Enhanced performance of CH4 dry reforming over La0.9Sr0.1FeO3/YSZ under chemical looping conditions

Catalytic dry reforming of methane is an attractive route for CO2 valorization that yields syngas (CO + H-2) for subsequent synthesis of chemical and fuels. Alternatively, chemical looping approaches based on discontinuous cyclic operation are lately gaining relevance because, among other advantages, these processes are less prone to deactivation, and they are amenable to be used for thermosolar fuel production. With this background, here we investigate the isothermal activity of CO2 and CH4 over La0.9Sr0.1FeO3 perovskite modified with yttria-stabilized zirconia (YSZ), comparing conventional catalytic activity, tested by continuous feeding an equimolar blend of these two gases, with the chemical looping process, where the inlet composition swings between CH4 and CO2 in 20 min intervals. Two preparation methods were used to obtain these composites: direct synthesis by Pechini method of the perovskite in the presence of YSZ support and mechanical mixing by ball-milling of the two presynthetized oxides. Catalytic activity feeding a CH4 and CO2 blend showed a moderate but rather stable activity (226 mu mols.min(-1).g(-1) of H-2 and 206 mu mols.min(-1).g(-1) of CO) at 850 degrees C for 24 h, with little difference between catalysts. Chemical looping operation at the same temperature, resulted in enhanced production of syngas, with the sample with perovskite synthetized on the support showing significantly higher peak performance (476 mu mols.min(-1).g(-1) of H-2 and 432 mu mols.min(-1).g(-1) of CO). The observed high H-2/CO ratio in the methane stage (up to 6.5) indicates the relevant contribution of methane cracking. Characterization of the fresh materials confirmed the formation of the expected phases in both cases, while after CH4 treatment at high temperature the perovskite decomposed mainly into La2O3 and reduced Fe phases. In addition, carbon is also deposited, mainly as multiwall nanotubes. However, the initial perovskite composition is recovered after re-oxidation with CO2, allowing a stable operation of the La0.9Sr0.1FeO3/YSZ system for at least five cycles.

Automated summary

Catalytic dry reforming of methane is an effective route for CO2 valorization, while chemical looping processes based on discontinuous cyclic operation show potential advantages in terms of stability and syngas production. The study found that perovskite modified with yttria-stabilized zirconia support achieved higher syngas production in chemical looping operation compared to continuous feed of CH4 and CO2 blend, with stable but moderate activity in the latter.