Kinetics of Fischer-Tropsch Synthesis on Co/Al_2O_3 Catalyst

摘要

The rate expression for Fischer-Tropsch synthesis has been obtained using a 25%Co/Al_2O_3 catalyst in a 1 liter continuous stirred tank reactor (CSTR) at 493K,1.99 MPa (19.7 atm),H_2/CO feed ratios of 1.0-2.4 with space velocities varying to produce 14 to 63% CO conversion.The catalyst was characterized using a variety of techniques including TPR,BET surface area and H_2 chemisorption.Adjusting the ratios of inert gas and added water permitted the impact of added water to be made at the same total flow rate and H_2 and CO partial pressures.The addition of water during FT synthesis had no measurable effect at lower partial pressure but decreased CO conversion relative to the same conditions without 25 volume % water addition.Even at the highest partial pressure of water,the catalytic activity recovered after water addition was terminated.The temporary reversible decline in CO conversion when water was added may be due to a kinetic effect of water by inhibition of CO and H_2 adsoption.The data of this study are fitted by a simple power law expression of the form r_(CO)=kP_(CO)~(0.2)P_(H_2)~(0.5)(1+mP_(H_2O)/P_(H_2))where k =1.164 (moles/h/g cat) and =0.93 at 1.99 MPa (19.7 atm) and 493K.