Density functional theory studies of zeolite structure, acidity, and reactivity

Abstract

Our recent application of quantum mechanical methods to the study of heterogeneous catalysis in zeolites is reviewed. We show that density functional theory (DFT) is a powerful means by which zeolite structure, acidity, and reactivity can be elucidated. The relative accuracy of DFT is comparable to that of traditional ab initio molecular orbital methods. However, the computational requirements of DFT are much less, allowing us to efficiently study the large systems needed for the realistic modeling of zeolite catalysis. We also demonstrate how the coupling of theoretical and experimental studies can greatly aid our atomic-level understanding of catalytic processes. We briefly describe the technical details of DFT and the factors that influence the accuracy of the results. Examples of DFT applied to the structure and acidity of H-ZSM-5 and substituted analogs are presented, as well as a combined DFT and NMR study of Hammett indicators adsorbed on an H-ZSM-5 model. Finally, the H/D exchange mechanism for benzene on zeolites is presented, demonstrating the important role DFT plays in the study of zeolite reactivity.