Abstract: In order to solve the problem that nitride affects the diesel ultra-deep desulfurization and the high hydrogen consumption caused by oversaturation during PAHs hydrotreating, based on the axial feed properties and reaction environment changes of fixed-bed diesel hydrotreating reactor, the dual-zone ultra-deep desulfurization and dearomatization composite diesel hydrotreating process (RTS-Apro) technology was developed. The results of the pilot test showed that the dearomatization of PAHs can be enhanced and the saturation of monocyclic aromatic hydrocarbons can be reduced when the temperature difference of the dual-zone reaction was 20―40 ℃ at the beginning of the operation and the preferable temperature difference in the middle and late stages was 40 ℃. Increased volume ratio of hydrogen to oil is favorable to the removal of refractory sulfides and the moderate saturation of PAHs. The results of industrial application showed that the average sulfur content of refined diesel products obtained was only 5 μg/g, and the average mass fraction of PAHswas only 1.6%, with low catalyst inactivation rate of only 0.5 ℃/month (calculated as 30 days in a month), which is conducive to the long-term stable operation of the catalyst.

Key words: diesel hydrotreating, ultra-deep desulfurization, aromatic saturation, RTS-Apro process