Reaction Behaviors of Polycyclic Aromatic Hydrocarbon Molecules in a Diesel Hydro-Upgrading Process Based on the Molecular-Level Reaction Kinetic Model

A molecular-level reaction kinetic model for the diesel hydro-upgrading (DHU) process was established on the basis of the structure-oriented lumping (SOL) method to describe the hydro-upgrading reaction network and investigate the reaction behaviors of polycyclic aromatic hydrocarbon (PAH) molecules. Twenty-two structural increments were selected to construct an 835 row × 23 column feed oil molecular matrix based on the composition analysis. Twenty-eight reaction rules were formulated to deduce molecular reactions according to the hydro-upgrading reaction mechanism. One-hundred ninety-seven structural vectors were used to represent the PAH molecules and 299 structural vectors were used to represent the monocyclic aromatic hydrocarbon (MAH) molecules. The reaction network containing about 24 600 reactions was generated and calculated by MATLAB programming. The reliability of the model was verified by industrial data. The molecular matrix transformation could clearly track the reaction path of the petroleum molecules and reveal the influence of the temperature and the hydrogen partial pressure on PAH molecules in the reaction network. The hydro-upgrading process containing the reactions of aromatic hydrogenation and ring opening reduced the PAH content and increased the cetane number (CN). At a hydrogen partial pressure of 10.0 MPa, the optimal reactor operating temperature range was 304.1–324.1 °C when the diesel yield was required to be larger than 88.0 wt % and the PAH content was less than 5.5 wt % in the refinery.