Opening the Toolbox: 18 Experimental Techniques for Measurement of Mixed Gas Adsorption

Abstract

Adsorption separation systems offer the possibility to replace or augment legacy separation systems with more efficient processes, resulting in enormous savings in energy. However, adsorption systems are not as easily evaluated as possible unit operations in process simulation software compared to distillation or absorption columns. The lack of ability to predict adsorption of gas mixtures represents a persistent barrier holding back implementation of adsorption separations. This shortcoming is the result of an equally persistent deficiency in the ability to measure adsorption of gas mixtures, despite the huge variety of existing methods to measure mixture adsorption. This work presents a comprehensive overview of 18 techniques used to measure mixture adsorption, including the equipment and principles used in each method as well as the strengths and shortcomings of each technique. This work also provides recommendations for which methods may best suit the individual needs of experimentalists interested in measuring mixture adsorption and includes an outlook on the future of mixture adsorption measurement.

Reproducible Sorbent Materials Foundry for Carbon Capture at Scale

“…Some recent work has further used this technique to (semi-quantitatively) measure the sorbent uptake. [15] Microstructural characterization of the sorbent powders will also be vital. While this can include simple high magnification optical imaging, a key measurement here is surface area and pore size.…”

“…The full adsorption behavior depends on the competitive adsorption of at least CO 2 , N 2 , O 2 , and H 2 O (each with an independent partial pressure) that each have their own temperature dependence. However, mixed gas adsorption measurements are notoriously difficult and scarce, [16] the BISON-20 database [17] of mixed gas adsorption studies only contains approximately 7,000 individual data points [15] and a recent study showed that < 2% of these measurements are repeatable. [18] This is particularly true in the case of DAC relevant concentrations: 450 µg/g (ppm) of CO 2 in ambient air is an unacceptably high concentration in terms of atmospheric science but is physicochemically challenging to measure.…”

“…[18] This is particularly true in the case of DAC relevant concentrations: 450 µg/g (ppm) of CO 2 in ambient air is an unacceptably high concentration in terms of atmospheric science but is physicochemically challenging to measure. [15,19,20,21] This requires careful design of the adsorption instrumentation to be able to accurately measure low concentrations of CO 2 . An autonomous agent is well suited to fully characterize the mixed gas adsorption behavior as it is able to rapidly explore this composition+temperature-space as needed for various capture applications.…”

“…There are several different complimentary measurement instrument designs for this mixed gas adsorption measurements. [15] Open system instrument designs (commonly called breakthrough instruments) involve gas flow through a packed adsorption column where the downstream composition is measured. This technique has the advantages of being able to simultaneously capture both adsorption uptake and kinetic information at a specified gas composition, total pressure, and temperature.…”

Simultaneous Estimation of Gas Adsorption Equilibria and Kinetics of Individual Shaped Adsorbents

“…Typically adsorption equilibria, specifically for a single component, is measured using volumetric and/or gravimetric techniques. [26][27][28] Techniques to measure both adsorption equilibria and kinetics can be broadly classified into three approaches. The first approach, grouped under "batch" techniques, involves using purposebuilt or commercial static adsorption instruments as is or with modifications to the instrument with a few milligrams of the sample.…”