Masashi Iino

Characterization of the extracts and residues from CS2-N-methyl-2-pyrrolidinone mixed solvent extraction

Abstract The extracts and residues obtained by extraction of five bituminous coals with CS 2 -N-methyl-2-pyrrolidinone mixed solvent (1:1 by volume) were characterized at room temperature. The extraction yields were 31.1–63.0% (daf) and the extracts were fractionated into acetone soluble (AS), acetone insoluble-pyridine soluble (PS) and pyridine insoluble-mixed solvent soluble (MS) fractions. The MS fraction, which was the heaviest fraction examined, had higher values of % oxygen, f a , molecular weight and spin concentration than the corresponding AS and PS fractions, but a similar degree of aromatic condensation. The quantities of volatile matter (daf) in the residues were similar or slightly less than those in the extracts.

Network structure of coals and association behavior of coal-derived materials

The characteristics of two kinds of network structure models, i.e., covalent and non-covalent network models, were given. The applicability of these network models was examined mainly from the amount of solvent–soluble components that originally existed in coal. More than 50% of extraction yields obtained with carbon disulfide–N-methyl-2-pyrrolidinone (CS2–NMP) mixed solvent with an additive for several bituminous coals suggest that the non-covalent network model is better than the covalent one for those coals. But network structures for other coals, which gave a low extraction yield such as lignites, are not clear. Association behaviors of coal-derived materials are also reviewed from their solubility, molecular weight, viscosity, and vapor pressure. Small-angle neutron scattering (SANS) measurements of coal extracts in the solution show the formation of large associates. Interactions responsible for the association of coal-derived materials such as coal extracts and liquefaction products are considered to be hydrogen bonds, π–π interactions between aromatic rings, and electrostatic interactions. No clear evidence for the contribution of charge transfer interactions has been obtained.

Diffuse reflectance spectra in near-i.r. region of coals; a new index for degrees of coalification and carbonization

Abstract The near-i.r. and i.r. spectra of various coals have been measured using a diffuse reflectance method. In the near-i.r. region, anthracite and some bituminous coals were observed to have broad absorption bands whose intensities increased with wavenumber. Brown coals did not show such bands. From the size-effect of coal powders on the diffuse reflectance spectra, the broad absorption bands can be attributed to the real electronic transitions of polycondensed aromatic hydrocarbons. The intensity of the broad absorption band increases with the rank of coalification and degree of carbonization. Since the broad bands change with coal treatments, including solvent extraction and maceral separation, they afford a new measure of the coal study.

Electric conductivity changes of polypyrrole and polythiophene films with heat-treatment

Abstract The electric conductivities of polypyrrole and polythiophene films have been measured as a function of heat-treatment temperature. From room temperature to 150°C, the conductivity of polypyrrole film remained constant. From 150 to 300°C, the conductivity dropped due to the decomposition of polypyrrole and the loss of dopant ion (ClO4−). Above 300°C, the conductivity increased again. Above 750°C, the conductivity was higher than that of the original film due to the formation of carbonaceous materials. The polythiophene film showed a similar tendency to the polypyrrole film. Chemical and spectroscopic methods such as elemental analysis, FT-IR and ESR were employed to determine the origin of the electric conductivity changes.

Effect of mild oxidation of bituminous coals on caking properties

Abstract Changes in caking properties, extraction yield, and coal structure on mild oxidation (at 100 °C) were examined for four caking coals. Fluidity decreased with increase in oxidation time for all coals, while changes in free swelling index (FSI) differed among the coals. FSI for Shin-yubari and Zao Zhuang coals increased during the initial stage of oxidation, suggesting that optimum fluidity was obtained by lowering the high fluidity of such coals. Extraction yields for two PSOC coals, using CS2-N-methyl-2-pyrrolidinone mixed solvent, were constant during oxidation for 22 h, but the fluidity decreased drastically. This indicates that reduction of caking properties by oxidation cannot be explained only by the decrease in extractable low molecular weight substances. The i.r. spectra indicated formation of CO, OH and ether groups accompanied by a slight decrease in aliphatic CH. The e.s.r. measurement suggested not only the formation of cross-linking by oxidation but also the cleavage of cross-linkages for prolonged oxidation.

Fluidity of coal residues after extraction with mixed solvents

Abstract The Gieseler fluidity of coal residues after their extraction with mixed solvents was investigated for four bituminous coals to elucidate the effect of low molecular weight extractable substances on the plasticity of coals. The maximum fluidity was found to decrease with an increase in extraction yield. At a low extraction yield, bulk softening was predominantly affected by the softening behaviour of low molecular weight substances originally present in coal, while the softening of pyrolytic products became dominant at a higher extraction yield. The resolidification temperature and the plastic range also decreased as the extraction yield increased. For a coal containing a higher concentration of extracts, the plastic range tends to increase. Three petroleum pitches were used as model compounds of the extracts. By addition of pitches to the residues of one coal, the maximum fluidity was shown to increase and the maximum fluidity temperature was found to be related to the pitch aromaticity. The role of the extracts in coal fluidity is discussed.

