Silica-supported iron nitride in Fischer-Tropsch reactions: II. Comparison of the promotion effects of potassium and nitrogen on activity and selectivity
Silica-supported iron nitride in Fischer-Tropsch reactions: II. Comparison of the promotion effects of potassium and nitrogen on activity and selectivity
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DOI：
10.1016/0021-9517(85)90338-0
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发表时间：
1985-02
影响因子：
7.3
通讯作者：
E. B. Yeh;L. Schwartz;J. Butt
中科院分区：
文献类型：
--
作者：
E. B. Yeh;L. Schwartz;J. Butt
研究了在钾和氮的催化下，二氧化硅负载铁催化剂催化CO转化为烃类的性能。在250°C， 1,7.8和14 atm下，在小于6%的差异转化范围内研究了反应。与先前的熔融或沉淀材料的研究相比，这些负载催化剂的行为存在显着差异。结果表明，与氮化催化剂相比，未促进的铁碳化物催化剂在较低压力下活性较高，而在较高压力下活性较低。此外，还发现含钾催化剂的活性低于无钾催化剂。与未促进的催化剂相比，氮化铁和钾促进的催化剂均表现出更高的烯烃选择性、更高的水气转换活性、更低的醇收率和更高分子量产物的比例。给出了各种催化剂在不同压力和转化水平下的产物分布参数。讨论了将醇类纳入分布图的意义，并提出了醇类形成的机理。根据氮原子给电子给带的供体模型理论，讨论了氮对催化反应的影响。从负载型氮化铁催化剂和钾促进催化剂的产物分布可以看出，氮和钾对费托反应具有相似的促进作用，并且fe - k -氮化物催化剂存在加性效应。
The performance of silica-supported iron catalysts promoted by potassium and nitrogen has been studied for the conversion of CO to hydrocarbons. Reactions were investigated at 250 °C and at 1, 7.8, and 14 atm in a differential conversion range of less than 6%. Significant differences exist in the behavior of these supported catalysts in comparison to prior studies of fused or precipitated materials. It was found that an unpromoted Fe-carbide catalyst was more active at lower pressures and less active at higher pressures than the nitrided catalyst. Moreover, it was found that potassium-promoted catalysts were less active than catalysts without potassium. Both Fe-nitride and potassium-promoted catalysts showed higher olefin selectivities, higher water-gas shift activity, lower alcohol yields, and larger proportions of higher molecular weight products than their unpromoted counterparts. The product distribution parameters are presented for all catalysts at different pressures and conversion levels. The significance of the incorporation of alcohols into the distribution plot is discussed and a mechanism for alcohol formation is proposed. The effect of nitrogen on the catalytic reaction is discussed in terms of a donor model theory in which nitrogen atoms donate electrons to the irondband. From the product distribution of the supported Fe-nitride and potassium-promoted catalysts, it is concluded that nitrogen and potassium have a similar promoting function on the Fischer-Tropsch reactions and further that an additive effect is observed for Fe-K-nitride catalysts.