Ru promoted cobalt catalyst on γ-Al2O3: Influence of different catalyst preparation method and Ru loadings on Fischer–Tropsch reaction and kinetics

Abstract

Abstract Ruthenium promoted cobalt catalysts supported on γ-Al 2 O 3 were prepared by stepwise and co-impregnation methods. The effects of impregnation order on activity and selectivity of the Fischer–Tropsch synthesis (FTS) were investigated using fixed bed microreactor. The catalysts were characterized by TPR, XRD and TEM. The selected Ru loading was 0.15 wt.% while that of Co was 15.0 wt.% in all of the prepared samples by different order of impregnation. The catalyst prepared by co-impregnation method shifted both steps of cobalt oxide reduction temperatures to lower temperatures by about 100 °C. However, temperature shift was lower for the catalyst prepared by stepwise impregnation method. The highest CO conversion and C 5+ selectivity and the lowest methane selectivity were obtained for the catalyst synthesized by co-impregnation method. Two other catalysts with 0.3 and 0.6 wt.% of Ru loadings on 15.0 wt.% Co were synthesized by co-impregnation and its effect on the FTS was investigated. The prepared catalysts showed an increase in CO conversion with the increase of Ru from 0 to 0.30 wt.%. However, further increase in Ru led to lower CO conversion for a Ru loading of 0.6 wt.%. The effects of temperature and H 2 /CO ratio for all catalysts were examined and their performance modeled by a Langmuir–Hinshelwood–Hougen–Watson (LHHW) rate expression.