Continous-mixture kinetics of coke formation from olefinic oligomers



A model for interpreting the molecular-weight distributions is presented for the olefinic oligomers and aromatic coke compounds that are experimentally observed in a catalyzed hexene isomerization process (the primary reaction). Reaction rate expressions for the secondary generation of hexene dimers, trimers and tetramers by irreversible reaction are represented in mass balances for a stirred-tank reactor. Dehydrogenation of the oligomers to form coke aromatics and their subsequent adsorption and desorption are included. A molecular-weight moment method allows solution of the model and computation of time dependence of molecular-weight distributions for all components. The model is consistent with observations of decreased catalyst deactivation rates when coke desorption rates approach coke production rates. Catalyst activity maintenance, which can occur under supercritical conditions, is also predicted by the model.