Molecular simulation of water removal from simple gases with zeolite NaA

Na+-gated water-conducting nanochannels for boosting CO2 conversion to liquid fuels

Robust, gas-impeding water-conduction nanochannels that can sieve water from small gas molecules such as hydrogen (H₂), particularly at high temperature and pressure, are desirable for boosting many important reactions severely restricted by water (the major by-product) both thermodynamically and kinetically. Identifying and constructing such nanochannels into large-area separation membranes without introducing extra defects is challenging. We found that sodium ion (Na⁺)-gated water-conduction nanochannels could be created by assembling NaA zeolite crystals into a continuous, defect-free separation membrane through a rationally designed method. Highly efficient in situ water removal through water-conduction nanochannels led to a substantial increase in carbon dioxide (CO₂) conversion and methanol yield in CO₂ hydrogenation for methanol production.

Selective Removal of Hydrogen Sulphide from Industrial Gas Mixtures Using Zeolite NaA

Hydrogen sulphide removal from simple gas mixtures using a highly polar zeolite was studied by molecular simulation. The equilibrium adsorption properties of hydrogen sulphide, hydrogen, methane and their mixtures on dehydrated zeolite NaA were computed by Grand Canonical Monte Carlo simulations. Existing all-atom intermolecular potential models were optimized to reproduce the adsorption isotherms of the pure substances. The adsorption results of the mixture, also confirmed by IAST calculations, showed very high selectivities of hydrogen sulphide to the investigated non-polar gases, predicting an outstanding performance of zeolite NaA in technological applications that target hydrogen sulphide capture.

Periodic model of an LTA framework

Zeolites are a group of microporous aluminosilicate frameworks with numerous applications in, for example, catalysis and ion-exchange and sorption processes. One of the most important tools for analyzing the properties of zeolite structures is vibrational spectroscopy. However, the complexity of these structures often leads to difficulties when attempting to interpret the resulting spectra, so an additional complementary tool is required: computational methods. The aim of this study was to formulate a simplified periodic model of an LTA framework containing alkali metal cations (either Li(+), Na(+), K(+), Rb(+), or Cs(+)) and to perform a set of ab initio calculations aimed at assessing the influence of these cations on the properties of the vibrational spectra of the LTA framework. Additionally, chemical bonding was analyzed by means of electron density topology analysis. Results obtained were compared with experimental spectra for alkali metal forms of zeolite A. It was found that the vibrational spectra obtained using the proposed model agree well with the corresponding experimentally derived spectra, meaning that the model can be used to analyze real spectra in detail.