Diffusion in coals

Suuberg, Eric M.; Otake, Yoshinobu; Sezen, Y.

doi:10.2172/6781207

Cited by 2 publications

(2 citation statements)

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“…These are covalent bonds, ionic linkages, hydrogen bonds, van der Waals forces, and π−π interactions. Of the five associative interactions hydrogen bonds, one of noncovalent associative interactions, are believed to play a key role to keep the macromolecular structure of low rank coals, − and hence utilization of the low rank coals is significantly affected by the hydrogen bonding. Since a large amount of water is retained in the lower rank coal due to the hydrogen bonds, drying is one of drawbacks for the utilization of the coal.…”

Section: Introductionmentioning

confidence: 99%

Estimation of Hydrogen Bond Distribution in Coal through the Analysis of OH Stretching Bands in Diffuse Reflectance Infrared Spectrum Measured by in-Situ Technique

et al. 2001

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A new method was presented to estimate the strength distribution of hydrogen bonds in coal. The hydrogen bonds include the coal intramolecule hydrogen bonds and coal-water hydrogen bonds formed by hydroxyls in coal. The method analyzes the FTIR spectrum ranging from 2400 to 3700 cm -1 obtained using the in-situ diffuse reflectance IR Fourier transform (DRIFT) technique with neat, undiluted, coal samples. The FTIR spectra during the heat-up of eight coals (seven Argonne premium coals and an Australian brown coal), an ion-exchange resin, and a lignin were measured every 20 °C from room temperature to 300 °C. Each spectrum was divided into six hydrogen-bonded absorption bands by a curve-resolving method, then the amount of hydroxyls contributing to each hydrogen bond was estimated by Beer's law by using different absorptivity for each band. The strength of each hydrogen bond was estimated using a relation presented by Drago et al. that is known as one of the "linear enthalpy-spectroscopic shift relations". Using this analysis method, changes in hydrogen bond distributions (HBD) with increasing temperature were successfully estimated for all the samples examined. By utilizing the HBD the changes in enthalpies associated with the desorption of adsorbed water, the glass transition, and the decomposition of COOH groups were well estimated. Only FTIR spectra measurements were found to be enough to obtain such enthalpies. This greatly simplified the calculation procedure and increased the accuracy of the enthalpies. The validity of the proposed in situ FTIR measurement method and the analysis method for obtaining HBD was well clarified.

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Section: Introductionmentioning

confidence: 99%

Estimation of Hydrogen Bond Distribution in Coal through the Analysis of OH Stretching Bands in Diffuse Reflectance Infrared Spectrum Measured by in-Situ Technique

et al. 2001

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show abstract

“…It is well-known that hydrogen bond, one of noncovalent associative interactions, plays a key role in keeping the macromolecular structure of low-rank coals. − Therefore, utilization of the low-rank coals is significantly affected by the hydrogen bond. Since a large amount of water is retained in the lower-rank coal due to the hydrogen bond, drying is one of drawbacks for the utilization of the coal.…”

Section: Introductionmentioning

confidence: 99%

Estimation of Hydrogen Bond Distributions Formed between Coal and Polar Solvents Using in Situ IR Technique

et al. 2001

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Recently, the authors have presented a new method to estimate the strength distribution of hydrogen bonds (HBD) in coal. The method analyzes the IR spectra ranging from 2400 to 3700 cm-1 that are obtained using an in-situ diffuse reflectance IR Fourier transform (DR) technique with neat, undiluted coal samples. Each spectrum was divided into six hydrogen bonded absorption bands by a curve-resolving method; then the amount of hydroxyls contributing to each hydrogen bond was estimated by Beer's law with different absorptivity for each band. The strength of each hydrogen bond was estimated using a relation presented by Drago et al. that is known as one of the “linear enthalpy-spectroscopic shift relations”. In this paper, the method was applied to estimate the hydrogen bond strength distributions formed between coal and several polar solvents: acetone, ethyl acetate, THF, DMF, and pyridine. The enthalpies accompanying the adsorption or desorption of the solvents, which correspond to the heats of adsorption, were also estimated from the HBDs. Only IR spectra measurements were found to be enough to obtain such enthalpies. This greatly simplified the calculation procedure and increased the accuracy of the enthalpies. The validity of the proposed in situ IR measurement method and the analysis method for obtaining HBD was well clarified by comparing the enthalpies obtained in this work with the heats of adsorption and the hydrogen bond formation enthalpies proposed by Arnett et al.

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Diffusion in coals

Cited by 2 publications

References 0 publications

Estimation of Hydrogen Bond Distribution in Coal through the Analysis of OH Stretching Bands in Diffuse Reflectance Infrared Spectrum Measured by in-Situ Technique

Estimation of Hydrogen Bond Distribution in Coal through the Analysis of OH Stretching Bands in Diffuse Reflectance Infrared Spectrum Measured by in-Situ Technique

Estimation of Hydrogen Bond Distributions Formed between Coal and Polar Solvents Using in Situ IR Technique

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