Power-to-Liquid catalytic CO2 valorization into fuels and chemicals: focus on the Fischer-Tropsch route

In the framework of limiting the concentration of CO2 in the atmosphere, the utilization of CO2 as a feedstock for the synthesis of different products, such as methanol, dimethyl ether and liquid fuels, is gaining a lot of interest. In particular, the Power-to-Liquid (PtL) concept which combines the CO2 hydrogenation with the production of hydrogen from water electrolysis, powered by renewable sources, seems a very interesting solution for the production of liquid fuels and chemicals. It also represents a storage solution for the intermittent renewable energies. In this work, the techno-economic feasibility of the CO2 hydrogenation into long-chain hydrocarbons, compared to the synthesis of other liquid or gaseous products (methanol, DME, hydrogen, methane...) is studied, as well as that of PtL compared to other renewable fuels production pathways. Even if the PtL process is not economically competitive on the market yet, some economic considerations predict a decrease in the production cost of PtL fuels, thus it is worth to study the synthesis of liquid fuels from CO2 and H-2 for its several advantages in terms of efficiency and sustainability of the process, especially for middle or long term prospects and for their potential applications as fuel for the heavy-duty, marine and aviation transport, but also as feedstock for the chemical industry. The review is then focused on the hydrogenation of CO2 into liquid fuels. A review of the performances of Fe and Co catalysts is also given, pointing up that iron catalysts are more suitable for the production of long-chain hydrocarbons, especially when potassium-promoted. A state-of-the-art about the kinetic modeling of the reaction and the current industrial demonstrators has also been reported. However, very few data are available and further investigation in this field should be done. This work, summarizing general information about the hydrocarbon synthesis from CO2 hydrogenation, shows the complexity of such a process and points out that further studies about the reaction mechanism, kinetics and the development of a highly active catalyst selective towards long-chain hydrocarbons are needed. This will help to increase the techno-economic feasibility of this challenging process.