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.

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