唐闲逸
, 张海永
TANG Xianyi, ZHANG Haiyong
中图分类号: TQ522.65
文章编号: 1005-3093(2016)06-0448-09
通讯作者:
收稿日期: 2015-12-1
网络出版日期: 2016-06-25
版权声明: 2016 《材料研究学报》编辑部 《材料研究学报》编辑部
基金资助:
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摘要
以中温煤沥青为原料, 研究其在弹管反应器中的炭化以及“反溶剂法”脱出喹啉不溶物(QI)后的精制沥青的炭化效果。结果表明: 含有较高QI的非精制沥青不能制备出较好的针状焦, 但在500℃, 0.2 MPa, 10h的炭化条件下, 能够得到相对较优热膨胀系数(CTE)的炭化结果; 以煤油和洗油为混合溶剂, 反溶剂法能够有效地脱除喹啉不溶物, 在芳脂比0.4, 沉降温度100℃, 搅拌时间0.5 h, 沉降时间4 h, 溶剂比1.8、2的条件下, QI含量分别降到0.0914%和0.0695%, 将其在500℃、0.2 MPa、10 h的条件下炭化, 可制备出热膨胀系数(CTE)较低的针状焦。
关键词：
Abstract
The carbonization in a tube bomb of medium-temperature coal tar pitch and the purified coal tar pitch, of which quinoline insoluble (QI) had been removed by anti-solvent method, was comparatively studied. The results show that coal tar pitch with high QI contents could not be suitable for preparation of needle coke of high quality. However, the coke which was obtained through carbonization under 0.2 MPa at 500℃ for 10 h had a relatively lower coefficient of thermal expansion (CTE). The QI could be removed effectively by anti-solvent method when kerosene and wash oil were mixed as solvents. By a precipitation process at 100℃ and precipitation time for 4 h with the ratio of wash oil to kerosene was 0.4 and stirring for 0.5 h, the QI contents of the refined coal tar pitch could be reduced to 0.0914% and 0.0695% for the ratios of solvents to coal tar pitch as 1.8 and 2 respectively. The needle coke which were prepared by such refined coal tar pitch showed lower CTE after being carbonized at 500℃, by 0.2 MPa and for 10 h.
Keywords：
我国含有丰富的煤沥青资源, 利用煤沥青制备针状焦可以实现煤沥青的高值化, 同时满足高功率电极的需求。针状焦具有长纤维结构, 取向性好, 石墨化程度较高, 且还具有低热膨胀系数、高密度、高导电率、低腐蚀和低晶胀等一系列优点, 是制造高功率及超高功率电极的骨料, 与普通电极相比, 可缩短冶炼时间1/3、减少能耗1/2, 提高生产能力约1.3倍[1]。针状焦的生产工艺包括原料预处理、延迟焦化和煅烧三个阶段[2]。而原料预处理过程中, 喹啉不溶物(QI)的脱除十分重要。
喹啉不溶物包括原生QI和次生QI, 关于QI的性质、组成及其对中间相形成的影响已有诸多报道[3~5]。原生QI一方面不利于中间相的转化, 含量过高会阻碍中间相小球体的融并, 在炭化过程中易生成镶嵌结构; 另一方面, 原生QI也存在一定的活性中心, 可以降低中间相转化的活化能, 促进中间相的成核[6~8], 故制备针状焦过程中, 要求原料QI含量降低到0.1%以下。
脱除原生QI的方法主要有溶剂法、真空蒸馏法、热溶过滤法、改质法、加氢法、离心脱除法及共炭化法等[9]。经过对原料调制, 可获得低QI含量的精制原料。Hirofumi Sunage等[10, 11]在专利中采用芳烃溶剂、脂肪烃溶剂与煤沥青混合, 图1为喹啉不溶物增大示意图, 通过调节芳脂比及溶剂比, 达到原料精制的目的; 孙振兴、孙艳锐等人[12, 13]也以不同的溶剂采用溶剂离心法, 有效脱除了煤焦油沥青的QI。
