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.     

煤系中间相沥青的制备与分离研究

以精制煤焦油沥青为原料,采用常压热聚合法进行中间相转化。根据产物中中间相沥青与母体沥青之间的密度差,将中间相沥青分离出来。系统考察了热聚合温度和恒温停留时间对中间相沥青的收率、软化点、族组成和光学显微形态的影响,采用FT-IR分析技术分析了中间相沥青的官能团结构。实验结果表明:聚合温度430℃,聚合时间4 h,中间相沥青的软化点为316℃,w(QI)为74.62%,w(TI)为73.81%,收率为12.5%。     

含碳耐火材料用中间相沥青的制备

以中温煤沥青为原料,通过热聚合-溶剂抽提法制备了中间相沥青,并考察了热聚合工艺参数(升温速率、热聚合温度和时间)对中间相形成的影响.采用热分析仪和红外光谱仪分析了热聚合前后沥青的热性能和结构变化,并在光学显微镜和扫描电子显微镜下观察了中间相沥青炭化前后的微观结构.结果表明,热聚合工艺参数直接影响热聚合反应过程及热聚合沥青的结焦值和中间相的产率,最佳热聚合条件为:3.5℃/min,440℃,10 h(升温速率、热聚合温度和时间).制得的中间相沥青结焦值为85.5%,热裂解温度在300 ℃以上,炭化结构为薄带状叠合的板状炭质结构.     

煤沥青热聚合改质研究

在热聚合反应釜中 ,研究了煤沥青中甲苯不溶物、喹啉不溶物、β树脂、软化点及结焦值等质量指标在热聚合改质过程中的变化规律 .实验结果表明 ,在热聚合过程中 ,煤沥青中甲苯不溶物、喹啉不溶物、软化点及结焦值等指标均随聚合温度升高和聚合时间延长都有变化性增加 ,而β树脂在实验条件下 ,开始随聚合温度升高和聚合时间延长 ,到一定值后 ,再提高温度 ,或延长时间则下降 ,存在一极大值区间 ,该结果得到重复性实验的确认 .结果显示 ,改质沥青的主要质量指标波动范围很小 ,可为今后的放大实验或工业生产提供重要依据 .     

热聚合改质过程中煤沥青组分转变规律的研究

在 2 0 L热聚合反应釜中 ,研究了中温煤沥青热聚合改质过程中各种沥青组分随热聚合温度和热聚合时间的转变规律 .结果表明 ,在煤沥青热解缩聚期间煤沥青的甲苯不溶物和次生喹啉不溶物组分生成转变具有一定的规律性 ,并指出了其对煤沥青生产的指导意义 .     

蒽油基沥青热转化特性研究

蒽油基沥青是人造炭/石墨材料的优质前驱体,对其热转化特性研究意义重大。本文采用多管井式电阻炉对蒽油基沥青进行常压热转化处理,通过工业分析、FTIR以及偏光显微镜对热转化过程中蒽油基沥青的族组成、结构参数及显微结构的变化规律进行了研究。结果表明:随着热转化温度的提高、时间的延长,蒽油基沥青产物的软化点、甲苯不溶物(TI)、喹啉不溶物(QI)、结焦值(CV)逐渐增大;通过偏光显微镜分析可知,当热转化温度达到440℃时,产物中开始出现中间相结构,并且随着热转化温度的升高和热转化时间的延长,中间相结构逐渐增多;蒽油基沥青产物的芳香性指数(I)与热转化温度和恒温时间均存在正相关关系。     

煤加氢液化残渣制备中间相沥青的研究

对神华煤加氢液化残渣依次使用正庚烷、甲苯、吡啶进行萃取,分别得到正庚烷可溶物(HS)、正庚烷不溶-甲苯可溶物(HI-TS)以及甲苯不溶-吡啶可溶物(TI-PS)3种可溶组分。分别以HI-TS及TI-PS两种组分为原料,采用直接热缩聚法,制备了中间相沥青(MP)。通过偏光显微镜、凝胶渗透色谱(GPC)等仪器分析手段对合成的中间相沥青进行了形貌及组成表征。实验结果表明:HI-TS组分在反应温度380℃,反应时间为6 h,TI-PS组分在反应温度380℃,反应时间4 h,均生成了光学组织结构好、中间相含量近100%的中间相沥青。     

炭阳极用煤沥青中间相的研究

选取热聚法、真空闪蒸法生产的煤沥青试样,全面分析了各项理化指标,重点研究了煤沥青的中间相含量及其黏度。试验结果表明,我国热聚法生产的煤沥青中间相含量高,为3.0%～6.9%,而真空闪蒸法生产的煤沥青几乎不含中间相。热聚法生产的煤沥青中主要指标甲苯不溶物、喹啉不溶物含量也较高,比国际上普遍采用的真空闪蒸法生产的煤沥青高出20%左右。煤沥青中喹啉不溶物及中间相的含量对黏度产生很大影响。在较低的温度条件下,我国热聚法煤沥青的黏度明显高于真空闪蒸法煤沥青。煤沥青的这些性质将对炭阳极的生产工艺参数及质量带来一定的影响。     

