Carbon deposition on borated alumina supported nano-sized Ni catalysts for dry reforming of CH4

Abstract

Borated alumina supported 5wt% Ni catalysts with B2O3 loading varying from 0wt%, 1wt%, 5wt% to 10wt% were prepared and characterized by XRD, H2-TPR, CO2-TPD, NH3-TPD, in situ DRIFTS study, and evaluated for dry reforming of methane. The addition of B2O3 influences the activity and stability of the catalysts significantly. Ni particle size increases from 5.8 to 9.1nm with increasing the B2O3 loading from 0 to 10wt%. In the kinetic control temperature region (700°C) there is no linear relationship between the Ni particle size and the catalyst activity/stability. The formation of strong Lewis acid sites causes severe carbon deposition on 1wt% and 10wt% B2O3 loaded Ni catalysts, hence decreasing catalytic activity and stability. The formation of weak Lewis acid sites and O–H groups on 5wt% B2O3 promoted Ni catalyst is found to significantly facilitate carbon removal and improve the stability of the catalysts. The reaction mechanism of dry reforming of methane over borated-alumina supported Ni catalysts is proposed, especially the promotional effect of OH groups on the suppression of carbon formation being emphasized.