Production of Liquid Hydrocarbons with CO₂as Carbon Source based on Reverse Water‐Gas Shift and Fischer‐Tropsch Synthesis

Abstract

Abstract The substitution of fossil fuels by renewable energy sources is needed to decrease greenhouse gas emissions, especially CO 2 . Wind and solar power are today considered as attractive alternatives for electric power generation, but are not suitable for providing base load. Thus, efficient storage of electrical energy is inevitable. Liquid hydrocarbons (HCs) exhibit an excellent volumetric energy density and offer various opportunities for storing electric energy. They can be produced by CO 2 and renewable H 2 (generated by water electrolysis) in a two step process. The first step is generation of syngas by reverse water‐gas shift (RWGS) at elevated temperatures; the second step comprises the production of liquid hydrocarbons by Fischer‐Tropsch (FT) synthesis. The experiments on RWGS with a commercial Ni‐catalyst show that a CO 2 conversion of around 80 % can be reached at 800 °C within a very short residence time of less than < 0.1 s. The experiments on FTS with Fe as catalyst and syngas containing different amounts of CO 2 indicate that the influence of CO 2 on CO conversion and product selectivities (including net CO 2 production by water‐gas shift) is insignificant if the inlet partial pressures of H 2 and CO are kept constant. If CO is substituted by CO 2 , less HCs are formed, the water‐gas shift is repressed, and methane selectivity increases.