Flexible conversion of CO2 and EE-H2 to middle distillate components by Fischer-Tropsch synthesis in microreactors using novel Fe catalysts (MicroFe)

The project dealt with the climate-neutral production of middle distillate components (primarily kerosene, diesel and heating oil) using Fischer-Tropsch synthesis. The concept envisages the provision of CO and CO2 from biomass, combustion exhaust gases or air. The hydrogen is obtained by water electrolysis, which is powered by "renewable" electricity. The focus of the work carried out was on the direct conversion of CO2 with hydrogen on Fe catalysts, which clearly distinguishes the approach pursued from the established Fischer-Tropsch synthesis process with CO as the starting material. The development of Fe catalysts was necessary because the known cobalt catalysts are not stable towards CO2 and iron allows flexible feed compositions due to its water gas shift activity. The first step was to develop novel Fe catalysts for the CO2-based Fischer-Tropsch synthesis. Numerous scientific and technical insights were gained, such as the use of alkali promoters or temperature control with pure CO2 utilization. The best two catalysts were scaled up for in-depth investigations for optimization and for tests to change the operating conditions. The best test point at 350 °C, 25 bar and a molar H2/CO2 ratio of 3:1 with a Na-promoted Fe2O3 catalyst led to a selectivity of the product fraction C10-C20 of 10 wt.% with a CO2 conversion of 45 %. By recycling the unreacted reactant stream, a CO2 conversion of up to 81 % (R=8) could be achieved with almost the same middle distillate selectivity. For the technological evaluation of the process, an exemplary application of the produced middle distillate as aviation turbine fuel with proof of fulfillment of the requirements (ASTMD4054 - 20a) was shown.

The IGF project 01IF21307N was funded by the Federal Ministry of Economics and Climate Protection as part of the "Industrial Collective Research" program based on a resolution of the German Bundestag.