Al-O-Zn type carriers were prepared using coprecipitation plus high-temperature calcination method.Two catalyst samples R1 and A1 with the same chemical composition were prepared by two different processes,i.e.,loading potassium followed by iron and the iron followed by potassium,respectively.Two catalyst samples were characterized using XRD,ICP-OES,nitrogen physical adsorption,field emission electron microscopy,and carbon dioxide chemical adsorption-temperature programmed desorption.The reaction performance of the catalysts for CO hydrogenation to olefins was evaluated in a pressurized fixed bed reactor.The results show that there are no significant differences in crystal phase composition,pore texture and microstructure between the two samples,and significant differences in the CO2-TPD curve characteristics.Sample R1 exhibits nearly symmetrical high-and low-temperature desorption peaks,while sample A1 mainly shows high-temperature desorption peaks.At the temperature of 290-420 ℃,pressure of 2 MPa,volumetric space velocity of 1500 mL/(g·h)and reaction time of 4 h,CO hydrogenation reaction was carried out to prepare olefins.Compared with the results under the action of sample A1,the maximum molar ratio of C2 olefin to paraffin under the action of sample R1 is about 500％higher,that of C3 olefin to paraffin is about 174％higher,that of C4 olefin to paraffin molar ratio is about 35％higher,and the maximum selectivity to C2=—C4=hydrocarbons is about 44％higher.Different preparation processes of the catalyst lead to significant changes in the characteristics of basic sites on the surface of catalyst sample.The hydrogenation is more effectively inhibited when the desorption peaks at high and low temperature are nearly symmetric(sample R1)in the CO2-TPD curve,as compared with the case where the desorption peaks at high temperature are dominated(sample A1),thus affecting the selectivity of the catalyst for hydrocarbons in the hydrogenation reaction of CO.
CO hydrogenationiron-based catalystpreparation procedurelight olefinsbasic siteolefin/paraffin molar ratio
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