Ni/γ-Al2O3 catalyst for efficient glycerol aqueous phase reforming

Abstract

Aqueous phase reforming (APR) of glycerol represents a promising pathway for sustainable fuel gas generation. Nickel-immobilized gamma alumina (Ni/γ-Al₂O₃) has been recognized as an effective alternative to noble metal catalysts, but the phase transformation from γ-Al₂O₃ to AlOOH under hydrothermal conditions negatively affects its long-term catalytic performance. To address this challenge, we synthesized a Ni/γ-Al₂O₃ catalyst via a Ni-exsolution technique from NiAl₂O₄ spinel oxide. The catalyst achieved a gasification yield of 49.2% with a fuel gas energy of 9.2 MJ kg⁻¹ of glycerol in 45 min at 250 °C, producing hydrogen, carbon monoxide, and methane, which is comparable to that of the Ru-catalyst. The spent catalyst was regenerated, resulting in an increased gasification yield of 52.6% and fuel gas energy of 10.3 MJ kg⁻¹ of glycerol, with enhanced H₂ (106.7%) and CH₄ (123.0%) production compared to the fresh catalyst. This remarkable performance is primarily attributed to improved crystallinity of γ-Al₂O₃ and strengthened Ni and γ-Al₂O₃ interactions induced by increased oxygen vacancies and electron density. This study highlights the significance of the metal exsolution approach in catalyst preparation, demonstrating that chemical structure modulation through regeneration is crucial for enhancing both the catalytic activity and durability of γ-Al₂O₃ supported catalysts in glycerol APR.