Increasing diesel demand coupled with the current poor margin environment is requiring therefining industry to discover and employ the most creative solutions to cost effectivelymaximize ultra-low-sulfur-diesel (ULSD) production from existing assets. Increased catalystactivity maximizes unit performance and ULSD production. However, using the highestactivity catalyst is not always the best option as other factors such as H2 consumption andunit H2 supply can be limiting or expensive when not managed effectively.Customized catalyst systems for ULSD production can be designed to balance activity andH2 consumption. Recent developments have shown that customized systems utilizing CoMoand NiMo catalysts in various proportions and in various configurations (stacked beds and“sandwich” beds) can yield unanticipated synergistic benefits when producing ULSD.Depending on the unique circumstances of each refiner, these synergistic benefits can beutilized to either process more ULSD feed, process a more difficult ULSD feed blend, or toextend cycle life.Pilot plant data are shown comparing the H_2 consumption and activity of individual CoMoand NiMo catalysts to various CoMo/NiMo customized catalyst systems. A commercialexample illustrating the use of a customized catalyst system in ULSD production is alsopresented. In this case, using a CoMo/NiMo/CoMo “sandwich” catalyst system allowed therefiner to process a more difficult feed (higher refractory S content, higher nitrogen, andhigher feed final boiling point) without sacrificing catalyst cycle length or increasing H_2consumption.
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