Comparative analysis of cerium incorporation techniques on Ni/Al2O3 catalysts for methane dry reforming: Surface promotion vs. structural support modification

Abstract

Two series of 5 wt.% Ni/Al 2 O 3 catalysts incorporating cerium (Ce) at loadings ranging from 1.0 to 3.0 wt.% were prepared by impregnation and subjected to systematic evaluation for the dry reforming of methane (DRM) at 700 °C. The two series were distinguished by the mode of Ce introduction: co-impregnation of Ce and Ni onto Al 2 O 3 (first series-denoted as 5NixCe/Al), and sequential two-step impregnation where, Ce was first incorporated into Al 2 O 3 prior to Ni deposition (second series-denoted as 5Ni/xCe+Al). These two preparation routes resulted in distinct physicochemical properties and catalytic performances. With respect to Al 2 O 3 -supported Ni, ceria addition was found to increase the surface area and pore volume, as well as it retards the formation of hardly reducible NiAl 2 O 4 . The degree of graphitization of the accumulated coke was also lower over ceria-incorporated catalysts. The co-impregnated catalysts exhibited finer dispersion of ceria without masking the active sites (than the sequential impregnated catalysts), where the finest dispersion of ceria held over 1 wt.% ceria co-impregnated a 5Ni/Al catalyst. This 5Ni1Ce/Al catalyst attains the highest CH 4 conversion of 51.3% and CO 2 conversion of 62.7% at the end of 400 min. The lower dispersion of ceria over the modified catalyst system masks catalytic active sites, leading to inferior catalytic activity, even below that of 5Ni/Al. Taken together, the findings highlight Ce incorporation as a practical and effective approach for upgrading Ni/Al 2 O 3 as promising catalytic materials for industrial DRM applications .