Measurement and Analysis of Mixture Adsorption Equilibrium in Porous Solids

Abstract

Most applications of adsorption involve fluid mixtures and porous solids. Three reference states with Gibbs definition of adsorption describe absolute, excess, and net adsorption frameworks. All depend on solid mass as the extensive property rather than surface area, an ambiguous concept for porous solids. Pure component isotherms by push-button apparatus are a first step to characterize adsorption, but process development also requires mixture data since models are not dependable. Mixture experiments are an order of magnitude more complicated than pure isotherms requiring careful design of apparatus and experiments. Thermodynamic relations are very useful for system and experimental design and for analysis of data. All relevant definitions and relations are explained in this paper and illustrated with a set of pure and binary mixture adsorption equilibrium data.

Experimental Evaluation of the Adsorption, Diffusion, and Separation of CH4/N2and CH4/CO2Mixtures on Al-BDC MOF

“…It is noteworthy that the equilibrium constant of methane agrees well with the previously reported gravimetric value (15), thus confirming the validity of the IGC method. In addition, the adsorption selectivity in equilibrium state can be estimated from the ratio of the equilibrium constants (41). As shown in Table 4, the selectivities of CH 4 /N 2 and CO 2 /CH 4 on the calcined Al-BDC MOF can then be calculated as 3.79 and 15.92, respectively.…”

Steam adsorption on molecular sieve 3A for sorption enhanced reaction processes

“…The trapezoidal rule has been used for approximating the integral by a summation over discrete measurement data. The breakthrough of tracer (q tracer = 0), prior to breakthrough of H 2 O, is integrated to obtain V g , the total interparticle and intraparticle gas volume, according to the Gibbsian surface excess concept (Sircar 2018;Talu 2011). After breakthrough, the tracer signal is used to quantify the outlet flow rate prior to and during breakthrough and Eq.…”

pyIAST: Ideal adsorbed solution theory (IAST) Python package

“…Pure-component adsorption isotherms are routinely measured with high accuracy using commercial instruments [13]. On the other hand, accurate measurements of adsorption isotherms in the presence of a mixture of gases are complicated and time-consuming [11,14] and require custom-built instruments [13]. To exacerbate this problem, modeling pressure and temperature swing adsorption processes requires mixed-gas adsorption data at many different gas compositions [15]; the required number of experiments to characterize composition space quickly becomes intractable as the number of components increases.…”