Brooks与Taylor[14]发现了中间相小球的生长、融并形成各向异性炭的过程, 并对其形成机理及微观结构进行了研究; Isao Mochida等[15]的“微域构筑”理论很好的解释了中间相液晶小球的形成并在体系中形成各纤维状、镶嵌型、广域型的各向异性结构。查庆芳、刘以红等人[16, 17]对石油系原料制备针状焦做了大量研究; 孙权等人[18]研究表明炭化过程中外加磁场对改善针状焦微结构具有显著的作用。我国煤系针状焦已产业化, 但其规模较小, 产品质量不稳定, 无法生产出优质的针状焦。
本文采用“反溶剂法”, 利用芳烃溶剂与脂肪族溶剂作为溶剂, 考察了不同溶剂比、芳脂比、沉降温度、沉降时间等因素对精制沥青的QI含量和收率的影响。同时对非精制沥青和精制沥青进行了炭化、煅烧制备针状焦, 通过偏光显微镜对生焦的光学结构进行分析, 通过扫描电子显微镜(SEM)与X射线衍射仪(XRD)进行相关分析, 并对其热膨胀系数(CTE)进行了测试, 以表征其性能。
中温煤沥青来自某煤化工公司, 磨研后作为原料(CTP0)。实验试剂主要有正己烷、甲苯、喹啉等, 均为分析纯; 用到的其它辅助材料有: 牙托粉、牙托水、抛光液等。
炭化反应装置见图2, 由一个沙浴炉和一套弹管反应装置构成。在100℃下将沥青软化, 取8~10 g进行炭化。得到的生焦沿轴向切为两块。一块用于偏光显微镜下的结构观察; 一块在管式炉中, N2氛围下, 5℃/min升温到1000℃恒温煅烧2 h。然后在真空条件下, 石英作为推杆, 测试室温~500℃下轴向的CTE(每个样品测试三次, 误差小于15%)。
图2 炭化反应装置示意图
Fig.2 Schematic diagram of experimental apparatus of carbonization
将80 g沥青原料与煤油与洗油(性质见表1)的混合溶剂在相应的沉降温度下预热后混合、搅拌、重力沉降后, 分离出上层溶液, 在-0.096 MPa, 170℃下蒸馏1 h, 得到精制沥青。
表1 煤油与洗油性质
Table 1 The properties of kerosene and wash oil
| Solvent | Initial boiling point /℃ | TV/℃ | Final boiling point/℃ | BMCI2 | |
|---|---|---|---|---|---|
| Kerosene | 0.794 | 103 | 191.2 | 281 | 24 |
| Wash oil | 1.001 | 212 | 259.6 | 330 | 109 |
原料沥青及精制沥青QI含量按国标GB/T2293-1997测定。族组分分析采用溶剂抽提法依次用正己烷、甲苯进行梯度抽提, 得到正己烷可溶物(HS)、正己烷不溶甲苯可溶物(HI-TS)、甲苯不溶喹啉可溶物(TI-QS)、QI 4个组分。核磁共振测试采用BRUKER AVANCE III600核磁共振波谱仪, 测定条件: 四甲基硅烷(TMS)作内标, CDCl3为溶剂, 共振频率600 MHz, BBI宽带探头, 5 mm样品管。
偏光显微结构利用贵阳新天光电科技有限公司的XP3D偏光显微镜。热膨胀系数采用ZRPY-1000热膨胀系数测定仪进行测定。形貌分析表征采用JEOL公司S-6700F场发射扫描电子显微镜(SEM)观察, 样品断面用GIKOIB-3离子喷涂机喷Pt处理后进行观察, 操作电压10 kv。真密度利用3H-2000 TD1型全自动真密度分析仪在20℃、0.79538bar的He气环境下利用气体膨胀置换法测定。
XRD采用Ultima IV型衍射仪, Cu靶, 电压为40 kv, 电流为40 mA, 步长为0.02°, 波长(λ)为0.15406 nm, 扫描速率为20°/min, 扫描范围为5°-90°(2θ)。由Bragg公式(1)和Scherrer公式(2)分别计算得到微晶层间距d及晶粒度D(平均微晶尺寸La和平均微晶堆砌高度Lc)。
其中β为半峰宽, λ为波长, K为校正因子(K002=0.89, K100=1)。
非精制原料CTP0性质见表2。可以看出, 原料中的S含量低于0.5%, N含量高于0.5%, N含量相对偏高, 硫、氮杂原子的存在使得针状焦在石墨化时容易发生“气胀”[20], 相邻分子间的相互作用会扰乱片层的平行堆砌, 导致生成各向同性或镶嵌结构[21]。1H-NMR的结果显示, α位的氢原子远远超过β和γ位氢原子的总和, 表明原料沥青具有较高的芳香度, 芳核缩合度很高, 芳香环取代度较低, 脂肪侧链多以α-甲基、α-亚甲基、α-次甲基短侧链为主。所以, 原料沥青是短脂肪侧链的芳香性较高的稠环物质。
表2 煤沥青性质
Table 2 The properties of coal tar pitch
