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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. 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 COx was studied by density functional theory (DFT) method and compared with experimental results. The (MoO3)n -graphene complexes show interesting magnetic properties and potentials for nanodevices. 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. To gain a better understanding of the MoO2 oxidation process, the adsorption and dissociation of O2 on MoO2 surface were studied by DFT method. The results show that O2 molecules prefer to be adsorbed on the five-coordinated Mo top sites. Density of states analysis shows strong hybridization of Mo 4d orbitals and O 2p orbitals in the Mo-O bond. Clean MoO2 slab and slabs with O2 adsorption are metallic conductors, while the surface with high O atom coverage is reconstructed and becomes a semiconductor. Surface Mo atoms without adsorbed O or O2 are spin-polarized. The oxygen adsorption shows ability to reduce the spin of surface Mo atoms. The adsorption energy of O2 and O atoms decreases as coverage increases. The transition states of O2 dissociation were located. The energy barriers for O2 dissociation on five-coordinated and four-coordinated Mo top sites are 0.227 eV and 0.281 eV, respectively.

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To achieve net-zero emissions by the year 2050, carbon capture, utilization and storage technologies must be implemented to decarbonize sectors with hard-to-abate emissions. Pressurized chemical looping (PCL) with a novel reactor design called a plug flow with internal recirculation (PFIR) fluidized bed reactor is proposed as an attractive carbon capture technology to decarbonize small- and medium-scale emitters. The objective of this work was to examine solid circulation rate, gas leakage between reactors, and purge gas fate in a cold flow chemical looping facility. These parameters were used to better understand the PFIR reactor and will be used to validate a computational particle fluid dynamic (CPFD) model of the PFIR reactor to inform the reactor operation and design for a hot flow PCL pilot plant. An energy balance across the fuel reactor was used to determine the solid circulation rate of the bed material, while helium and argon tracer gases were used to determine the amount of gas leaking between reactor sections and the fate of the purge gas, respectively. Statistical analyses were completed to determine the statistical significance of the data. At the base case condition, the solid circulation rate was 3000 kg/h. Approximately 10% of the fluidizing gas that entered the air reactor moved to the fuel reactor indicating that, with reacting flow, there will be nitrogen infiltrating the fuel reactor, decreasing the purity of the carbon dioxide effluent stream. Furthermore, approximately 31% of the fluidizing gas entering the fuel reactor moved to the air reactor, indicating that, with reacting flow, there will be natural gas leaking into the air reactor, which will increase carbon dioxide emissions. Finally, over half of the purge gases move to the adjacent reactor, which helps prevent gas leakage between reactor sections. The effect of static bed height, weir opening height and purge configuration on solid circulation rate, gas leakage and purge fate were investigated. The bed height has a small effect on the solid circulation rate and no effect of gas leakage, over the range of bed heights tested. Furthermore, increasing the weir opening height increases both solid circulation rate and gas leakage until the top of the circulation zone is reached. After this point, there is no change in either solid circulation rate or gas leakage. In terms of purge configuration, there appears to be no benefit for having two purge rows. Either one purge row or having a row of blanked tuyeres appear to be optimal as they decrease gas leakage, while having little effect on solid circulation rate. At the jet velocity tested, the vertical purge configuration prevented the solids from circulating, so it is not recommended for this purge configuration to be used in a PFIR reactor without further testing of different jet velocities. Across all configurations, it was shown that as more purge gas moves into the adjacent reactor section, less gas leakage between reactor sections occurs. It iii was also determined that the primary method of gas movement between the reactor sections is likely via bubbles and/or jets. The next step is to complete the validation of CPFD model of the PFIR reactor using the data presented herein. Additional conditions can also be run in the cold flow chemical looping pilot facility to fill in any gaps that are found during the CPFD model validation, or to fill in research gaps in better understanding the PFIR reactor.

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