Effect of different oxidation treatments on the chemical structure and properties of commercial coal tar pitch

Different oxidation treatment was used for the increase of the softening point of a commercial coal tar pitch. H₂SO₄, HNO₃, H₂O₂ and air are selected as treatment reagents. These preliminary investigations show that the oxidation treatment of commercial coal tar pitch with different reagents at 160 °C and heat treatment to 250 °C causes considerable changes in the chemical composition of obtained pitches. This leads to increase of TI and QI fraction, and results in considerable increase in the softening point of the pitches. The yield of modified pitches is considerable in the case of treatment with H₂SO₄, H₂O₂, and HNO₃ and lesser in the case of air blowing. The data obtained also indicate some differences in the composition and softening point of pitches obtained after modification with different reagents. These differences could influence the applicability of the obtained pitches in the various areas of carbon material production.     

Improvement and control of the quality of binder pitch for graphite electrodes

Factors influencing the coke yield and the softening point (SP) of pitches were studied to ascertain procedures for the improvement and control of their quality. The coke yield of pitches from different tar sources is expressed as a linear function of the BI content. Pitches were prepared by distillation under constant operating conditions. The coke yields of pitches, determined by thermogravimetric analysis (TGA), increased with their benzene insoluble (BI) content, which is controlled by reflux heat treatment. Softening point increased with the nitrogen content as well as BI content. Therefore, increasing the BI content and decreasing the nitrogen content increases coke yield without any change in the softening point of binder pitches for graphite electrodes.     

The effect of primary quinoline-insoluble material on the formation of secondary quinoline-insolubles in electrode binder pitches

The influence of primary quinoline-insoluble material (QI) on the subsequent formation of secondary QI has been investigated using two pitches derived from the same tar feedstock. One was prepared by heat treating the pitch without prior modification of the tar, and the other after nearly all the primary QI had been removed from the tar by filtration. No significant differences were observed between the two pitches in terms of the rate of secondary QI formation or softening point increase.     

针状焦用煤沥青的调制研究

介绍了煤系针状焦用原料的要求及调制方法,讨论了2种工业上原料精制的工艺,并重点阐述了国内外对原料的组分、反应性、软化点、流变性、残炭值和结晶度等方面的改性研究进展。在此基础上对煤沥青调制研究在国内的发展前景进行了展望。     

Rheological characteristics of coal tar and petroleum pitches with and without additives

An extensive study of rheological characteristics of coal tar and petroleum pitches with and without additives, namely, petroleum coke, natural graphite and carbon black has been made. It is found that all pitches, pure or mixed with a carbon additive are not Newtonian as reported in the literature, but behave Theologically as Bingham plastics with certain yield stress and plastic viscosity at all temperatures of measurement between 85–180°C. The yield stress and plastic viscosity both decrease with increase in temperature of the pitch. A pure petroleum pitch having the same softening point as that of a coal tar pitch is found to have a lower viscosity compared to that of the latter at all temperatures of measurement. This suggests that the criterion of softening point as a measure of suitability of a coal tar pitch binder in the manufacture of artificial carbon is not sufficient for petroleum pitches. Addition of ten parts of carbon black by weight of pitch results in a considerable decrease in viscosity change with temperature of the coal tar pitch compared to almost insignificant change in the case of the petroleum pitch of the same softening point. However, the addition of petroleum coke or natural graphite makes the pitch more viscous but does not change the temperature dependence of viscosity of either of the two types of pitches. The implications are discussed.     