| Sample | CTP0 | CTP1 | CTP2 | CTP3 | CTP4 | Sample | CTP0 | CTP1 | CTP2 | CTP3 | CTP4 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| C,% | 92.14 | 93.64 | 92.06 | 92.87 | 92.66 | Har ,% | 79.60 | 80.48 | 77.64 | 75.31 | 74.55 |
| H,% | 4.75 | 4.90 | 5.80 | 5.05 | 5.04 | Hα ,% | 17.16 | 18.76 | 20.05 | 21.12 | 21.88 |
| O3,% | 1.67 | 0 | 0.25 | 0.81 | 1.01 | Hβ ,% | 3.11 | 0.46 | 1.74 | 3.26 | 3.52 |
| N,% | 1.20 | 1.15 | 1.37 | 0.96 | 0.96 | Hγ ,% | 0.13 | 0.30 | 0.57 | 0.31 | 0.05 |
| S,% | 0.24 | 0.31 | 0.52 | 0.31 | 0.33 | fa5 | 0.9477 | 0.9488 | 0.9256 | 0.9328 | 0.9307 |
| C/H | 1.62 | 1.59 | 1.32 | 1.53 | 1.53 | σ5 | 0.08 | 0.089 | 0.097 | 0.105 | 0.109 |
| Ash,% | 0 | 0 | 0 | 0 | 0 | HS,% | 13.64 | 49.80 | 31.39 | 70.50 | 85.40 |
| H2O,% | 0.50 | 0.59 | 0.17 | 0.35 | 0.39 | HI-TS,% | 72.06 | 46.24 | 66.57 | 28.27 | 14.46 |
| SP4 | 77.8℃ | 23.8℃ | 22.4℃ | - | - | TI-QS,% | 12.79 | 3.87 | 1.97 | 1.19 | 0.10 |
| - | - | - | - | - | QI,% | 1.49 | 0.09 | 0.07 | 0.04 | 0.03 |
图3给出了CTP0在不同温度、压力和足够长的炭化时间下炭化得到的各向异性结构偏光显微结构。由于原料未经处理, QI含量较高, 中间相小球不能很好地融并长大, 炭化产物形成大量镶嵌结构。但在图3b与j图中, 镶嵌结构尺寸较大, 已有流域性结构的发展趋势。由于CTP0中HS含量过低, HI-TS过高, 黏度较大, 在炭化过程中, 气体从原料中溢出, 较高的HI-TS固化速度使得气流拉焦的作用并不明显, 且黏度过大导致气体带出的原料无法回流, 从而形成较多较大无规则气孔。
图3 不同炭化条件生焦偏光显微照片
Fig.3 Polarized light micrographs of green coke lumps at different carbonization conditions (A, B, C: 460℃, 0.2, 0.4, 0.6 MPa, 16 h; D, E, F: 480℃, 0.2, 0.4, 0.6 MPa, 16 h; G, H, I: 500℃, 0.2, 0.4, 0.6 MPa, 10 h; J, K, L: 520℃, 0.2, 0.4, 0.6 MPa, 10 h)
表3是生焦煅烧后针状焦CTE值, 所有炭化条件下, 均无法制备出CTE较小的优质针状焦。但在460℃、0.4 MPa、16 h与500℃、0.2 MPa、10 h条件下, CTE值相对较小。由于HS较低, 体系黏度过大, 较高的压力阻止了气体有序溢出, 明显减弱了气流拉焦作用。
表3 针状焦性质
Table 3 Properties of needle cokes
| Sample | CTE (×10-6/℃) | RD6 (g/cm3) | Yield7(W%) | Sample | CTE (×10-6/℃) | Sample | CTE (×10-6/℃) | Sample | CTE (×10-6/℃) |
|---|---|---|---|---|---|---|---|---|---|
| CTP1 | 0.56 | 1.95 | 52.1 | A | 2.60 | E | 2.59 | I | 2.92 |
| CTP2 | 0.47 | 2.09 | 53.0 | B | 1.84 | F | 3.19 | J | 2.28 |
| CTP3 | - | - | 49.3 | C | 2.83 | G | 1.85 | K | 2.19 |
| CTP4 | - | - | 42.9 | D | 2.18 | H | 1.98 | L | 2.82 |
