Coke resistance and enhanced H₂ generation via boron promotion on Co/rod-shaped Al₂O₃ in methane dry reforming

Dry reforming of methane (DRM) has been widely recognized as an efficient approach for converting CH₄ and CO₂ greenhouse gases into alternative H₂ energy. This study examined the function of B promoter (0.1-0.5 wt%) on Co catalysts supported by rod-shaped mesoporous alumina (MA) through DRM performance and coke suppression. Active metal dispersion was enhanced via doping a small B amount of 0.1-0.3 wt% and Co₃O₄ crystalline size was reduced from 10.93 to 8.77 nm. Co₃O₄ reduction to Co0 active metal was achieved via CoO intermediate phase formation and the reducibility of Co₃O₄ to CoO was considerably eased with rising B loading. Regardless of B content, stable CH₄ conversion above 74% was evidenced with time-on-stream at 973 K and boron promotion effectively boosted CH₄ and CO₂ conversions to 91.21% and 82.19%, respectively. Additionally, 0.3 wt% was the optimal B loading in terms of highest CO₂ conversion and H₂ yield (86.22%). Although amorphous and graphitic carbons were inevitably formed on used DRM catalysts, the B promotion of 0.1-0.3 wt% impeded carbonaceous deposition and reduced total carbon deposition percentage from 2.23% to 1.50% because of lesser crystal size, higher oxygen vacancy and obstructed graphene islands nucleation. The mechanistic DRM pathway based on boron-enhanced oxygen vacancy was also suggested to address coke removal in this study.