Effects of promoters on carburized fused iron catalysts in Fischer-Tropsch synthesis
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摘要: 研究了K、Ru和La助剂对碳化和未碳化的熔铁催化剂在结构、比表面积、晶相和催化行为上的影响,运用了XRD、XPS、TPD和N2物理吸附-脱附等分析手段对所制备的催化剂进行表征。实验结果表明,无论是否碳化,K助剂的添加都提高了C5+的选择性。助剂Ru使碳化后催化剂活性明显下降,但对未碳化的催化剂影响极小。La助剂的加入由于其包覆了碳化铁,因此,严重抑制了催化剂的碳化和活性。在产物分布上,Ru和La促进了氢气的吸附,提高了甲烷的选择性。K改性后未碳化的催化剂产物分布最优,其中,甲烷选择性为4.04%,C5+选择性为75.84%。Abstract: The effects of K, Ru or La promoters on the structure, surface area, crystal phase, and catalytic behavior during FT synthesis of carburized and uncarburized fused Fe catalysts were studied by XRD, XPS, TPD, N2-physisorption and catalytic reaction evaluation techniques. Addition of K improved selectivity of C5+ products for both the carburized and uncarburized catalysts. Addition of Ru suppressed catalytic activity of the carburized catalyst, but had little influence on the uncarburized one. Addition of La led to the encapsulation of the iron carbide, which consequently severely inhibited the carburization and decreased the activity. While Ru and La promote the formation of light components due to their ability to promote hydrogen adsorption. The performance of the reaction in the experiment indicated that the U-K catalyst had the best product distribution, in which the methane selectivity was 4.04%, and the C5+ selectivity was 75.84%.
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Key words:
- Fischer-Tropsch synthesis /
- carburization /
- promoter /
- activity /
- C5+ selectivity
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Table 1 Textural properties of the catalysts
Sample SBETa/(m2·g−1) vporeb/(cm3·g−1) dporec/nm C 4.80 0.026 22.91 U 3.02 0.014 19.10 C-K 3.58 0.027 47.13 U-K 2.48 0.027 64.37 C-Ru 39.03 0.033 10.70 U-Ru 17.91 0.050 15.03 C-La 10.11 0.046 35.18 U-La 6.54 0.032 17.06 a: BET surface area, b: Cumulative volume of pores by BJH adsorption, c: Average pore diameter calculated by 4 × vpore/SBET -
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