Effect of Al2O3 Support on Co-Based SiO2 Core–Shell Catalysts for Fischer–Tropsch Synthesis in 3D Printed SS Microchannel Microreactor

Fischer Tropsch Synthesis (FTS) using syngas, a mixture of carbon monoxide (CO) and hydrogen (H 2 ), obtained from renewable sources in the presence of a catalyst, is an excellent route to long-chain hydrocarbons and fuels. In this study, cobalt-mesoporous silica catalysts for FTS were prepared by two procedures-Co@SiO 2 at 200 °C, and high pressure in an autoclave (AC), Co@SiO 2 (One Pot or OP) at room temperature and 1 atm; the effect of Al 2 O 3 on Co-SiO 2 as Co@SiO 2 Al 2 O 3 (One Pot or OP) core–shell catalysts was investigated for FTS at 20 bar in 3D printed stainless steel (SS) microchannel microreactors. These catalysts were characterized by different techniques such as N 2 physisorption, XRD, SEM, TEM, H 2 -TPR, TGA–DSC, and XPS. The N 2 physisorption studies show that the BET surface area of Co@SiO 2 (Autoclave) is much higher than that of Co@SiO 2 (One Pot), and the surface area decreases upon the addition of Al 2 O 3 to yield Co@SiO 2 Al 2 O 3 (OP) catalyst. In TPR analysis, the Co@SiO 2 (OP) based catalyst had much higher reduction temperature than the Co@SiO 2 (AC) catalyst. The XRD analysis shows that the Co@SiO 2 (Autoclave) based catalyst is more crystalline when compared to other catalysts. The TEM and SEM images revealed agglomerations in the case of Co@SiO 2 (OP) and Co@SiO 2 Al 2 O 3 (OP) based catalysts. The TGA analyses of as-synthesized catalysts, before calcination, showed good stability of the catalysts. The oxidation state and binding energy of all catalysts, evaluated by XPS analysis, show a significant shift based on the catalyst preparation. All F-T reactions were carried out in a 3D-printed SS microreactor at 20 bars in the temperature range of 200–370 °C with H 2 /CO molar ratio of 2:1. The highest CO conversion for Co@SiO 2 AC, Co@SiO 2 Al 2 O 3 OP, Co@SiO 2 OP are 85%, 45%, and 27% respectively. The highest selectivity to C 4+ % was observed for Co@SiO 2 AC in SS Microreactors in the temperature range of 200–300 °C, and the % selectivity for the C 4+ follows the order: Co@SiO 2 AC > Co@SiO 2 Al 2 O 3 OP > Co@SiO 2 OP. Graphical Abstract