Engineering dual bed hydrocracking catalyst towards enhanced high-octane gasoline generation from light cycle oil

Abstract

Processing of light cycle oil (LCO) by hydrotreating and subsequent hydrocracking process harbors tremendous significance due to more stringent environmental regulations and growing demand for high-octane gasoline. However, the commercial single bed hydrocracking catalysts normally over-saturate multi-ring aromatics in LCO, leading to increased H2/energy consumption and reduced octane number. Herein, novel dual bed catalyst strategy is first proposed to enhance the hydrocracking performance, which contains fresh and used Ni-Mo/HY-Al2O3 catalysts as upstream and downstream bed catalyst, respectively. In order to select suitable downstream catalyst, the used industrial Ni-Mo/HY-Al2O3 catalysts in reactor after running for almost 1 year were divided into almost 20 layers through sampling along the axial positions, and then systematically analyzed by multi-techniques, including XPS, HRTEM, Py-IR, TPD, TGA and XRD. It is found that the first 20% of all catalyst layers suffer from serious deactivation due to coke formation, leading to the loss of Ni-Mo-S phase and acidic sites. Employing this first 20% of used catalysts as downstream catalyst, the weaker hydrogenation performance could avoid excessive hydrogenation and maintain mono-aromatics content. As expected, the designed dual bed catalyst leads to superior octane number, higher liquid yield of C5+ and lower H2 consumption than the commercial single bed catalyst. This strategy not only offers a scenario to boost the hydrocracking performance, but also sheds new light on the efficient utilization of used catalyst.