The aim of this work was to investigate the influence of the catalyst acidity in vacuum residues hydroconversion processes. We use a grafting procedure in order to incorporate silicon at the surface of alumina carriers. Then, corresponding NiMoP catalysts with different concentrations of silicon in the support were evaluated in order to assess the conversion rate and mechanism of a Safaniya vacuum residue in a batch reactor at 370�C. Combined multi-techniques analysis were used, in order to characterize both the sulphided active phase (TEM, XPS, IR-CO, model molecules tests) and acidity (IR-CO, model molecules tests). We also check that support texture was not modified by the incorporation of silicon.Grafting procedure allows us to both monitor textures but also hydrogenation rate, the one being assessed by toluene hydrogenation. In addition, we also slightly increase acidity strength of the catalysts. Nevertheless, it remains obvious that nickel disponibility must be affected by silicon. As a matter of fact, NiMoP catalyst with same texture, same hydrogenating power, but also different level of acidity reveal no change in conversion (?370+ and ?540+ ; HDAsC7) or hydrogenation performance (HDS, HDV). Nonetheless, we prove that acidity can enhance the cracking of aliphatic chains of asphaltenes without increasing their aromaticity. It leads to an original way of cracking of asphaltenes, different from the well known thermal mechanisms.

How silica grafting can improve the residue hydroconversion of alumina-supported NiMo catalysts

246th National Meeting (2013)

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