Abstract
Herein, we report on the activity and selectivity of bulk gamma-Mo2N catalysts for Fischer-Tropsch lower olefin (FTO) synthesis. An increase in surface area and a decrease in crystallite size were observed for gamma-Mo2N catalysts prepared with the increased molar amount of citric acid (CA), used as a chelating agent during the catalyst synthesis. The reaction products were mainly C-2-C-3 hydrocarbons in the temperature range of 230-300 degrees C at 2 MPa with a reactant feed composition of CO:H-2:Ar = 42.7:34.6:20.8 and a gas hourly space velocity (GHSV) of 1.3 mol/(g(cat).h). The catalytic activity of the gamma-Mo2N catalysts increased with increased CA:Mo molar ratio and with temperature. However, the hydrogenation activity of the catalysts also increased, resulting in increased selectivity to paraffins. Selectivity to olefins prefers low CA:Mo, that is, low surface area and large crystallite size of gamma-Mo2N. The gamma-Mo2N catalyst prepared with a CA:Mo ratio of 1 had 56.4 C atom% C2+ hydrocarbon selectivity, 62.4% of which was olefin with 37.8 C atom% selectivity to propylene at 275 degrees C.