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In the upgrading of heavy petroleum oils and residues by hydrotreating, multiple-reactor fixedbed units loaded with different types of catalysts are extensively used. Catalysts for such hydrotreating processes are chosen on the basis of activity, selectivity, and life. The performance of the overall hydrotreating process with regard to various reactions, such as hydrodemetallation (HDM), hydrodesulfurization (HDS), hydrodenitrogenation (HDN), asphaltenes cracking (HD-Asph), and conversion to distillate and catalyst life-on-stream, is clearly linked to the performance of the catalyst in different reactors. Information regarding the activity, selectivity, kinetics parameters, and deactivation of the individual catalysts are, therefore, highly desirable for optimizing reactor loading in a multiple catalyst system. In the present work, a comparative study was conducted on the kinetics of various reactions such as HDS, HDV, HDNi, HDN, CCR reduction, and asphaltenes conversion in hydrotreating Kuwaiti atmospheric residue (KU-AR) over three types of catalysts. The results showed diverse kinetics behavior of different hydrotreating reactions. The diverse kinetics behavior of the different reactions and the strong dependence of the kinetics parameters on catalyst type are consistent with the kinetic aggregation theory. The results are discussed in comparison with those available in published literature.

In the upgrading of heavy petroleum oils and residues by hydrotreatment, multiple-reactor fixed-bed units loaded with different types of catalysts are used extensively. Catalysts for such hydrotreatment processes are chosen on the basis of activity, selectivity, and life. The performance of the overall hydrotreatment process, with regard to various reactions, such as hydrodesulfurization (HDS), hydrodenitrogenation (HDN), hydrodemetallization (HDM), asphaltenes cracking (HDAsph), and conversion to distillates, as well as catalyst life-on-stream, are clearly linked to the performance of the catalyst in different reactors. Information regarding the activity, selectivity, kinetic parameters, and deactivation of the individual catalysts are, therefore, highly desirable for optimizing reactor loading in the multiple-catalyst system. This paper presents the performance tests for various reactions on two types of industrial hydrotreating catalysts: those used at the midsection and the tail-end of a graded catalyst system designed to hydrotreat atmospheric residual oils. The tests were conducted using straight-run Kuwait atmospheric residue, a demetallized residue, and a demetallized/desulfurized residue. The activity and kinetic parameters for different reactions that are typically occurring during the hydroprocessing of these feedstocks were determined. The results revealed significant changes in activity, depending on the feedstock used for the tests. Furthermore, apparent rate orders and rate constants for some reactions were significantly changed. The study demonstrates the importance of proper selection of the feedstocks used in the performance evaluation and screening of candidate catalysts for graded catalyst systems for residual-oil hydrotreatment.

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