【作者】 王哲；

【导师】 刘丽影；

【作者基本信息】 东北大学 ， 动力工程及工程热物理， 2020， 硕士

【摘要】 随着科技的进步,能源的消耗越来越多,CO2等温室气体的排放量逐年增加,导致温室效应越来越严重,不仅对环境造成了恶劣影响还严重破坏了生态系统的平衡。想要有效缓解温室效应,必须采取一定的措施降低CO2的排放。燃煤电厂排放的烟气中含有大量的CO2气体,因此从电厂烟气入手减少CO2排放无疑具有巨大的减排潜力。常规的CO2吸附剂对于CO2捕集具有较高的吸附能力,但是烟气中存在的水蒸气会大量降低传统吸附剂的吸附量。因此,研究吸附剂在含湿环境中保持良好吸附性能的吸附剂具有重大意义。本文以吡咯单体为原料,通过氧化聚合法得到前驱体聚吡咯,通过XRD和FT-IR表征并与文献对比,证明成功合成了前驱体聚吡咯(PPy)。再以KOH为活化剂与PPy以不同比例混合,在N2氛围中高温化学活化,成功制备了氮掺杂多孔碳吸附剂。通过XRD和FT-IR分析证明氮掺杂多孔碳的成功制备,氮气吸脱附曲线证明NPC-2(KOH:PPy=2:1)具有最高的比表面积;CO2吸附测试得到样品NPC-2的吸附量最大,达到7.16 mmol/g;扫描电镜分析得到NPC-2具有较规整的块状形貌,与前驱体聚吡咯的球状颗粒形貌完全不同,颗粒大小约为几十微米。对NPC-2进行XPS分析确定其化学结构,得到C元素占据主要部分,其次是N元素在样品中占9.68%,且吡咯氮的强度最大,有利于CO2吸附。对NPC-2进行CO2和N2吸附测试,得到常压下273、303、333 K时的CO2吸附量分别为 7.16、3.5 和 2.1 mmol/g,N2 吸附量分别为 0.38、0.24 和 0.16mmol/g。对 NPC-2的 CO2吸附进行了 Langmuir、Dual-site Langmuir(DSL)、Freundlich、Toth 四个模型的拟合,得知DSL模型具有最好的拟合相关系数。利用IAST模型对最好样品NPC-2进行CO2/N2吸附选择比计算,在常压下温度为273、303和333K的吸附选择比为分别为30、22和18,证明NPC-2可以用于烟气中CO2/N2的分离。另外,用克劳修斯方程对NPC-2进行了 CO2吸附热的计算,由于氮元素掺杂后增加了吸附剂表面的吸附能,所以得到CO2吸附热随着吸附量的增加而增加。穿透实验装置为实验室内自行组装搭建,对氮掺杂多孔碳进行不同温度下的穿透实验,探究合成吸附量最高的样品NPC-2的双组分CO2/H2O吸附能力,得知温度对CO2和H2O的吸附均产生影响,随着温度的升高,CO2和H2O的吸附都呈下降的趋势。不论干燥环境还是潮湿环境下,CO2的吸附量都随温度的升高而降低。用LBET模型对CO2和H2O双组分的吸附进行拟合,在三个温度下的CO2和H2O的拟合都得到了较高的拟合相关系数。研究结果表明,氮掺杂多孔碳有较高的CO2捕集能力,且有较高的CO2/N2吸附选择比,可以有效分离CO2和N2,在水蒸汽存在的情况下,依然可以保持较好的CO2吸附性能,可以应用于含湿工业烟气中的CO2捕集。更多还原

【Abstract】 Energy consumption is increasing with the advancement of science and technology.The emission of greenhouse gases such as CO2 is increasing year by year,resulting greenhouse effect seriously,which not only has a bad impact on the environment but also undermines the balance of the ecosystem.In order to effectively alleviate the greenhouse effect,some measures must be taken to reduce CO2 emissions.The flue gases emitted by coal-fired power plants contains a large amount of CO2,so reducing CO2 emissions from power plant flue gas undoubtedly has a huge potential for emission reduction.Conventional CO2 adsorbents have a higher adsorption capacity for CO2 capture,but the presence of water vapor in the flue gas greatly reduces the adsorption capacity.Therefore,it is of great significance to research adsorbents that maintain good adsorption properties in a wet environment.In this paper,the pyrrole monomer was used as raw material to synthesis the precursor by oxidative polymerization,and the characterization by XRD and FT-IR and comparison with the literature proved that the precursor polypyrrole(PPy)was successfully synthesized.Then KOH was used as the activator mixed with PPy in different ratio to prepare N-doped porous carbon by chemical activate at a high temperature in N2 atmosphere.The preparation of polypyrrole and N-doped porous carbon was confirmed by XRD and FT-IR analyses.The N2 adsorptiondesorption curves proved that NPC-2(KOH:PPy=2:1)has the highest specific surface area.CO2 adsorption test obtained the sample NPC-2 has the highest adsorption capacity.The maximum adsorption amount was 7.16 mmol/g.SEM showed that NPC-2 had a relatively regular morphology,which was completely different from the spherical shape of the precursor polypyrrole.XPS analysis was performed on NPC-2 to determine its chemical structure.It was found that element "C" occupies the main part,followed by element "N" which accounts for 9.68%in the NPC-2,and the intensity of pyridonic-N is the largest,which is conducive to CO2 adsorption.The CO2 and N2 adsorption tests were carried on NPC-2,and obtained CO2 adsorption amounts of 7.16,3.5 and 2.1 mmol/g under normal pressure at 273,303 and 333 K,respectively,and N2 adsorption amount were 0.38,0.24 and 0.16 mmol/g,respectively.The models of Langmuir,Dual-site Langmuir(DSL),Freundlich and Toth were fitted to CO2 adsorption of NPC-2,and the DSL model have the best fitting effect.The I AST model was used to calculate the CO2/N2 adsorption selectivity of NPC-2 at different temperatures.The adsorption selectivity of 273,303 and 333 K at atmospheric pressure were 30,22 and 18,respectively,which proved that NPC-2 can be used for gas separation.The calculation of CO2 adsorption heat of NPC-2 shows that the heat of adsorption increases with the increase of adsorption amount because nitrogen doped into carbon framework.The breakthrough device is self-assembled,and the NPC-2 is subjected to test at different temperatures.The binary adsorption capacity CO2/H2O of NPC-2 has an effect with temperature.With the increase of temperature,the adsorption of CO2 and H2O tends to decrease,and the saturated vapor pressure of water becomes higher and higher,which lead to the partial pressure of water vapor becomes much higher.The both of single and binary CO2 adsorbed decreases with increasing temperature.At last,the LBET model was used to fit the binary adsorption,and gave a high fitting correlation coefficient on CO2 and H2O at three temperatures.The results show that N-doped porous carbon has a higher CO2 adsorption capacity and CO2/N2 adsorption selectivity,which can effectively separate CO2 and N2.And this porous carbon can be used in CO2 adsobed in the presence of water,which imply that it can be applied to CO2 capture in flue gases.更多还原