The improvement of refining catalysts remains an important target of the petroleum industry. This is peculiarly the case for hydrotreatment processes where the upgrading of heavy crudes and residues is still a challenge. To improve the performances of the catalyst, metal sulphides activity and hydrogenation is widely addressed in the literature. The deactivation rates and the solutions to lower the phenomenon are also taken into consideration. The common point raised here to progress deals with the role of the support (alumina), peculiarly about the role of the nanoporous texture on the accessibility of the feedstock molecules to the active sites. For heavy petroleum fractions, among these large molecules to be considered, asphaltenes play a major role and are often pointed out to be responsible for the industrial issues. The macrostructure of asphaltenes is complex, characterized by a multi-scale aggregation behavior, strongly influenced by environmental parameters, as for instance the temperature. We have proposed in this contribution to investigate the diffusion and adsorption process into the porosity of various monomodal and bimodal alumina supports. An original experimental device was made up. It consists in immersing catalytic supports, under the form of extrudates into an asphaltene solution in toluene. Optical microscopy observations of a cut of the cylindrical extrudates were carried out in order to follow the asphaltene penetration as a function of the contact time. Asphaltene solutions and supports were characterized for reaching a good asphaltene mass balance. The influence, on the mass transfer and the penetration depth, of various parameters such as temperature, asphaltene concentration of the solution, asphaltene size polydispersity, asphaltene geographical origin and alumina porous texture was appraised. Finally, an endeavor for the process modeling is proposed. The adsorption equilibrium was modeling according to the Langmuir’s type isotherm. A model considering the radial diffusion in a cylinder was used providing an average diffusion coefficient.

Asphaltenes transport into hydrotreatment catalysts at high temperature

255th National Meeting (2018)

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