Abstract: Based on the intensive studies on the chemical reactions of hydrotreating and hydroupgrading process, a flexible hydroupgrading process, MHUG-II, having three reaction zones and separate feeding systems was developed and put into practice in pilot plant. The influence of reaction parameters on the product distributions and product qualities was investigated, as well as the adaptability of MHUG-II process to various feedstocks. Test results showed that as comparing with conventional hydroupgrading process under similar operating conditions, during MHUG-II process the yield of diesel fraction increased 8.41 percentage points, the cetane number of treated diesel was higher 2.7 units and the potential content of aromatics in naphtha was 3.9 percentage points more. MHUG-II process enhances the selectivity of hydroupgrading reactions significantly; it is an optimum approach to be used to produce clean diesel fuel from various inferior feedstocks including FCC light cycle oil, straight-run diesel fraction and coker gas oil economically.

Key words: separate feeding, hydroupgrading, cetane number, polycyclic aromatic hydrocarbon, clean diesel fuel