Greenhouse gas CO2 hydrogenation to fuels: A thermodynamic analysis

Abstract

Over the past few years, chemical conversion of CO2 to alternative fuels such as methanol, dimethyl ether (DME), and hydrocarbons (HCs) is one of the hot topics in chemical engineering. Taking this into consideration, we have investigated the effects of wide range of temperature, pressure and H2/CO2 ratio (with and without CO) on the hydrogenation of CO2 to methanol, DME, and HCs by minimizing the Gibbs free energy. The energy calculations indicate that HC synthesis reaction has the minimum Gibbs free energy change. High pressure, low temperature, and high H2/CO2 ratio favored the methanol and DME synthesis. The HC synthesis is favored by high pressure, low temperature, and high H2/CO2 ratio, but the presence of CO has a major effect on the HC selectivity. The presence of CO suppresses CO2 conversion in all the three reactions studied. CO2 conversion is maximum for the HC synthesis at H2/CO2 > 3. The experimental data obtained from laboratory scale fixed bed reactor show a reasonable comparison with the simulation results. The thermodynamic analysis combined with the catalyst development and chemical kinetics are expected to lead towards a competent methodology for CO2 conversion. © 2018 American Institute of Chemical Engineers Environ Prog, 38: 98–111, 2019.