The main interaction between pyridine and zeolites leads to form a hydrogen bond between the N atom of pyridine and OH groups of zeolites. The present work reports a theoretical study about the structural, vibrational and topological properties of the charge distribution of the molecular complexes between pyridine and a series of acids sites of zeolites. The calculated structural parameters...

For many years, researchers have been developing theoretical methods of estimating reaction rates and energetics when experimental measurements are not available. Recent advances have led to composite energy methods with near chemical accuracy. The performance of these new methods for predicting activation energies and rate constants have not been evaluated for large hydrocarbon cracking reacti...

We have developed a computational framework for the adsorption of linear alkanes in protonated aluminosilicates. These zeolites contain trace amounts of water that form hydrated proton complexes. The presence of hydrated protons makes the simulations at the fully atomistic level difficult. Instead of constructing an elaborate and complex model, we show that an approach based on a coarse-grainin...

Benzene alkylation with ethene over zeolite H-ZSM-5 has been investigated using density functional theory. Three different reaction mechanismsstwo one-step schemes and one two-step schemeshave been studied on three cluster models of increasing size representing parts of the H-ZSM-5 framework. In the one-step schemes ethene protonation and C-C bond formation occur simultaneously. The two-step sc...

Natural zeolites occur in over 40 countries and are mined in 11 of these at a rate of around 250 thousand tonnes per year. Discovery of the characteristic ion-exchange, dehydration and selective-adsorption properties of these zeolites, which are related to their unique honeycomb structure, stimulated the development of severa1 processes for the manufacture of synthetic zeolites. These synthetic...

The recently proposed united atom force field by Dubbeldam et al. (Phys. Rev. Lett. 2004, 93, 088302) for the adsorption of alkanes in MFI-type zeolites was extended to other zeolites in this work. Its applicability to FER-type zeolites was evaluated in detail, for which the Henry coefficients, the isosteric heat of adsorption, the adsorption isotherms, as well as the locations of alkanes in th...

We study the background associated with phenomena observed in zeolites using combinatorial and geometric techniques. We define combinatorial d-dimensional zeolites and show that not all combinatorial zeolites have a unit distance realization inR , and of those that have a unit distance realization, not all have non-overlapping unit-distance realizations. Only few classes of finite 2-d zeolites ...

We describe a hierarchy of approximations (MP2[x]) that allow one to estimate second-order Møller-Plesset (MP2) energies in a large basis set from small-basis calculations. The most cost-effective approximation, MP2[K], is significantly cheaper than full MP2 but numerical tests on small atoms and molecules indicate that it is nonetheless accurate. We conclude that MP2[K] is an attractive level ...

The direct experimental evidence shows that ethylbenzene disproportionation is a transition state shape selective reaction on zeolites: a bimolecular reaction mechanism via diphenylethane-mediated pathway on large-pore zeolites X and Y (ca. 0.74 nm) and a monomolecular reaction mechanism on medium-pore zeolites ZSM-5 (ca. 0.56 nm) via the ethoxy-mediated intermolecular ethyl group transfer. The...

Attenuated second-order Møller-Plesset perturbation theory (MP2) within the finite aug-cc-pVTZ (aTZ) basis set is developed for inter- and intra-molecular non-bonded interactions. A single attenuation parameter is optimized on the S66 database of 66 intermolecular interactions, leading to a very large RMS error reduction by a factor of greater than 5 relative to standard MP2/aTZ. Attenuation in...