Effect of B and Sn on Ni catalysts supported on pure- and on WO3/MoO3-modified zirconias for direct CH4 conversion to H2

Abstract

Methane cracking for hydrogen production was studied over monometallic/bimetallic Ni catalysts supported on pure or WO3/MoO3-modified zirconias. The catalysts were reduced easily with methane at 773K, indicating that regeneration studies can be performed without using hydrogen. Ni–B and Ni–Sn bimetallic catalysts presented different behaviors when exposed to methane at 773K. The former, because of its low thermal stability, behaved as a well dispersed phase with small nickel crystallites, while the latter behaved as a bimetallic catalyst. For all catalysts, except for Ni–Sn, the metallic particles, after 8h of methane exposure at 773K, were mostly concentrated at the tip of the carbon filaments, whereas zirconia surface was found to be free from these filaments. Additionally, our results suggest that the presence of Sn does not improve catalytic performance for hydrogen production by methane cracking, considering the catalytic systems under study. Rather, adding Sn seems to inhibit access to Ni sites, which are necessary for the C–H bond activation of methane and then for the nucleation of carbon species.