CBE PhD Thesis Defense: “Electrochemical and Heterogeneous Catalysis for Selected Industrial Commodities”

            Novel high-surface-area catalysts were synthesized for selected industrial chemical reactions, conducted in heterogeneous reactors and electrochemical reactors. Atomic layer deposition (ALD) was used to synthesize highly dispersed metal catalysts and to deposit uniform oxide thin films on porous supports.

            The interaction between Cu catalyst and its oxide support was studied for the water-gas-shift reaction, a critically important reaction for maximizing the H₂ production from syngas. The ALD-prepared Cu catalyst demonstrated ten times more reactivity than the impregnated Cu catalyst with the same metal loading and surface area. The selected oxide supports did not show promotion effects for the reaction, but some mild stabilization over long-term aging was observed. In another case, the selective oxidation of butane to maleic anhydride was studied on an ALD-prepared vanadium phosphate catalyst with eight times more surface area compared to the commercial bulk catalyst. Furthermore, an ALD-prepared CaO/MgAl₂O₄ catalyst was studied for the aldol condensation of furfural and ketones/aldehydes to form precursors of lubricant oils and surfactants. The side reaction, Cannizaro reaction, was investigated for the long-term use of this catalyst.

            Lastly, ammonia synthesis was studied in a solid oxide electrochemical cell made with the state-of-the-art proton conductor BZCYYb (BaZr_0.1Ce_0.7Y_0.1Yb_0.1O_3−δ). Instead of using both high temperature and high pressure in the commercial Haber-Bosch process, this reaction was carried out under ambient pressure. The proton recombination was found to be barrierless on the cell surface, greatly limiting the selectivity to ammonia. The implications of this phenomenon and its suppression were discussed.