Kinetics of the synergy effects in heavy oil upgrading using novel Ni-p-tert-butylcalix[4]arene as a dispersed catalyst with a supported catalyst

This study investigates the promotional effects of implementing a co-catalytic system for hydrocracking of vacuum gas oil (VGO) that includes both dispersed and supported solid catalysts. A novel nickel-based p-tert-butylcalix[4]arene (Ni-TBC[4]) was employed as a dispersed catalyst in addition to a commercial first-stage hydrocracking supported catalyst. Slurry-phase hydrocracking was conducted isothermally under a hydrogen pressure of 8.5 MPa in a batch autoclave reactor by varying the reaction temperature (390–450 °C) and duration (0.5–1.5 h). The use of the synthesized metallocalixarene as a dispersed catalyst precursor enhanced the hydrogenation activity and noticeably reduced the coke and gas formation. The yields of coke and gases decreased upon introducing the dispersed catalyst along with the supported solid catalyst by 35.86% and 13.90%, respectively. The yield of naphtha increased from 15.27 wt% to 16.36 wt%, and that of distillate increased from 52.17 wt% to 53.57 wt% compared with the use of the supported catalyst, while the conversion of VGO was unchanged at about 83.20%. The value of the dimensionless catalytic activity parameter proved the existence of the synergy between the two catalysts since it is much higher than that acquired through the algebraically calculated yields. A five-lump discrete kinetic scheme was developed based on the experimental data governed from both the standalone supported catalyst and the mixed catalysts. The model incorporated the conversion of VGO to distillate, naphtha, and C₁–C₅ gaseous hydrocarbons in addition to coke deposition. The activation energy of the distillate formation was reduced from 65.39 kcal/mol to 57.32 kcal/mol by adding a Ni-TBC[4] catalyst precursor in the presence of supported catalyst.