Abstract
In the calculation of the absolute adsorption of supercritical gas adsorbed on the microporous materials, most existing methods regard the adsorbed density as a constant, which is very unreasonable. In this study, an extended pressure point method combined with Langmuir adsorption model is proposed in which the varying adsorbed density under different pressures is considered at the same time. The utility of the proposed method to correlate accurately the experimental data for supercritical gas adsorption system is demonstrated by high-pressure methane adsorption measurements on two groups of shale samples. Taking advantage of the proposed method, we can obtain the adsorbed density and the adsorbed volume corresponding to different pressures. Compared with the conventional methods under the assumption of fixed and parameterized adsorbed density, the proposed method yields better fitting results with the experimental data. Our work should provide important fundamental understandings and insights into the supercritical gas adsorption system.
Highlights
Supercritical gas adsorption on the microporous materials is the physicochemical basis of many important engineering processes and industrial applications, such as the hydrogen storage on activated carbon, sequestration of carbon dioxide in coalbed, gas-in-place calculation of shale (Ge et al, 2016; Moellmer et al, 2011; Pini, 2014; Qi et al, 2017; Tang and Ripepi, 2017; Tang et al, 2017)
Gas molecules are affected by two kinds of forces: the force between the gas molecules and the force of the adsorbent surface exerting on the gas molecules (Fitzgerald et al, 2003)
In order to determine the varying adsorbed density under different pressures, this paper proposes the extended pressure point method (EPPM)
Summary
Supercritical gas adsorption on the microporous materials is the physicochemical basis of many important engineering processes and industrial applications, such as the hydrogen storage on activated carbon, sequestration of carbon dioxide in coalbed, gas-in-place calculation of shale (Ge et al, 2016; Moellmer et al, 2011; Pini, 2014; Qi et al, 2017; Tang and Ripepi, 2017; Tang et al, 2017) It occurs through a physical interaction between the gas molecules and the adsorbent surface, creating a region whose density is different from that of the homogeneous bulk phase (Pini, 2014). The relationship between the Gibbs excess adsorption and the absolute adsorption is given as (Hu et al, 2018; Tian et al, 2016)
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