Dry reforming of methane (DRM) has been widely studied as a potential route for conversion of greenhouse gases to syngas, which can further be converted to useful fuels. DRM produces a high purity syngas with H2/CO ratio ≤ 1, but is highly endothermic process. Nobel metal catalysts show very high activity and stability towards DRM but are economically not viable. Hence, nickel based catalysts are investigated due to availability, cost and good performance. Most studies conducted on DRM have shown issues of catalyst deactivation due to carbon deactivation and sintering of the catalyst at operating conditions of DRM. Thus, a thermally stable catalyst with significant activity and less carbon deposition is desired. Pyrochlores are thermally and chemically stable crystalline metal oxides with general formula A2B2O7 which are tolerant at reforming conditions. In our work, Lanthanum Zirconate pyrochlore (La2Zr2O2) was substituted partially with Ni at Zr site to produce activity towards DRM. Three catalysts were prepared with Ni substitution at Zr site (B site), however, the difference is the La site (A site) substitution. LNZ3 has no substitution at La site while LCNZ3 has Ca and LSNZ3 has Sr partial substitutions at La site. Ca and Sr substitutions are expected to reduce carbon deposition on the catalyst. Several spectroscopic and thermal characterizations were carried out to study the catalyst. XRD of fresh catalyst showed peaks corresponding to the base pyrochlore and small peaks of NiO. Also, a perovskite phase was observed in the catalysts. A significant increase in the lattice constant value of the pyrochlore was seen, suggesting Ni substitution into the pyrochlore structure. XPS and SEM-EDS analysis were done to compare the surface and bulk compositions of the catalysts. TPR showed reduction peaks at different temperatures, indicating different interaction strengths of Ni in the structure. From TPR, it was observed that Sr and Ca substitution promoted stronger interaction of Ni with the lattice structure. All the catalysts showed significant activity towards DRM at 750°C, however, Sr and Ca substituted catalysts show better stability during the reaction. Also, post reaction TPO was performed to analyze the carbon deposition on the catalysts.

Dry reforming of methane in Ni substituted lanthanum zirconate pyrochlores: Effect of Ca and Sr substitutions at La site

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

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