Sorption behaviors of methanol vapor by coal extracts and residues

Abstract Four Argonne coal samples (Pocahontas No.3, Upper Freeport, Illinois No.6, and Beulah-Zap coal) were extracted with a carbon disulfide–N-methyl-2-pyrrolidinone (CS2–NMP) mixed solvent at room temperature. To clarify the nature of the coal–methanol interaction, the mechanism of sorption, and the micropore and bulk structure of each coal fraction, sorption of methanol vapor by the extract fractions and residues was investigated using an automatic vapor adsorption apparatus. The sorption behavior of the residues with the low extraction yields was similar to that of the raw coals, regardless of rank. In contrast, the sorption for residues with the high extraction yields greatly increased compared to the raw coals, which suggests that more microporosity was formed by the extraction. For all fractions examined, experimental values were fit by the Langmuir–Henry dual-mode sorption model, which suggests that methanol sorption by the coal fractions can be explained by the adsorption on the surface described by a Langmuir isotherm and penetration (dissolution) into the bulk described by Henrys law. The Henrys dissolution constant, kD, was found to be similar in magnitude for both the extract fractions and residue from Upper Freeport coal, in agreement with the results of methanol swelling.

Irreversible structural changes in coals during heating

A differential scanning calorimetry (DSC) study on the extraction residues of coals giving different extraction yields (which were prepared by changing the solvent composition of a carbon disulfide-N-methyl-2-pyrrolidinone mixed solvent extraction) was carried out. For the residues from Upper Freeport coal (APCS-1) with extraction yields lower than 30 wt % (daf), an endothermic peak similar to that given by the raw coal was observed around 350 °C. This endothermic peak disappeared on the second and third scans, indicating that the peak is due to irreversible structural changes in coals. For the residues from the high extraction yield experiments, the peak was not observed up to 400 °C, even during the first scan. The reason for these endothermic peaks was discussed from the relationship among the extraction, swelling, and structural changes of coals.

Effect of oxidation on caking properties: oxidation of extract and residue

Abstract The extract (E) and residue (R) from Lower Kittanning bituminous coal were oxidized separately at 100 °C, and the caking properties for the mixtures of R + E , R ox + E , R + E ox and R ox + E ox (R ox and E ox represent oxidized R and E) were measured. It was observed that oxidation of the residue and the extract decreased fluidity and swelling ability, but a stronger effect was seen for oxidation of the residue. This is because the residue was more susceptible to oxidation, and the formation of low molecular weight substances from the residue enhances fluidity. However, bulk softening was affected by oxidation of the extract, suggesting that bulk softening is mainly due to the physical transformation of the extractable substances. From the FT-i.r. measurement, a more prominent increase of hydroxyl and carbonyl groups caused by oxidation was observed for the residue, while the loss of aliphatic and aromatic hydrogens was more significant in the extract.

Effect of lighter constituents on the solubility of heavy constituents of coals

Zao Zhuang, Shin-Yubari and Upper Freeport bituminous coals were extracted with a carbon disulfide/N-methyl-2-pyrrolidinone (CS2/NMP) mixed solvent at room temperature. Extracts were further fractionated with acetone to give acetone-soluble (AS) and acetone-insoluble (AI) fractions; the AI fraction was further extracted with pyridine to give pyridine-soluble (PS) and pyridine insoluble (PI) fractions. Despite the fact that they were part of the whole solute in the original extract, the PI fractions from all coals were only partially soluble in the mixed solvent. Combination of the AS and PS, which are lighter fractions than the PI, from the parent coal with the respective PI fraction greatly enhanced the solubility of PI in the mixed solvent. In addition, the solubility in mixed solvent of the PI fraction from Zao Zhuang coal was increased by addition of AS and PS fractions from Miike, Shin-Yubari, and Illinois No. 6 coals; the amount of enhanced solubility in comparison with the solubility of PI alone depended on the coal fraction used, i.e. AS and PS. In general, the enhancement caused by PS fractions was greater than that by AS fractions. The mechanism of solubility enhancement of the heavy constituent (PI fraction) by the addition of lighter constituents (AS and/or PS) is discussed, from the viewpoint of differences in the chemical structures of the constituents, i.e. AS, PS and PI fractions.