Reducing the Environmental Impact of Hydrogen with Chemical Looping Reactors

After common hydrocarbon fuels are used and oxidized, they are often emitted into the atmosphere rather than recycled. Our laboratory is developing a new type of chemical reaction process we term “chemical looping hydrogenation” that enables efficient and selective hydrogen transfer to molecular hydrogen acceptors. Whereas our work to date on this reactive process focused on tungsten oxides (WO_x), this presentation will focus on a summer research project I undertook to explore mixed-metal oxides based on Mo and W as viable catalysts. My work focused on the following research question: to what extent does mixing Mo and W change the extent of hydrogen uptake in the oxide and thus hydrogenation of molecular acceptors? Hence, the objective of this research was to assess the use of W_xMo_1-xO₃ compounds over a range of metal ratios as catalysts in both electrochemical and thermochemical looping hydrogenation.

Five samples containing increasing ratios of W to Mo were synthesized from ammonium precursors and analyzed with X-ray diffraction (XRD) and a transmission electron microscopy(TEM). To examine the potential of these samples for hydrogen looping electrochemically, a series of cyclic voltammetry measurements were conducted. Oxide samples were further prepared for thermochemical analysis through wet impregnation with platinum as a catalyst for hydrogen insertion via spillover. The samples were then reacted sequentially with H₂(g) for hydrogen uptake and C₂H₂ as a model hydrogen acceptor to complete full chemical looping hydrogenation. These results provided a promising basis for continuing work on mixed metal oxides in the context of chemical looping hydrogenation.