Effect of additive (W, Mo, and Ru) on Ni-B amorphous alloy catalyst in hydrogenation of p-chloronitrobenzene

Liang Fu Chen, Yu Wen Chen

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Abstract

A series of W-, Ru-, and Mo-promoted Ni-B amorphous nanocatalysts were prepared by chemical reduction of the precursors of promoters, respectively, and nickel acetate with sodium borohydride in methanol/water (1:1) solution. The catalysts were characterized by X-ray diffraction, nitrogen sorption, X-ray photoelectron spectroscopy, differential scanning calorimetry, and transmission electron microscopy. With a specific concentration of promoter, the particles of the Ni-B catalysts became smaller. The catalysts also demonstrated higher thermal resistance, protecting the amorphous structure from high-temperature treatment. The correlation of the catalytic performance to both the structural and the electronic characteristics was discussed. W6+ and Mo 6+ cations were not reduced by NaBH4. They formed oxides or hydroxides since the preparation solutions were basic. They acted as spacers and prevented Ni-B from sintering and agglomeration. Ru3+ could be reduced by NaBH4 to Ru metal. Ru is also a catalyst for this reaction. The promoted Ni-B catalysts were proved to be effective during the hydrogenation of p-chloronitrobenzene in this study for enhancing the thermal stability and the catalytic activity. Mo and W additives not only served the role of spacer to increase the dispersion of active sites and protect the amorphous structure, but also changed the composition of Ni-B catalyst, which caused the increase of amorphous B in Ni-B catalysts. With the increase of concentration of boron, the coordination number of Ni reduced, showing that the Ni active sites became more highly unsaturated. For hydrogenation of p-chloronitrobenzene, these promoted catalysts exhibited higher activities than unpromoted catalyst and Raney nickel. The catalysts also exhibited high selectivity to p-chloroaniline. Mo-Ni-B showed the highest activity.

Original languageEnglish
Pages (from-to)8866-8873
Number of pages8
JournalIndustrial and Engineering Chemistry Research
Volume45
Issue number26
DOIs
StatePublished - 20 Dec 2006

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