Adsorption of Nitrogen, Oxygen, and Argon in Mono-, Di-, and Trivalent Cation-Exchanged Zeolite Mordenite

Abstract

Adsorption of nitrogen, oxygen, and argon is studied in zeolite mordenite (Si/Al = 5.5) with mono-, di-, and trivalent Na+, Li+, K+, Cs+, Ca2+, Sr2+, Ba2+, La3+, and Ce3+ as extraframework cations. Adsorption capacity, selectivity, and heat of adsorption show a strong dependence on the nature as well as the extent of the extraframework cations. The cation-exchanged mordenite samples show adsorption selectivity toward nitrogen from its mixture with oxygen or argon. The electrostatic interaction between adsorbate molecules and the cations are largely responsible for the observed nitrogen selectivity of the mordenite samples because nitrogen has higher quadrupole moment than oxygen or argon. The relationships between the adsorption properties and charge densities of extraframework cations show that the interaction of adsorbate molecules depends not only on the cation type but also on the positions of these cations in the mordenite structure.

Influence of alternative cations distribution in AgxLi96-x-LSX on dehydration kinetics and its selective adsorption performance for N2 and O2

“…4A-B (b-f), it is clearly indicated that the adsorption capacity of nitrogen in highly cation exchanged Ag x Li 96-x -LSX decreases sharply with an increase in the size of cations that agrees well with the literature. 31 In the case of lithium cations, the curve shows highest nitrogen adsorption capacity with small cation size. Yang et al reported, 10 the ionic radius of Ag + is (1.26 Å) considerably larger than that of Li + (0.68 Å).…”

“…However, the strong bonds between N 2 and Ag + cannot only be attributed to the ion-quadrupole interaction, but also relatively slow desorption and high heats of adsorption involves weak π-complexation bonds that play an important role in the reduction of N 2 adsorption and confirmed in the literature. 10,31 On the basis of these observations, it is therefore inferred here that near fully exchanged Ag x Li 96 -x -LSX zeolites as compared to their Li x Na 96-x -LSX zeolite analogs are not favorable for use in adsorption-based separations, not only because of the low N 2 adsorption capacity and N 2 /O 2 selectivity, but also have strong affinity for N 2 at low pressures that can easily create a low-pressure high "knee" in the adsorption isotherm, which results in difficulty of N 2 desorption for the purpose of adsorbent regeneration as shown in Figs. 4A-B (b-f) and found in good agreement with the literature.…”

Methane preconcentration by adsorption: a methodology for materials and conditions selection

“…For example selectivities of various MOFs and other materials for different gas compounds have been investigated by comparing the equilibrium adsorption capacity at specific conditions (Li et al 2009;Pawar et al 2009). In cationexchanged zeolite mordenite and MOFs, selective properties have been quantified by taking the ratio of the Henry's constants or comparing the isosteric enthalpy of adsorption of each gas (Peter et al 2005;Liu et al 2008;Moellmer et al 2012). More sophisticated methods of measuring the selectivity of CH 4 adsorption over N 2 adsorption are also reported, for example breakthrough measurements, however these experiments are tailored to specific process conditions and require elaborate experimental apparatus beyond the scope of this study.…”

A dechlorination pathway for synthesis of horn shaped carbon nanotubes and its adsorption properties for CO2, CH4, CO and N2

“…(1)), the obtained value of first Virial coefficient (A) was further used for the calculation of Henry's constant with the help of Eq. (2) [34].…”