【作者】 李鑫；

【导师】 王永洪；

【作者基本信息】 太原理工大学 ， 化学工程（专业学位）， 2020， 硕士

【摘要】 随着经济的快速发展,大量的化石能源消耗排放的二氧化碳（CO₂）破坏了全球大气的碳平衡,引发全球气候变暖,威胁人类生存。在气候问题备受关注的国际大背景下,对温室气体CO₂的回收以及利用成为当前全球性共识。膜分离技术由于其分离效率高、能耗低以及环境友好等优点,在气体分离领域方面备受青睐。通常用于气体分离的聚合物膜材料由于其不耐酸碱,不耐高温等弊端而很大程度下限制了其在分离领域的应用。炭分子筛膜（CMSMs）作为一种新型的无机膜是由含碳物质经高温热解炭化而成的。为了进一步提高炭分子筛膜的气体分离性能,以掺杂含氮炭材料的混合基质膜（MMMs）作为炭分子筛膜前驱体,以调节所制备CMSMs的孔结构及对CO₂亲和性。具体研究内容及结论如下:（1）选用三聚氰胺作为添加剂,引入到均苯四甲酸酐-4,4?-二氨基二苯醚（PMDA-ODA）型聚酰胺酸聚合物膜中制得混合基质膜,然后经热解炭化制备得到氮掺杂混合基质炭分子筛膜。采用红外光谱（FTIR）、X-射线衍射（XRD）、BET孔径分析和CO₂吸脱附对膜结构与性能进行表征;研究了热浸温度、热浸时间和三聚氰胺掺杂量对不同动力学直径的气体分离性能的影响和膜的老化性能等。结果表明:在温度为25°C和压力为1 bar纯气体条件下,掺杂5 wt%三聚氰胺的混合基质CMSMs显示出优异的CO₂/N₂分离性能,其CO₂渗透性和CO₂/N₂选择性分别为94 Barrer和193。这是由于膜炭化过程中三聚氰胺原位生成g-C₃N₄,片层状g-C₃N₄的增长了气体分子的扩散路径,改善了CO₂/N₂选择性;另一方面,三聚氰胺的三嗪单元结构与CO₂分子之间强的相互作用强化了CO₂的吸附选择性,从而为所制备的掺氮CMSMs提供一定的吸附选择性。耐久性测试表明:掺杂5 wt%三聚氰胺的CMSMs在70天内依然可以保持出色的CO₂/N₂选择性。（2）先通过水热反应制备了三聚氰胺修饰的葡萄糖炭球前驱体,高温炭化并活化造孔之后,将其加入到PMDA-ODA型聚酰胺酸聚合物膜中,制备得到混合基质膜,然后经程序升温至650℃热解炭化制备得到掺杂含氮多孔葡萄糖炭球的混合基质CMSMs。系统的研究了制备多孔炭球的活化时间、活化温度、KOH用量和含氮多孔炭球（NPC）的含量对所制备的混合基质炭分子筛膜分离性能的影响,重点考察不同动力学直径的气体渗透性能、老化性能和混合气渗透性能等。结果表明:在温度25°C和压力为1 bar条件下,当NPC含量为5 wt%时,混合基质CMSMs的CO₂渗透性和CO₂/N₂选择性分别为826 Barrer和87。这是由于多孔炭球的存在为混合基质炭分子筛膜提供额外的气体传递通道;而且炭球的活性位点可以增加其与酸性气体之间的相互作用,为混合基质CMSMs提供一定的吸附选择性,从而提高混合基质炭分子筛膜的选择性。当NPC含量达到5 wt%时,其混合气CO₂的渗透性及CO₂/N₂选择性分别为807 Barrer和83。此外,掺杂5 wt%NPC的混合基质CMSMs在70天内可以保持出色的CO₂/N₂选择性。更多还原

【Abstract】 With the rapid development of economy,a large number of CO₂ from fossil energy consumption has destroyed the carbon balance of the global atmosphere,which causes global warming and threatens human survival.Under the background of climate issues,the recovery and utilization of the greenhouse gas CO₂ have become the current global consensus.Membrane separation technology exhibit a large amount of advantages such as high separation,low energy consumption and environmental friendly,thus it has attracted much attention.The polymer membrane materials are largely limited to their applications of gas separation,due to their disadvantages such as lower acid and alkaline resistance,poor temperature resistance.As a new type of inorganic membrane,the carbon molecular sieve membranes（CMSMs）are formed by high temperature pyrolysis and carbonization of carbonaceous materials.In order to further improve the gas separation performance of CMSMs,the mixed matrix membrane（MMMs）doped with nitrogen-containing carbon materials is used as the precursor of CMSMs to adjust the pore structure and affinity of CO₂ of the as-prepared CMSMs.The specific research contents are as follows:（1）Melamine is selected as the additive,which is introduced into pyromellitic anhydride-4,4?-diaminodiphenyl ether（PMDA-ODA）type polyamic acid polymer membrane to prepare the mixed matrix membranes.Then,the nitrogen-doped mixed matrix carbon molecular sieve membranes are prepared by pyrolysis carbonization.The structure of the membrane is characterized by Fourier transform infrared spectroscopy（FTIR）,X-ray diffraction（XRD）,Brunauer Emmett Teller（BET）,CO₂ adsorption and desorption curve;the effects of pyrolysis temperature,thermal soak time,melamine doping amount and different inorganic fillers on the separation performance of membranes are systematically discussed.Simultaneously,the separation performance of different dynamic diameter gases and mixed gas,the aging performance of the membranes are investigated.The results show that the mixed matrix CMSMs doped with 5wt%melamine shows the excellent CO₂/N₂ separation performance at 25℃and1 bar under pure gas conditions.Its CO₂ permeability and CO₂/N₂ selectivity are94 Barrer and 193,respectively.This is due to the in-situ formation of g-C₃N₄during membrane carbonization,which increase diffusion of gas molecules at the presence of the g-C₃N₄ sheet material.On the other hand,the strong interaction between triazine unit and CO₂ molecules enhanced the adsorption selectivity of CO₂,thus providing a certain adsorption selectivity for the prepared nitrogen doped CMSMS.The durability test of nitrogen-doped CMSMs shows the excellent CO₂/N₂ selectivity for 70 days.（2）The melamine-modified glucose-carbon sphere is prepared by hydrothermal method firstiy.After that,the precursor is actived to produce pores,and then added to the PMDA-ODA type polyamic acid membrane to prepare the mixed matrix membrane.The mixed matrix CMSMs doped with nitrogen-containing carbon spheres are prepared by pyrolysis at 650℃.The effects of activation time,activation temperature,KOH dosage and NPC loading on gas separation performance are investigated.At the same time,gas permeability performance with different dynamic radii,aging performance and mixed gas performance are studied systematically.When the NPC loading is 5 wt%,the CO₂permeability and the CO₂/N₂ selectivity of the mixed matrix CMSMs are 826Barrer and 87,respectively.This is due to the following two respects.On the one hand,the presence of porous carbon spheres provides the additional gas transmission channels for mixed matrix carbon molecular sieve membranes.On the other hand,the active sites of carbon spheres can increase the interaction with acid gases,providing a certain adsorption selectivity for mixed matrix CMSMs.Therefore,the selectivity of the mixed matrix carbon molecular sieve membrane is improved.The mixed gas test show that when the NPC loading reaches 5 wt%,the CO₂ permeability and CO₂/N₂ selectivity are 807 Barrer and 83,respectively.More importantly,the durability test of CMSMs doped with 5 wt%NPC shows that it can maintain excellent CO₂/N₂ selectivity for about 70 days.更多还原