在相同温度下, 低压条件下制备的针状焦CTE相对较优。在相同压力下, 较高的炭化温度制备针状焦的光学结构相对较优, 随着温度的升高, 更多稠环物质的侧链断裂, 形成较多气体小分子溢出, 有效增强了气流拉焦作用, 但过高的温度会导致反应加快, 过快的固化, 使得气流拉焦的作用无明显的效果。
2.2.1 芳脂比对QI脱除效果 固定溶剂比为1:1、搅拌时间0.5 h、沉降时间2 h、沉降温度100℃, 采用不同芳脂比的混合溶剂处理原料沥青, 其QI含量与精制沥青收率变化见图4。
图4 QI含量与收率随芳脂比变化
Fig.4 The change of the content of QI and the yield with the ratio of wash oil to kerosene
可以看出, 当溶剂比一定时, QI含量与收率随着芳脂比的增大而增大。芳脂比增大, 芳烃溶剂增多, 溶剂的BMCI值增大, 溶剂对沥青的溶解能力提高, 收率必然增加。但芳烃溶剂增多的同时溶液的黏度也增大, 不利于QI颗粒在溶液中自由迁移, 使得QI不能很好附着在粘性颗粒上团聚, 在重力沉降阶段被分离, QI也随着芳脂比升高而升高。在芳脂比0.2时, 溶液的黏度较低, 溶剂的BMCI值较小, 精制沥青的QI含量降低到0.1%以下, 满足针状焦的原料对QI的要求, 但此时收率较低。
综合考虑QI含量及收率, 选择芳脂比0.4作为QI脱除的实验条件。
2.2.2 沉降温度对QI脱除效果 固定溶剂比为1:1、芳脂比为0.4、搅拌时间0.5 h、沉降时间2 h, 在不同沉降温度下, QI含量与精制沥青收率的变化见图5。可以看出, 随着沉降温度的升高, 精制沥青的QI含量逐渐降低, 收率明显增加。溶液体系的温度与黏度的变化趋势有关, 在一定温度范围内, 随着温度的增加, 溶液的黏度随之降低, 而物质的溶解度随着温度的升高而增加, 故随着温度的升高, 溶液的黏度下降, QI在溶液中自由迁移能力增强, 物质的溶解量上升, 导致QI下降的同时, 收率升高。当沉降温度从100℃升高到110℃时, QI含量从0.2067%明显下降到0.1572%, 当温度继续升高, QI含量继续减少, 但减小的趋势趋于平缓。140℃时, QI含量下降到0.1042%, 仍然无法得到较好的精制沥青。考虑到所使用的煤油的初馏点为103℃, 温度过高会增加溶剂的损耗。此外, 温度高时对设备的要求也比较苛刻, 所以沉降温度选为100℃。
图5 QI含量与收率随沉降温度变化
Fig.5 The change of the content of QI and the yield with precipitating temperature
2.2.3 沉降时间对QI脱除效果 图6是在溶剂比1:1、芳脂比0.4、搅拌时间0.5 h、沉降温度100℃, 不同沉降时间下, QI含量与精制沥青收率的变化。
图6 QI含量与收率随沉降时间变化
Fig.6 The change of the content of QI and the yield with precipitating time
大小不同的QI颗粒沉降所需的时间各不相同, 随着沉降时间的增加, 上层溶液中颗粒较小的QI团聚, 沉降到底层残渣中被分离出。随着沉降时间的增加, 溶液中被溶解的物质同时团聚而被沉淀, 得到的沉降不溶物增加, 故QI含量与收率同时下降。从图中可以看到沉降时间为6h时, QI含量降到0.07%, 但是此时收率也下降到27%左右。
因此, 综合考虑这两方面的因素, 将QI脱除实验的沉降时间选为4 h。
2.2.4 溶剂比对QI脱除效果 图7为芳脂比0.4、搅拌时间0.5 h、沉降温度100℃、沉降时间4 h, QI含量与精制沥青收率随着溶剂比的变化。
图7 QI含量与收率随溶剂比变化
Fig.7 The change of the content of QI and the yield with the ratio of solvents to coal tar pitch
随着溶剂比的增大, 体系黏度和密度降低, 有利于QI的脱除。溶剂比较小时, 体系的黏度较大,部分颗粒较小的QI在沉降过程中无法在溶液中自由迁移, 导致不能被完全沉降下来。随着溶剂比的增大, 体系黏度下降, QI能够更好地在溶液中迁移, 颗粒较小的QI也更容易团聚变大被沉降到残渣中, 很好地被脱除。有效地减小了溶液中QI的含量。当溶剂比为2、2.5、3时, 得到的精制沥青QI含量分别为0.0695%、0.036%、0.0314%, 都达到了制备优质针状焦对精制沥青QI含量的要求。当溶剂增多, 溶解度一定时, 在一定范围内, 溶解量能够增加, 精制沥青的收率随着溶剂比增大而增大且缓慢的趋于稳定。所以当溶剂比从2.5增大到3时, 收率增长趋势变得平缓。随着溶剂比的增大, QI含量继续下降。但当溶剂比为2.5时, 溶液能溶解的量趋于饱和, 而QI也基本被脱除, 所以QI含量与精制沥青的收率趋势均变得平缓。
