【作者】 王晓瑞；

【导师】 钱仁渊；

【作者基本信息】 南京工业大学 ， 化工工艺， 2005， 硕士

【摘要】 本研究以中温煤沥青为原料,经空气氧化后,采用化学活化法制备出了比表面积高于1800m2/g 的活性炭材料。结果证明,以煤沥青为原料同样可以制备出高比表面积活性炭,这一研究不仅解决了活性炭原料来源受限问题,而且为大量的炼焦副产品找到了经济合理的利用路线。煤沥青具有独特的化学性质,如软化点低,挥发分高,性能不稳定等,以煤沥青为原料直接制备的活性炭比表面积较低。为得到高比表面积活性炭,在参考大量文献的基础之上,选取空气氧化热聚合法对煤沥青进行稳定化预处理,再以预处理得到的前驱体制备活性炭,其比表面积远远高于处理前直接制备的活性炭比表面积。同时,采用挥发分、甲苯不溶物(TI)、元素分析、傅立叶红外(FTIR)、X 射线衍射(XRD)、偏光显微镜及扫描电镜(SEM)等表征手段对前驱体性能进行测试,发现以2℃/min 的速率升温至420℃,再恒温2h 得到的前驱体性能最佳,所制备的活性炭性能也达到最佳。除原料性能对活性炭的影响较大外,制备过程中,很多因素对活性炭的比表面积、孔隙结构及吸附性能都有影响,所以本实验中分别考虑了前驱体粒度、碱炭比、润湿剂无水乙醇的添加量等配比因素的影响,并且采用正交实验设计方法对制备过程中炭化温度、炭化时间、活化温度、活化时间等工艺因素的影响进行了考察。实验发现,前驱体粒度对活性炭的性能有一定影响,但无明显规律;活性炭比表面积及碘吸附值随碱/炭(即碱的添加量)的增加而增加,但高的碱/炭将增大中孔比例;无水乙醇的加入导致活性炭比表面积及碘吸附性能下降,但是却对微孔的生成有利。在制备过程中,工艺条件对于比表面积的影响大小依次为:炭化时间>活化时间>炭化温度>活化温度,且炭化温度450℃、炭化时间30min、活化温度800℃、活化时间100min时所制得的活性炭比表面积最大;对碘吸附影响大小依次为:活化时间>炭化时间>活化温度>炭化温度,且在考察的水平范围内,炭化温度350℃、炭化时间30min、活化温度800℃、活化时间80min时所制得的活性炭碘吸附值最大。根据KOH活化机理,活性炭发达的孔隙结构及高的比表面积主要产生于活化阶段,因此适当的活化温度和时间是保证活化反应充分进行的一个重要条件。活更多还原

【Abstract】 The research is about the active carbon prepared by chemical activation, the medium temperature coal-tar pitch was oxidized in atmospheric before chemical activation, then the specific surface area of the active carbons beyond 1800m2/g. The result shows coal-tar pitch can be used to prepare high specific surface area active carbon too. It not only resolves the problem of material source, but also finds an economical and reasonable route for massive coke by-products. Coal-tar pitch has special chemical property, such as low softening point, high volatile matter, unsteadiness behavior etc, so the active carbon prepared form coal-tar pitch directly has low specific surface area. In order to getting high specific surface area active carbon, the research select stabilizing pretreatment of coal-tar pitch by atmospheric oxidation thermal polymerization process based on many documents. The specific surface area of active carbon prepared from precursor is higher than active carbon prepared from coal-tar pitch. It can be found that the optimal pretreatment process is that heats the coal-tar pitch at rate of 2℃/min to 420℃, then constant temperature for 2 hours. Under this condition, the precursor has the best property by testing of volatile matter content, methylbenzene non-dissolve matter (TI) content, elemental analysis, FTIR, XRD, polarizing microscope and SEM, and the active carbon prepared from this precursor has the best property. There are many factors affect the specific surface area, pore structure and adsorptive capacity of active carbon in the process, so the influence of precursor’s particle size, alkali/carbon and wetting agent (absolute alcohol) addictive level on active carbon was considered in this paper. At the same time, carbonization temperature, carbonization time, activation temperature and activation time in the process were taken into account by orthogonal design method. The result shows that precursor’s particle size affect property of active carbon directly, but there is not obvious rule; specific surface area and iodonium adsorbance of active carbon increase with alkali/carbon increasing, but high alkali/carbon leads to mesopore proportion increasing; the absolute alcohol make the specific surface area and iodonium adsorbance of active carbon decreased, but it is available to the growing of micropore. It also can be found that the process of conditions have influence on specific surface area as following during the process, carbonization time>activation time> carbonization temperature >activation temperature. So the optimum conditions are the carbonization temperature 450℃, carbonization time 30min, activation temperature 800℃and activation time 100min respectively. While the influences on iodonium adsorbance are activation time>carbonization time>activation temperature> carbonization temperature, and the optimum conditions are carbonization temperature 350℃, carbonization time 30min, activation temperature 800℃and activation time 80min. According to KOH activation mechanism, developed pore structure and high specific surface area are mostly produced from activation phase, so proper activation temperature and activation time are important conditions for sufficient reaction. Short activation time is not enough for sufficient reaction, for it can not produce developed pore structure and high specific surface area. While long activation time and high activation temperature can lead to deep activation reaction and excess micropore agglutination, then lead to specific surface area decreased. However, the influence of carbonization phase on specific surface area is greater than activation phase. There are three reasons: firstly, precursor has high graphitizing degree after carbonization phase, which is a disadvantage to high specific surface area active carbon; secondly, KOH dehydration in carbonization phase offer activation (K2O and CO2 composed to K2CO3 and K2O reduce to K) integrant K2O, which is important premise step; thirdly, carbonization phase not only produce carbonization, but also company with activation, even to rather degree, which effect the following phase, that is activation.更多还原