Original preasphaltenes and asphaltenes in coals |
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| Affiliation: | 1. The Key Lab of Fuel Cell Technology of Guangdong Province, School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510640, China;2. State Key Laboratory of Photocatalysis on Energy and Environment, Fuzhou University, Fuzhou 350002, China;1. School of Chemistry and Pharmaceutical Engineering, Sichuan University of Science & Engineering, Zigong 643000, PR China;2. School of Pharmacy, Guangdong Medical University, Dongguan, 523808, PR China;3. Department of Chemistry, Faculty of Science, University of Lucknow, Lucknow 226 007, India;4. Department of Chemistry, University of Malaya, 50603 Kuala Lumpur, Malaysia |
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| Abstract: | The preasphaltene (PA) and asphaltene (A) fractions from untreated coal show a direct relationship of PA/A (w/w) to the carbon content of coal. Their thermal stability was investigated by in-situ pyrolysis FTIR, and the results show that PA has higher thermal stability than A. By means of a vacuum FTIR method, five types of hydrogen bonds formed by hydroxyl groups were clearly observed in PA and A, i.e., OH-π, self-associated OH, OH–ether oxygen, cyclic OH groups, and OH–N. The self-associated OH and OH–ether oxygen are the two main hydrogen bonds. The insolubility of PA in benzene and A in hexane is determined by the hydrogen bond strengths of the acid/base fraction but is not strongly related to their structural parameters and molecular weight. The acid/base associated strength of preasphaltenes and asphaltenes is estimated to be within the following ranges, asphaltenes, <5.15 kJ/mol; preasphaltenes, 5.15–30.9 kJ/mol. |
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