(558ar) The Use of Gaseous Metal Oxide As an Oxygen Carrier in Coal Chemical Looping Combustion

Traditional chemical looping technologies utilize solid oxygen carriers and has some disadvantages, especially when solid fuels like coal are used. In this work, a novel chemical looping process using gaseous metal oxide as oxygen carrier was proposed. The reaction of activated charcoal with gas-phase MoO₃ was studied for the first time. The experiments were conducted isothermally at different temperatures in a fixed-bed reactor. The apparent activation energy of the reaction was calculated and suitable kinetic models were determined. The results and analysis showed that the proposed concept has potential in both coal chemical looping combustion and gasification process and offers several advantages over traditional chemical looping process.

To further investigate the mechanism of carbon oxidation by gas-phase MoO₃, the adsorption of a gaseous (MoO₃)₃ cluster on a graphene ribbon and subsequent generation of CO_x was studied by density functional theory (DFT) method and compared with experimental results. A comprehensive analysis of plausible reaction mechanisms of CO and CO₂ generation was conducted. Multiple routes to CO and CO₂ formation were identified. The (MoO₃)₃ cluster shows negative catalytic effect for CO formation but does not increase the energy barrier for CO₂ formation, indicating CO₂ is the primary product. Mechanism of the homogenous MoO₃ - CO reaction was studied and showed relatively low energy barriers. The DFT result accounts for key experimental observations of activation energy and product selectivity. The combined theoretical and experimental approach contributes to the understanding of the mechanism of reactions between carbon and metal oxide clusters.