【作者】 解小玲；

【导师】 曹青；

【作者基本信息】 太原理工大学 ， 化学工程与技术， 2014， 博士

【摘要】 针状焦具有热膨胀系数低、密度大、耐腐蚀、导电导热性好、机械强度高等优良的综合性能，能满足环境条件十分苛刻的要求。因而，它是高温电弧炉炼钢用高功率电极和超高功率电极的首选材料。研究表明，由针状焦所制碳电极，同原有普通碳电极相比，可降低一半耗能。此外，在锂离子电池负极材料、超级电化学电容器等方面亦得到重要应用。我国是生产和消费煤炭的大国，在煤炭深加工如炼焦过程中会产生约2~3wt.%的煤沥青。2013年焦炭的生产量就达4.76亿吨，因此，产生的煤沥青的数量相当可观。对其高效利用，可实现资源的科学利用和有效配置。深入研究煤沥青改性及外在条件对中间相形成产生的影响，以期揭示科学规律，对提高或改善针状焦结构具有重要的帮助，进而提高针状焦综合性能，其研究对提升煤炭资源的利用率、延伸煤炭深加工的产业链条及改变只焦不化的产业结构具有重要意义。本论文以中温煤沥青为原料，通过改变不同条件对去除喹啉不溶物的精制煤沥青进行炭化，研究了温度、压力、时间及电场强度等对中间相、半焦和针状焦的结构及其性能的影响；在此基础上，研究了溶剂预处理煤沥青、提取中间相炭微球、添加石墨烯、改性煤沥青等对中间相及针状焦结构的影响，并对其电化学性能进行了较为详细的研究。采用扫描电子显微镜(SEM)、X射线衍射仪(XRD)、偏光显微镜、红外光谱分析(FT-IR)、循环伏安法(CV)及电化学交流阻抗(EIS)等方法对精制煤沥青、中间相、半焦及针状焦的结构及性能进行了表征分析。得到的主要结论如下：1、在压力为0.5MPa、电场强度为300kV/m、炭化温度为470℃条件下，保温3h，得到的中间相小球完善均匀，而且中间相小球所占比例达到了52.3%。在升温速率为0.5℃/min，终温为600℃，保持时间为2h时，生成半焦的结构比较完善。进一步经过煅烧处理，可明显改善针状焦的结晶性，即分子的层面堆积高度增大，分子层间排列趋于致密，纤维结构更发达，石墨化程度得到明显提高。2、用不同极性和结构的溶剂对去除一次性喹啉不溶物的煤沥青进行抽提，以去除沥青中杂原子，分析了不同溶剂的抽提效果。结果表明，不同溶剂对杂原子的去除效果不同。其中，采用庚烷和四氯化碳混合溶剂抽提得到的煤沥青杂原子O、N和S含量明显降低。它们的存在不利于芳香分子共轭程度的增加；相比而言，硫原子对其影响最为显著，而N和O对纤维的取向程度影响较弱。3、通过提取中间相微球并以其作为下一次制备煤沥青中间相的晶种，实验系统研究了对其中间相结构产生的影响。结果表明，经过二次、三次和四次晶种存在的环境下产生的中间相，其微球的数量随着次数的增加，出现开始迅速增多而后缓慢增加的现象。其中，经过二次、三次和四次晶种存在下得到的中间相沥青，其微球数量所占比例分别为45.4%、69.8％、71.2％；而经三次和四次晶种存在下制备的煤沥青产生的针状焦，其光学纤维组织分别可达89%和80%。在搅拌下表现出更好的电容性和更清晰完善晶体结构。4、探讨了在煤沥青中添加了石墨烯作为晶核对中间相形成过程及其对半焦和针状焦产生的影响。结果表明，随着石墨烯量的增加，微球的数量也逐渐增多，合适添加量为0.2wt%。当添加量超过0.2wt.%，微球数量的变化不再显著；其中，由添加0.2wt.%的石墨烯得到中间相用于制备半焦和针状焦，其光学纤维组织结构比较完善；同未添加石墨烯的半焦及针状焦相比，电容性增大。5、采用烷基化试剂溴代正丁烷和溴代正丙烷作为改性剂，研究了改性后对煤沥青中间相纤维组织和对针状焦结构及电化学性质产生的影响。结果表明，经溴代正丁烷改性的煤沥青MCTP-7B，其软化点降低到64℃，残炭率增加了24%；经溴代正丙烷改性的煤沥青MCTP-7P，其软化点降低到63℃，残炭率增加了15%。其中，由7wt.%的溴代正丙烷改性得到的MCTP制得的针状焦，SEM形貌呈长纤维组织；电化学测试表明，稳定性和可逆性都有所提高。更多还原

