Structure-property Relationships of Transition Metal Carbides for CO2 Hydrogenation

Download or read book Structure-property Relationships of Transition Metal Carbides for CO2 Hydrogenation written by Mitchell Juneau and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Atmospheric concentrations of CO2 have risen almost 50% since the Industrial Revolution, however active CO2 removal, utilization and emissions reductions strategies offer a pathway towards a carbon-neutral future. The conversion of captured CO2 to commodity chemicals and fungible fuels via hydrogenation reactions adds value to the captured CO2 and provides an alternate feedstock for petrochemicals. However, the high stability of CO2, challenging economics of industrial-scale CO2 conversion, and process desire for single-product outlet streams necessitate the use of active, selective, low-cost, and stable catalysts. One commonly studied pathway of converting CO2 to petrochemicals involves activating CO2 with H2 to form CO and then hydrogenating this product via Fischer-Tropsch synthesis to enable carbon chain growth into higher value long-chain hydrocarbons. Initial studies identify Mo2C as a low-cost alternative to precious metal catalysts in converting CO2 to CO via reverse water-gas shift (RWGS). Alkali metal promotion of Mo2C is shown to increase CO yield, establishing K-Mo2C/y-Al2O3 as a top performing RWGS catalyst with regard to CO production rate and catalyst cost per mol of CO generated. Investigation into Mo2C-support interactions isolates Lewis acidity as a key descriptor, as the formation of Mo oxycarbide phase promotes high RWGS activity and CO selectivity. Pilot-scale, alkali promotion and support analyses provide a framework for rational catalyst design of Mo2C that can be extended to other transition metal carbides to tune catalytic performance Previous studies over TMCs indicate moderate oxygen binding energy (OBE) is correlated with enhanced CO2 hydrogenation activity. Tungsten carbide is also predicted to have comparable OBE to Mo2C yet demonstrates inferior activity likely due to low accessibility of active sites caused by particle agglomeration during high temperature synthesis. SiO2 is found to promote the highest CO yield as a support over Mo2C, and consequently used to encapsulate WxC particles in a micelle-based synthesis shown to produce sub-10 nm tungsten carbide nanoparticles. These nanoparticles exhibit substantially greater CO yield compared to a non-encapsulated control, prompting further investigation into WxC as an extension of this rational catalyst design framework."--Pages xi-xii.