Preparation of carbon fibre precursors from the pyrolysis and copyrolysis of Avgamasya asphaltite and Göynük oil shale: vacuum distillation and hexane extraction

Göynük oil shale (GOS) and Avgamasya asphaltite (AA) mixed in various ratios were used as raw materials for pitch precursors. Pure GOS and AA and their mixtures were pyrolysed at 550 °C and the resultant tars were vacuum distilled at 300 °C and 3 Torr for 60 min to produce pitch precursors. The pitch obtained in the highest yield was further modified by extraction with hexane. Structural characterisation by FTIR and ¹H and ¹³C NMR, and elemental analysis of the vacuum distillation pitches and the vacuum-distilled hexane-extracted pitch showed that vacuum distillation did not increase the softening point and toluene-insoluble (TI) content of the pitches. Further extraction with hexane removed significant amounts of aliphatic components from the pitch and increased the softening point to 136 °C. The vacuum-distilled, hexane-extracted pitch showed good spinnability into fibres of 15-20 μm diameter. The as-spun fibres were stabilised by nitric acid. The green fibres were pre-treated with air at low temperatures in order to complete stabilisation before the carbonisation process at 1000 °C. SEM images of the carbonised fibres showed surface defects due to pitch composition and/or insufficient stabilisation.     

煤沥青基中间相沥青的制备研究

以纯化的煤焦油沥青为原料,考察了热聚合温度和恒温时间对中间相沥青的收率、光学显微形态、软化点和族组成的影响.结果表明:反应温度在420℃,恒温5 h时得到了软化点为312℃的流线体型中间相沥青,其收率为79.1%;热聚合反应在相对较低的温度400℃,反应时间为10 h时形成了软化点为305℃、收率为81.4%的优质广域型可纺性中间相沥青.对该原料煤沥青而言,通过控制热聚合反应温度和恒温时间可以达到制备优质中间相的目的.     

苯丙烯醛改性煤沥青的工艺研究

在硼酸的作用下,用苯丙烯醛对煤沥青进行改性。研究了反应物配比对改性沥青甲苯不溶物含量、残炭率及软化点的影响,并研究了反应时间对残炭率和软化点的影响。结果表明:改性沥青的甲苯不溶物含量及残炭率随苯丙烯醛含量的增加先增大后减小,软化点随苯丙烯醛的增加而减小。随着反应时间的延长,软化点逐渐升高,残炭率先增大后减小。当硼酸与煤沥青质量分数为7%,苯丙烯醛与煤沥青质量分数为10%,并且反应时间为3 h时,改性效果最好,此时改性沥青的残炭率为68%。     

Effects of the time of combined vibration grinding and the compacting pressure on the density and shrinkage of graphite MPG-7 workpieces

A technique for the manufacturing of graphite MPG-7 was developed on a laboratory scale with the use of the following new raw materials: uncalcined isotropic shale tar coke and three high-temperature pitches. The caking capacity and density of the test samples of MPG-7 after molding, burning, and graphitizing were determined. It was found that the optimum concentration of a binding agent determined from the caking capacity decreased from 40 to 28% as the volatile matter content of coke increased from 4.5 to 9.5% and the softening temperature of pitch decreased from 148 to 135°C. In this case, the total shrinkages of the test samples decreased from 60 to 54%, and their densities decreased from 1.98 to 1.76 g/cm³. The optimum time of combined vibration grinding was determined, and the range of compacting pressures was chosen. The relationships between the densities of the test samples burned under laboratory and production conditions, as well as between the densities of burned and graphitized samples, were obtained. These relationships make it possible to predict the density level of MPG-7 material reached under plant conditions.     

中国炭材料用煤沥青的生产和应用

介绍了中国煤沥青资源生产和应用现状，剖析了影响煤沥青市场的几个因素，探讨了改质煤沥青的应用前景以及在炭材料生产中应用时面临的问题，讨论了中国煤沥青质量评价体系，并对炭材料生产用煤沥青的质量指标进行了详细的分析。     

可纺沥青的生产工艺

介绍了可纺沥青生产的原料、设备、工艺流程和工艺操作,阐述了工艺控制的关键点.结果表明,以乙烯裂解焦油为原料,经过常减压闪蒸、气提、短程蒸馏等工序,通过控制反应温度和压力,可生产软化点260～270℃的可纺沥青,该沥青最适宜抽丝生产沥青基碳纤维.     

