A new hydrotreating process scheme for upgrading cracked feedstock was developed to produce diesel fraction low in sulfur and aromatics from a combination of heavy straight-run gas oil and heavy-cycle oil feeds. The process uses a high-temperature, high-pressure stripper (HPHTS) to separate the feed into a gas phase, which is hydrotreated with a WNiPd/Al2O, catalyst, and in a liquid phase which is hydrotreated with a WNiPd/TiO2Al2O3 catalyst. Heavy diesel and product were fractionated, and then naphtha, jet fuel, diesel and 350 degrees C+ cuts separated in three sub-fractions that were analyzed by GC-FID, GC-AED, GC-MS, and H-1 NMR and C-13 NMR techniques. In some cases sub-fractions are separated in sub-subfractions by elution on a particular column for detail analyses of species. The catalysts were characterized to determine their physical properties, bulk, and on-surface composition before and after deactivation reactions. The activity and selectivity of these catalysts, fresh and deactivated, were tested with synthetic feed and with heavy diesel at different operating conditions. Two long-term tests have been performed at different temperatures with the new catalysts. The experimental data was used to adjust the kinetic and deactivation constant of a model previously developed. The effect of recycle is also evaluated in pilot plant studies. A simulation program was used to compare the performance during a cycle length of the new hydrotreating system with that of the commercial process, which uses a MoNi/Al2O3 catalyst to obtain diesel with 10 ppm of sulfur. Differences in catalysts, operating conditions of the reactors, and the main reactions occurring during the hydrotreating are discussed. (C) 2013 Elsevier B.V. All rights reserved.
