Hydrocracking Reaction Model of Petroleum Heavy Cuts Using Molecular Reconstruction

The aim of this work was to develop a compositional model of hydrocracking process using a conversion reactor model, available in commercial process simulators. The model was based on 3 different vacuum gas oils feeds (boiling point of 370 - 510 degrees C) and their corresponding hydrocracking products (LPG-Liquefied Petroleum Gas, naphtha, kerosene, diesel and UCO: Unconverted Oil). Due to the complexity of the feeds, the reaction system and limitations of molecular structures that support the commercial simulator, feeds and products were characterized using 40 molecules to represent feeds and 113 additional molecules to represent products, structures obtained through molecular reconstruction. The reconstruction strategy of this model was multi-feed; i.e., the same molecules represent the three feeds, but with different composition. The additional molecules to represent products were the result of including a set of reactions according to the literature: hydrodearomatization (HAD), hydrodesulfurization (HDS), hydrodealkylation (HDAL) and hydrodecyclization (HDC). Two reaction layers were needed to represent adequately the reaction system. The model molecules were exported to a steady-state process simulator (Pro/II-Simsci) and the topology of the plant was built. The conversion parameters corresponding to the defined reaction set were optimized to reproduce both product (gases and liquids) yields and properties (TBP, density, refractive index, sulfur and nitrogen). Thus, a rigorous model of conversion was obtained for hydrocracking of vacuum gas oil which predicts yields and properties of distillates, with results very close to the experimental.