Synthesis of pitch materials from hydrogenation of anthracite

A Pennsylvania anthracite was ground, carefully dried and hydrotreated into materials with properties resembling those of pitches. The hydrotreatment was carried out using two hydrogen donors, 9,10-dihydroanthracene (DHA) and 1,2,3,4-tetrahydronaphthalene (THN), and two catalysts, molybdenum hexacarbonyl (Mo(CO)₆) and ammonium tetrathiomolybdate (ATTM). Due to the high reactivity at low temperatures, the degree of hydrogenation was probed in the temperature range 300, 350 and 400 °C. The optimum hydrogen donor, catalyst and hydrogenation temperature were 1,2,3,4-tetrahydronaphthalene, ammonium tetrathiomolybdate and 300 °C, respectively. This was reflected in an increase in the hydrogen-to-carbon atomic ratio (H/C) from 0.33 for the original anthracite to 0.42 for the pitch-like material from anthracite. Further, differential scanning calorimetry (DSC) showed that the anthracite-derived pitch material had a glass transition temperature (T_g) around 81.6 °C and softening point of 205.7 °C. This indicates that the softening behavior of the anthracite-derived pitch is similar to that of high-softening-point coal tar pitches. The anthracite-derived pitch material was evaluated by producing a small carbon body directly from the anthracite-derived pitch, and partial binding was observed.     

Stabilisation of low softening point petroleum pitch fibres by HNO3

This paper deals with the stabilisation of low softening point pitch fibres obtained from petroleum pitches using HNO₃ as oxidising agent. This method presents some advantages compared with conventional methods: pitches with low softening point (SP) can be used to prepare carbon fibres (CF), the stabilisation time has been reduced, the CF yields are similar to those obtained after general methods of stabilisation, and the initial treatments to increase SP when low SP pitches are used to prepare CF, are avoided. The parent pitches were characterised by different techniques such as diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), elemental analysis and solvent extraction with toluene and quinoline. The interaction between HNO₃ and the pitch fibres, as well as the changes occurring during the heat treatment, have been followed by DRIFTS.     

三种不同原料中间相沥青的性质表征

为更深入地理解不同原料制备的中间相沥青的性质差别,从挥发分、饱和度、分子量分布、有序度的角度研究了以萘、煤沥青、精制煤液化沥青（DCLR）为原料的3种中间相沥青,分析手段包括偏光显微镜、元素分析、TGA、红外光谱（FTIR）、MALDI-TOF MS、XRD、拉曼。结果表明：萘系中间相沥青分子量最高且分布窄,挥发分低,饱和基团含量高,分子柔性大,平面性和规整性较差,分子堆砌紧密度较低,有序度较差,因此具有较低的软化点和广域流线型光学组织结构;煤系中间相沥青分子量较高,分布最宽,挥发分高,饱和度低,烷基侧链少,分子刚性和平面性较大,易堆积成紧密结构,因此具有较高的软化点,流动性差,较难形成流线型光学组织结构;DCLR系中间相沥青分子量低且分布窄,挥发分较高,含有一定量的饱和基团,分子具有一定的韧性,分子刚性和规整性较好,有序度高,因此流动性较差,软化点较高。     

铝电解槽用石墨化阴极材料的研究

以4种国产焦炭、3种国产煤沥青为原材料，采用热模压成型、一次焙烧、高压浸渍、二次焙烧和石墨化等工艺开展了铝电解槽用石墨化阴极材料的研究。在对原材料结构和理化性能分析的基础上，考察了原材料种类和配比不同的15个试样在热处理过程中的收缩率和体积密度的变化，并对石墨化后的试样的各项理化性能与工业发达国家生产的石墨化阴极炭块的性能指标进行了对比分析。结果表明，以国产焦炭和煤沥青为原材料，经过适当的混配和热处理工艺得到的石墨化阴极材料试样，其综合性能指标已达到铝电解槽对高性能石墨化阴极材料的要求。     

Carbon foams prepared from coal tar pitch for building thermal insulation material with low cost

