Structure, reactivity and catalytic properties of nanoparticles of nickel ferrite in the dry reforming of methane

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• 作者：R. Benrabaa^a ; A. Lö ; fberg^b ; A. Rubbens^b ; E. Bordes-Richard^b ; ^{Elisabeth.Bordes@univ-lille1.fr} ; R.N. Vannier^b ; A. Barama^a
• 关键词：Nickel ferrite ; Dry reforming of methane ; Disordered spinel ; Behavior in reducing atmosphere
• 刊名：Catalysis Today
• 出版年：2013
• 出版时间：30 March, 2013
• 年：2013
• 卷：203
• 期：Complete
• 页码：188-195
• 全文大小：823 K

文摘

Nickel ferrite NiFe₂O₄ (spinel) was prepared and characterized by several physicochemical methods, and its catalytic properties were investigated in the reforming of methane with CO₂ to syngas. Nanoparticles were prepared by coprecipitation (CP), hydrothermal synthesis (HT) and sol-gel process (SG). The methods of preparation influenced strongly the textural and structural properties, as well as their reactivity. X-ray diffraction patterns showed that only HT and SG methods delivered pure NiFe₂O₄ nanoparticles (6-10 nm size). However the cell parameter a calculated by Rietveld analysis being respectively larger (HT) or smaller (SG) than the standard value, a non stoichiometric defective mixed spinel could have been formed. The reducibility of samples was studied by two methods. H₂-temperature programmed reduction showed the formation of Ni⁰ at increased temperature along SG ¡Ö HT < CP series, after which step Ni_xFe_2?xO₄ decomposed to iron suboxides and finally to Fe⁰. In situ reduction by H₂ carried out by HT-XRD showed that the ultimate compound was ¦Ã-Ni_xFe_1?x alloy, formed above 400 (SG, HT) or 450 ¡ãC (CP). The catalytic activity in the dry reforming of methane was higher with HT and SG than with CP, but values of conversion of CH₄ and CO₂ were low as compared with efficient catalysts in the literature. After being pre-reduced by hydrogen at 400 ¡ãC, a large improvement was observed with SG sample only, in which case the conversions of methane and CO₂ at 800 ¡ãC amounted to 80 and 93 mol % , respectively, with H₂/CO = 1.2.