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In this work, a comparative study on the combined effects of hydrodynamics and kinetics on the hydrodesulfurization (HDS) of a straight-run gas oil (SRGO) using a trickle-bed reactor with and without diluent (SiC) and different catalyst volume (0.1, 0.07, and 0.050 Â 10 À3 m 3 , respectively) was carried out. The tests were conducted in a pilot plant under conditions close to those used in industrial-scale units (5492 kPa, 445.4 m 3 (STP)/m 3 H 2 /oil ratio, 623-643K, 0.9 and 2.5 h À1 LHSV values). The catalyst used was ORDER REPRINTS a commercial CoMoP/Al 2 O 3 formulation shaped as tri-lobed extrudates (1/20 in, nominal size) or as crushed particles (d p ¼ 1.2 Â 10 À3 m). Contrarily to that usually claimed, the undiluted systems showed better performance than those comprising small diluent (SiC) particles (d p $ 5 Â 10 À5 m). Calculations to evaluate hydrodynamic variables (plug-flow behavior, wall effects, wetting, and back-mixing) were carried out in order to explain the observed facts. The possible influences of the size of the diluent particles used are discussed.

A study on the hydrotreating performance of sulfided NiMo supported in NH4+Y‐ and H+Y‐modified Al2O3 is reported. The effect of the addition of the corresponding NiMo‐exchanged zeolites was also investigated. The materials were characterized (by N2 physisorption and surface acidity measurements) and evaluated in the upgrading of a middle distillates (LCO‐SRGO) mixture under industrial conditions. The main effects of the integration of the NiMo‐exchanged zeolite (from the NH4+‐faujasite) were an improvement of textural properties and the creation of strong surface Lewis sites. The corresponding sulfided formulations showed higher hydrodesulfurization and hydrodearomatization activities than the catalyst prepared from the protonic zeolite.