Coke Deposition in CHA Zeolite Predicted by CO2 Adsorption Isotherms and Molecular Simulation.

Molecular sieves used in catalytic and adsorptive processes in the petroleum/petrochemical industry are subject to deactivation by coke deposition. Here, we apply CO2 adsorption isotherms associated with molecular simulation models to extract additional information from the coke deactivation process. We developed a predictive molecular simulation model for naturally occurring zeolite CHA with multiple cation mixtures. The model was validated based on experimental CO2 adsorption isotherms. N-heptane, benzene and naphthalene were tested as model coke molecules to describe deactivation as a function of carbon concentration. The n-heptane molecule was the one that best represented coke from the available experimental data. In addition to predicting deactivation, the combined use of CO2 adsorption isotherms with the molecular simulation model can discriminate the nature of coke molecules. The procedure described can be applied to other molecular sieve structures, in catalysis and adsorption, and to other model molecules for coke.