Abstract: The effect of CO2 addition during Fischer-Tropsch synthesis was investigated over the Fe-Mn catalyst in a fixed-bed reactor. The CO2 addition enhanced the reverse reaction rate of the water-gas shift and inhibited the CO2 formation rate. The CO2 selectivity decreased rapidly when a large amount of CO2 was added into the feed gas (n(H2)/n(CO)=2.03, GHSV (H2+CO)=4010h-1, p(total)=1.50 MPa, T=533 K), while the hydrocarbon formation rate decreased slightly and the overall oxygenate formation rate decreased. Under the reaction conditions ofn(H2)/n(CO)=1.00, GHSV (H2+CO)=8000h-1, p(H2+CO)=1.50 MPa, and T=593 K, the CO2 addition decreased the surface hydrogen concentration, leading to an increase in olefin/paraffin ratio and higher C5+selectivity in reaction products. The hydrocarbon formation rate appreciably increased with increasing CO2 partial pressure, and the hydrocarbon yield also gradually increased. In addition, the oxygenate formation rate also increased with CO2 partial pressure.

Key words: iron, manganese, Fischer-Tropsch synthesis, syngas, carbon dioxide, water-gas shift