2种煤沥青的中间相热聚合行为研究

以中温煤沥青(MTCP)和改质煤沥青(MCP)为原料，采用热聚合反应方法，在相同的反应时间下，研究不同反应温度下2种煤沥青的中间相热聚合行为。采用软化点仪、偏光显微镜、X射线粉末衍射仪(XRD)以及激光共焦拉曼光谱仪(Raman)对中间相沥青表征和分析。结果表明，2种煤沥青在相同工艺条件下呈现出相似的中间相聚合行为。偏光显微镜照片说明2种煤沥青聚合所得到的中间相类型均为镶嵌结构。XRD与Raman分析表明随着聚合温度的升高，中间相沥青内部芳香片层分子的取向性更好，排列更为规整。MTCP经过430℃、8 h聚合，可制备软化点为319℃的中间相含量高于80%的中间相沥青；MCP经过420℃、8 h聚合，可制备软化点316℃,中间相含量高于80%的中间相沥青。     

炭素前驱体性质对活性炭比表面积的影响

煤沥青由于软化点低，挥发分含量高等特点，不易直接用于制备活性炭，实验采用空气氧化热聚合方法对煤沥青进行稳定化处理．为考察炭素前驱体的结构、性能对由其所制备的活性炭的比表面积的影响，实验以不同升温速率加热煤沥青进行热聚合处理，并将得到的前驱体制备成活性炭．结果表明，在本实验条件下得到的前驱体的挥发分含量、甲苯不溶物含量差异较小，对活性炭比表面积影响不大，而其结构对活性炭比表面积影响较大．其中含有中间相小球的前驱体最利于制得高比表面活性炭，镶嵌型结构的次之，而区域型结构相对不利于得到高比表面积活性炭．     

Modification of the carbonization properties of coal-tar pitch by supercritical fluid extraction

The carbonization properties of coal-tar pitch were modified by supercritical fluid (SCF) extraction. Pitches extracted with supercritical toluene (SCFE pitch) contained none of the quinoline insoluble (QI) matter responsible for anisotropic structures with small unit sizes. The size of anisotropic structures from SCFE pitches was closely related to the β-resin (toluene insoluble and quinoline soluble fraction) content. Anisotropic structures from blended pitches prepared to have the same β-resin content as SCFE pitches (by blending toluene soluble (TS) and β-resin fractions obtained through a conventional liquid solvent extraction) were smaller. Extraction of the β-resin fraction with supercritical toluene could be interpreted by the co-solvent effects of the TS fraction dissolved in the extract phase. The high concentration of TS fraction in the extract phase enhanced the solubility of the β-resin fraction into this phase. In the raffinate phase, the heavier β-resin components, which are unsuitable for the development of mesophase structures, coagulated and formed unextractable QI matter through reduction in the concentration of the TS fraction. Since the TS concentration in both the phases depends on pressure and the ratio of the amounts of supercritical toluene and pitch, the control of the β-resin content in the SCFE pitches is possible through the adjustment of these two parameters.     

Comparative studies of the modification of coal-tar pitch

Properties of coal-tar pitches modified by sulfur addition, air blowing, and nitrogen blowing were compared to find an appropriate method of preparing a matrix precursor for carbon/carbon (C/C) composites. Raw and modified pitches were characterized by softening point, thermal analysis (TGA), elemental analysis, solubility in toluene and quinoline, and gel permeation chromatography. Both sulfur addition and air blowing very effectively increased softening point and coke yield by dehydrogenative polymerization of pitch molecules. Air-blown pitch, however, had less thermal stability than the pitch with added sulfur and showed more weight loss at high temperatures. Property changes in nitrogen-blown pitch were mainly induced by eliminating volatile matter of low molecular weight. Sulfur addition is suggested to be the most promising method for preparing matrix precursor because it had the highest yield among those with similar softening points.     

热聚合改质过程中煤沥青热解缩聚行为的研究

在20升热聚合反应釜中对中温煤沥青进行热聚合改质处理，研究了热聚合改质过程中煤沥青热解缩聚行为，讨论了煤沥青结焦值随聚合时间和聚合温度的变化，并找出了热聚合改质过程中煤沥青结焦值和甲苯不溶物之间的关联性。     

Pyrolysis of polycarbonate in coal-tar pitch

The thermal degradation of polycarbonate in coal-tar pitch was studied. The composition of the liquid products of pyrolysis was determined with the use of gas chromatography–mass spectrometry; the modified coal-tar pitch and the pyrolysis residue were studied by Fourier transform IR spectroscopy, elemental analysis, and the determination of softening point, concentrations of substances insoluble in toluene and quinoline, and yields of volatile substances. Because of chemical interaction with coal-tar pitch, the thermal degradation of polycarbonate in coal-tar pitch occurs at considerably lower temperatures than destruction without a solvent with high selectivity for phenol and p-isopropylphenol. Hydrogen transfer from the coal-tar pitch to the polycarbonate degradation products initiates polycondensation reactions in the coal-tar pitch.     

