Study of the role of the support material in the manganese promotion of cobalt-based Fischer-Tropsch synthesis catalysts

IF 4.8 2区化学 Q2 CHEMISTRY, PHYSICAL

Applied Catalysis A: General Pub Date : 2025-09-28 DOI:10.1016/j.apcata.2025.120611

Oscar Ivanez, Edd A. Blekkan

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Abstract

The manganese promotion of cobalt−based catalysts for the Fischer-Tropsch synthesis was investigated using four different supports. Different loadings of manganese were deposited on the catalysts using incipient wetness impregnation before the impregnation of cobalt and rhenium. All the Mn-promoted catalysts exhibited an increase in chain growth probability and olefin content in the products. This enhanced C₅₊ selectivity is attributed mainly to decreased methane production. The promotion of the catalytic activity was dependent on the support material. On γ−Al₂O₃ the catalyst activity increased with increasing manganese loading. Using a narrow pore silica support (SiO₂−N) a maximum in the activity was found at an intermediate manganese loading. Further addition of Mn decreased the activity and worsened the product distribution with an increase in methane selectivity. The catalysts supported on TiO₂ and wide pore silica (SiO₂−W), did not show major activity changes with Mn addition. The addition of Mn decreased the metallic surface area in most cases, indicating blocking of Co sites. The pore structure and the metal−support interactions play a role in how the Mn and Co are dispersed, yielding enhanced or inhibited activity. The origin of the promotion was investigated with CO and syngas adsorption experiments coupled with recording DRIFTS spectra. The results indicated a decrease in CO bond energy due to an increase in electron density of the Co with the Mn addition. The electronic effect appeared to be in balance with the site blocking of Mn. Therefore, choice of support and preparation conditions of the materials are important.

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载体材料在钴基费托合成催化剂中锰促进作用的研究

采用四种不同的载体，研究了锰对钴基费托合成催化剂的促进作用。在钴和铼浸渍之前，采用初湿浸渍法在催化剂上沉积不同负载的锰。锰促进催化剂的链生长率和烯烃含量均有所提高。C5+选择性的提高主要是由于甲烷产量的减少。催化活性的提高依赖于载体材料。在γ−Al2O3上，催化剂活性随着锰负载的增加而增加。使用窄孔二氧化硅载体（SiO2−N），在中等锰负载下活性最大。Mn的进一步加入使反应活性降低，产物分布恶化，甲烷选择性提高。负载在TiO2和大孔二氧化硅（SiO2−W）上的催化剂的活性随Mn的加入没有明显的变化。在大多数情况下，Mn的加入减少了金属的表面积，表明Co位点的阻塞。孔结构和金属-载体的相互作用在Mn和Co的分散、产生增强或抑制活性中起作用。通过CO和合成气吸附实验，并结合记录的DRIFTS光谱，研究了促进的原因。结果表明，锰的加入增加了CO的电子密度，降低了CO的键能。电子效应似乎与Mn的位点阻断相平衡。因此，材料的支撑和制备条件的选择非常重要。

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来源期刊

Applied Catalysis A: General 化学-环境科学

CiteScore

9.00

自引率

5.50%

发文量

415

审稿时长

24 days

期刊介绍： Applied Catalysis A: General publishes original papers on all aspects of catalysis of basic and practical interest to chemical scientists in both industrial and academic fields, with an emphasis onnew understanding of catalysts and catalytic reactions, new catalytic materials, new techniques, and new processes, especially those that have potential practical implications. Papers that report results of a thorough study or optimization of systems or processes that are well understood, widely studied, or minor variations of known ones are discouraged. Authors should include statements in a separate section "Justification for Publication" of how the manuscript fits the scope of the journal in the cover letter to the editors. Submissions without such justification will be rejected without review.