High-temperature Coal Tar Research Articles

Deep hydrogenation of coal tar over a Ni/ZSM-5 catalyst

We have developed a Ni/ZSM-5 catalyst and utilised it to completely hydrogenate a series of condensed arenes, including naphthalene, anthracene and phenanthrene, under relatively mild conditions. The yields of decalin, perhydroanthracene and perhydrophenanthrene reached 100%, 98.8% and 25.8%, respectively. By analyzing the isomer distribution of the perhydroarenes, we proposed a mechanism of biatomic hydrogen transfer, which was further proven via the hydrogenation of 9,10-diphenylanthracene. Through hydrotreatment over the Ni/ZSM-5 catalyst, both high-temperature coal tar rich in condensed arenes and low-temperature coal tar mixing arenes with alkanes were greatly upgraded. The majority of arenes in the coal tars were deeply and even completely hydrogenated, which may open up a route for further processing and application of coal tar as clean fuels.

The Isolation of Condensed Aromatics from a High-temperature Coal Tar

A high-temperature coal tar collected from Xuzhou Coking Plant, Saint-Gobain Pipelines (Xuzhou) Co., Ltd. was exhaustively extracted with petroleum ether (PE). The extract was sequentially eluted with PE and PE/carbon disulfide mixed solvent with PE volume contents of 90, 80, 60, 50, and 40% to afford eluates 1 to 6 (E 1 to E 6), respectively. The eluates were analyzed with gas chromatography/mass spectrometer. In total, 12 condensed arenes with 3 to 6 rings and 14 heteroatomic condensed aromatics with 2 to 4 rings were detected in E 4 to E 6.

Separation of acearylenes from high-temperature coal tar

High-temperature coal tar was extracted with petroleum ether (PE) under ultrasonic irradiation and the extracts were analyzed with gas chromatograph/mass spectrometer. The acearylene fractions including acenaphthylene, aceanthrylene and cyclopentapyrene were enriched together and named E, which was then transferred to a cartridge in Isolera-One flash chromatography. Three groups of compounds were eluted out with ethyl acetate/PE mixed solvent (volume ratio 1:9) and named E1, E2 and E3 according to their main components. Acenaphthylene accounted for 78.2% in E1, aceanthrylene 71.6% in E2 and cyclopentapyrene 75.9% in E3, respectively. The three groups of acearylenes were purified by Sephadex LH-20 column chromatography with ethanol/cyclohexane mixed solvent (volume ratio 1:4), and then confirmed with nuclear magnetic resonance spectrometer. This method indicates that flash chromatography has a good effect on separating the compounds with a similar structure after extraction under ultrasonic irradiation.

Microstructure, Properties and Lignin-Based Modification of Wood–Ceramics from Rice Husk and Coal Tar Pitch

Wood–Ceramics are prepared from a shaped mixture of rice husk and high-temperature coal tar pitch by pyrolysis at different temperatures. Subsequently, the wood–ceramics are modified by pyrolysis of different mixture precursors with adding lignin. The effect of pyrolysis temperature, lignin content and lignin types on the microstructure, yield, volume shrinkage, open porosity ratio and bending strength of the wood–ceramics is discussed, respectively. The results show that the microstructure, volume shrinkage ratio, and bending strength of wood–ceramics are significantly dependent on the pyrolysis temperature, lignin content and types. When the pyrolysis temperature increases from 500 to 1200 °C, the (002) crystal planes peaks of the wood–ceramics move to a higher diffraction angle and the intensity of these peaks increase. The volume shrinkage ratio and bending strength of the wood–ceramics increase from 41.2 to 55.5 % and 10.2 to 31.2 MPa, respectively. Moreover, the open porosity ratio first decreases from 35.6 to 26.2 %, and then increases to 30.1 %. The enzymatic hydrolysis lignin (EHL) plays an important role in improving the order and graphitization, porous content and open porosity of the EHL-modified wood–ceramics, whereas the lignosulfonate causes the bending strength of the lignosulfonate-modified wood–ceramics to decrease.

