Rational Design of Y-Promoted Co/Al2O3 Catalysts with Bimodal Porosity for Dry Reforming of Methane: Enhanced Reducibility, Surface Basicity, and Coke Resistance

Dry reforming of methane (DRM) provides an attractive pathway for the simultaneous utilization of CH4 and CO2 to produce syngas; however, Co-based catalysts typically suffer from metal sintering, formation of hardly reducible cobalt aluminate (CoAl2O4), and severe carbon deposition under high-temperature conditions. Herein, Y-promoted Co catalysts supported on alumina with tailored pore architectures were developed, with particular emphasis on a hierarchical bimodal porous Al2O3 support (Al2O3-BA) integrating ordered mesopores and interconnected macroporous channels. Compared with mesoporous Al2O3-SA and commercial γ-Al2O3-supported counterparts, the 10Co-5Y/A2O3-BA catalyst exhibited smaller Co3O4 crystallites and more uniform nanoparticle dispersion, indicating mitigated agglomeration. H2-TPR analysis revealed enhanced reducibility with a shift of the main reduction peak to lower temperature and a markedly suppressed high-temperature CoAl2O4 feature, suggesting weakened metal–support interaction. CO2-TPD demonstrated an increased population of medium-strength basic sites, favoring CO2 adsorption and activation. XPS indicated a higher Co2+/Co3+ ratio and an increased proportion of surface-adsorbed oxygen species, implying modified surface electronic properties. These structural and surface characteristics translated into superior catalytic performance. The bimodal catalyst delivered the highest CH4 and CO2 conversions over 650–800 °C and maintained stable activity during a 24 h test at 750 °C, achieving 86.5% CH4 conversion, 91.5% CO2 conversion, and an H2/CO ratio of 0.92. Postreaction analyses revealed significantly reduced carbon deposition compared with mesoporous counterparts. Overall, the synergy between Y promotion and hierarchical bimodal porosity effectively modulates metal–support interaction, enhances reducibility and CO2 activation, and suppresses coking, providing a rational strategy for designing durable Co-based catalysts for DRM.