Calcium chabazite adsorbent for the gas chromatographic separation of trace argon-oxygen mixtures

Abstract

Calcium chabazite used as a gas chromatographic packing provides a practical means for analyzing trace levels of a variety of permanent gases including oxygen and argon. An outstanding feature of properly activated calcium chabazite is its ability to resolve argon and oxygen at temperatures above 343 K. The level of dehydration achieved for this adsorbent has a direct Influence on its efficiency and ability to resolve Ar and 02. In addition, we found that treating the chabazite at elevated temperature in an oxidizing atmosphere improves the resolution and lowers the detectability limits for determining oxygen. Part-per-billion levels of Ne, Ar, 02, N2, CH4, and CO could be measured by using a calcium chabazite column, in combination with a helium ionization detector. The column efficiency and resolution of this adsorbent were measured as a function of corrected flow rate and column temperature for Ar-02 mixtures. Trace Ar and 02 were base-line-resolved In under 2 min by using a 6-ft column of this adsorbent at 343 K. Thus, calcium chabazite provides a practical adsorbent for analyzing a wide variety of gases with conventional instrumentation.

Cage and Window Effects in the Adsorption of n-Alkanes on Chabazite and SAPO-34

“…Because of the restricted pore size, mainly adsorption of small gaseous molecules has been studied on CHA. − An overview of the application of natural CHA in the purification and separation of gases is given in the review by Ackley et al CHA can be used for separation of nitrogen, oxygen, argon and methane and removing water from HCl gas streams. − Adsorption of water, ethanol, and their mixture on a zeolite-rich tuff containing philipsite and chabazite was studied by Caputo et al Separation of water from propanol in vapor phase on Mordenite/ZSM-5/chabazite membranes was achieved by Salomon et al Zhang et al showed that NaCHA and CaCHA are promising materials for high-temperature CO 2 separation. In a Grand Configurational-Bias Monte Carlo (GCMC) simulation study, the segregated nature of CO 2 /CH 4 mixture adsorption in cage-type zeolites such as DDR, CHA, LTA, and ERI is demonstrated .…”

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“…Since Ar is in a smaller amount compared to O 2 , a sorbent with a preferential adsorption capacity for Ar would be ideal. However a study of the existing literature revealed that although some sorbents such as mordenite, calcium chabazite (Furuyama et al, 1984;Knaebel et al, 1987;Maroulis and Coe, 1989;Jasra et al, 1996), and Agmordenite (Knaebel and Kandybin, 1993) showed a small adsorptive preference for Ar compared to O 2 , the equilibrium selectivity was not high enough to enable the separation. Kinetic separation of O 2 and Ar using molecular sieve carbon (MSC) is another possibility.…”

Separation of permanent gases by single-column gas liquid chromatography with liquid nitrogen as the stationary phase

“…The separation and analysis of gaseous mixtures containing some or all of the gases neon, nitrogen, carbon monoxide, argon, oxygen, krypton, and methane is a common analytical problem of interest in the production and analysis of commercial gases, as well as natural, artificial, and even extraterrestrial atmospheres. Gas-solid chromatography with molecular sieves, other zeolites, and porous polymers has been used successfully for such separations (1)(2)(3)(4)(5). However, analyses of mixtures of different compositions or concentrations often require specially designed separation strategies, systems, or conditions.…”