Single-Event MicroKinetics for coke formation in catalytic cracking

Abstract

A Single-Event MicroKinetic model taking into account coke formation based on elementary steps has been developed for the catalytic cracking of hydrocarbons. Coke is proposed to be formed out of coke precursors. Both coke precursors and coke formation are accounted for in terms of the same families of elementary steps as those involved in the cracking process. The coke precursors are defined as three-ring aromatic molecules. The actual and critical step for coke formation is considered to be the alkylation of coke precursors that are present in the feedstock or that are formed during the catalytic cracking. The inclusion of coke precursors formation in the reaction network leads to an important expansion of the network. Appropriate rules are defined to keep the size of the network within tractable limits. The rate equations for the initial coke formation do not contain supplementary kinetic parameters. The only extra parameter required to be determined from experimental coking data is the average molecular mass of the coke. The developed model is implemented in a simulator of an industrial FCC riser-reactor. The calculated product and coke yield profiles are typical for industrial practice.