Collective action of water molecules in zeolite dealumination

When exposed to steam, zeolite catalysts are irreversibly deactivated by loss of acidity and framework degradation caused by dealumination. Steaming typically occurs at elevated temperatures, making it challenging to investigate the mechanism with most approaches. Herein, we follow the dynamics of zeolite dealumination in situ, in the presence of a realistic loading of water molecules by means of enhanced sampling molecular dynamics simulations. H-SSZ-13 zeolite is chosen as a target system. Monte Carlo simulations predict a loading of more than 3 water molecules per unit cell at representative steaming conditions (450 °C, 1 bar steam). Our results show that a higher water loading lowers the free energy barrier of dealumination, as water molecules cooperate to facilitate hydrolysis of Al–O bonds. We find free energies of activation for dealumination that agree well with the available experimental measurements. Clearly, the use of enhanced sampling molecular dynamics yields a major step forward in the molecular level understanding of the dealumination; insight which is very hard to derive experimentally

Tracking Structural Deactivation of H-Ferrierite Zeolite Catalyst During MTH with XRD

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Регіональні аспекти удосконалення системи управління персоналом на державній службі

У статті розкривається суть регіональних вимірів удосконалення системи управління персоналом на державній службі та висвітлюється досвід Управління державної служби Головдержслужби України в Миколаївській області на шляху до прозорості влади і залучення громадськості до державотворення.The article reveals the essence of regional measurements of improvement the HR Management system in the civil service and reports the experience of the Office of Civil Service of The Main Department of Civil Service of Ukraine in the Mykolaiv region towards transparency in government and public involvement in the nation

From Catalytic Test Reaction to Modern Chemical Descriptors in Zeolite Catalysis Research

For the successful implementation of catalysts in industrial processes, three overall goals are optimized: activity, selectivity, and stability. This review will address the role of chemical descriptors in aiding and guiding the development of optimal zeolite catalyst designs with the above performance criteria in mind. It will focus on both gas‐phase and liquid‐phase catalysis with a special focus on methanol to hydrocarbon, and biomass valorization reactions. By way of preface, the research on constraint and spaciousness indices is discussed. These indices can be considered the original chemical descriptors of catalysis research