A comprehensive thermodynamic equilibrium analysis of direct CO2 hydrogenation to light olefins product

Thermodynamic equilibrium analysis is a powerful tool for assessing the feasibility of chemical reactions and product distributions under different operating conditions. This study investigates the feasibility and intrinsic nature of each possible reaction in CO2 hydrogenation using the equilibrium constant (K) method and calculating thermodynamic parameters. In addition, the equilibrium product distribution and CO2 conversion of CO2 hydrogenation to light olefins (CTO) process determined at temperature range of 200–400℃, pressure of 1–50 bar, and different H2/CO2 feed ratios (1, 2, 3, and 4) using Gibbs free energy (GFE) minimization method. The results indicate that, elevated temperatures strongly promote the formation of light olefins while effectively suppressing coke deposition, pressure exerts a moderate enhancing effect, and a higher H2/CO2 ratio, particularly at lower temperatures, significantly reduces coke formation while having only a minor influence on light olefins selectivity. In contrast, CO2 conversion decreases markedly with increasing temperature, while higher pressure and elevated H2/CO2 ratios enhance the conversion. Ultimately, the maximum selectivity of light olefins (1.22 ×10−7) was obtained at 400℃, 50 bar, and H2/CO2 = 3, under which coke formation was completely suppressed, although the corresponding CO2 conversion was only 7.6 %. These findings highlight not only the intrinsic nature of the CTO process and the influence of operating conditions on its equilibrium product distribution, but also provide valuable guidance for catalyst development in the absence of extensive experiments.