Small molecule substances as molecular probes of structure and texture of coal under sorption process and modelling
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Small molecule substances as molecular probes of structure and texture of coal under sorption process and modelling Marta Wójcik1 · Grzegorz S. Jodłowski1 Received: 2 December 2018 / Revised: 17 October 2019 / Accepted: 18 June 2020 © The Author(s) 2020
Abstract Multiple Sorption Model (MSM) is used to simulate sorption isotherms and the effect of the multiplicity of physicochemical parameters is reduced by introducing an invariant procedure using a few sorbates that are small molecules. This study presents the use of water, methanol, carbon dioxide and methane as test molecules to determine the structure and texture of coal and energy parameters. Parallel calculations for a set of sorption systems on the same coal sample recursively yield the most probable estimates. The procedure was tested for 6 coal samples with different carbon content. Effect of simulations made by MSM is evaluated on measurements of sorption isotherms. Result obtained by the analysis shows that smaller submicropores are in better contact with sorbate molecule and bigger one contact is weaker-contacts play vital role in energy contribution to the molecule. Tendency of significant absorption for CO2 and CH3OH and insignificant for H2O and CH4 is confirmed on the basis of thermodynamic dissertation/calculation. Keywords Structure · Texture · Coal · Molecular probes · Multiple sorption model
1 Introduction As carbon is a complex copolymer containing a plurality of components, and thus a complicated structure and texture, examining its properties as an adsorbent is a demanding task. The classic adsorption theories assume a large simplification of the structure of this material and for this reason the calculated parameters are only of comparative nature. Even today, some researchers consider sorption in polymeric materials as dual, despite the obvious fact that there are pores smaller than the penetrant molecules (Camboni and Sokolov 2016). On the other hand, in the Multiple Sorption Model (MSM) developed in the team, a multiplicity of sorption phenomena from absorption/solubility (Tsoulou et al. 2008), through expansion to multi-layer adsorption, is assumed (Jodłowski and Wójcik 2013; Jodłowski et al. 2007). This fact is confirmed by laboratory tests that show that swelling depends both on the volume of the penetrant
* Marta Wójcik [email protected] 1
AGH- University of Science and Technology, Faculty of Energy and Fuels, al. A.Mickiewicza 30, 30‑059 Cracow, Poland
molecules and on the space between the objects in the polymer (Ulrich et al. 1999). Such a multitude of phenomena significantly complicates the problem of modeling sorption in a carbon copolymer. Therefore, it was decided to use the procedure of simultaneous/parallel simulation of sorption isotherms on the same carbon sample for several sorbates of various structure. From the previous studies, the picture emerges that steam, methanol vapor, carbon dioxide and methane are good and sufficient probes for determining the structure and texture of coal. The simultaneous use o
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