Simultaneous Low-Cost Carbon Sources and CO2 Valorizations through Catalytic Gasification

The inherent CO2 gasification reactivities of chars derived from a series of plentiful carbon sources, including petroleum coke (petcoke), coal with various ranks, biomass, and even municipal solid wastes, have been systematically investigated in this work. Among these, switchgrass char exhibits the best activity, while petcoke char behaves the worst toward CO production. The results from sample characterizations indicate that the inherent char reactivity during CO2 gasification is closely related to its physical properties such as the alkali metal and oxygen contents as well as the H/C atomic ratio. In addition, the effect of the reaction conditions (i.e., temperature, pressure, space velocity, particle size of char, and CO and CO2 concentrations in the gas feedstock) on char CO2 gasification has also been explored. Moreover, a set of supported catalysts have been developed to further promote the char reactivity toward CO2 gasification at moderate temperature, among which K–Ca/ZnO–CeO2 ranks at the top in terms of CO2 conversion and CO production and demonstrates excellent stability during a long-term cumulative run. Through careful analyses of the collected catalyst characterization results, a novel catalyst design composed of two redox metal/metal oxide pairs supported on an oxygen ion conductor, based on the reported K–Ca/ZnO–CeO2 system, has been proposed for future catalyst development with even better CO2 gasification performance for fluidized bed applications with much easier catalyst recovery and thus minimized catalyst loss.