综上所述, 不论是从精制沥青QI含量还是收率来看, 当溶剂比≥1.8时, 此时制得的精制沥青基本达到制备针状焦对原料的要求。
将溶剂比为1.8、2.0、2.5、3.0制备得到的精制沥青(CTP1、CTP2、CTP3、CTP4)作为炭化原料, 其主要性质分析见表2。可以看出, 脱除掉QI以后的精制沥青N含量依然高于0.5%, 1H-NMR的结果同样显示出显示四组精制沥青依然是短脂侧链的芳香性较高的稠环物质, 但HS、HI-TS、TI-QS、QI含量均发生了变化。
4组精制沥青在500℃、0.2 MPa、10 h条件下炭化, 炭化后生焦的偏光显微结构如图8所示, 将其切割煅烧后针状焦的性质见表3。CTP3与CTP4中精制沥青HS较高, 炭化后收率较低, 在弹管中形成的生焦成骨架形(图9), 煅烧后无法制备成测试CTE样品。
图8 精制沥青炭化生焦偏光显微照片
Fig.8 Polarized light micrographs of Green coke carbonization by purified coal tar pitch
由图8可以看出, 4组精制沥青所炭化得到的生焦形成大片各向异性流域性结构与少量镶嵌结构, 明显优于同样条件下原料沥青炭化所得到的生焦H, 气孔明显减少且变小成圆形。精制以后的沥青HS升高, 很好的改变了沥青的黏度, 使得在炭化过程中, 气体可以缓慢有规律由下至上的溢出, 减缓了固化速度, 产生很好的气流拉焦作用, 形成结构较好的流域性各向异性组织。
根据日本的Isao Machida等[22]对各向异性结构的划分, 图3中G生焦的表面各向异性组织尺寸大多属于M和D与微量的SF; CTP1生焦的表面略低于50%各向异性结构属于SF、LF和FD, 有约50%的D与M结构存在, 其D类结构也明显大于CTP0中的颗粒; CTP2炭化制备的生焦的表面70%各向异性组织结构属于SF、LF和FD, 其余的基本为D, 有微量的M; CTP3与CTP4生焦的表面分别有38%与25%的各向异性结构属于SF、LF和FD, 其余大部分为M类的镶嵌组织。所以以此流域性结构分类, 生焦炭化流域性发展大小顺序为:
由此可见, 脱除掉QI的沥青, 在炭化过程中的各向异性结构发展得到很好的改善, 煅烧后的CTE值也明显降低, CTP1与CTP2煅烧后形成的针状焦的CTE值分别降低到0.56×10-6/℃与0.7×10-6/℃。
图10为生焦G、CTP1与CTP2煅烧后形成的针状焦的XRD谱, 各样品在26°左右均有明显的特征峰, 对应标准卡片, 各试样的晶体结构均为Graphite- 2H 六方晶系。由于针状焦中存在的不同石墨化度的组分, 形成的多条衍射线叠加而导致不对称的线形, 峰形较宽化。将其特征峰放大(见图11), 详细结构参数见表4。从表中可以看出, CTP1与CTP2的层间距均小于G, 结晶度较好, 但G的平均微晶尺寸要大于CTP1与CTP2。
表4 针状焦XRD微观结构参数
Table 4 Microstructural parameters of XRD of needle cokes
| Sample | β002E-2/rad | 2θ002/(°) | β100E-2/rad | 2θ100/(°) | d002/nm | D/nm | |
|---|---|---|---|---|---|---|---|
| La(100) | Lc(002) | ||||||
| CTP1 | 1.107 | 25.700 | 0.934 | 43.079 | 0.3463 | 0.177 | 0.127 |
| CTP2 | 1.066 | 25.859 | 0.854 | 43.263 | 0.3442 | 0.194 | 0.132 |
| G | 1.074 | 25.480 | 0.423 | 43.383 | 0.3493 | 0.391 | 0.131 |
图12为CTP1与CTP2煅烧后制备的针状焦SEM像。可以看出, 煅烧焦是由大量方向性较一致排列的薄片形的流域结构组成, 其放大以后的结构类似针状结构。CTP1的流域性针状结构明显宽于CTP2。因此, 针状焦的类似针状的流动文理, 是在气流拉焦作用下形成的流域性结构方向一致的薄片堆叠而形成的。
非精制中温煤焦油沥青中QI含量较高, 不宜直接作为制备针状焦原料。在不同炭化工艺条件下, 各向异性组织形成大量的镶嵌结构, 制备的针状焦CTE值较高。
“反溶剂法”能有效地脱除非精制中温煤沥青中的QI且得到较好的精制沥青收率, 炭化后得到大量流域性结构较好的生焦, 各向异性组织结构明显得到改善, 制备的针状焦CTE值达到优质针状焦的要求。
QI含量在炭化过程中对较好各向异性组织流域性结构的形成是非常重要的一个因素。同时, 沥青的HS、HI-TS、 TI-QS组成的比例对沥青黏度以及气流拉焦作用的影响, 也对各向异性组织流域性的结构的形成有着重要的影响。
The authors have declared that no competing interests exist.
