Hydrotalcite supported Co catalysts for CO hydrogenation

Abstract

It is well known that the catalytic performance of Co catalysts depends on supports and promoters. The focus of this work was to investigate the catalytic activities for CO hydrogenation of Co catalysts supported on the solid base, hydrotalcite (HT), and to probe the role of support in the reaction. A cobalt catalyst containing 10 wt% cobalt supported on HT was prepared using the incipient wetness impregnation method. Pre-calcined HT (CHT), alumina and magnesium oxide were also employed as supports for comparison purposes. Catalysts were characterized by surface area and porosity analysis, XRD, TEM/STEM/EDX, TPR and H 2 chemisorption. The catalytic activity was tested using a fixed-bed reactor at 230 °C, 1.8 atm, and H 2/CO = 2. It was found that the hydrotalcite supported catalyst showed the highest steady-state reaction rates. The activities of Co/HT reduced at different reduction temperatures (from 300 to 600 °C) were also compared. Reduction at 500 °C resulted in the highest activity; however, CH 4 selectivity was also enhanced as the reduction temperature increased. The product distributions for Co/HT obeyed an Anderson–Schulz–Flory distribution. The α values were not impacted by the different reduction temperatures for Co/HT. The characterization and reactivity results suggest that the thermal stability properties of hydrotalcite, BET surface area, particle size of Co, the interaction between Co and the support, and the reducibility of Co were all important in governing the catalytic performance of the Co catalysts for CO hydrogenation. Our study suggests that HT is a promising support for Co for Fischer–Tropsch synthesis because it gives high activity (higher than Co/Al 2O 3) without the need for a reduction promoter.