Asphaltenes diffusion/adsorption through catalyst alumina supports - Influence on catalytic activity

Bertrand Guichard (1) , Florine Gaulier (1) , Jérémie Barbier (1) , Thibaut Corre (1) , Jean-Louis Bonneau (1) , Pierre Levitz (2) , Didier Espinat (1)

1 IFPEN - IFP Energies nouvelles
2 PHENIX - PHysicochimie des Electrolytes et Nanosystèmes InterfaciauX

Refining heavy or extra heavy oil is still an important challenge for petroleum chemistry. The research performed in the field of hydroprocessing technologies covers different sides of the domain laying from the reactor and process aspects to heterogeneous catalysts development. Historically, at a large scale of time, the worldwide trend seems to indicate a decline of light conventional crude oil availability, the latest being gradually replaced by heavier non-conventional resources that contain asphaltenes and high concentrations of nitrogen and sulfur compounds. It emphasizes the need for conversion of the heaviest feeds and for improving the corresponding refining catalysts. One 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. Among these large molecules to be considered, asphaltenes play a major role and are often pointed out to be responsible for the industrial issues: plugging porosity, coking support and metal sulphide active phase, poisoning hydrogenating metal. 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 tried in this contribution to confront the abilities of various monomodal and bimodal alumina supports to let asphaltenes diffuse and adsorb into their porosity. An experimental device dedicated to assess the diffusion and adsorption of carriers has been used. The influence, on the mass transfer and the penetration depth, of various parameters such as temperature, asphaltene concentration of the solution, and alumina porous texture was appraised. It is clearly shown that extrudates requires several days do reach an equilibrium, suggesting a very low diffusion kinetic. The diffusion kinetic can be speed-up using an adapted support, especially with high pore diameter and macroporous pores but even if the extrudates of macroporous support might be likely to adsorb till its chemical saturation, i.e. an asphaltene content equal to 1.4 mg/m2 consistent with previous publications for those species. As a consequence, NiMoP-B14 is the best catalyst for all the reactions reaching 50% of gain for HDAsC7 and 40% in HDV. It highlights a clear link is established between catalytic performances and diffusion and could be usefull for designing the best carriers to be used in heavy feed hydrporocessing.

Mots clés: Asphaltenes; Diffusion; Adsorption; Catalyst; Hydroprocessing; Reactivity

Domaines: Catalyse

Bertrand Guichard, Florine Gaulier, Jérémie Barbier, Thibaut Corre, Jean-Louis Bonneau, et al.. Asphaltenes diffusion/adsorption through catalyst alumina supports - Influence on catalytic activity. Catalysis Today, 2018, 305, pp.49-57. ⟨10.1016/j.cattod.2017.10.016⟩. ⟨hal-01855384⟩