Search

We present a systematic study of metal-organic frameworks (MOFs) for the storage of oxygen. The study starts with grand canonical Monte Carlo simulations on a suite of 10 000 MOFs for the adsorption of oxygen. From these data, the MOFs were down selected to the prime candidates of HKUST-1 (Cu-BTC) and NU-125, both with coordinatively unsaturated Cu sites. Oxygen isotherms up to 30 bar were measured at multiple temperatures to determine the isosteric heat of adsorption for oxygen on each MOF by fitting to a Toth isotherm model. High pressure (up to 140 bar) oxygen isotherms were measured for HKUST-1 and NU-125 to determine the working capacity of each MOF. Compared to the zeolite NaX and Norit activated carbon, NU-125 has an increased excess capacity for oxygen of 237 % and 98 %, respectively. These materials could ultimately prove useful for oxygen storage in medical, military, and aerospace applications. [ABSTRACT FROM AUTHOR]

Abstract: Adsorption equilibrium data for oxygen and argon are needed for design of adsorptive separation processes to produce pure oxygen from air and also for adsorptive gas storage applications. Carbon molecular sieves may be used to accomplish a rate-based separation of oxygen and argon and, as we show, may also be useful for gas storage. Given the limited data available, particularly at high pressures, volumetric methods are applied in this paper to measure surface excess isotherms of oxygen and argon on a carbon molecular sieve, Shirasagi MSC-3R Type 172. Temperatures are considered from 25 to 100°C with pressures as high as 100bar. Isotherms are compared at 25°C, including new data measured for nitrogen. Adsorbed-phase excess loadings are high, approaching 10mol/kg at 100bar. The oxygen capacity of the carbon molecular sieve at high pressure is comparable to that of a superactivated carbon on a mass basis, and it is higher on a volumetric basis. The excess adsorption isotherms are modeled using a multi-temperature Toth equation, which provides an excellent description. A carbon molecular sieve is shown to be a promising adsorbent for oxygen storage. [Copyright &y& Elsevier]