Separation of arenols from a high-temperature coal tar

A high-temperature coal tar collected from Xuzhou Coking Plant, Saint-Gobain Pipelines (Xuzhou) Co., Ltd. was exhaustively extracted with petroleum ether (PE). The extract was sequentially eluted through silica gel with PE and PE/ethyl acetate (EA) mixed solvents (volume ratio 2:1) to afford two eluted fractions. The extract and eluted fractions were analyzed with gas chromatography/mass spectrometry. In total, 14 arenols were detected, including phenol, cresols, xylenols, fluorenols, phenanthren-3-ol and pyren-1-ol.

Preparation of Superior Coal-tar Pitch from a High-Temperature Coal Tar by Solvent Extraction

A high-temperature coal tar was sequentially extracted in a batch extraction system with petroleum ether, methanol, acetone, carbon disulfide, and isometric acetone/carbon disulfide mixed solvent to afford extracts 1 to 5 (E1 to E5). All the extracts were analyzed with gas chromatography/mass spectrometry. As the heaviest extract, E5 mainly consists of condensed arenes with five or more rings according to gas chromatography/mass spectrometry analysis. Lighter components were removed from E5 by ultrasonic extraction with petroleum ether and subsequent rotary distillation in a vacuum up to 300°C. The lighter components-free E5 proved to be a high quality coal-tar pitch by analysis with an XP-203E hot stage polarizing microscope.

Supercritical fluid extraction and fractionation of high-temperature coal tar

The high-temperature coal tar sample was separated into 10 narrow oil fractions and one solid-phase pitch product by supercritical fluid extraction and fractionation using n-pentane as solvent at 220°C and pressure from 5 to 15 MPa. Results show that the accumulative yields increase with the extract pressure especially at the lower pressures, and the yield increase rate decrease gradually. The total yield of the oil extract is 78.36%, and the raffinate pitch yield is 21.64%, which is far below that of the conventional distillation. Elemental analysis and chromatograph-mass spectrometer analysis show that with the increase of the extraction pressure, the atomic ratio of carbon to hydrogen, the average ring numbers, as well as the average molecular weight of narrow oil fractions also increase gradually.

Experimental investigation of high-temperature coal tar upgrading in supercritical water

The upgrading of high-temperature coal tar in supercritical water (SCW) was investigated using an autoclave reactor. The effects of temperature (673–753 K), pressure (24–38 MPa) and residence time (1–80 min) on product distribution were studied. The yields and characteristics of products in SCW were compared with those obtained in N 2. In order to study the reaction mechanism of coal tar upgrading, the experiments of model compounds were carried out in SCW at 673 K and 34 MPa for 20 min. The results indicate that the asphaltene conversion and the maltene yield are significantly higher in SCW. The H/C atom ratios of oil obtained in SCW are higher than those obtained in N 2. More valuable aromatic compounds such as naphthalene, fluorene and anthracene are obtained in SCW. The results of model compounds suggest that water in SCW could participate in coal tar upgrading and promote the formation of light products.

Examination of soil contaminated by coal-liquids by size exclusion chromatography in 1-methyl-2-pyrrolidinone solution to evaluate interference from humic and fulvic acids and extracts from peat

Soil from a redundant coke oven site has been examined by extraction of soluble materials using 1-methyl-2-pyrrolidinone (NMP) followed by size exclusion chromatography (SEC) of the extracted material. The extracted material was found to closely resemble a high temperature coal tar pitch. Standard humic and fulvic acids were also examined since these materials are very soluble in NMP and would be extracted with pitch if present in the soil. Humic substances derived from peat samples and NMP-extracts of peats were also examined. The results show that the humic and fulvic substances were not extracted directly by NMP from peats. They were extracted using caustic soda solution and were different from the peat extracts in NMP. These results indicate that humic and fulvic acids were soluble in NMP in the protonated polyelectrolyte form but not in the original native polyelectrolyte form. The extraction of soil using NMP followed by SEC appears to be a promising method for identifying contamination by coal-based industries.

