Optimization Methodology\nof Dual-Bed Catalyst Stacking\nSystems to Produce Ultralow-Sulfur Diesel

An optimization methodology is proposed\nto minimize the\ncatalyst\nloading cost and the start-of-run temperature of a hydrotreating unit\nproducing ultra-low sulfur diesel by applying a dual-bed catalyst\nstacking configuration. The methodology involves prior estimation\nof kinetic parameters for the hydrodesulfurization reaction using\nexperimental data from single-bed evaluations of each catalyst followed\nby statistical analyses. The variables in the objective function are\nthe order of the two catalyst beds inside the reactor, their volumetric\nproportions, and the start-of-run temperature, along with the restrictions\nof the target sulfur content (15 ppm) and operating constraints. The\nresults suggest that the difference between the estimated reaction\norders of the catalysts influences their optimal sequence and volumetric\npercentages in a dual-bed configuration to maximize the synergetic\neffect. The benefits of using an optimized catalyst stacking system\ninclude a reduction of 2.6 °C in the start-of-run temperature\nand an 18.75% cut in the total catalyst cost over a 10-year planning\nhorizon compared to a high-activity catalyst single bed.