A new approach is provided to resolve the large-scale applications of coal tar pitch. Carbon foams with uniform pore size are prepared at the foaming pressure of normal pressure using coal tar pitch as raw materials. The physical and chemical performance of high softening point pitch(HSPP) can be regulated by vacuumizing owing to the cooperation of vacuumizing and polycondensation. Results indicate that the optimum softening point and weight ratio of quinoline insoluble are about 292℃ and 65.7%, respectively. And the optimum viscosity of HSPP during the foaming process is distributed in the range of 1000-10000 Pa·s. The resultant carbon foam exhibits excellent performance, such as uniform pore structure, high compressive strength(4.7 MPa), low thermal conductivity(0.07 W·m~(-1) ·K~(-1)), specially, it cannot be fired under the high temperature of 1200 ℃.Thus, this kind of carbon foam is a potential candidate for thermal insulation material applied in energy saving building.     

改性煤沥青在炭素生产中的应用

概述了沥青的分类和性质以及沥青改性、改性方法,讲述了在改性煤沥青生产应用中的要求,改性沥青的应用过程、效果和缺点。根据实验数据阐述了在改性煤沥青生产应用中的温度选择。结果表明,改性煤沥青特有的高软化点和粘度决定了在熔化、输送和混捏过程对温度的要求较高。数据分析表明软化点不能够准确指导下料温度,而粘度与下料温度呈正比例关系。因此,粘度可以作为下料温度的一个可靠的参考指标。     

Molten storage and carbonization characteristics of premium grade coal-tar pitch: Influence of crude tar type and distillation conditions

A growing trend towards the transport and use of molten rather than solidified pitch has caused tar distillers to examine the relative stability of pitches while held in storage tanks. The scope of laboratory storage-stability tests can be extended to higher temperatures as a method of studying the earliest stages of pitch polymerization/carbonization. Some indications of the ultimate performance of the pitch in the end-use process can be gained. Crude tar has a strong influence on the ultimate properties and performance of a pitch. Seven tars have been made into 120 °C Mettler softening-point pitches by two distillation methods to study their subsequent storage and carbonization behaviour. The behaviour exhibited by each pitch allows a judgement on overall ‘reactivity’ and on the sensitivity to thermal conditions in the distillation of each tar. Two distillation schemes were adopted: batch distillation followed by heat treatment; and batch distillation at a pressure which was progressively reduced. The results show that time at elevated temperature has a major effect on the properties and performance of the resulting pitch. Vacuum distillation allows lower processing temperatures. Larger amounts of secondary quinoline-insolubles were formed under the ‘distillation with heat treatment’ scheme. Complete wetting of coke by pitch took place at lower temperatures for the vacuum-distilled pitches. Heat-treated pitches increased more rapidly in softening point and lost more mass when thermally soaked. Distillation under vacuum conditions resulted in significantly modified pitch carbonization characteristics.     

The influence of the type of quinoline insolubles on the quality of coal tar binder pitch

Seven pitches containing three types of quinoline insolubles, QI, were produced from a single coke oven coal tar. The tar was centrifuged into QI-rich and QI-lean fractions. A blend of the two fractions yielded a typical graphite electrode binder pitch. The QI content of the pitch derived from the QI-lean tar was increased through the addition of natural QI concentrate, or QI as a furnace carbon black, or QI as mesophase by means of heat treatment. The pitches were evaluated as binders by measuring the flexural strength of 19 mm diameter graphite electrodes. The results show that the typical electrode pitch is superior, and that increasing the QI content of the QI-lean material did not upgrade it. The results also show that the flexural strength of the derived graphite is not simply related to the coking value of a binder.     

Influence of wet and preheated coal charging on the nature of quinoline insolubles of coal tars and their derived pitches

Differences between primary quinoline insoluble (QI) material of coal tars and their derived pitches caused by preheating carbonization have been studied using microscopic techniques, Coulter Laser particle size analysis and solid-state ¹³C NMR. The selected tars were produced from the same coal using wet and preheated charging at the INCAR experimental coking test plant, which operates on a semi-industrial scale. Specific operational conditions were successfully applied not only to reduce the ash content and the QI and toluene insoluble (TI) contents in the tars produced by the preheating process, but also to modify the nature of the QI particles. In addition, structural changes in the insoluble materials formed during the pitch production from the tar have been monitored.