In this study, ZIF-8 precursors were prepared to investigate the effect of pyrolysis temperature on the structure of supports. Catalysts were modified with K promoters to further optimize their performance, and the structural characteristics of the catalysts were elucidated through a series of characterizations. The prepared CN supports exhibit high nitrogen content and BET surface area. The Fe/CN-500 catalyst demonstrates the optimal performance: with a low loading of 10%, the CO conversion reaches 85.6%, which is significantly higher than that of the pure C support (20.2%). After modification with K promoters, the catalytic performance was significantly enhanced. K modification facilitated the reduction of Fe species and strengthened the adsorption capacity for CO. The 0.5% K-Fe/CN-500 catalyst exhibited the optimal performance, with a CO conversion of 61.7%, a C2-C4 olefin selectivity (C2=-C4=) of 26.2%, an O/P value of 2.9, and a remarkably high C5+ selectivity of 55.2%. These results demonstrate excellent selectivity toward liquid fuels and effective regulation of product distribution. This study provides insights into the design of catalyst supports for Fischer-Tropsch synthesis.
费托合成(Fischer-Tropsch synthesis,FTS)是将合成气(CO,H2混合气)在催化剂作用下转化为碳氢化合物和含氧化合物的非均相催化过程,是有效缓解石油资源短缺的重要技术[1]。Fe基催化剂,具有价格低廉、制备方便、水煤气变换(water gas shift,WGS)反应活性高和烯烃选择性高等优点,成为FTS反应中被重点研究的催化剂之一[2-3]。然而,FTS反应遵循ASF(Anderson-Schulz-Flory)分布,即反应产物的分布宽泛、调控难度大。因此,高效催化剂设计是FTS反应的核心。负载型Fe基催化剂可通过载体的结构效应、表面性质调变及与活性组元Fe的协同作用,实现对产物分布的有效调控,是目前研究的热点之一[4-5]。在FTS反应体系中,金属氧化物载体(如Al2O3, SiO2),经热处理后容易形成硅酸盐等难还原物种,降低活性组分的还原度,从而降低催化剂载体的活性[6]。碳材料虽然具有较高比表面积和良好的孔道结构,但其与金属之间的相互作用较弱,容易导致金属纳米粒子在反应过程中聚集和烧结长大,进而降低碳材料催化剂的稳定性[7]。一般情况下,通过对碳材料表面功能化的方法(如杂原子掺杂、表面氧化和活化、接枝和磺化等),来提高碳材料催化剂的稳定性和反应性能[8-9]。
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