【Abstract】 Needle coke has potential application under condition of harshenvironmental due to low thermal expansion coefficient, high density, corrosionresistance, good conductivity, high mechanical strength and excellentcomprehensive performance, especially apply for the high and ultra high powerelectrode in high-temperature electric arc furnace steelmaking. The researchesshow that the needle coke electrode can reduce half of the energy consumption,compared with the original ordinary carbon electrode. In addition, needle cokealso has important applications in anode materials for lithium ion batteries andsuper capacitors etc. China is a power country of coal production andconsumption. About2~3wt.%coal tar pitch will be in the deep processing ofcoal such as coking process. The coke production was an estimated4.76millions tons in2013, so, it would give rise to a fairly substantial amount of coaltar pitch production. It can realize the use of science and effective allocation ofresources via high efficient utilization of coal tar pitch. It is most important tostudy on modification of coal tar pitch and influence of external conditions on the formation of the mesophase, in order to improve the structure of needle cokeand the utilization rate of coal resources, which has important significance forextending industry chain of coalprocessing and changing changing industrystructure of coking processing.In this paper, the medium temperature coal tar pitch were selected as rawmaterial for investigation. By means of carbonizing the coal tar pitch removedquinoline insolubles in different condition, Influences of temperature, pressure,time and electric field intensity on the structure and properties of mesophase,semi-coke and needle coke were studied. On this basis, The further researcheswere carried out about influences of solvent pretreatment of coal tar pitch,extraction of MCMB, adding grapheme, modification of coal tar pitch onstructure of mesophase and needle coke and the electrochemical properties.Scanning electron microscopy (SEM), X ray diffraction (XRD) analysis,polarizing microscopy, infrared spectroscopy (FT-IR), cyclic voltammetry (CV)and electrochemical impedance spectroscopy (EIS) and other methods wereadopted to characterize and analyze structure and properties of the refined coaltar pitch, mesophase, semi-coke and needle coke.The research results are as follows:1. Mesophase microbeads were of perfect uniform and the conversion ratereached52.3%under pressure0.5MPa, electric field intensity300kV/m,heated at470℃for3h. Semi-coke structure was of the most perfect heated at600℃for2h with heating rate of0.5℃/min. The calcination treatment could improve the crystal structure of needle coke, which perform increasing thestacking height of molecules enlarging the molecular layer arrangement andimproving the fiber structure and graphitization degree of needle coke.2. The heteroatom of refined coal tar pitch was removed by extraction withdifferent polarity and structure solvent. The extraction effect was analyzed indifferent solvent. The results showed that the removal effections of hetero atomswas different in different solvents. The heteroatom O, N and S of coal tar pitchcould be decreased obviously using heptanes and carbon tetrachloride solventextraction. These hetero atoms were not conducive to the increase of aromaticmolecular conjugate degree. In contrast, the effect of sulfur atom was the mostsignificant, and influence of N and O on orientation degree of fiber was weak.3. Extracted mesophase microsphere is used as the next crystal seed forpreparation of mesophase. Effects of extraction on mesophase structure havebeen systematically studied. The results showed that the microspheres numberof mesophase microspheres by multiple extraction MCMB preparationincreased rapidly along with the increase of extraction times and then slowlyincrease. Mesophase pitch was prepared using the seeds got at the second times,the third times and the forth times, and the proportion of microspheres isrespectively45.4%,69.8%and71.2%. Needle coke was prepared using thethird times and the forth times seed, and the proportion of optical fibermicrograph is respectively89%and80%. Under the stirring conditions, needlecoke showed better capacity better and more clear and perfect crystal structure. 4. The influences of coal tar pitch adding grapheme as crystal nucleus onmesophase formation process and structure of semi coke and needle coke hasbeen discussed. The results showed that with the increase of the quality ofgraphene, the number of microspheres gradually increased. Appropriate addingamount is about0.2wt%even the amount is more than0.2wt.%, the change ofmicrospheres number is no longer significant. The optical fiber structure wasmore perfect and capacitive was greater, compared with the semi-coke andneedle coke without the addition of grapheme.5. Using alkylation reagents like n-butyl bromide and n-propyl bromide asmodifier, the influence of modification on the fiber structure of coal tar pitchmesophase and structure and electrochemical properties of needle coke wasstudied. The results showed that the softening point of MCTP-7B modified byn-butyl bromide was reduced to64℃, char yield was increased by24%. Whilethe softening point of MCTP-7P modified by n-propyl bromide was reduced to63℃, char yield was increased by15%. Moreover, the morphology of needlecoke, prepared from coal tar pitch modified by7wt%of n-propyl bromide,presented long fibrous texture. The electrochemical tests showed that thestability and reversibility of needle coke were all improved.更多还原