Multiscale Modeling as a Tool for the Prediction of Catalytic Performances: The Case of n-Heptane Hydroconversion in a Large-Pore Zeolite

The optimization of predictive kinetic models for catalytic processes is a topical challenge. In the present work, a predictive multiscale single-event microkinetic model based on the data obtained by density functional theory (DFT) calculation for n-heptane hydroconversion in large-pore zeolites has been obtained. It was validated by a large set of kinetic data obtained by high-throughput kinetic experiments, performed with a well-balanced Pt/Beta zeolite catalyst. DFT calculations show that secondary cations are much less stable than tertiary cations and adsorbed alkenes. This is of prime importance in the quantification of type B isomerization reaction barriers depending on the type of the carbenium ion. Cracking reaction barriers are also strongly affected by the nature of the cation that cracks and that of the cracking products. The agreement between simulated and experimental kinetic data is satisfactory, showing the reliability of the multiscale kinetic approach. Only a few parameters were adjusted to improve the correspondence with experiments. The analysis of the simulated coverage demonstrates a very low proportion of acidic sites involved in the adsorption and further reactions in the relevant experimental conditions. When these occur, tertiary carbenium ion intermediates appear in a significantly higher concentration with respect to other species. This works opens the route to a better prediction of the catalytic performance of large-pore zeolites in alkane hydroconversion.

Automated summary

In this study, a predictive multiscale single-event microkinetic model based on density functional theory (DFT) calculation was developed for the hydroconversion of n-heptane in large-pore zeolites. The model was validated by experimental kinetic data and showed satisfactory agreement. The results provide important insights into the catalytic performance of large-pore zeolites in alkane hydroconversion.