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首页> 外文期刊>Journal of industrial and engineering chemistry >Studies of carbonaceous species in alkali promoted iron catalysts during Fischer-Tropsch synthesis
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Studies of carbonaceous species in alkali promoted iron catalysts during Fischer-Tropsch synthesis

机译：费-托合成过程中碱助铁催化剂中碳质物质的研究

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摘要

The effects of La, Mg and Ca promoters on carbonaceous surface and bulk iron carbide species formed in the alkali promoted iron catalysts are studied under realistic Fischer-Tropsch synthesis (FTS) conditions. Compositions of bulk iron phase and phase transformations of carbonaceous species during pretreatment and FTS reaction were characterized using the temperature-programmed surface reaction with hydrogen (TPSR-H2) and XRD techniques. Many carbonaceous species on surface and bulk were qualitatively and quantitatively identified by combined TPSR-H2 and XRD spectra of the alkali promoted iron catalyst. These species, sorted by the their reactivity with H2 from high to low, were recognized as (a) adsorbed, atomic carbon; (b) amorphous, lightly polymerized hydrocarbon or carbon surface species; (c) bulk carbides and (d) disordered and moderately ordered graphitic surface carbons. The results revealed that while the surface basicity of the iron catalyst increased the CO dissociation proceeds faster than carbon hydrogenation. This phenomenon leads to excessive carbon deposition and formation of inactive iron carbide phases and graphitic type carbonaceous surface species, and consequently leads to catalyst deactivation.
机译：在实际的费-托合成（FTS）条件下，研究了La，Mg和Ca助催化剂对在碱助铁催化剂中形成的碳质表面和块状碳化铁物种的影响。使用氢的程序升温表面反应（TPSR-H2）和XRD技术表征了预处理和FTS反应过程中的块状铁相组成和碳质物质的相变。通过碱促进铁催化剂的TPSR-H2和XRD光谱相结合，定性和定量地鉴定了表面和主体上的许多碳质物种。这些物质按其与H2的反应性从高到低排序，被认为是（a）吸附的原子碳; （b）无定形的，轻度聚合的碳氢化合物或碳表面物质; （c）块状碳化物和（d）无序且中等序的石墨表面碳。结果表明，尽管铁催化剂的表面碱度增加，但CO的离解比碳的氢化快。这种现象导致过多的碳沉积，并形成惰性碳化铁相和石墨型碳质表面物质，因此导致催化剂失活。

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