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@SiO2 at 200 & DEG;C, and high pressure in an autoclave (AC), Co@SiO2 (One Pot or OP) at room temperature and 1 atm; the effect of Al2O3 on Co-SiO2 as Co@SiO2Al2O3 (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@SiO2 (Autoclave) is much higher than that of Co@SiO2 (One Pot), and the surface area decreases upon the addition of Al2O3 to yield Co@SiO2Al2O3 (OP) catalyst. In TPR analysis, the Co@SiO2 (OP) based catalyst had much higher reduction temperature than the Co@SiO2 (AC) catalyst. The XRD analysis shows that the Co@SiO2 (Autoclave) based catalyst is more crystalline when compared to other catalysts. The TEM and SEM images revealed agglomerations in the case of Co@SiO2 (OP) and Co@SiO2Al2O3 (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 & DEG;C with H-2/CO molar ratio of 2:1. The highest CO conversion for Co@SiO2 AC, Co@SiO2Al2O3 OP, Co@SiO2 OP are 85%, 45%, and 27% respectively. The highest selectivity to C4+ % was observed for Co@SiO2 AC in SS Microreactors in the temperature range of 200-300 & DEG;C, and the % selectivity for the C4+ follows the order: Co@SiO(2)AC > Co@SiO2Al2O3 OP > Co@SiO2 OP.