Characterization of high-temperature coal tar and supercritical-water extracts of coal by laser desorption ionization-mass spectrometry

A sample of high-temperature coal tar and the coal liquids derived from supercritical water extraction catalyzed by Ca(OH) 2 were examined in their molecular mass distributions, using laser desorption ionization-mass spectrometry. The main peaks observed in both the high-temperature coal tar and the supercritical-water extracts were located at m/z 200–400. Trace signals were observed at the molecular masses up to 15,000 Da for the high-temperature coal tar. Many polycyclic aromatic hydrocarbons (e.g., pyrene, benzofluorene, chrysene and coronene) without lateral groups, were presumably responsible for the intense massed peaks in the high-temperature coal tar. None of these compounds were found in the coal extracts; the components in the coal extracts were found to be rich in hydroxyl and alkyl sides. The results indicated that the hydrolysis of ether bonds is important in the cleavage of the macromolecular structure of low-rank coals to tarry components, under the catalytic effect of Ca(OH) 2 in supercritical water. Less nitrogen-containing aromatics were found in the coal extracts.

Development of Mesophase from a Low-Temperature Coal Tar Pitch

In this study, a low-temperature coal tar pitch (CTP1) was subjected to carbonization in order to study the formation, growth, and development of mesophase achieved under different conditions. The results were compared to those obtained with a petroleum pitch (PP) and a conventional high-temperature coal tar pitch (CTP2). CTP1 was converted to mesophase at a considerably lower temperature, and also mesophase develops and coalesces at a markedly higher rate for this pitch. Volatile matter removal is a key factor in mesophase formation, but chemical composition also plays an important role, with substituted cata-condensed compounds constituting very reactive components in terms of anisotropic material development. More specifically, the oxygenated functional groups and aliphatic substituents facilitate the growth of mesophase. In particular, the high concentration of phenolic compounds present in CTP1 seems to contribute to the fast coalescence of mesophase spheres. The effect of several additives was also ...

A Comparative Tg-Ms Study of the Carbonization Behavior of Different Pitches

The purpose of this work was to study the formation of mesophase spherules from a low-temperature coal tar pitch under carbonization conditions. For comparison, the carbonization of a high-temperature coal tar pitch and a petroleum pitch were also considered. Different operating conditions during the carbonization process were used in an attempt to cover different degrees of mesophase formation and development for each pitch. The parent pitches and the semicokes thus obtained were analyzed by elemental analysis, optical microscopy, and Fourier transform infrared spectroscopy (FT-IR). More significantly, the samples were subjected to thermal decomposition under well-controlled operating conditions from room temperature to 850 °C in a thermogravimetric analyzer (TG). The use of a mass spectrometer linked to the TG (TG-MS) provides additional data about the devolatilization process, yielding information about the evolution of different volatile products and about possible chemical reactions occurring during thermal decomposition. Thus an insight into the process of mesophase formation is obtained. The results from FT-IR, elemental analysis, and the TG-MS tests were compared with the different extents of mesophase formation, checked by optical microscopy. According to the results, several stages can be distinguished as temperature increases in the carbonization process of the pitches. In the low-temperature coal tar pitch, the devolatilization of light components, especially phenols, accounts for the most significant weight loss. Moreover, cross-linking contributes greatly to the formation and development of mesophase, resulting in the predominance of bulk mesophase in a relatively short time in the case of the low-temperature coal tar pitch.

