Abstract: In order to improve the economic benefits of the whole plant, according to the type of catalyst filled in the 1.2 Mt/a hydro-upgrading unit and the reaction mechanism of cycloalkyl diesel processing, the composition of the crude oil in the whole plant was optimized to achieve long-term stable operation. By adjusting the operating conditions of the unit, optimizing the crude oil processing ratio, and adding filtration facilities, the flexible switching of the unit under different production conditions was realized. The optimized results indicated that, on the basis of the loaded high diesel selectivity catalyst, it could flexibly switch 3 working conditions, such as producing No.2 fuel oil, national VI vehicle diesel and providing raw materials for downstream precision fractionation units, while keeping maximum diesel yield. The long-term operation results of the unit showed that the deactivation rate of hydrofining catalyst was 0.28 ℃/month(a month was counted as 30 days), and that of hydroupgrading catalyst was 0.24 ℃/month, both of which were relatively low and had good operational stability.

Key words: hydro-fining, hydro-upgrading, naphthenic, national Ⅵ diesel, naphtha