Swelling and dissolution of the macromolecular structure of bituminous coals

Peppas, Nikolaos A.

doi:10.1016/s0032-3861(97)00031-1

Cited by 6 publications

(5 citation statements)

References 5 publications

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“…In all of the cases the transport mechanism of pyridine might be considered as anomalous (non-Fickian) transport. The n values measured in the present work are very close to Fickian transport mechanism boundaries since the non-Fickian diffusion coefficients in the literature usually are in the range of 0.6−1.0, ,,, therefore it will not be erroneous to claim that the diffusion of pyridine in a low rank coal like Elbistan lignite (53.0% C) was with a process somewhere between Fickian and relaxation controlled as discussed by Ritger and Peppas …”

Section: Resultssupporting

confidence: 80%

Diffusion of Solvents in Coals: 1. Measurement of Diffusion Coefficients of Pyridine in Elbistan Lignite

Seferinoğlu

Yürüm

2000

Energy Fuels

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The aim of the present report is to measure the diffusion coefficients at temperatures about 20-27 °C, the activation energies of diffusion, and to determine the type of transport mechanism of diffusion of pyridine in macromolecular structure of Turkish Elbistan lignite (C: 53.0 wt %, dmmf). The raw coal sample was demineralized with HCl and HF by standard methods. The raw and demineralized coal samples were extracted with pyridine. Pyridine uptake of the coal samples was recorded at temperatures 20-27 °C in an adiabatic setup until a constant weight was attained. The extent of swelling of original and treated coal samples in pyridine were measured. Pyridine extraction created a fraction of enlarged particle size due to irreversible solvent swelling. The diffusion coefficients were measured from the slope of graphs of M t /M ∞ versus t 1/2 . The diffusion of pyridine in the raw coal seemed to be less, compared to those of the treated coal samples. Extraction of the raw coal with pyridine extended the pyridine diffusion in the coal very little. The formation of new carboxylic acid groups in acid-washed samples enhanced diffusion of pyridine. In all of the samples the diffusion constants increased linearly with an increase in the temperature. The greater diffusion coefficients are encountered with the coal samples which swelled more in pyridine. It seemed that the diffusion coefficients increased with swelling and acid washings as a result of structural variations decreasing the activation energy of diffusion of the solvent to the coal. The transport mechanism of pyridine in the macromolecular coal network of Elbistan lignite was not relaxation controlled. The diffusion of pyridine in the low rank Elbistan lignite obeyed generally Fickian mechanism or an intermediate case of Fickian-anomalous mechanism.

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Section: Resultssupporting

confidence: 80%

Diffusion of Solvents in Coals: 1. Measurement of Diffusion Coefficients of Pyridine in Elbistan Lignite

Seferinoğlu

Yürüm

2000

Energy Fuels

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“…The diffusion exponents, n , were calculated to be between 0.58 and 1.00 in all of the experiments done at all temperatures, indicating an anomalous diffusion mechanism. The anomalous coefficients of diffusion in the literature usually are in the range of 0.6−1.0. ,− Although the literature is similar to our results, it is clear that those different techniques, models, and assumptions (crystal shape and size) may strongly affect the results.…”

Section: Resultssupporting

confidence: 79%

Diffusion of Volatile Organic Chemicals in Porous Media. 2. Alcohol/Templated Porous Carbon Systems

2006

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The aim of the present report was to measure the diffusion coefficients, modes of transport, and activation energies of some alcohols into templated porous carbons. Diffusion coefficients and activation energies of methanol, ethanol, n-propanol, and n-butanol into the templated porous carbons were measured, and the modes of transport of alcohols was determined at 24-28 °C. As the molecular weight of the alcohols increased, diffusion coefficients decreased and activation energy for diffusion increased. The diffusion constants increased linearly with an increase in the temperature. The diffusion of alcohols in the porous carbons obeyed the anomalous transport mechanism. With increasing molecular weight of the volatile alcohols, the activation energies also increased.

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“…The tendency of the changes in tgd parameter in the graphs suggests that both additives cause a decrease in the maximum of dielectric losses corresponding to the dielectric glass-rubber transition and shift this maximum towards lower temperatures in comparison to the data for coals pyrolyzed without additives. This points to the plasticizing effect of the two additives on organic material of the investigated coals during carbonization [21,26]. Since plasticized coals have a greater conformation mobility of fragments of macromolecules, the change in their orientation will be facilitated in an alternating electric field.…”

Section: 2mentioning

confidence: 87%

The influence of addition of coal tar pitch (CTP) and expired pharmaceuticals (EP) on properties and composition of pyrolysis products for lower and higher rank coals

Zubkova

Czaplicka

Puchala

2016

Fuel

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Swelling and dissolution of the macromolecular structure of bituminous coals

Cited by 6 publications

References 5 publications

Diffusion of Solvents in Coals: 1. Measurement of Diffusion Coefficients of Pyridine in Elbistan Lignite

Diffusion of Solvents in Coals: 1. Measurement of Diffusion Coefficients of Pyridine in Elbistan Lignite

Diffusion of Volatile Organic Chemicals in Porous Media. 2. Alcohol/Templated Porous Carbon Systems

The influence of addition of coal tar pitch (CTP) and expired pharmaceuticals (EP) on properties and composition of pyrolysis products for lower and higher rank coals

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