Zeolite acidity ranking by the framework–sorbate interaction energy simulation

A new simulation protocol, based on molecular mechanics with systematic sampling, was developed to calculate efficiently the adsorption structure of sorbates on zeolite without long-time simulations. Using this technique in combination with the force field parameters appropriately chosen, the interaction energies between zeolite framework and sorbates were calculated. They could reproduce the tendency of the experimental heat of adsorption of ammonia, pyridine, 2-methylpyridine, and isopropylamine on mordenite, ZSM-5, and Y. The higher heat of adsorption could be explained from the favorable framework–sorbate interaction, the importance of which should be recognized. The simulation procedure established here allows the selection of the best types of zeolite from a large number of candidates for its simplicity by ranking them according to their acidity or activity, and would assist catalyst development in industry by providing a research guideline.