(580d) The Shale Gas-to-Syngas Chemical Looping Process for High Purity Syngas Production

The shale gas-to-syngas (STS) chemical looping processes is being developed at The Ohio State University for the production of high-purity syngas from shale gas. In contrast to conventional processes for syngas production, the STS process eliminates the need for additional steam or molecular oxygen from an air separation unit (ASU). The STS process utilizes a unique co-current moving bed gas-solid reducer reactor for the partial oxidation of gaseous fuels to syngas with metal oxide oxygen carriers. The reduced oxygen carriers from the reducer are regenerated in an oxidation operation with air in the combustor reactor. A modified Ellingham Diagram is developed to search for suitable metal oxides for the production of high-purity syngas. Various metal oxide compounds with desirable thermodynamic properties were identified. Through the combination of the suitable metal oxides and co-current moving bed reducer, high fuel conversion and syngas purity can be achieved. In this study, active iron-titanium composite metal oxide (ITCMO) materials are used as the oxygen carrier for the demonstration of the STS process. The co-current moving bed provides a desirable gas-solid contacting pattern that minimizes carbon deposition while maximizing the syngas yield. The syngas produced in the STS process can achieve a flexible H₂:CO molar ratio with little CO₂, unconverted CH₄, and steam, which is desirable for downstream processes to produce methanol, dimethyl ether, gasoline, and other fuels and chemicals. The experimental results for reaction kinetics including oxygen carrier recyclability and pressure effects were obtained from thermogravimetric analysis (TGA), and syngas generation results from fixed bed, bench-scale moving bed, and sub-pilot scale moving bed reactor demonstrations were achieved in this study. The bench and sub-pilot demonstrations confirmed the syngas produced from the STS process is consistent with the thermodynamic equilibrium for the reduced ITCMO material.