Acidity of two-dimensional zeolites

For electrostatics, ultra-thin zeolite layers have a higher acidity (lower deprotonation energy) than their bulk counterparts with the same composition.

The Effect of Zirconium Incorporation on the Brønsted Acidity of Zeolite: A DFT Study

The incorporation of zirconium atoms into the framework of some aluminosilicate molecular sieves can enhance the reactivities of some typical strong Brønsted acid needed reactions, and the strengthening of Brønsted acidity were regarded as one possible reason. In this study, the effects of zirconium incorporation on the Brønsted acidity of zeolite with CHA structure were characterized by means of periodic density functional theory (PDFT) calculations. Results from deprotonation energy and NH3 adsorption energy are consistent and show that no significant acidity enhancement is found in comparison to Zr-free sample. The results indicate new catalytic mechanism should exist.

A Computational Study of the Translational Motion of Protons in Zeolite H-ZSM-5

ABSTRACTThe potential energy profile for proton translational motions between two neighboring Alsites in zeolite H-ZSM-5 is calculated by a combined quantum mechanics-interatomic potential function approach. Thepotential energies of the six stable intermediate proton positions and the five transition structures along this path show an almost symmetrical trend reaching the maximum in the middle between these sites. Therefore, the maximum barrier will decrease with decreasing SiO2/Al2O3 ratio of thezeolite. For the SiO2/Al2O3 ratio examined (190) an activation energy of∼ 210 kJ/mol is calculated. This is much lower than the energy of deprotonation, about 1300 kJ/mol. The deprotonation energy of an Al-OH-Si bridge is obviously partially compensated by the proton affinity of the Si-O-Si bridges.