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煤基活性炭赋磁调孔机理的研究

Study on Principles of Magnetization and Pore Size Regulation of Coal-Based Activated Carbon

【作者】 张军

【导师】 解强;

【作者基本信息】 中国矿业大学(北京) , 化学工艺, 2010, 博士

【摘要】 根据不同应用途径的要求调控活性炭的孔结构是实现活性炭定向制备的关键,而活性炭的赋磁是解决活性炭分离和回收难题的有效途径之一。论文以我国典型煤种为原料,以研究、筛选的过渡金属化合物为添加剂,一步法制备出了孔结构可调的煤基磁性活性炭;采用气体吸附、SEM、XRD、FT-IR、TGA和VSM等手段及活性炭碘值、亚甲基蓝值测试等方法对制备活性炭的孔结构、表面形貌、微晶结构、表面化学、磁性能及吸附性能等进行了表征。结果表明,铁系、镍系添加剂经炭化、活化后分别转化为具有强磁性的Fe、Fe3O4及金属镍,为活性炭赋磁;过渡金属化合物的添加提高了炭化过程煤的热解速率,阻碍了胶质体生成阶段自由基与基本结构单元的有序化和石墨化进程,利于形成无定形结构,为活化阶段造孔和调控打下基础;铁、镍系添加剂对活化过程具有催化作用,促进中孔发育,对微孔的影响较小。以筛选的Fe3O4为磁性添加剂在初步优化的工艺条件下(添加量为6.0%、炭化温度600℃、活化温度880℃),活性炭比表面积、比饱和磁化强度分别达到993.5 m2·g-1 2.4158 emu·g-1改变Fe3O4的添加量,可以调整活性炭微孔和中孔的比例,实现活性炭孔结构的定向调控。

【Abstract】 Pore size regulation plays an important role in the directional preparation of activated carbon, while magnetization of activated carbon is an effective approach to separating and recovering the spent activated carbon. In this paper, a simple one-step synthetic method was presented and studied for preparing magnetic activated carbon with regulated pore size from coal in the presence of transition metal compounds. The pore structure, surface morphology, microcrystalline structure, surface chemistry, magnetic properties and adsorption performances were characterized by N2 adsorption, SEM, XRD, FT-IR, TGA and VSM, iodine value and methylene blue value, respectively. The results show that Fe, Fe3O4 and Ni with strong magnetism transforme by iron-based and nickel-based additives during carbonization and activation process provided magnetism for activated carbon. In carbonization process, pyrolysis is intensified by addition of transition metal compounds, which hinderes the condensation of free radicals in the colloid formation stage, decreases the ordering extent of basic structural unit and degree of graphitization. It is beneficial to form amorphous structure in order to lay a foundation for pore-making and regulation in activation process. Beside, iron and nickel based additive could catalyze activation process and promote the formation of mesopores while has minor effect on microspores. Finally, Fe3O4 is screened out to be the best magnetic additive. With an addition of 6.0% Fe3O4, at carbonization temperature of 600℃and activation temperature of 880℃,the specific surface area and the specific saturation magnetization of derived coal-based magnetic activated carbon are 993.56m2·g-1,2.4158emu·g-1, respectively. When the amount of Fe3O4 varies, the ratio of micropores and mesopores in activated carbons can be easily regulated.

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