Effect of the preparation method on the hydrogenation activity of Ni/SBA-15 catalysts: Comparison of EDTA complexation and DPU

The SBA-15 material was synthesized and used as a support for nickel catalysts with 4 and 10 wt.% metal loadings. Three preparation methods were used: a conventional incipient wetness impregnation with a nickel(II) nitrate solution (IM method), impregnation with a [Ni(EDTA)](2-) complex solution (ED method) and deposition-precipitation with urea (DP method). The support and catalysts were characterized by N-2 physisorption, X-ray diffraction (XRD), UV-vis diffuse reflectance spectroscopy and temperature-programmed reduction. The reduced nickel catalysts were also characterized by high resolution transmission electron microscopy and powder XRD. Catalysts were evaluated in the hydrogenation of naphthalene in order to compare their catalytic performance (activity and selectivity). The obtained results show that the preparation method affected the dispersion and size distribution of nickel nanoparticles deposited on the SBA-15 surface as well as the degree of their reduction. ED and DP methods led to a better dispersion of Ni and higher hydrogenation activity in comparison with the conventional IM procedure. In addition, the catalysts' selectivity to decalins and their ability to isomerize cis-decalin to trans-decalin were also affected by the preparation method used, increasing in the following order: XNS-IM < XNS-DP < XNS-ED for both Ni loadings (4 and 10 wt.%). Therefore, the importance of the method used for the preparation of the Ni/SBA-15 catalysts was demonstrated.