Effect of diluents in controlling sediment formation during catalytic hydrocracking of Kuwait vacuum residue

Conversion of low-value petroleum residues to high-value distillates by catalytic hydrocracking has gained considerable importance in recent years. One of the common operating problems encountered in the process is the formation of coke-like sediments in the products. The carbonaceous sediment materials usually deposit on the reactor and downstream vessels as well as on catalyst surface and cause both operability and rapid catalyst deactivation problems. Prevention or suppression of coke-like sediment deposition is highly desirable alleviate equipment fouling problems and to attain high conversions in residue hydrocracking operations. In the present work, the influence of adding some aromatics-rich gas oil streams, such as heavy cycle gas oil (HCGO) and light cycle oil (LCO), produced in the FCC units to vacuum residue on various conversions as well as on sediment formation was investigated. The results revealed that mixing aromatics-rich gas oils with vacuum residue feed was very effective in reducing sediment formation even at very high conversion levels (>80%). The diluents, however, did not have any appreciable benefits in improving the yield of distillates and the extent of other hydrotreating reactions. The results are consistent with the asphaltenes phase separation mechanism. The addition of aromatics-rich diluents may improve the solubility of the asphaltene cores in the product oil medium and control the onset of their precipitation.