Influence of Fe2O3 crystal phase on the performance of Fe-based catalysts for CO2 hydrogenation
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摘要: 以共沉淀法制备FeAl母体,采用浸渍法添加Zn、K和Cu助剂制成催化剂,利用低温N2物理吸附、XRD、H2-TPR等手段对FeAl母体和催化剂进行表征,并用固定床反应器考察它们的CO2加氢反应性能。XRD结果表明,加入Al助剂、并采用无水乙醇洗涤沉淀能促进酌-Fe2O3晶相生成,其中,Al2O3/Fe2O3质量比为10%的母体具有最强的酌-Fe2O3衍射峰;加入Al使得母体中的a-Fe2O3晶粒粒径变小,引起比表面积明显增大;浸渍助剂过程没有改变上述两种效应。母体比表面积增大提高了助剂Cu的分散度,促进了催化剂还原,但酌-Fe2O3晶相的生成才是催化剂的CO2加氢反应活性被提高的主要原因。Abstract: FeAl precursors (remarked as P) were prepared by co-precipitation method. Then they were impregnated with promoter Zn, K and Cu into ZnKCu/FeAl catalysts (remarked as C). The precursors and catalysts were characterized by low temperature N2 adsorption, XRD and H2-TPR. CO2 hydrogenation over these catalysts was investigated in a fixed-bed reactor. With the addition of Al, the specific surface area of FeAl precursors and ZnKCu/FeAl catalysts was increased relative to that of Al-free samples. On the contrary, the crystallite size of a-Fe2O3 was decreased by the added Al. The dispersed degree of Cu was raised in the catalysts containing Al. It is benefit for the reduction of ZnKCu/FeAl catalysts. However, the specific surface area and a -Fe2O3 crystallite size of P-10 and C-10, in which the Al2O3/Fe2O3 mass ratio is 10%, were similar to those of P-5 and C-5 with 5% Al 2O3/Fe2O3 mass ratio, respectively. The phenomena were resulted from the strong g-Fe2O3 phase in P-10 and C-10. It was evidenced that g-Fe2O3 was formed only in the case of Fe and Al were co-precipitated, and the precipitate was washed by anhydrous ethanol in this study. The catalyst with strong g-Fe2O3 phase was more active in CO2 hydrogenation than the catalysts with none or weak g-Fe2O3 phase. This correlation was supported by the comparison between two catalysts with the same Al content, but different Fe2O3 phases in them.
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Key words:
- Fe-based catalyst /
- Al content /
- Fe2O3crystal phase /
- CO2hydrogenation
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