(323f) Design and Properties of Supported Tungstate Catalysts for Oxidative Coupling of Methane (OCM)

Methane is the largest component of natural gas and possesses numerous thermodynamic and kinetic challenges in its selective one-step conversion to value-added products.  At the same time, creating one-step catalytic processes is of critical importance in monetizing natural gas due to the remote locations of extraction sites and high transportation costs, but no economically viable process exists.  Current state of the art involves multi-step capital intensive syngas production, water-gas shift to control the CO/H₂ followed by Fischer Tropsch or methanol synthesis.  We present on the structure and property of optimized WO_x catalytic sites supported on SiO₂ promoted with Na and Mn to improve current yield of C₂ products during OCM.  We performed synthesis, molecular and electronic structural characterization under reaction conditions (operando Raman and Density Functional Theory) on the current most selective catalyst, supported Mn/Na₂WO₄/SiO₂. These studies isolated the catalytic active site(s), determined their molecular/electronic structures and establish their fundamental structure-activity relationships.  These combined experimental and theoretical findings can be used to guide the rational design of advanced OCM catalysts by tuning of the catalytic active site(s) to molecular engineer improved activity and selectivity performance. The new insights that will be presented will lead to the development of conceptually new catalyst models that will have the potential to enable development of CH₄ single-step OCM catalytic processes using a bottoms up approach via catalytic active site(s), rather than top down approach of catalytic screening experiments.