Kinetics for hydrocracking based on structural classes: Model development and application



A kinetic model for hydrocracking of an industrial feedstock, fully incorporating the carbenium ion chemistry, was developed. Individual hydrocarbons in the reaction network were relumped into 8 lumps per carbon number: n-alkane, mono-, di- and tribranched alkanes, mono-, di-, tri- and tetraring cycloalkanes. The rate coefficient of a reaction in the relumped network resulted from the product of the rate coefficients of the elementary reaction steps with lumping coefficients. The former were obtained from regressions on gas-phase hydrocracking data of model components. Lumping coefficients were calculated based on the assignment of all (cyclo)alkanes and the corresponding carbenium ions to structural classes comprising species with identical thermodynamic properties. The simulation of an industrial reactor with vacuum gas-oil feed revealed the relative unimportance of transfer limitations for hydrocracking of saturated hydrocarbons and the model's ability to detail the influence of process conditions on the product composition.