| [1] |
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| [2] |
Effect of pretreatment methods of raw material on coking of needle coke from coal tar pitch by delayed coking ,原料预处理方法对延迟焦化成焦的影响 ,
介绍了针状焦的工业生产方法,分析了不同的原料软沥青处理方法以及原料的结构和组成对延迟焦化成焦的影响.
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| [3] |
Influence of primary QI and on pitch pyrolysis with reference to unidirectional C/C composites , |
| [4] |
Microstructure characteristics of toluene and quinoline insolubles from coal-tar pitch and their cokes ,
<h2 class="secHeading" id="section_abstract">Abstract</h2><p id="">The structural composition of coal–tar pitch used in the preparation of the special binder-pitch, was determined with special emphasis on the optical properties of the β-resins, as typical components necessary to obtain electrodes of best quality through the pyrogenetic processes of baking and graphitization. In addition to raw toluene- and quinoline-insolubles (TI, QI), the corresponding cokes were analysed to evaluate, by structural composition and microtexture, the behaviour of pitch fractions during carbonization. The results suggest the dependence of the texture development on the type of toluene- and quinoline-insolubles and β-resins during processing conditions, which influence the mesophase formation. An original and important result of the carbopetrographical study is represented by the identification and evaluation of β-resins in the coke texture.</p>
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| [5] |
Effects of quinoline-insoluble particles on the elemental processed of mesophase sphere formation ,
ABSTRACT Quantitative evaluation was made on effects of primary quinoline insolubles (PQI) on the elemental rate processes of mesophase sphere formation from a coal tar pitch. An original coal tar pitch containing 3 wt.% PQI and a PQI free coal tar pitch derived from the original pitch were heated at 703 K for various periods of time. Time dependent changes in number/volume-based concentrations and radius distribution of mesophase spheres were quantified through microscopic observation and an image analysis. The quantified results were further analyzed by a kinetic model considering the three rate processes; generation, growth and coalescence of spheres. The model analysis revealed that PQI increases the total frequency of sphere generation by five times, decreases the rate constant of coalescence by an order of magnitude, and decreases the linear growth rate to less than half. It was also found that PQI delays the commencement of the sphere generation and expands the time period of the generation.
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| [6] |
The structure and behavior of QI material in pitch ,
The QI material in coal-tar pitches is characterized by optical and scanning electron microscopy. Five main groups of QI are distinguished, primary, secondary, isotropic, foreign inclusions and material of unusual shape. Isotropic QI is considered to consist of asphaltene-like molecules dispersed in the pitch. It is found in air and acid-treated pitches and increases the coke yield compared with untreated feedstock pitches. Mesophase extracted from heat treated A240 pitch is heat treated in isolation and after mixing with fresh A240 pitch. At 375掳C, mesophase partially dissolves in the fresh pitch if decacyclene is present. At 400掳C, mesophase spheres heated in isolation coalesce only to a limited extent. The presence of fresh pitch is necessary for unhindered coalescence of extracted mesophase spheres and the development of optical texture of maximum size.
