Influence of Oxygen Species on Sr–Mo Oxides for CO ₂ -Promoted Soft Oxidative Vapor-Phase Dehydrogenation of Ethylbenzene

Direct dehydrogenation accounts for nearly 90% of global styrene production, but its widespread use is hindered by significant energy consumption. In this article, we propose to synthesize a varied ratio of Strontium–Molybdenum bimetallic oxide catalysts with an impactful oxygen species analyzed by X-ray photoelectron spectroscopy, electron paramagnetic resonance, and H2-TPR analysis. The chemical composition and the effective utilization of CO2 as a soft oxidant result in the ethylbenzene conversion of 74% and styrene selectivity of 78% at 575 °C with a feed flow of 0.5 mL h–1 for the Strontium–Molybdenum bimetallic oxide with a 1:1 atomic wt % (SM11) ratio catalyst. The effective contribution of the vacant and lattice oxygen and the metal–oxygen bond of the SM11 catalyst explains the favorable dehydrogenation activity and its stability toward the desired product for longer time-on-stream studies with a stability up to 72 h. The rate of ethylbenzene’s disappearance varied between zero and first order, and the rate of reaction increased with an increase in temperature, while the highest energy of activation was obtained to be 42.12 kJ mol–1 for molybdenum oxide, followed by a 40.75 kJ mol–1 value for the SM11 bimetallic oxide catalyst. Additionally, the thermodynamic study depicted a positive value for the change in enthalpy, explaining the endothermic nature of the reaction, indicating favorable conditions for the oxidative dehydrogenation reaction. This proposed study provides excellent efficiency and practicality, demonstrating the potential for process integration and styrene production.