Research Of Molybdenum Sulfide Catalysts For Slurry-phase Hydrocracking Of Residue

With the inferior quality of crude oil and the environmental protection regulations being strict,slurry-phase hydrocracking has been considered as the most important technology for the deep conversion and clean utilization of heavy oils/residues.And it is of great importance in the refining industry,in which,catalyst plays a key role in this process.Highly dispersed Mo S₂ catalyst has excellent hydrogenation performance and has become the key of the slurry process.In this paper,a series of Mo S₂ catalysts with different sizes were prepared by a surfactant-assisted hydrothermal/solvothermal method.Adjusting the average slab length and stacking layer number is a strategy to enhance the exposure of the edge sites in Mo S₂nanostructures.And the performance of Mo S₂ catalysts on slurry-phase hydrocracking of residue was investigated.It was found that intercalation species could increase the spacing of Mo S₂ layers and decrease the number of layers.Raising the initial temperature and using excessive sulfur sources can create a large number of crystal defects and make curved nanosheets with many folds.This characteristic catalyst has a large number of active edge sites,and the anticoke performance is obviously improved.Solvothermal synthesis can reduce the size of catalyst,shorten the slab length,and reduce stacking layers.However,nanoparticles tend to aggregate because of their high surface energy.The crystallinity of catalysts is low and the Mo S₂ layers are easy to stacked in the reaction process,resulting in reduction of active edge sites.The anticoke performance is weakened.In order to further improve dispersion stability of catalysts in heavy oil,we explored the surface organic modification via two strategies.The hydrothermally synthesizsed catalyst is heat-treated in oleic acid to modify the surface of the catalyst and improve the dispersion of the catalyst.The other is addition of two organic modifiers into the solvent ethylene glycol to prepare oil-soluble single-layered Mo S₂ catalyst.It was found that although the modified catalyst by oleic acid increased the dispersion stability in oil,the crystallinity of the catalyst increases and layer spacing decreases,so the hydrocracking performance was not improved.However,the oil-soluble single-layered Mo S₂ catalyst have more active edge sites by“One-step surface organic modification”method.Moreover,the dispersion stability of modified Mo S₂ catalyst improved.So the oil-soluble single-layered Mo S₂ catalyst show a better catalytic activity in residue hydrocracking.