Pyridine Insolubles Research Articles

Molecular dynamic simulation on the oxidation process of coal tar pitch

Molecular dynamic (MD) simulations based on the reactive force field (ReaxFF) were successfully used for the study of coal tar pitch (CTP) oxidation process under medium temperature. Three CTP components were divided into three fractions: pitch acetone solubles (PAS), pitch pyridine soluble-acetone insolubles (PPS), and pitch pyridine insolubles (PPI). A series of ReaxFF MD simulations were conducted to study the influence of temperature and oxygen content on CTP oxidation mechanism. The results demonstrate that the oxidation process is initiated by generation of CO bonds and OO bonds following intramolecular hydrogen transfer. The phenoxyl free radical which is initially formed by the cleavage of hydroxyl and the oxidization of benzene ring is an important intermediate product, it plays a key role in the formulation of H2O, CO2 and glyoxal, and it also promotes the combination of two small molecules. The cleavage of CH bonds is more likely to happen when temperature is larger than 650 K. The PPI fraction is more stable compared with PAS and PPS components. The major reaction pathways are analyzed, and it’s observed that the reaction pathways are able to reproduce and explain the experimental findings in the CTP oxidation process.

Optimization of 1H and 13C NMR Methods for Structural Characterization of Acetone and Pyridine Soluble/Insoluble Fractions of a Coal Tar Pitch

1H and 13C high-resolution liquid-state NMR methods were used for the quantitative characterization of different molecular weight fractions of a coal tar pitch (CTP). Three fractions were studied: pitch acetone solubles (PAS), pitch pyridine soluble-acetone insolubles (PPS), and pitch pyridine insolubles (PPI). Standard liquid-state NMR methods were modified and calibrated for use with undeuterated quinoline or undeuterated 1-methyl-2-pyrrolidinone (NMP) as the solvent. This made it possible to calculate the average structural parameters for the higher molecular weight (MW) fractions of the coal tar pitch. Quantitative comparisons of structural differences between the solubility-separated fractions of the pitch are reported. The aromaticity and the average number of aromatic rings per polynuclear aromatic structure were both found to decrease with increasing solubility. Similarly, pericondensed and all other quaternary carbon species were found to decrease with increasing solubility. This suggests that “c...

連続装置によるビクトリア褐炭の液化 （ＩＶ） 褐炭液化反応に及ぼす予熱条件の影響

The effect of preheating conditions on the liquefaction reaction of Victorian brown coal (Yallourn) was investigated using a process development unit (PDU) with three stirred tank reactors and three preheaters connected in series. Four kinds of solvents (RS, RS +CLB, RS+HDAO and RS+CLB +HDAO) were used for liquefaction to examine the relationship between the solvent properties and the effect of the preheating conditions. RS, CLB, HDAO were the recycled solvent fraction (b. p.180-420°C), heavy liquefaction product derived from the brown coal (coal liquid bot-tom, b. p.>420°C) and coal liquid product further hydrogenated over Ni-Mo catalyst (b. p.<250°C), respectively. For all experiments, the liquefaction was carried out in the presence of iron-sulfur catalyst (Fe2O3, S/Fe atomic ratio 1.2) under the conditions of temperature 450°C and pressure 14.7 MPa.When the feed slurry was preheated up to 410°C for- 2 min. with hydrogen gas of 10 wt. % on daf coal, the distillate yield (b.p.<420°C) decreased 5-13 wt.% on daf coal for all kinds of the solvent in comparison with the case where reaction at the pre-heating stage was negligible. The decrease in the distillate yield resulted from the sup-pression of the conversion of the heavy fraction (CLB) into the solvent fraction (180-420°C). At the preheating stage, CO2 and H2O evolved and the coal of 20-30 wt % converted to preasphaltenes (benzene insoluble-pyridine solubles). The oxygen-contain-ing functional groups decomposed rapidly at more than 350°C, resulting in the formation of many radicals in the coal (Plorg.). Since the greater part of the coal remained as pyridine insolubles (Plorg.), the retrogressive reaction caused by the radicals in the Plorg. was considered to reduce the conversion of the heavy fraction into the distillate at the liquefaction stage.Based on these results, it is concluded that the usual preheating conditions of the liquefaction process decreased the liquedaction performance. This indicates that the distillate yield increases if the retrogressive reaction at the preheating stage is suppres-sed by controlling the preheating conditions and solvent quality such as hydrogen donor ability and catalyst activity.

