3D-printing of optimized catalyst's support geometries for syngas-synthetic chemicals conversion in fixed bed reactors

The storage of renewable energy is an important point in the roadmap of the European energetic plan, following a development strategy of low-carbon technology. In this context the development of flexible power-to-liquid (P-to-L) and power-to-gas (P-to-G) processes for energy storage is one of the most promising solutions for the smooth transition from a driven fossil fuel society to a driven renewable sources society. In this regard, Fischer-Tropsch (FT) synthesis is used to obtain valuable chemicals from syngas (H2/CO mixture) through a catalytic reaction. The syngas can be obtained from renewable sources such as the co-electrolysis of CO2 + H2O in a SOEC electrolyzer. Therefore, in this way it is possible to contribute to the CO2 reduction and the renewable synthesis of valuable chemicals. In order to design energy conversion devices, 3D-printing as additive manufacturing (AM) technique has been recently gaining relevance. The 3D-printing technique offers more advantages respect to the classical way of production by extrusion, such as the capability to increase shape complexity while reducing waste material and manufacturing cost. In this work, an efficient cobalt (Co) based catalyst for the Fischer-Tropsch synthesis is developed by using modelling software, called CAD (Computer-Aided-Design), 3D-printing technology and an impregnation method. As catalyst`s support and 3D-printing material, α-Al2O3 is employed because of the low cost of this ceramic material and its positive effects on Co based catalyst for FT synthesis. Moreover, the addition of small amount of rhenium (Re) as promoter of the Co improves the availability of Co active sites. In order to reach a trade-off between the effectiveness of the catalyst and the conditions to evaluate the catalyst in a fixed bed reactor (FBR), an eggshell Co-promoted Re-3D-printed supported α-Al2O3 with a diameter of about 1 mm and active catalytic layer of 20 μm is designed. Characterization techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), Specific Surface area (BET), Thermal programming reduction/oxidation (TPR/TPO), among the most relevant ones, are applied in order to characterize the materials during the design and synthesis process of the catalyst, after thermal treatment in different conditions as well as after the FT reaction. The designed catalyst is tested in a fixed bed reactor (FBR). Finite elements modelling (FEM) is performed to determine the temperature and pressure conditions to carry out the evaluation of the catalyst and to compare the performance of the modelled catalytic bed with the experimental results. Experimental results show that the designed eggshell Co-promoted Re/3D-printed supported α-Al2O3 catalyst provides a conversion of syngas of around 55 % and a selectivity toward C5+ of about 81 % at 210 °C and 20 bar with a gas hourly space velocity (GHSV) of 993 NmL/(h*gcat) and syngas composition of H2:CO ratio equal to 1.7. The experimental results are in agreement with the FEM simulations.