Bimetallic Fe-Ni/SiO2 catalysts for furfural hydrogenation: Identification of the interplay between Fe and Ni during deposition-precipitation and thermal treatments

• Published in: Catalysis today Vol. 334; pp. 162 - 172
• Main Authors: Shi, Dichao, Yang, Qifeng, Peterson, Christi, Lamic-Humblot, Anne-Félicie, Girardon, Jean-Sébastien, Griboval-Constant, Anne, Stievano, Lorenzo, Sougrati, Moulay T., Briois, Valérie, Bagot, Paul A.J., Wojcieszak, Robert, Paul, Sébastien, Marceau, Eric
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.08.2019; Elsevier
• Subjects: Bimetallic catalysts; Chemical Sciences; Furfural; In situ measurements; Material chemistry; Mössbauer spectroscopy; X-ray absorption spectroscopy; In situ measurements; Bimetallic catalysts; Furfural; X-ray absorption spectroscopy; Mössbauer spectroscopy; Heterogeneous Catalysis; 57Fe Mössbauer spectroscopy; MCR-ALS; Hydrogenation; Iron catalysts
• ISSN: 0920-5861; 1873-4308
• DOI: 10.1016/j.cattod.2018.11.041

[Display omitted] •Co-deposition of Ni(II) and Fe(II) by DPU requires the absence of oxidizing species.•The result is an ill-crystallized Fe-containing Ni(II) 1:1 phyllosilicate phase.•Fe reduction is triggered by Ni reduction but needs high temperatures to be complete.•fcc Fe-Ni particles are formed with a standard deviation in composition of 8 at %.•A surface enrichment in Fe is evidenced by Mössbauer spectroscopy. Supported Fe-Ni catalysts have been reported for their activity and selectivity in the hydrogenation of unsaturated organic molecules. However, the control of the size and composition of the bimetallic nanoparticles remains a bottleneck when oxide-supported catalysts are prepared by impregnation, and alternative procedures should be investigated. Starting with Ni(II) and Fe(II) sulfates as precursor salts, deposition-precipitation with urea (DPU) on SiO2 in an inert atmosphere initially leads to the formation of an ill-crystallized Fe-containing Ni(II) 1:1 phyllosilicate, which reduces under hydrogen at 700 °C into bimetallic fcc Fe-Ni nanoparticles of 5.4 nm in average. Compared with the composition of the DPU solution (50 Fe at %, 50 Ni at %), an excess of Ni is detected on the catalyst (38 Fe at %, 62 Ni at %), due to the preferential reaction of Ni2+ ions with silica. In situ X-ray absorption spectroscopy and 57Fe Mössbauer spectroscopy show that the reduction of Fe ions to the metallic state is triggered by the formation of reduced Ni centers above 350 °C, and, from then, proceeds progressively, resulting in an excess of Fe in the outer shells of the bimetallic particles. The composition of individual Fe-Ni particles evidences a standard deviation of 8%. The bimetallic Fe-Ni/SiO2 catalyst gives high yields in furfuryl alcohol in the hydrogenation of furfural, in contrast with an analog Ni/SiO2 catalyst that favours side-reactions of etherification, hydrogenolysis and hydrogenation of the furan ring.