Dry Reforming of Methane: Study of Pyrochlore Catalysts Performance

The dry reforming of methane (DRM) using CO₂ has recently received increased attention as this reaction converts two greenhouse gases into syngas, from which a variety of chemicals and liquid fuels can be produced, these liquid fuels can more readily be shipped via pipeline than the natural gas feedstock. Optimal operating conditions for dry reforming reactors involve temperatures above 800 °C; however, at these temperatures it is difficult to find a catalyst that exhibits high activity for extended periods. To-date, many catalyst materials have been investigated for DRM, including unsupported transition metal carbides and sulfides, supported group VIII metals, and more recently perovskites and hydrotalcites. Further, recent experimental data suggests pyrochlore materials as ideal catalysts, since they have exhibited high activity, high thermal stability and extended lifetimes. The general formula of pyrochlores is A₂B₂O₇, where A represents a rare-earth metal and B represents a transition metal. In this work, we use Density Functional Theory (DFT) for the in silico screening of catalyst performance for a range of pyrochlore materials, aiming to identify the combination of rare-earth and transition metals that gives the highest activity.  For these computational studies, VASP simulation software, which uses a plane-wave DFT model, was used to evaluate system energetics. Specifically, DFT was used to optimize the structure of reactants, intermediates, and transition state species as well as quantize energy barriers associated with DRM elementary reaction steps. These data were subsequently used to guide experimental efforts focused on the development of optimal pyrochlore catalyst materials for DRM.