###### Abstract
Other oxygen carrier compositions have been reviewed recently [29; 30], and from these studies, it is apparent that mixed oxides composed of several redox-active oxides can have synergistic effects with regard to their activity and syngas selectivity. An important problem to overcome in the chemical looping-based reforming scheme is the deposition of carbon on the surface of the oxygen carrier due to the cracking reaction of methane that is catalyzed by metallic iron. Carbon deposits could potentially be combusted in the oxidation step of the process (see below) and therefore lower the CO\({}_{2}\) capture efficiency. Perovskite-based oxygen carriers (e.g., LaFeO\({}_{3}\) with various dopants partially substituting the cations La and Fe) have shown promise in reducing carbon deposition while possessing a high selectivity towards syngas and a high reactivity due to their high oxygen mobility [30]. Our recent experimental studies have demonstrated that some perovskite-based oxygen carrier formulations (e.g., La\({}_{0.85}\)Sr\({}_{0.15}\)FeO\({}_{3}\) or La\({}_{0.85}\)Sr\({}_{0.15}\)Fe\({}_{0.95}\)Al\({}_{0.05}\)O\({}_{3}\)) possess excellent long-term stabilities in reactor systems of different scales. With the purpose of delving further into the potential of gas switching chemical looping integration for H\({}_{2}\) production, this study aims to evaluate one of these experimentally proven oxygen carriers in an integrated plant model. Instead of requiring a catalytically-active component (e.g., Nickel), this material possesses thermodynamic properties that enable the partial oxidation of methane (or natural gas) to syngas at near 100% selectivity, as reported by [PERSON] et al. [31]. The Gas Switching Partial Oxidation (GSPOX) Process Concept  
Relative to the GSR process, GSPOX enables the reforming step to be split into separate partial oxidation and water splitting steps. In addition, the Lanthanum-based oxidation carrier presents the opportunity to overcome the equilibrium limitations faced by catalytic natural gas reforming at higher pressures. The process configurations presented in this study aim to quantify the potential efficiency benefits of these oxygen carrier features. Figure 1 shows the 3-step GSR operation and the two four-step GSPOX operating modes investigated. The first GSPOX configuration is designed to produce an H\({}_{2}\)-rich syngas with minimal steam addition for maximum H\({}_{2}\) production efficiencies. In this case, the key GSPOX benefit is avoidance of equilibrium limitations in the reforming step, eliminating the need for high S/C ratios to achieve sufficient methane conversion at elevated pressures. The second GSPOX configuration targets combined H\({}_{2}\) and power production. In this case, the reforming step is split into partial oxidation and water splitting steps and the H\({}_{2}\) from the water-splitting step is used for low-carbon power production. For the GSPOX H\({}_{2}\)-mode simulations, the process flowsheet is similar to previous GSR studies [22]. A schematic of the GSPOX H\({}_{2}\)-power concept is presented in Figure 2 The water-splitting step in the GSPOX process produces an H\({}_{2}\) stream with some N\({}_{2}\) and CO from undesired mixing between the different reactor steps. This stream does not meet H\({}_{2}\) export purity requirements, but it is well-suited for combustion with the hot depleted air stream from the oxidation step for highly efficient low-carbon power production. Meanwhile, the 2:1 H\({}_{2}\):CO stream from the partial oxidation step is sent to a PSA unit for separating out ultra-pure H\({}_{2}\) for export. The remaining PSA off-gas stream is sent to the reduction step where it is oxidized to yield a high-purity CO\({}_{2}\) stream after water condensation. This PSA off-gas stream contains enough heating value to supply heat for the endothermic reforming reaction and the pre-heating of surplus air in the oxidation step for power production.