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On the nature of water interacting with Bronsted acidic sites. Ab initio molecular dynamics study of hydrated HSAPO-34

Article Abstract:

Several scientific investigations on the synthetic zeolitic catalyst of aluminophosphate type HSAPO-34 demonstrated the protonation of intrazeolitic water molecules by Bronsted acid sites. Ab initio molecular dynamic studies and geometric optimizations were performed to examine the water protonation phenomenon in HSAPO-34. The findings attributed the water protonation at the Bronsted acidic sites to the presence of a hydrogen-bonded water dimer which acts as a proton acceptor at the site.

Water chemistry

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Bronsted acid sites in HSAPO-34 and chabazite: an ab initio structural study

Article Abstract:

Research was conducted to provide a structural and spectroscopical characterization of the Bronsted acid sites and their neighborhoods. Ab initio plane-wave calculations on periodic models were used to analyze the structure of Bronsted acid sites and the effects of the Al -> Si and Si -> P substitution in chabazite and AlPO4-34 frameworks, respectively. Results are in reasonable agreement with experimental data and empirically established trends.

Catalysts, Substitution reactions

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Molecular dynamics studies of sodium diffusion in hydrated Na+-zeolite-4A

Article Abstract:

Research was conducted to examine sodium diffusion in hydrated Na+-zeolite-4A using molecular dynamics simulations at 298 K for a range of hydration. It was observed that the self-diffusion coefficient of the mobile ions increased with hydration, in agreement with the results of conductivity experiments. Results demonstrate that the sodium ions in the Na(2) and Na(3) sites are preferentially hydrated at low hydration.

Hydration, Rehydration solutions, Diffusion, Diffusion (Physics), Ionic mobility

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