Study On Co/?-Al₂O₃ Catalysts For Heavy Hydrocarbons Synthesis

The process of synthesis gas to heavy hydrocarbons has been proposed as an important technology for producing diesel and paraffin,where the key is to look for efficient and cheap catalyst.With its features of high activity,low water gas shift reaction and high selectivity to heavy hydrocarbon,cobalt-based catalysts have been one of the most important catalysts for Fischer-Tropsch.In this paper,Co/?-Al₂O₃ catalysts were prepared by the incipient wetness impregnation with different promoters.The prepared catalysts were characterized by N2 adsorption,X-ray diffraction?XRD?,H2 temperature programmed reduction?H2-TPR?,CO temperature programmed desorption?CO-TPD?,H2 temperature programmed desorption?H2-TPD?,and X-ray photoelectron spectra?XPS?and were tested for catalytic performance in a fixed-bed reactor.The results showed that the promoters can affect the degree of reduction of catalysts,and enhance the adsorption of CO and H2 on the catalyst surface.Thus,the catalytic performance can be improved.For Ce modified Co/?-Al₂O₃ catalysts,when the content of Ce was 3 wt%,the catalyst had higher CO conversion and selectivity to heavy hydrocarbons.However,the addition of Ce also increase the methanation of the catalyst.For Zr modified Co/?-Al₂O₃ catalysts,when the content of Zr was 4 wt%,the catalyst had best catalytic performance.Using La to promote the Co/?-Al₂O₃ catalysts modified by Zr,the activity and the selectivity of heavy hydrocarbons of the catalysts can further increase.Compared to other catalysts,0.6La-Zr-Co catalyst showed higher activity,achieving 91.97%CO conversion,85.23%Cs+ selectivity and 42.11%C19+ selectivity at 220?,2MPa,and 1000 h^-1.