Novel Differential Column Method for Measuring Multicomponent Gas Adsorption Isotherms in NaY Zeolite

Separation and purification of gas mixtures using selective adsorbents is widely used in different industries such as gas drying, air separation, and H₂ purification. Equilibrium analysis involving adsorption of binary gas mixtures provides important information related to the adsorbent performance in the separation of gases. In this study, a novel technique termed “differential column technique” was developed for binary isotherm measurement employing streams containing carbon dioxide, carbon monoxide, and ethylene at different compositions. This technique is based on measuring the gas desorption by changing equilibrium pressure conditions. The isotherm curve was generated by summing desorption amounts desorbed at each pressure step. Through the application of this technique, the single-component isotherms of CO₂, CO, and ethylene on zeolite NaY were measured, and the isotherms were compared to the results obtained by a standard gravimetric technique. (The average relative deviation is less than 6%.) The main advantage of the technique is the significant time savings, e.g., one experimental run is required to generate an isotherm compared to multirun experiments using a standard breakthrough technique, in addition to using a simpler experimental setup and generally smaller amount of sample (agglomerated or in a powder form). Another important feature of this technique is the relatively simple extension that allows measurements of gas mixture equilibria. As such, the proposed technique has the potential to be used as a fast screening technique for adsorbent selection based on single-component or mixture analysis. To investigate the consistency of the proposed technique, the binary isotherms of competitive, CO₂–C₂H₄, and noncompetitive, CO₂–CO, mixtures were investigated at different gas compositions. In addition, the effects of sorbate concentrations in the gas phase and interactions with the NaY zeolite active surface were investigated in relation to the adsorption selectivity and capacity, i.e., strong interaction of both CO₂ and ethylene with NaY site resulted in close adsorption selectivity 0.8 ≤ <i>S</i>_{CO₂/C₂H₄} ≤ 1.7, while CO₂ adsorbed more selectively compared to CO, 14 ≤ <i>S</i>_CO₂/CO ≤ 30, as a result of weak CO interaction with the adsorbent sites. Finally, the binary adsorption isotherms and selectivity were predicted by the multisite Langmuir model using the single component’s isotherm parameters. Modest agreements (error ≤ 28%) were obtained between the predicted and experimental results

• • _&quot;&apos;Ill Diffusion and Immobilization Mechanisms in Zeolites Studied by ZLC Chromatography*

Abstract. Zero Length Column chromatography was used to study mass transfer in zeolites involving coupled diffusion and immobilization mechanisms, A modeling based on Volterra integral equation technique was utilized to simulate sorption and desorption kinetic curves and compare results of the simulations with experimentally obtained curves, This approach was applied to analyze sorption kinetics in the model system: toluene/silicalite-l (75UC-178&apos;~C), The system generally shows a non-Fickian behavior and can be described by diffusion coupled with immobilization

An insight into clustering of halogenated anesthetics molecules in metal-organic frameworks: Evidence of adsorbate self-association in micropores

In order to better understand the adsorption of volatile halogenated anesthetics on metal organic frameworks (MOFs), sevoflurane vapor adsorption experiments were performed on commercial MOF-177 at different temperatures. Due to the surface homogeneity of such an adsorbent, arising from its almost unimodal pore size distribution and the absence of specific, coordinatively unsaturated adsorption active sites, sevoflurane adsorption isotherms exhibited a peculiar deviation from the Langmuirian behavior. Consequently, they show a "kink" at a specific pressure that increases with increasing equilibrium temperature. Successful modeling of such data by means of the Talu-Meunier equation confirmed clustering of adsorbate molecules inside adsorbent micropores, similarly to water vapor adsorption on activated carbon, which may play an important role when designing a system using MOFs as the potential adsorbents for capturing anesthetics

Adsorbent for halogenated anaesthetics

An adsorbent for halogenated anaesthetics includes: an inorganic material; and an organic material providing a framework for the inorganic material. The inorganic material may be chromium and the organic material may be terephthalic acid. The adsorbent may be formed or configured such that the adsorbent includes coordinatively unsaturated sites or such that the inorganic material may form octahedral structures. The adsorbent is formed or configured to be substantially regenerated at approximately room temperature and to provide selectivity for sevofluorane in water vapour of approximately 1.0. A method of producing an adsorbent includes: selecting an appropriate chemical containing an inorganic material; selecting an organic material to provide a framework for the inorganic material; dissolving the base chemical in water; mixing the organic material with the dissolved base chemical; heating the mixture; filtering the mixture to remove excess organic material; and drying the filtrate