Dry reforming of methane (DRM) is one of the most promising processes for the production of syngas. Nickel based catalysts are well studied for DRM, but are susceptible to coking and sintering at high temperatures. Thus, a thermally stable catalyst which can resist coking and sintering is needed. Pyrochlores, which are thermally stable oxides, are promising catalysts. In the present work, Lanthanum Zirconate (La2Zr2O7) pyrochlores doped with Sr and Ni on A (La) and B (Zr) sites respectively, were tested for their activity and stability towards DRM. Two catalysts, LSNZ1 and LSNZ6, with different Ni loadings (1wt% Ni and 6wt% Ni respectively) were prepared using the modified Pechini method. Ni is the active metal while Sr is expected to reduce the carbon deposition by creating oxygen vacancies. Catalysts were analyzed using thermal and spectroscopic characterization techniques for DRM. Activity tests were done by passing a reactant stream comprising 1:1 ratio of 10%CH4/He and 10%CO2/He (at 900°C temperature and a GHSV of 24,000 cm3 gcat-1 hr-1) over the catalysts for about 45 hrs. XRD of fresh catalysts indicated the presence of a perovskite phase of Ni and NiO phase apart from pyrochlore structure. An increase of 0.037Å in lattice constant of pyrochlore structure suggests atleast a portion of Ni might have been substituted into the pyrochlore lattice. XPS and SEM-EDS analysis confirmed that Ni was present more in the bulk (perovskite and pyrochlore phase) than on the surface. On both the catalysts, TPR showed two major reduction peaks at different temperatures, suggesting different interaction strengths of Ni in the structure. LSNZ1 has slightly lower reduction temperatures than LSNZ6. TPSR (Fig.1) showed lower light-off temperature for LSNZ6 than LSNZ1 indicating that LSNZ6 is more active. During 45hr runs at DRM conditions, higher CH4 and CO2 conversions were observed with LSNZ6 than LSNZ1. Also, steady state was achieved much faster with LSNZ6. Both the catalysts showed negligible amounts of carbon deposition from post reaction TPO suggesting that the addition of Sr limited carbon deposition at the conditions tested here.

Deactivation study on Ni based pyrochlores in dry reforming of methane

256th National Meeting (2018)

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