Cation exchange modification of clinoptilolite – Screening analysis for potential equilibrium and kinetic adsorption separations involving methane, nitrogen, and carbon dioxide

Autor: D.A. Kennedy, F.H. Tezel
Rok vydání: 2018
Předmět:
Zdroj: Microporous and Mesoporous Materials. 262:235-250
ISSN: 1387-1811
Popis: In this study, natural clinoptilolite was modified by cation exchange using alkali metal cations (Li+, Na+, K+, Rb+, Cs+), alkaline earth metal cations (Be2+, Mg2+, Ca2+, Sr2+, Ba2+), transition metal cations (Fe3+, Ni2+, Cu2+, Zn2+, Ce3+), and acid treatment (H+). The composition and structural properties of the modified samples were assessed using EDS and XRD analysis, and compared to the original clinoptilolite sample. Adsorption isotherms for CO2, N2, and CH4 gases were measured using a microgravimetric adsorption analyser. For all of the clinoptilolite samples, the adsorption equilibria and the diffusion rates were measured at 303 K over a pressure range from 0 to 8atm. The results of this screening analysis show that the cation exchanged clinoptilolites exhibit a wide range of adsorption characteristics, which make them suitable for a variety of gas separation applications by pressure swing adsorption. The high adsorption selectivity towards CO2 and CH4 found with the Cs+ exchanged clinoptilolite makes it advantageous for possible CH4/N2 and CO2/N2 equilibrium separations. Reduced CH4 equilibrium capacity resulting from pore blocking in the Ca2+ exchanged clinoptilolite leads to high selectivity for CO2/CH4 and N2/CH4 selective adsorbent. However, the potential of this material is limited due to increased microporous diffusion resistance. While both Li+ and Ni2+ clinoptilolites exhibit low CH4/N2 ideal selectivity, they present high N2/CH4 kinetic selectivity, thereby making them suitable for possible N2/CH4 kinetic separations.
Databáze: OpenAIRE
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