Bioethanol Steam Reforming for Hydrogen Production over Ni-Cr/SBA 15: Influence of Metal Loading and Ni/Cr Ratio

This work examines the influence of metal loading and the Ni/Cr ratio of Ni-Cr/SBA-15 catalysts on bioethanol steam reforming for the first time. The characterization of the synthesized samples reveals that higher Cr amounts result in lower Ni crystallite sizes due to the promoting effect of Cr, thereby enhancing the dispersion of the active phase. The catalytic performance has been evaluated in terms of ethanol conversion and H₂ TOF (min^-1). Ethanol conversion exhibits an increasing trend with higher Ni content, reaching up to 90% for samples containing 15 wt.%. By increasing the Cr content (lower Ni/Cr ratio) the results evidence a similar trend. A synergistic effect between Ni and Cr was appreciated in conversion values when the Ni content was below 11 wt.% and the Cr content exceeded 2 wt.%, which coincides with a smaller Ni crystallite size. Concerning the H₂ TOF, the catalyst with the lowest Ni content (7 wt.%) exhibited a higher value with a notable enhancement upon increasing the Cr loading. However, a considerable decrease in H₂ TOF was observed for samples with higher Ni loading. Therefore, the best catalytic performance, achieving nearly complete ethanol conversion and high hydrogen production, was reached when using catalysts with 7 wt.% Ni; the Cr loading should be increased to around 2 wt.%.