Chemistry / Kimya

Permanent URI for this collectionhttps://hdl.handle.net/11147/4072

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End date: 1999Subject: search.filters.subject.Coal

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  • Article
    Citation - WoS: 39
    Citation - Scopus: 43
    Adsorption of Peo/Ppo Triblock Co-Polymers and Wetting of Coal
    (Elsevier Ltd., 1999) Polat, Hürriyet; Chander, Subhash
    The adsorption characteristics of PEO/PPO/PEO triblock co-polymers on coal were investigated using surface tension and contact angle measurements. Although these surfactants have been widely used as wetting agents, it was observed that they increased the hydrophobicity of coal at concentrations below about 10-6 M. Surface tension studies were carried out to explain the reasons for this behavior. The surface tension versus concentration profiles displayed three distinct regions. In region I, surface tension decreased linearly and monomers were proposed to be the dominant species. This region extended to a surfactant concentration of about 10-6 M. In region II, a transition region between regions I and III, dimers, trimers, etc., were considered to form. In region III, micelles formed and surface tension was independent of concentration. The concentration at which monomers associate to form dimers, etc., is referred to as the critical association concentration (cac). The contact angle of coal increased when concentration was raised from low values to the cac. It decreased when the reagent concentration was above the cac. Finally, at concentrations above the cmc, the wetting of coal was complete and contact angle was zero.
  • Article
    Citation - Scopus: 15
    Estimation of the Average Aromatic Cluster Size Based on Solid-State Nmr Measurement of Coal
    (Japan Institute of Energy, 1999) Kidena, Koh; Murata, Satoru; Artok, Levent; Nomura, Masakatsu
    Measurements of solid-state NMR of eight Argonne Premium Coal Samples were conducted to estimate the average aromatic cluster size in these coals. Firstly, the carbon distribution was obtained from SPE/MAS 13C-NMR. Secondary, 1H-CRAMPS NMR spectra gave the hydrogen aromaticity of coal. Combination use of the hydrogen aromaticity and elemental analysis data could afford the amount of tertiary aromatic carbon. The parameter of χ b, the mole fraction of aromatic bridgehead carbons in all aromatic carbons, could be derived from above NMR data and elemental analysis of coal. χ b is directly correlated to the number of aromatic carbon atoms per aromatic cluster, C. In this study, the value of C varied from 10 (corresponding to the size of naphthalene) for Beulah-Zap and Wyodak coals to 23 (corresponding to the size of coronene) for Pocahontas No. 3 coal.