Gasoline-range hydrocarbon synthesis over Co/SiO2/HZSM-5 catalyst with CO2-containing syngas

Selective synthesis of gasoline-range hydrocarbons (C5-C12) was investigated in a fixed-bed micro reactor using two series of CO2-containing syngas with various mole CO2/(CO + CO2) and H2/(CO + CO2) ratios, where Fischer-Tropsch synthesis(FTS) and in situ hydrocracking/hydroisomerization were performed over bifunctional Co/SiO2/HZSM-5 catalyst. CO2 was converted at 0.15-0.55 of CO2/(CO + CO2) ratio under H2-rich condition (H2/(CO + CO2) = 2.0), highest conversion of 20.3% at 0.42. Further increasing CO2 content decreased CO2 conversion and quite amount of CO2 acted as diluting component. For the syngas with low H2 content or H2/(CO + CO2) ratio(< 1.85, H2/CO = 2.0), the competitive adsorption of CO, H2 and CO2 resulted in low CO, CO2 and total carbon conversion, which was 57.9%, 12.7% and 31.4% respectively at 0.74 of H2/(CO + CO2) ratio(H2/CO/CO2/N2 = 40.8/20.4/34.8/4). FTS results indicated that high H2 content and proper H2/(CO + CO2) ratio were favorable for the conversion of CO2-containing syngas. More than 45% selectivity to gasoline-range hydrocarbons including isoparaffins was obtained under the two series of syngas. It was also tested that the catalytic activity of Co/SiO2/HZSM-5 kept stable under CO2-containing syngas(< 7.5%). And the quick catalytic deactivation under high CO2 containing syngas(H2/CO/CO2/N2 = 45.3/23.2/27.1/3.06) was due to carbon deposition and pore blockage by heavy hydrocarbon, tested by thermal gravimetry, N2 physisorption and scanning electron microscopy(SEM).