Coal concentrated solutions were prepared by dissolving pyridine soluble portions of Upper Freeport (UF) and Illinois No. 6 (IL) coals into N-methyl-2-pyrrolidinone (NMP). Gellike materials, that are not macroscopically phase separated, were produced at concentrations ranged between 30 and 50 wt % coal extract. Viscoelastic properties of the materials were characterized by means of controlled strain oscillatory rheometry at temperatures ranging from 223 to 273 K. An application of the time-temperature superposition rule allowed construction of master curves at reduced temperatures empirically, yielding data for the frequency dependencies of the modulus over a wide range, i.e., 10-6-106 Hz. The moduli of the viscoelastic materials formed from IL were larger than those from UF at equivalent temperature and frequency, principally because of the larger number of hydroxyl groups in IL extract than UF extracts. Effects of hydrogen bonds and aromatic-aromatic interactions on the viscoelastic properties were examined through O-methylation and hydrogenation of the extracts. Both modifications reduced the moduli of the materials, but affected the viscoelastic properties in different ways. Effect of hydrogen bonds on the dynamic modulus was more significant at higher frequencies, whereas the effect of aromaticaromatic interactions was more significant at lower frequencies.
All Science Journal Classification (ASJC) codes
- General Chemical Engineering
- Fuel Technology
- Energy Engineering and Power Technology