Adsorption of methanol, ethanol, n-propanol, and n-butanol by Pocahontas No. 3, Upper Freeport, Illinois No. 6, and Beulah-Zap Argonne premium coals was investigated to clarify the effect of alkyl group bulk on adsorption and to evaluate the micropore and cross-linked structure of coals. A strong steric effect was found for all coals. The sorption isotherms could be fitted to the Langmuir−Henry dual-mode equation, and the total sorption could be divided into adsorption and diffusion (dissolution) components, which were separately estimated. For all coals, the Henry's law constant k D decreased as the size of substituted group increased in the order methyl < ethyl < propyl, and the k D for n-butanol was similar to that for n-propanol. There was a significant decrease for the high-rank Pocahontas No. 3 and Upper Freeport coals. In contrast, the k D for the Upper Freeport extraction residue was quite large for all alcohols, compared to those of the raw coal, although the pore saturation constant was not greatly affected. The increase in k D for the residue is mainly the result of an increase in the physical diffusion sites (voids) formed by extraction.
We used a molecular mechanics/molecular dynamics computational method to simulate solvent swelling of the pyridine-insoluble (PI) fraction obtained from extraction of Upper Freeport bituminous coal, an Argonne premium coal sample. The effects of benzene and cyclohexane on swelling were examined and compared with previous results for methanol. A model structure for the PI fraction was placed in a periodic boundary cell. As solvent molecules were introduced into the cell, the potential energy of the PI−solvent system decreased and the volume of the cell increased up to the limiting number of solvent molecules9 for benzene and 2 for cyclohexanethat could be added to produce stable structures. The contribution of the electrostatic interaction to the decrease in the total energy of the PI−solvent system was larger than those of the hydrogen bond and van der Waals interactions, regardless of the solvent used. Swelling ratios estimated from the ratio of the weight increase with the number of the solvent molecules introduced were in good agreement with the ratio determined experimentally from sorption data, and were much lower than ratios obtained from volumetric swelling measurements.
A differential scanning calorimetry (DSC) study on the extraction residues of coals giving different extraction yields (which were prepared by changing the solvent composition of a carbon disulfide-N-methyl-2-pyrrolidinone mixed solvent extraction) was carried out. For the residues from Upper Freeport coal (APCS-1) with extraction yields lower than 30 wt % (daf), an endothermic peak similar to that given by the raw coal was observed around 350°C. This endothermic peak disappeared on the second and third scans, indicating that the peak is due to irreversible structural changes in coals. For the residues from the high extraction yield experiments, the peak was not observed up to 400°C, even during the first scan. The reason for these endothermic peaks was discussed from the relationship among the extraction, swelling, and structural changes of coals.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.