Power-to-liquid (PtL) technologies will be an integral part of the energy transition, allowing CO2 to be reused as a resource and thus avoiding the further use of fossil fuels. Notably, the cement industry currently employs limestone as a raw material, which in turn leads to the emission of process-related CO2 during decarbonization in the clinker production process. This study investigates the utilization of CO2 and its catalytic conversion into valuable polyolefins through the identification of suitable process routes (Fischer-Tropsch and methanol synthesis). The techo-economic assessment reveals that the PtL process utilizing the reverse water-gas shift (rWGS) reaction for synthesis gas production, the Fischer-Tropsch synthesis, and a steam cracker technology for producing lower olefins is the most cost-effective and technically feasible process, yielding in costs of 14.92 € kg^(-1) product. A sensitivity analysis indicates the enormous reliance, particularly on electricity and chemical process investment, as well as significant expenses associated with future electrolysis cell manufacturing costs.
The rWGS reaction, which is still in the early stages of technological development, is necessary for the production of synthesis gas demanded as feed gas for the Fischer-Tropsch reactor. The present study compares the simulated and experimental results of the conversion of CO2 with hydrogen via rWGS, utilizing a Ni/Al2O3 catalyst, two perovskite catalysts, and the support material Al2O3 in an experimental test rig. The Ni/Al2O3 catalyst generates a considerable amount of methane under low temperatures (< 750 °C) and ambient pressure, and this is heightened by elevating the pressure (reaching up to 28.3 vol.-\% CH4 at 550 °C and 8 bara). The perovskite catalysts indicate low methane formation from 550 °C on, and this further increases to a maximum of 2.7 vol.-% CH4 in the product gas at the same temperature and a pressure of 8 bara.
In the concluding section of this work, the use of perovskite catalysts in the PtL process chains is investigated, specifically in Fischer-Tropsch synthesis incl. product separation and the rWGS reactor as pre-conversion unit. A comparison of the performance of perovskite catalysts with Ni/Al2O3 catalysts is executed based on ASPEN simulations. Depending on the technical evaluation of liquid product quantity, PtL efficiency, carbon efficiency, and carbon deposition, the use of a perovskite catalyst is superior to the Ni/Al2O3 catalyst in all key figures. However, an additional reforming step of the recycled gas streams from the Fischer-Tropsch reactor and an additional CO2 and H2 separation unit is required.