Comparative study of the kinetics of methane steam reforming on supported Ni and Sn/Ni alloy catalysts: The impact of the formation of Ni alloy on chemistry

We report the results of detailed kinetic studies for methane steam reforming on supported Ni and Sn/Ni surface alloy catalysts. The kinetic data were interpreted in terms of mechanism-based overall rate expression. We show that the activation of CH bonds in methane is the rate-controlling step on both catalysts. Isotopic CH4/CD4 labeling studies were performed to independently verify the proposed mechanism. The role of Sn is to displace Ni atoms from under-coordinated sites on Ni particles and to move the critical reaction channels to more abundant well-coordinated sites. We show that previously observed increased resistance to carbon deactivation of Sn/Ni compared to monometallic Ni in hydrocarbon reforming reactions can be attributed to the Sn-induced lowering in the binding energy of carbon on low-coordinate sites, which serve as carbon nucleation centers, and to an enhanced propensity of Sn/Ni to oxidize carbon surface species. The conclusions derived from the experimental studies are in agreement with DFT calculations.

Sn atoms dispersed on supported Ni catalysts alter catalytic methane steam reforming by (i) changing the nature of the active sites, (ii) increasing the overall activation barrier, and (iii) improving the catalyst tolerance to carbon-induced deactivation.Figure optionsDownload high-quality image (111 K)Download as PowerPoint slide