Numerical modeling and optimization of product selectivity and catalyst activity in Fischer-Tropsch synthesis via response surface methodology: Cobalt carbide particle size and [formula omitted] ratio effects

Abstract

The effects of cobalt carbide (Co2C) catalyst particle size and usage ratio (H2/CO) on the Fischer-Tropsch selectivity, cobalt time yield and turnover frequency were investigated through statistical modeling by means of response surface methodology based on the data obtained over seven SiO2 supported cobalt catalysts at three different usage ratio levels. The effects of predictor variables on responses are illustrated in contour and surface plots and analyzed based on both model equation and plots. C5+ selectivity was found to increase with increasing Co2C particle size up to the range of 9.6–11.75 nm, after which decreases slightly. Furthermore, a linear relationship was detected between CH4 selectivity and C5+ selectivity for predicted data at all H2/CO ratios (0.5–2) in the Co2C particle size range of 5.3–9.4 nm. Multi-objective optimization conducted for the enhancement of C5+ selectivity predicted the particle size of 6.795 nm and usage ratio of 0.500 as optimum conditions.