Flexible Conversion of CO₂ and EE-H₂ to Middle Distillate Components by Fischer-Tropsch Synthesis in Microreactors with the Help of Novel Fe-Catalysts (MicroFe)

The reduction of CO₂ emissions to limit global warming is a central goal of the international community. In the framework of the Paris UN climate agreement, it was decided in 2015 to limit global warming to a maximum of 2°C compared to the pre-industrial age. The German Federal Government is pursuing this goal as part of its energy system transformation policy, which envisages a drastic reduction in fossil CO₂ emissions by 80% in 2050.
Since there is currently no alternative to liquid fuels in air traffic, the use of CO₂-neutral synthetic middle distillate and especially kerosene is becoming increasingly more attractive. For the production of synthetic middle distillate components, Fischer-Tropsch synthesis (FTS) is a suitable method. In the classic process variant, the synthesis gas consists of H₂ and CO, although more recent work is also investigating the use of CO₂. In the FTS process, a broad spectrum of short- and long-chain paraffinic and olefinic hydrocarbons is produced, depending on the operating conditions, reactor and catalyst type. Distillative fractionation of the liquid AGV product finally results in the production of petrol, kerosene, diesel, heating oil and also waxes.
For a sustainable reduction of CO₂ emissions, the hydrogen required for FT synthesis must be obtained from the electrolysis of water and the electrical current from renewable energy sources. This concept thus also includes the storage of the strongly fluctuating regenerative energy sources in the form of chemical energy (middle distillate), which is supplied to the aircraft for energetic use. Possible CO₂ sources for FT synthesis are (i) waste gas streams from combustion and waste incineration plants, (ii) biogas, and (iii) perspectively even CO₂ from the air, while CO and partly also H₂ can be produced by gasification of biomass and waste or reforming of biogas.
Innovative microreactors for Fischer-Tropsch synthesis enable a drastic increase in fuel yield in relation to the reactor volume through optimised temperature control. This means a considerable improvement in load flexibility, which is of particular importance for the coupling of regenerative energy sources. Frequent startup and shutdown processes due to flexible operation can, however, lead to a faster degeneration of the comparatively cost-intensive and toxic cobalt catalysts that are usually used if the reactor is operated incorrectly. In addition, cobalt catalysts do not have a water gas shift activity, so that these catalysts react quite sensitively to the CO/CO₂ ratio in the feed gas.

Against this background, the research project aims to develop a process for the load-flexible conversion of CO₂ and RE-H₂ to middle distillate, in particular also kerosene, using Fischer-Tropsch synthesis. At the core of this process are microreactors and novel iron catalysts. The project is expected to achieve the following development goals:

• Development of a new type of FTS catalyst based on iron, which is characterised by the following properties: (1) toxicological safety, (2) favourable price, (3) high yield of middle distillate components, (4) long-term stability under dynamic conditions


• Integration of the novel Fe-catalyst in microstructured FTS reactors


• Detailed analysis of the product composition of the FTS product or middle distillate fraction