Choice of Extraction Voltage and Matrix in the Matrix-assisted Laser Desorption/Ionization Time-of-flight Mass Spectrometry of Coal Tar Pitch — Pyridine Insolubles

Variations in molecular mass distributions observed by matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectrometry as a function of changes in the ion accelerating voltage and composition of the matrix have been investigated, using the pyridine-insoluble fraction of a coal tar pitch. With increasing ion extraction voltages (10, 20 and 30 kV) and in the absence of added matrix, spectra clearly showed increases in intensity, particularly at higher masses. The use of higher ion extraction voltages may be considered as providing a more complete inventory of ionized species, apparently significantly enhancing the kinetic energy imparted to larger molecular weight materials. Magnitudes of molecular masses at maximum ion intensity observed using a set of different matrices may be ordered as follows: m/z 1500 [dimethoxy-4-hydroxycinnamic (sinapinic) acid], m/z 1400 (2,5-dihydroxybenzoic acid), m/z 900 [2-(4-hydroxyphenylazo)-benzoic acid], m/z 900 (α-cyano-3-hydroxycinnamic acid), m/z 300 (9-anthracenecarboxylic acid) and m/z 300 (no matrix and a sample loading comparable with the with-matrix experiments). Maximum ion intensities, in the absence of matrix, were found at values which varied from about 300 m/z up to about m/z 1500 as sample loading varied from very low (i.e. suitable for with-matrix operation) up to a visibly black spot. In the absence of a quantitatively based criterion for distinguishing between signal and instrument noise at high mass, accurate high mass limits were not available. However, in each case, ion signals could clearly be observed at values greater than m/z 100 000. The present MALDI spectra do not necessarily show the highest molecular mass materials present in the sample. In view of the observed changes in the spectra with ion extraction voltage and matrix composition, it seems conceivable that higher voltages and/or specific matrices, other than those used in the study, may lead to the detection of larger molecules. © 1997 John Wiley & Sons, Ltd.

95/00229 Initial stage liquefaction of coal in the process of rising temperature, III. 13C-NMR spectra of pyridine insolubles

95/00229 Initial stage liquefaction of coal in the process of rising temperature, III. 13C-NMR spectra of pyridine insolubles

昇温過程における液化初期反応 ＩＩＩ ピリジン不溶分の｀１３´Ｃ‐ＮＭＲスペクトル

In the previous paper, the initial stage liquefaction of several coals was examined by using a pipe reactor which was designed to recover six heat-treated samples in the heating process up to ca. 450°C and the yield of pyridine insolubles (PI) of the heat-treated slurry was shown to depend on the coal rank and decrease to less than % in some coals. In this paper, solid-state 13C-NMR spectroscopy of PI is applied to examine the mechanism of the initial stage liquefaction of Lingan bituminous coal, Illinois and Wandoan subbituminous coals and Wabamun lignite. The followings are derived from the analysis of NMR spectra. The spectra of PI samples of Lingan coal heat-treated up to 423°C are almost the same and those of Illinois and Wandoan coals are scarcely changed up to 372°C and 409°C, respectively. It is therefore considered that PS (pyridine solubles) of each coal is composed of the compounds with almost the same functional group distribution as that of PI of the raw coal. The PI values of the three coals decrease largely at higher temperatures than the above-mentioned as previously presented. The followings are discussed in this temperature range. It is shown in Lingan coal that the compounds relatively rich in aromaticity become PS and the components with relatively low aromaticity remain as PI. In the case of Illinois coal, the small aromatics with side chains such as alkyl groups become PS and the components composed of the relatively large aromatic ring crosslinked by alkyl chains remain as PI. In the case of Wandoan coal, the compounds with the long alkyl chains are changed to PS and the components relatively rich in aromaticity crosslinked by alkyl chains are recovered as PI. Wabamun coal shows a completely different behavior from these three coals, that is, the aliphatic compounds become PS successively with increasing tempera-ture without an abrupt change and the components with high aromaticity remain as PI.

