A facile method to increase metal dispersion and hydrogenation activity of Ni/SBA-15 catalysts

Abstract

In the present work, two series of Ni catalysts supported on SBA-15 were prepared: the first one using Ni(II) complex with ethylenediaminetetraacetic acid (EDTA) as a precursor and the second one using nickel(II) nitrate aqueous solutions. Nickel loading in the catalysts varied between 1 and 20wt.%. The aim of the study was to evaluate the effect of the addition of EDTA on the characteristics of the prepared Ni catalysts and their activity and selectivity in the hydrogenation of aromatics (structure-activity relationship). Characterization of the catalysts was performed by nitrogen physisorption, thermogravimetric analysis, UV–vis diffuse reflectance spectroscopy, temperature programmed reduction, small-angle and powder XRD. Reduced Ni catalysts were characterized by XRD as well as by high-resolution transmission electron microscopy and tested in the hydrogenation of naphthalene. It was found that catalysts prepared from impregnation solutions of Ni(NO3)2 or Ni(II)-EDTA complex had different textural characteristics and dispersion of Ni species. For both calcined and reduced catalysts, the dispersion of NiO and Ni nanoparticles, respectively, significantly increased when EDTA was used in the catalysts’ preparation. In line with this, catalysts prepared from the Ni(II)-EDTA precursor were much more active in the hydrogenation of naphthalene than those prepared without this ligand. In addition, they showed high selectivity for decalin formation, which can be attributed to their high hydrogenation ability. Therefore, it was shown that the addition of EDTA to the impregnation solutions used for the preparation of the Ni/SBA-15 catalysts is a facile method to significantly improve their hydrogenation performance.