精制沥青中间相热转化的研究

以2种精制沥青(LSP和HSP)为原料,通过常压热转化反应,研究了热转化过程中产物的QI和TI随反应时间的变化规律.分析表明,随着反应温度的升高和反应时间的延长,沥青的各向异性组分不断增加.其中LSP沥青生成的中间相小球大于HSP沥青生成的中间相小球.400℃恒温9h,LSP沥青的软化点达到242℃,HSP沥青的软化点达到220℃.     

Relationship between chemical structure and secondary quinoline insoluble formation in electrode binder pitches

The relationship between the rate of secondary quinoline insoluble (QI) formation in coal-tar pitches and variations in their chemical composition is examined. Production of significant concentrations of secondary QI is shown to be accompanied by mesophase formation, the significance of which is discussed in terms of electrode binder performance.     

Structural modification of coal-tar pitch fractions during mild oxidation—relevance to carbonization behavior

Modified pitches with softening points of about 175 °C were prepared by air-blowing at 300 °C of coal-tar pitches from different commercial coke-oven tars. The modifications induced by the mild oxidation were monitored using solvent and extrographic fractionation, elemental analysis, ¹H NMR and HPLC. Optical microscopy was used to follow the effect of air-blowing on carbonization behaviour. Low molecular weight cata-condensed PAHs and those with basic nitrogen and hydroxylic functionalities present in extrographic fractions F2 and F4, respectively, are preferentially polymerized pitch constituents. In contrast, peri-condensed PAHs in extrographic fractions F2 and F3, are practically unreactive under the oxidation conditions used. The mild oxidation enhances the tendency of quinoline insoluble (QI) particles to form aggregates in an early stage of thermal treatment, modifying the mode of mesophase development and leading to a non-homogeneous optical texture. The enhanced propensity of QI to aggregation is discussed in terms of structural peculiarities of the parent pitch and possible oxidative polymerization reactions.     

Mesophase pitches for 3D-carbon fibre preform densification: rheology and processability

Synthetic mesophase pitches, produced from naphthalene (ARA24, ARA24r), were examined in terms of fluidity and thermal stability in comparison with other mesophase, isotropic pitches, or mesophase pitch/softening molecules blends. Their interest for carbon/carbon (C/C) composites processing by liquid impregnation or vacuum transfer inside three-dimensional carbon preform is discussed. Viscosity versus reduced temperature plots is reported on the same graph to compare the studied pitches and to define a suitable C/C processing window. Methylnaphthalene-based pitch is a good candidate with viscosity and stability adapted to the processing temperature and high carbon yield.     

Rheological investigation of coal-tar pitch during its transformation to mesophase

Rheological characteristics of two coal-tar pitches, during their transformation to mesophase, have been followed by rotational viscometry. In certain instances samples were also taken, enabling the mesophase microstructure to be correlated with the flow behaviour. Flow curves established that the pitches are Newtonian liquids at low temperatures, but non-Newtonian character appears at temperatures above 380 °C. Scanning the viscosity-temperature curve of a binder pitch showed that the viscosity began to change, as a result of polymerization processes, at about 240 °C. In both pitches the apparent viscosity, at all rates of shear, increased very rapidly at temperatures above 420 °C when the mesophase content was in excess of 25%. Shear-thinning behaviour was apparent and a peak in the apparent viscosity-temperature curves appeared at all the rates of shear investigated. It is suggested that the systems can be regarded as emulsions. Initially an emulsion of mesophase in isotropic liquid exists but this transforms, at higher temperatures, to one of isotropic liquid in mesophase. The maximum in the apparent viscosity appears to correspond to the phase inversion point.     

Supercritical fluid extraction of coal-tar pitch: Part 2. Extraction of the lower molecular weight species with aliphatic solvents

Extraction of coal-tar pitches has been carried out with a number of aliphatic hydrocarbons at temperatures between 210°C and 300°C and pressure of 10 or 15 MPa resulting in extraction yields of up to 50%. The toluene-insoluble (TI) content, molecular weight and the rate of mesophase formation of the residual (refined) pitches increase as the extraction yield increases. The molecular weight of the extract also increases with extraction yield. The volatiles produced during mesophase formation from a supercritical hexane-extracted pitch were analysed by NMR and mass spectrometry and were similar to the hexane extract.