Evidence for the associated structure of bituminous coal

Previous studies have shown that coal swelling is not reversible and highly dependent on coal concentration in a solvent. This rules out the conventional coal structural model of a covalently cross-linked three-dimensional network. Many coal molecules may be physically associated by relatively strong intra- and intermolecular interactions. Coal swelling in selected solvents was examined for fractionated samples of two high volatile C bituminous coals to investigate the role of physical associations in coal structure. The dependence of coal concentration on swelling in tetrahydrofuran and toluene was similar for pyridine soluble and insoluble fractions. Solvent swelling of pyridine solubles was smaller than that of pyridine insolubles. Pyridine extract was mixed with iodine and further fractionated into pyridine soluble and insoluble fractions. The swelling ratio of the pyridine solubles was much smaller than that of the pyridine insolubles. The difference between swelling with toluene and with tetrahydrofuran was larger for pyridine insolubles than for pyridine solubles. All these results indicate that significant portions of coal molecules are not a three-dimensional network, but are physically associated.

昇温過程における液化初期反応 （ＩＩ） 炭種の影響

The initial stage liquefaction of six coals, Estevan, Wabamun, Taiheiyo, Wandoan, Illinois No.6 and Lingan coals, was studied. Heat-treatment of coal and a hydrogenated anthracene oil slurry (1: 3 by weight) was carried out using a pipe reactor which was designed to recover six heat-treated samples at progressively higher temperatures. About 3.4min. were required to raise the temperature from room temperature to around 450°C.Pyridine insolubles, PI, decreased with an increase in temperature in all coals studied. In the cases of Taiheiyo and Illinois No.6 coals, PI values of the sixth samples (445°C) were less than 10%, showing that the initial stage liquefaction reaction of both coals was almost completed. The sixth samples of Wandoan and Lingan coals had small PI values of less than 16%. Estevan and Wabamun coals had PI values of around 45% in the sixth samples.In the cases of Taiheiyo, Wandoan, Illinois No.6 and Lingan coals, the change of viscosity of each slurry with temperature showed a maximum. This maximum is caused by the swelling and disintegration of coal particles with increasing temperature. Estevan and Wabamun coals, which did not have small PI values in the sixth samples, did not show such a maximum.The viscosity and weight-average molecular weight of filtrate increased as the reaction progressed.Hydrogen released from hydrogen donor components in the hydrogenated anthracene oil played an important role in the initial stage of coal liquefaction. Judging from the relation between PI value and the amount of released hydrogen, the coal conversion per unit amount of released hydrogen was found to largely depend on coal rank.

Cokes and graphites produced from anthracene, acridine, and phenazine

The effect of substitution of nitrogen into the 9 position and 9,10 positions of anthracene in place of C-H groups on the kinetics of carbonization to yield pyridine insolubles (PI) and the properties of the cokes and graphites produced have been studied. Acridine and phenazine exhibit higher carbonization rates than does anthracene. Carbonization of each of these heterocyclics leads to lowtemperature cokes exhibiting large flow domain, isochromatic regions and good graphitizability. However, the elimination of nitrogen from the low-temperature cokes upon their calcination does result in the production of cokes and graphites of lower particle densities and higher surface areas. The result is that these carbons have higher reactivities to air and they probably will lead to the production of artifacts of inferior mechanical properties.

