Zeolite reactivity

Among the numerous theoretical approaches applied to the zeolite reactivity problem, we focus our attention mainly on calculations, which use recently developed ab initio molecular dynamics techniques. After a very brief overview of the main features of this methodology, we discuss some applications taken from the modeling of zeolite chemistry the characterization of the catalytic sites, the protonation of a water molecule and the mechanism of the protolytic reactions of alkanes. 

Results from these CP-MD calculations show that we in fact have a more complicated situation than dealing with simple hydrogen bond or ion-pair complex formation as methanol interacts with a zeolite acidic proton. Stich and coauthors conclude that the zeolite reactivity can be understood only by taking three factors into account simultaneously zeolite topology, sorbate loading, and dynamic effects. The examples above illustrate that the capabilities of modern modeling techniques will allow us to accept this challenge. 

This chapter presents different facets of adsorption. Unfortunately, there is not sufficient space to provide case studies for any of the hundreds of unique applications of adsorption. On the other hand, most of the topics discussed here are the subject of dozens of technical papers each year, many of which appear in specialized journals, including (alphabetically) Adsorption, Carbon, Langmuir, Microporous and Mesoporous Materials (formerly Zeolites), Reactive Polymers, and other more general titles. Some subjects are also treated in much greater detail in books, many of which are listed in the bibliography that follows. 

The thermal decomposition of 2-CEES on nanocrystalhne zeohtes was probed by FTIR spectroscopy. Comparison of the reactivy of nanocrystaUine NaZSM-5, silicalite and NaY indicated that NaZSM-5 was most effective for 2-CEES thermal oxidation and that external surface silanol sites were important to the zeolite reactivity. The adsorption and reaction of DMMP on nanocrystalline NaY was investigated using FTIR and sohd state NMR spectroscopy. External surface silanol and EFAL sites were implicated in the thermal oxidation of DMMP on nanocrystaUine NaY. Thus, the nanocrystalline zeolites can be envisioned as new bifunctional catalyst materials with active sites on the external surface playing an important role in the intrinsic reactivity of the material. Future studies will focus on optimizing the activity of nanocrystaUine zeolites for CWA decontamination apphcations by taUoring the surface properties. 

Pidko EA, van Santen RA. Theoretical chemistry of zeolite reactivity. In Cejka J, Corma A, Zones S, editors. Zeolites and catalysis synthesis, reactions and applications. Weinheim Wiley-VCH 2010. 

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