Characterization and hydrotreating performance of NiMo catalysts supported on nanostructured titanate Original Research Article

A nanostructured protonated titanate, synthesized by alkaline hydrothermal treatment of TiO2, has been investigated as a precursor support for NiMo hydrotreating catalyst and compared to alumina and titania as reference carriers. Each of the three powders was extrudated and calcined to obtain the properly shaped support, which was analyzed with respect to textural and acidity properties and then metal impregnated by insipient wetness method and sulfided at constant conditions to produce the final catalyst. The corresponding NiMo catalysts in the precursor oxide form were characterized by X-ray diffraction (XRD), thermogravimetry (TGA), transmission electron microscopy (TEM), temperature programmed reduction (TPR) and N2 adsorption, whereas the active sulfided form was thoroughly examined by TEM and tested as for their tetralin hydrogenation activity. The results indicated that in spite of the higher surface area of the precursor NiMo-catalyst supported on the nanostructured carrier, its layered nature and one-dimensional morphology was lost after sulfidation under H2S/H2 atmosphere at 300 °C. The dispersion of the sulfided active phase as examined by high resolution TEM was similar to that exhibited by the counterparts supported on alumina and nanocrystalline anatase, which was in agreement with the similar activities for tetralin hydrogenation found for the three tested catalysts. On the other hand, the titanate derived catalyst showed higher yields of ring opening of tetralin than the alumina supported catalyst, which was tentatively explained by the higher Brönsted acidity of the nanostructured support as measured by decomposition of adsorbed n-propylamine.