The importance of carbonization conditions on the character of phenanthrene coke and its graphitizability

The coking of liquid phenanthrene in a batch reactor was followed by measuring the formation of pyridine insolubles as a function of time over the temperature range 510–570°C. Following an induction period, the disappearance of pyridine solubles is first order, with the rate constants having an activation energy of 65 kcal/mole. This is significantly higher than the activation energy (46 kcal mole ) associated with the rate constants describing the carbonization of the isomer, anthracene. As the rate of carbonization increases, the low-temperature cokes produced decrease in their subsequent graphitizabilities. Further, the reactivity to air of the graphitized carbons is increased.

Carbonization of anthracene in a batch reactor

The coking of liquid anthracene in a batch tubular reactor was followed by measuring the formation of pyridine insolubles and the disappearance of anthracene as a function of time over the temperature range 465–525°C. Conditions, that can affect coking behavior and rates, like partition of the feed between liquid and vapor, agitation of the reactor, and whether the gas pressure in the reactor is autogeneous or imposed are considered. Carbonization primarily involves hydrogen-transfer reactions and condensation (polymerization) of free radicals into larger molecular weight species. Cleavage (cracking) of hydroaromatic species, giving smaller liquid and gas phase molecules, is at a minimum under the conditions used in this study.

昇温過程における石炭の液化初期反応 Ｉ 昇温条件の影響

In order to investigate the initial stage liquefaction of coal in the process of rising temperature, heat-treatment of slurries consisting of wandoan coal and hydrogenated anthracene oil (1: 3 by weight) were carried out under three heating patterns with a pipe reactor which was designed to obtain six samples in the course of heating.Solvent insoluble matters such as toluene insolubles (TI) and pyridine insolubles (PI), viscosities and relative weight average molecular weight to polystyrene of filtrates, 50% mean particle size of unreacted coal and concentrations of hydrogen donor components in filtrates were affected by heating pattern.TI and PI began to decrease at about 300°C and 250°C, respectively. Both decreased steeply above 400°C.Relation between viscosities of heated slurries at room temperature and heating patterns were not observed, but in any case, viscosities of heated slurries increased with an increase in sampling temperature.50% mean particle size of unreacted coal gradually increased up to about 400°C by swelling and decreased above 400°C by disintegration. The disintegration of unreacted coal steeply increased°Ciscosities of filtrates and weight average molecular weight because of solubilization of coal into the vehicle.Concentrations of hydrogen donor components such as dihydrophenanthrene, tetrahydrofluoranthene and dihydropyrene in the filtrates decreased with an decrease in TI and PI, that is, those components contributed effectively to coal liquefaction.

The Dissolution of Heat-treated Acenaphthylene Pitch

Abstract About half of the pyridine insolubles in heat-treated acenaphthylene pitch was dissolved into hydrogenated pitch. Observation with optical and scanning electron microscopes showed that the components dissolved consisted of small mesophase spherules with an optically isotropic texture.

Effect of solvent extraction sequence on the apparent distribution of coal liquid products

Asphaltenes and are terms widely used in coal liquefaction experimentation. They should represent well defined coal fractions which are obtainable by standard, reproducible and accurate methods. However, anyone in this field will immediately realize that there is a variety of methods being used [1--3]. Each method is internally consistent and therefore meaningful to the user, but a comparison of results from different laboratories is very difficult and sometimes meaningless. In our work, we have defined the following solvent extraction fractions: oils = n-pentane solubles asphaltenes = n-pentane insolubles, benzene solubles = benzene insolubles, pyridine solubles pyridine insolubles = unreacted coal This is an extension of petroleum chemistry terminology [4] since petroleum contains only oils and asphaltenes. It is also noted that the use of the term pre-asphaltenes does not necessarily imply that this fraction is formed before asphaltenes, but may actually form from a polymerization of asphaltenes and/or oils. Even with the above solvents, we found it necessary to determine the effect of the solvent extraction sequence. Three techniques were examined as identified below and described in the following section: 1. direct extraction 2. forward sequential extraction 3. reverse sequential extraction