Scalable combustion synthesis of copper-based perovskite catalysts for CO2 reduction to methanol: Reaction structure-activity relationships, kinetics, and stability

Abstract

The selectivity of the CO2 hydrogenation can be tuned easily by altering the chemical Cu oxidation state, the correlated synergistic effect between copper, alkaline metal elements and support, and operation. In this mechanistic work, several perovskite-containing Cu/Sr/Ti materials were prepared, using one-step solution combustion method, by varying characteristic system parameters, including fuel selection relationship, maximal reference Cu loading, the type of deposition and the size of nanoparticles, Sr/Ti ratio, physical calcination temperature and the series of reactions. The activity under application was measured at relevant functional methanol synthesis conditions (200–280 °C, 20–50 bar and 8,000–24,000 h−1), validated to be stable, and connected with component physicochemical properties, identified applying X-ray powder diffraction (XRD), benchmarking and Rietveld refinement, N2 physisorption, the scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy- (EDS), the temperature-programmed reduction of H2 (H2 TPR), N2O pulsed surface oxidation (N2O PSO) and the temperature-programmed desorption of CO2 (CO2 TPD) interactions. Aqueous citric acid was assessed as the most suitable energy source; the optimal experimental heating was at 650 °C, balancing remaining nitrate ions, thermal sintering, and active Cu sites, while adsorption surface area was high. Additionally, a long-term stability determination test of the best-manufactured product (Cu5Sr3Ti2OX) was performed, deactivation was analysed, and derived kinetic model was constructed, which adequately described intrinsic catalytic behaviour over a broad operational range investigated. Graaf kinetics were assumed to be suitable for commercial Cu/ZnO/Al2O3, integrating the sorption, rates, and equilibrium into macro-kinetics, removing resistances of transport phenomena. Semiconductors as substrates facilitate the extrapolation of solar-driven photo-thermal catalysis.