97/02658 Compositional studies of high-temperature coal tar by g.c.-FT-i.r. analysis of middle oil fractions

97/02658 Compositional studies of high-temperature coal tar by g.c.-FT-i.r. analysis of middle oil fractions

97/01791 Hydrogen transfer from Tetralin and Decalin to high-temperature coal tars. Relation with carbon deposit formation

97/01791 Hydrogen transfer from Tetralin and Decalin to high-temperature coal tars. Relation with carbon deposit formation

Compositional studies of high-temperature coal tar by g.c.-FT-i.r. analysis of middle oil fractions

Capillary gas chromatography-Fourier transform infrared spectrometry-gas chromatography retention indices (g.c.-FT-i.r.-RI), combined with slope factors for the relation between retention indices and boiling points for homologous series, enables the composition of middle oil fractions in high-temperature coal tar to be determined. The identification of a component can be confirmed by its g.c. retention index and a computerized search of spectral libraries. More than 41, 53, 64 and 60 compounds were isolated and identified in middle oil fractions F 3, F 4, F 5 and F 6 respectively. There is an obvious immediate application in tar distillation processing and pollution monitoring where such compounds may be present.

97/01186 Hydrogen transfer from Tetralin and Decalin to high-temperature coal tars. Relation with carbon deposit formation Pajak, J. et al. Fuel Process. Technol., 1996, 48, (1), 73–81

97/01186 Hydrogen transfer from Tetralin and Decalin to high-temperature coal tars. Relation with carbon deposit formation Pajak, J. et al. Fuel Process. Technol., 1996, 48, (1), 73–81

96/05650 Composition studies of high-temperature coal tar by capillary gas chromatography/Fourier transform infra-red — Analysis of middle oil fraction

96/05650 Composition studies of high-temperature coal tar by capillary gas chromatography/Fourier transform infra-red — Analysis of middle oil fraction

Hydrogen transfer from tetralin and decalin to high-temperature coal tars. Relation with carbon deposit formation

Studies of pyrolysis of a coal charge containing various quantities of water from 0.8 to 15 wt.% in a two-stage reactor were performed. The rate of formation of solid carbon deposits was followed and some properties of high-temperature tars were investigated. These tars differ in elemental composition and hexane solubility. Hydrogen acceptor abilities were evaluated by reaction with tetralin at 320°C and with decalin at 400°C. Hydrogen transfer from decalin to several model organic compounds was also studied. The rate of carbon deposit formation and hydrogen acceptor abilities of tars are different for various quantities of water in the starting coal charge. The relation between the hydrogen transfer properties of tars expressed as the ratio of decalin hydrogen transfer (DHT) to tetralin hydrogen transfer (THT) and the rate of carbon deposit formation seems to indicate the importance of hydrogen transfer during secondary pyrolysis.

95/05908 Analysis of extract of high-temperature coal tar by combined capillary gas chromatography-mass spectrometry

95/05908 Analysis of extract of high-temperature coal tar by combined capillary gas chromatography-mass spectrometry

Identification of large molecular mass material in high temperature coal tars and pitches by laser desorption mass spectroscopy

Molecular masses of up to 12 000 Da have been identified by laser desorption mass spectroscopy (l.d.-m.s.) in a number of coal tars and extracts. Observed molecular masses were greater than any hitherto detected in coal-derived liquids; fractions of high temperature coke oven tars have been used for verification of initial findings. Low molecular mass materials have been analysed using similar experimental procedures, to confirm the absence of laser or other apparatus derived high molecular mass clusters. Spectra extending to 12 000 Da show an envelope between 1000 and 3000 Da and a low molecular mass envelope between 12 and 400 Da, the latter apparently indicating the presence of carbon clusters. At high laser power densities, the 1000 to 3000 Da envelope was observed to lose intensity, with parallel gain in intensity of the low mass carbon cluster envelope, suggesting increased breakdown of substrate molecules under increasing laser power density. Comparisons with results from g.c.-m.s. and probe m.s. are presented, showing masses up to 600 Da. Limited structural information about the large molecular mass materials can be inferred from the present results, suggesting the presence of small aromatic groups with mass differences corresponding to methyl groups, ethylene bridges and benzo groups.