Modelling the Two-Stage Pyrolysis Gasoline Hydrogenation

A model is developed based on a two-stage hydrogenation of pyrolysis gasoline to obtain a C6-C8 cut suitable for extraction of aromatics. The first stage hydrogenation takes place in a trickle bed reactor while the second stage hydrogenation is carried out in a two compartment fixed bed reactor in which hydrogenation of olefins takes place in the first compartment while the sulphur is eliminated in the second compartment. The key component in this stage is considered to be cyclohexene whose hydrogenation was found to be the most difficult among other olefins in the feed. The LangmuirHinshelwood kinetic expression was adopted for hydrogenation of cyclohexene and its kinetic parameters were determined experimentally in a micro-reactor. The model was solved for the whole process of hydrogenation, including hydro-desulphurization. The predictions of the model were compared with the actual plant data of an industrial scale pyrolysis gasoline hydrogenation unit and satisfactory agreement was found between the model and the plant data.