Microwave modification of cobalt supported on beta silicon carbide catalyst for Fischer–Tropsch synthesis

Microwave irradiation (MIR) has been investigated as a way of modifying a 12 wt% Co/β-SiC catalyst during catalyst synthesis. The Co/β-SiC catalysts were characterized by N2 physisorption, XRD, H2-chemisorption, SEM, TPR, XPS analysis and evaluated for Fischer–Tropsch synthesis. The characterization results showed that certain bulk properties such as surface area, metal particle size and morphology were not affected by MIR. In contrast, the elemental mapping revealed that the MIR affected the Co distribution on the β-SiC support. The TPR analysis showed that 10 s and 15 s exposure to MIR leads to a shift of the reduction temperature peaks to higher temperatures compared to 20 s MIR exposure that shifted to lower temperatures. The catalytic testing results revealed that MIR affects the performance of the Co/β-SiC catalyst in a very complex way. Based on the TPR observations, stronger metal-support interactions were observed for the Co/β-SiC catalysts modified by MIR leading to an increase in CO conversion (10 s and 15 s exposure). Exposure to MIR for 10 s favored the formation of light hydrocarbons (e.g. 26% lower olefins selectivity at 220 °C and 20 bar), and 15 s exposure to MIR led to the formation of long-chain hydrocarbons (72% C5+ selectivity at 220 °C and 20 bar). The 20 s exposure to MIR was detrimental to the Co/β-SiC catalyst due to poor Co distribution.