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| [7] |
Structural characteristics of quinolone Insoluble fraction and their Influence on mesophase transformation ,
不同喹啉不溶物的特性及对中间相转化过程的影响 ,URL 摘要
采用￣１３Ｃ－ＮＭＲ、 ｘ－ｒａｙ衍射、扫描和透射电镜研究了二种ＱＩ──原生ＱＩ、次生ＱＩ（喹啉不溶物）结构，并通过热转化试验考察了它们对中间相热转化过程的影响。结果表 明，原生ＱＩ是由炭黑状固体小圆球组成，并包含有煤粉、焦粉等夹杂物，属非晶态混和物。它在中间相转化过程中，促使中间相小球体较早生成，并阻碍中间相球 体融并，导致中间相热转化最终固体产物的镶嵌结构生成。次生ＱＩ微晶排列有序性较好，属中间相组织或中间相前躯体，对中间相的成长过程有利。
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| [8] |
Catalytic Carbonization of aromatic hydrocarbons-Ⅸ: carbonization mechanism of heterocyclic sulfur compounds leading to the anisotropic coke , |
| [9] |
Progress of pretreatment methods of raw material for needle coke from coal tar ,煤系针状焦原料预处理技术进展 ,
针状焦是生产超高功率石墨电极 的新型材料。据针状焦成焦机理,煤焦油和煤焦油沥青作为针状焦生产原料时必须进行预处理将其中的喹啉不溶物等杂质除去。煤系针状焦原料的预处理方法主要包 括溶剂法、过滤法、离心分离法、加氢法、改质法及溶剂-加氢法。上述方法均可将煤焦油和煤焦油沥青中的喹啉不溶物降至满足针状焦生产的要求,其中溶剂法中 的溶剂-沉降法现已得到工业化应用。
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| [10] |
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| [11] |
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| [12] |
Removal quinolone-insolubles from medium coal tar pitch ,中温沥青的喹啉不溶物脱除 , |
| [13] |
Removal of quinoline-insolubles in soft coal tar pitch by mixed solvent method, Journal of Beijing Institute of Petro-chemical 混合溶剂法脱除软沥青的喹啉不溶物 ,
煤沥青中含有较多的喹啉不溶物会影响炭材料的性能。以软沥青为原料,采用混合溶剂离心法对其 进行脱除喹啉不溶物试验研究。考察了芳烷比、溶剂比、离心时间、离心温度对精制沥青的喹啉不溶物含量和收率的影响。结果表明：当芳烷比一定时,精制沥青喹 啉不溶物含量和收率随溶剂比的增大而减小;当溶剂比一定时,精制沥青喹啉不溶物含量和收率均随芳烷比的增大而增加;离心时间越长,所得精制沥青喹啉不溶物 含量越低,收率也越低;离心温度升高,有利于喹啉不溶物脱除,离心温度的较优选择为80℃。通过调整混合溶剂的比例,可以方便地控制净化过程的收率和喹啉 不溶物含量。
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| [14] |
The formation of graphitizing carbons from the liquid phase , |
| [15] |
Axial nano-scale microstructures in graphitized fibers inherited from liquid crystal mesophase pitch ,
Nano-scale structures of a mesophase pitch based carbon fiber were characterized using a high-resolution scanning electron microscope (HR-SEM) and a scanning tunneling microscope (STM). Fibril was found to be sectioned by a number of pleat units, being aligned parallel along the fiber axis. The periodical size, thickness and height of pleat unit was estimated as 30–60 nm, 20–30 nm and around 7 nm, respectively. In a pleat, graphitic units of 30–60 nm long and 2–4 nm wide run principally perpendicular to the axis. The basal plane of graphite was observed at the largest magnification. Such a series of nano-structures should be related intimately to the performance of the fibers. The formation mechanism of such series of nano-structural units is discussed in relation to the nano-structure of the liquid crystal mesophase pitch and its deformation during the spinning.
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| [16] |
Composition changes in The co-caboniazation of FCC slurry and VR ,减压渣油与 FCC油浆共炭化的化学组成变化 ,
考察了齐鲁石化胜利炼油厂北催化油浆(FCC)和胜利减压渣油 (VR)在490℃、0.8MPa下不同混合比的原料和不同反应时间的中间产物的HS、TS、PS、PI 及其1h中间产物的HS和TS的1H-NMR.数据结果反映了体系的反应速度.掺入FCC油浆抑制了VR的反应活性,降低了体系的反应速度,增加了基质的 溶解度;1h中间产物的组成结构更接近于原料及反应体系的反应性和基质的溶解度,1h中间产物的芳香度越高,取代基越少,侧链越短,基质对VR中的活性反 应组分在炭化早期生成的高度缩合物质的溶解度越大.
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| [17] |
Needle coke from petroleum residue—a study of the thermal behavior of the middle fraction of the residue ,石油渣油制备针状焦研究-中间馏分热反应研究 ,
石油渣油的组成复杂,分子量分布宽,直接焦化不能生产针状焦.采 用一定的预处理技术将渣油中适宜制备针状焦的组分保留,可获得理想的焦化原料.通过以辽河减压渣油为原料,经溶剂萃取对渣油进行"掐头去尾"处理,获得了 分子量分布窄、杂质含量少的中间馏分A及馏分B.对馏分A、B分别进行热反应研究,结果表明:渣油的预处理效果明显,中间馏分热反应产物具有光学各向异性 物含量高、取向性好等特点,是制备针状焦的理想原料.
