Effect of preparation temperature and ions doping on size, morphology and catalytic activity of Co-B amorphous nano catalyst

M H Loghmani,A F Shojaei

doi:10.4314/bcse.v29i1.9

Abstract

Binary and quaternary amorphous nano powders are prepared by wet reduction method. Cobalt boride nano catalyst is synthesized at 10 and 60 ºC. Effect of preparation temperature on size and morphology was studied. Co-M-Zr-B (M: Cr, Mo and W) as quaternary catalysts are also prepared in order to studying ions doping on chemical and physical properties. Indeed, the obtained materials are characterized by XRD, FE-SEM, TEM, BET and ICP techniques. No distinct peak could be observed in XRD patterns indicating that the all catalysts possessed amorphous. The catalytic activity of the synthesized catalysts is investigated for the reduction reaction of 4-nitrophenol to 4-aminophenol in the presence of excess NaBH4 in aqueous medium at room temperature (298 K). It is found that our catalysts are highly active for high concentrations of 4-NP, 25-200 ppm. KEY WORDS: Amorphous, Nano catalyst, Metal boride, Reduction, Nitrophenol Bull. Chem. Soc. Ethiop. 2015, 29(1), 105-116DOI: http://dx.doi.org/10.4314/bcse.v29i1.9

Highlights

In the past two decades, nanotechnology has been developed quickly in various fields
Chemical reduction reaction is most frequently used in preparing Cobalt boride (Co-B) amorphous alloys [11,12,13,14,15]; the regular Co-B samples obtained via direct reduction of cobalt salt solution with a sodium borohydride solution usually display low surface area, broadly distributed particle size, and poor thermal stability against crystallization due to aggregation, because the reduction reaction is vigorous and exothermic [16, 17]
X-ray diffraction (XRD) patterns of all catalysts were prepared and no distinct peak could be observed in XRD patterns indicating that the all catalysts possessed amorphous phase

Summary

Introduction

In the past two decades, nanotechnology has been developed quickly in various fields. Metal nanoparticles have been attracting great attention because of their remarkable catalytic performance in hydrogenation, oxidation, and reduction reactions [1,2,3]. Amorphous Cobalt boride (Co-B) catalysts, prepared by reduction of metal salts with a reducing agent, have attracted great attention in catalysis owing to their unique properties such as isotropic structure, high concentration of coordinative unsaturated sites, relevant chemical stability, and low cost. The exothermic nature of the reduction reaction involves high surface energy causing metal–boride particles to agglomerate This particle agglomeration lowers the effective surface area of the catalyst powder limiting its catalytic activity. Direct hydrogenation of 4-NP catalyzed by Pt, Pd and Ru is employed for the production of 4-AP [19, 20] Such kind of catalysts seems to be not suitable for the industrial application

Methods

Results

Conclusion