Oxidative dehydrogenation of n-butane on zinc-chromium ferrite catalysts

Q4 Chemical Engineering 分子催化 Pub Date : 1994-09-13 DOI:10.1016/0304-5102(94)00071-9

H. Armendariz , J.A. Toledo , G. Aguilar-Rios , M.A. Valenzuela , P. Salas , A. Cabral , H. Jimenez , I. Schifter

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引用次数: 13

Abstract

The role of chromium as a promoter of butadiene selectivity in n-butane oxidative dehydrogenation on ZnCr_xFe_2-xO₄ (0<x<1.09) catalysts was studied. Catalysts have a spinel structure with Cr³⁺ replacing Fe³⁺ in octahedral sites. Mössbauer spectroscopy studies showed that the substitution of iron by chromium modifies the electron density of the iron nuclei in the ZnFe₂O₄ structure. Iron nuclei showed the lowest electron density for x=0.5–0.6, hence the electron density of oxygen in FeO bond has to be enhanced. n-Butane oxidative dehydrogenation also showed a maximum in butadiene selectivity at x=0.5–0.6. These results suggest that chromium increases butadiene and CO₂ selectivities, with simultaneous decrease of butenes and cracking products explained by an enhancement of the lattice oxygen basicity, which promotes the acid-base type dissociation of the CH bond during butene activation.

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锌铬铁氧体催化剂上正丁烷氧化脱氢反应的研究

研究了在ZnCrxFe2-xO4 (0<x<1.09)催化剂上，铬作为正丁烷氧化脱氢反应中丁二烯选择性促进剂的作用。催化剂具有尖晶石结构，在八面体中Cr3+取代Fe3+。Mössbauer光谱研究表明，铬取代铁改变了ZnFe2O4结构中铁核的电子密度。当x= 0.5-0.6时，铁原子核的电子密度最低，因此FeO键中氧的电子密度必须增强。正丁烷氧化脱氢对丁二烯的选择性在x=0.5 ~ 0.6时达到最大值。这些结果表明，铬增加了丁烯和CO2的选择性，同时丁烯和裂解产物的减少可以解释为晶格氧碱度的增强，这促进了丁烯活化过程中C氢键的酸碱型解离。

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