Comparative Study of Single- and Two-Stage Slurry-Phase Catalytic Hydrocracking of Vacuum Residue for Selective Conversion of Heavy Oil

The selective conversion of asphaltenes to light products while inhibiting coke formation is the most challenging in the heavy oil upgrading process. Herein, single-and two-stage slurry-phase catalytic hydrocracking of vacuum residue (VR) at various reaction temperatures (350-430 degrees C) were performed to elucidate the advantages of low temperature conditions and the synergistic effect of two-stage operation on asphaltene conversion. Despite the slow reaction rate at a low reaction temperature, almost no coke was produced, and the selective conversion of asphaltene to deasphalted oil (DAO) was improved with a large amount of H2 consumption. To overcome the low reaction rates at low temperatures, catalytic hydrocracking was performed at two-stage temperatures (380 and 430 degrees C). Two-stage catalytic hydrocracking showed a synergistic effect of suppressing coke formation while maintaining an enhanced reaction rate compared to single-stage catalytic hydrocracking. This is because the first stage of hydrocracking at 380 degrees C facilitates the saturation of heavy polyaromatic molecules, which can easily crack in the second stage at 430 degrees C. However, because two-stage hydrocracking requires a slightly longer reaction time than single-stage hydrocracking to achieve the same conversion, the efficiency of asphaltene conversion must be considered by setting appropriate operating conditions.