Optimization of Operating Conditions for CO Hydrogenation to Hydrocarbon via Response Surface Method

Clean hydrocarbon is an alternative source of other fuels like coal and natural gas. Based on the literature, the significance of hydrocarbon production via Fischer-Tropsch synthesis (FTS) process cause to develop a new mathematical algorithm response surface methodology (RSM)/ design of experiment (DOE). The influence of important factors, like pressure, temperature and feed ratio (H2/CO) on the performance of the FTS are examined. The experiments are conducted in the range of: P = 1.9-3.75 bar, T = 523-563 K, and H2/CO ratio = 0.85-1.85 at set space velocity (2000 h-1). A second-order model is developed via RSM in terms of independent input variables to describe the CO conversion and selectivity of CO2 and C5+ as the responses. It is concluded that at low temperature and H2/CO ratio, CO2 selectivity increase significantly and C5+ selectivity decreases appreciably when pressure increases. Moreover, at low pressure an increase in temperature, reduces CO conversion. According to contour plots and analysis of variance (ANOVA), it is illustrated that the maximum CO conversion was obtained at P = 3.21 bar, T =563 K and H2/CO = 1.85 while for C5+ the maximum is observed at P = 3.67 bar, T = 529.1 K, and H2/CO = 0.91, and CO2 selectivity is minimized at P = 1.93 bar, T = 563 K and H2/CO = 1.85.  The predicted conversion and selectivity are in good accordance with experimental results which is an indication of the accuracy of RSM methodology in designing and optimizing the FT process.