Integral Mass Balance (IMB) Method for Measuring Multicomponent Gas Adsorption Equilibria in Nanoporous Materials

Abstract

To assess the performance of an adsorbent for a particular gas separation, and for process design, it is necessary to determine multicomponent gas adsorption equilibria, either experimentally or from predictions based on models or theory. The experimental techniques commonly used for this purpose, however, are time-consuming and typically require large samples. In this article, we describe a new approach, called the Integral Mass Balance (IMB) method, which combines the controlled flow of a gas mixture with in situ gravimetric measurement and gas composition analysis using quadrupole mass spectrometry. The IMB method allows very rapid equilibrium multicomponent gas adsorption measurements to be performed on samples weighing only a few grams. The method is demonstrated and validated by performing binary O2/N2 adsorption measurements on a commercial 5A zeolite, at ambient temperature and a total pressure of 0.915 MPa. Excellent agreement with previously published data was found, using a 3.5 g sample, with a measurement time of only 4 h for a 20 point isotherm. In contrast, other techniques of equivalent accuracy would require around 20 days of experimental effort to collect a comparable amount of data. Selectivities were also calculated and shown to agree with previously published results. In principle, the technique could readily be extended to measure gas adsorption from ternary or higher mixtures.

Adsorption of Carbon Dioxide, Water Vapor, Nitrogen, and Sulfur Dioxide on Activated Carbon for Capture from Flue Gases: Competitive Adsorption and Selectivity Aspects

“…Therefore, this cannot be explained by experimental uncertainty, and it is possible that while CO 2 surface excess is described accurately by IAST, the N 2 adsorption determined experimentally is lower than the IAST calculation. It has been reported that the N 2 experimental selectivity for N 2 and O 2 adsorption on a 5A zeolite experimental was also lower than the IAST selectivity. , Binary CO 2 /H 2 O adsorption data for 5A and 13X zeolites showed a discrepancy with predictions of IAST but are described well by a virial excess mixing coefficient (VEMC) model, which has corrective terms for nonidealities . Adsorption of CO 2 /N 2 binary mixtures on zeolite ZSM-5 showed that no models gave a satisfactory description over the entire range mole fractions.…”

“…The equilibrium gas concentrations are determined, and this allows the amounts adsorbed to be determined by using either from pressure in a fixed volume instrument or gravimetrically. (2) The integral mass balance method involving a controlled flow of a gas mixture with analysis of the outlet gas compositions by using mass spectrometry and sample mass by gravimetric methods . Only very limited experimental data are available on the kinetic effects in multicomponent systems.…”

“…Competitive adsorption of CO 2 and N 2 was studied by using a Hiden Isochema IGA-003-MC gas sorption analyzer instrument coupled with a Hiden dynamic sampling mass spectrometer. The integral mass balance method involves the controlled flow of a gas mixture combined with in situ gravimetric measurement and gas composition analysis using quadrupole mass spectrometry . The F400 activated carbon sample (∼3.7 g) was suspended from the microbalance in a stainless steel mesh bucket, and this was located in the adsorption reactor cell.…”

“…SO 2 and CO 2 may interact with water in the pores to form acidic species. The CO 2 /N 2 competitive adsorption was determined by the integral mass balance (IMB) experimental method . The competitive adsorption of CO 2 /N 2 and SO 2 /CO 2 was investigated by using IAST, and the results for CO 2 /N 2 from both methods were compared.…”

“…The CO 2 /N 2 competitive adsorption was determined by the integral mass balance (IMB) experimental method. 19 The competitive adsorption of CO CO 2 was investigated by using IAST, 16 and the results for CO 2 /N 2 from both methods were compared. The results for adsorption of the main flue gas components are discussed in terms adsorption thermodynamics, kinetics, and species selectivity.…”