High Pressure Excess Isotherms for Adsorption of Oxygen and Nitrogen in Zeolites

Abstract

High-pressure oxygen is an integral part of fuel cell systems, many NASA in situ resource utilization concepts, and life support systems for extravehicular activity. Due to the limited information available for system designs over wide ranges of temperature and pressure, volumetric methods are applied to measure adsorption isotherms of O(2) and N(2) on NaX and NaY zeolites covering temperatures from 105 to 448 K and pressures up to 150 bar. Experimental data measured using two apparatuses with distinctly different designs show good agreement for overlapping temperatures. Excess adsorption isotherms are modeled using a traditional isotherm model for absolute adsorption with a correction for the gas capacity of the adsorption space. Comparing two models with temperature-dependent coefficients, a virial isotherm model provides a better description than a Toth isotherm model, even with the same number of parameters. With more virial coefficients, such as a cubic form in loading and quadratic form in reciprocal temperature, the virial model can describe all data accurately over wide ranges of temperature and pressure.

MOF Crystal Chemistry Paving the Way to Gas Storage Needs: Aluminum-Based soc-MOF for CH4, O2, and CO2 Storage

“…1a,7,8 In contrast, studies pertaining to high-pressure oxygen (O 2 ) storage are still scarce. 9 The availability of high amounts of O 2 is of prime importance in the health care domain, particularly in the treatment of respiratory insufficiencies and in hyperbaric oxygen changes for the treatment of carbon monoxide poisoning. Correspondingly, a large amount of oxygen is used to enrich air during catalyst regeneration in the catalytic cracking units.…”

Transferable force fields for adsorption of small gases in zeolites

“…22 The adsorption and diffusion of alkanes have also been widely studied in both pure silica and alumino-substituted zeolites. 9, 11,13,17,21,24,[31][32][33][34][35][36][37] Despite current efforts, the development of transferable force fields for describing the adsorption in zeolites (especially at low temperatures) remains a complex task. 22,[26][27][28][29][30] The adsorption and diffusion of other small gases such as nitrogen, argon, oxygen, or carbon monoxide have also been reported in zeolites but in lesser amount.…”

Adsorption of oxygen onto zeolites at pressures up to 15 MPa

“…NIST's REFPROP extension to MS Excel was applied to determine densities (quoted accuracy of 0.1% of value). The ARC data reported here is the volumetrically measured absolute adsorption as opposed to the excess adsorption reported by Wang et al 6 …”

“…Pressures range up to about 15 MPa (2200 psia) though limited by the saturation pressure where applicable. The VU group has set out to measure oxygen adsorption at higher temperatures (from 250 K to 430 K) 6 .…”