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| [18] |
The influence of a magnetic field during carbonization on the microstructure and electrical conductivity of needle cokes ,炭化过程中的磁场作用对针状焦结构及导电性能的影响 ,
<p><span style="font-size: 9pt; line-height: 150%">以中温煤沥青为原料，在载磁压力反应釜中进行热缩聚炭化合成针状焦；采用在线电阻测量法测定针状焦形成过程中磁场对电导的影响规律；通过偏光显微镜及X射线衍射仪对产物的形貌和组织结构进行表征。结果表明: 外加磁场对于改善针状焦微结构具有显著的作用，并能有效提高针状焦的电导特性，减小制备过程对温度的依赖性；适宜的压力有利于热缩聚反应的进行，提高成焦的收率；磁场还可以通过塞曼效应对自由基产生影响，提高自由基有效利用率，加快聚合反应速率；在磁场与压力的协同作用下，针状焦的石墨化性能也获得大幅度提升。<br /></span></p>
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| [19] |
Compositions and structure characterizations of coal tar refined soft pitch ,煤焦油精制软沥青组成及结构的表征 ,
以高温煤焦油为原料,蒸馏至280℃后得到煤焦油软沥青,经溶剂 萃取沉降方法获得精制软沥青,软化点为32℃(环法).索氏抽提法测得的族组成为:庚烷可溶物53.67%,庚烷不溶甲苯可溶物39.47%,甲苯不溶物 6.86%,喹啉不溶物0.06%.相对平均分子量是292,平均分子式为C22.22H16.32 N0.12S0.06O0.33,杂原子含量总和小于1.红外分析结果表明:其杂原子氧以R-O-R,Ar-O-R结构存在,杂原子氮以R-NH-R和 -N结构存在,且以-N-为主.采用改进的Brown-Lander模型得其平均结构为五元稠环;紫外分析表明,线性排列为主、面性排列为辅,即样品的化 学结构应以渺位缩合为主,迫位缩合为辅.
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| [20] |
Carbonization of coal tar pitch denitrogenated by metal sulfates ,
After adsorbtion removal of nitrogen compounds with dried metal sulfates, carbonization of extracted fractions from a coal tar pitch (CTP, N = 1.1 wt %) was studied for production of needle coke of low nitrogen content without puffing since nitrogen in the coke is believed to provoke puffing at rapid graphitization. A nitrogen-free coke (N, 0.01 wt%) with excellent flow texture was produced from the early two eluents of MI-TS (methanol-insoluble but toluene-soluble) by removing the basic nitrogen compounds through the sulfate column. Adsorbing denitrogenation through batch treatment with the supported sulfate also significantly reduced the nitrogen content of cokes produced from TS (toluene-soluble) without deterioration of their anisotropic texture. A low-nitrogen coke (N, 0.26 wt %) from the denitrogenated TS exhibited much smaller volume increase of micropores (< 0.1 渭m ) after rapid graphitization than coke from the original CTP, suggesting very little puffing. The efficiency of combining extractive fractionation for NH species with adsorbing separation of basic nitrogens is briefly discussed for practical application in order to minimize the amount of adsorbent.
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| [21] |
The Basic theory on formation process of shape structure of needle coke ,针状焦形态结构形成过程基本原理 ,
论述了重质渣油和沥青在热转化过程中形态结构变化的基本规律和化学反应机理。在此基础上,对影响针状焦微细结构形成的工艺和化学因素作了讨论。
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| [22] |
Carbonization in the tube bomb leading to needle coke: III. Carbonization properties of several coal tar pitch ,
Carbonization properties of several coal-tar pitches of different origins were studied, by using tube bomb, to correlate their analytical characteristics with their carbonization properties and to find their respective optimum carbonization conditions for the production of excellent needle coke. The pitch rich in naphthenic structure produced an excellent needle coke of low CTE and uni-axially arranged flow texture under a wider range of carbonization conditions, whereas the pitches of high oxygen and alkyl contents or of very high aromaticity gave cokes of larger CTE under the standard carbonization conditions of 500 掳C, 8 kg/cm 2 , because of more mosaic texture or poor uni-axial orientation in the resultant cokes. However, the two kinds of poor pitches were found to produce better cokes under their respective appropriate conditions. The former one did at a slightly lower carbonization temperature of 480 掳C and the latter one did under a lower carbonization pressure of 4 kg/cm 2 . A lower temperature allowed the development of bulk mesophase through the moderation of carbonization reactions for the former reactive pitch. The lower pressure improved uni-axial arrangement of mesophase molecules at the solidification stage through the sufficient gas evolution of good timing for the latter highly aromatic pitch. The higher pressure of carbonization delayed the solidification to be off-timing to the gas evolution. The mechanism of needle coke formation was discussed to explain the respective optimum conditions for the pitches of different analytical characteristics.
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