Experimentally Verified Alkane Adsorption Isotherms in Nanoporous Materials from Literature Meta-Analysis

Abstract

Identification of independent experimental replicate measurements of well-defined physical properties provides a useful way to assess the reproducibility of literature reports of these properties. Prior meta-analysis of this kind for single-component adsorption of CO2 and alcohols in nanoporous materials showed that ∼20% of reported isotherms for these molecules were inconsistent with available replicate measurements. In this paper, we extend this analysis to the single-component adsorption of alkanes in nanoporous materials using a collection of 2998 experimental isotherms. Among these isotherms, 846 replicates were identified and analyzed. Many more replicates are available for CH4 adsorption than for any other alkane. Our analysis finds that 15% of the replicate alkane isotherms are inconsistent with other replicate measurements. After discarding these outlier isotherms we report graphical and numerical consensus isotherms for 93 independent combinations of adsorbate, adsorbent, and temperature as well as an assessment of another 124 independent systems for which two replicate isotherms are available.

Surprising Use of the Business Innovation Bass Diffusion Model To Accurately Describe Adsorption Isotherm Types I, III, and V

“…Accurate predictions of mixture adsorption based on the most commonly used method to predict co-adsorption, the ideal adsorbed solution theory (IAST), rely on highly accurate pure-component adsorption fits, especially in the low-pressure region . In addition, assessing the reproducibility of repeated isotherm measurements is only possible with mathematical models describing the isotherms. − For these applications, an accurate, simple, descriptive prediction of the adsorption data is more practical than a complex isotherm model with multiple fitting parameters even if the parameters provide a more quantitative description of system properties. Even more problematic, isotherm models developed for specific adsorbate/adsorbent systems are often limited in their extendibility to other systems with similar isotherm shapes due to a lack of knowledge of required properties for fitting parameters.…”

A Surprising Use of the Business Innovation Bass Diffusion Model to Accurately Describe Adsorption Isotherm Types I, III, and V

“…Accurate predictions of mixture adsorption based on the most-commonly used method to predict co-adsorption, the Ideal Adsorbed Solution Theory (IAST), relies on highly accurate pure-component adsorption fits, especially in the low-pressure region 4 . In addition, assessing the reproducibility of repeated isotherm measurements is only possible with mathematical models describing the isotherms [5][6][7] . For these applications, an accurate, simple, descriptive prediction of the adsorption data is more practical than a complex isotherm model with multiple fitting parameters even if the parameters provide a more quantitative description of system properties.…”

The Dilemma of Reproducibility of Gating Isotherms for Flexible MOFs

“…In a well-designed case study, CO 2 physisorption isotherms have been statistically evaluated for several MOFs, concluding a mere 34% consistency in measured isotherms for the MOFs investigated . A further detailed study analyzing the adsorption isotherms for various adsorptives on specific MOFs further points to discrepancies in reported data and the importance of replicated measurements and development of so-called consensus isotherms and also highlights the importance of reporting the sample handling protocols. , The adsorption isotherms of MOFs are subjective to the careful preparation of the sample which involves various steps, such as proper activation (desolvation), handling, storage, and equilibration of the system during the isotherm collection. The extended meta-analysis of literature-reported isotherms performed by Sholl, Walton, and co-workers also reveals challenges in the reproducibility of synthetic procedures reported for MOFs, further complicating the reproducibility of the adsorption capacities .…”