PMDA-ODA型聚酰亚胺炭/碳纳米管杂化膜的制备及气体分离性能研究

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宋成文, 姜大伟, 李琳, 孙美悦, 王同华. PMDA-ODA型聚酰亚胺炭/碳纳米管杂化膜的制备及气体分离性能研究. 无机材料学报, 2012, 27(9): 923-927
SONG Cheng-Wen, JIANG Da-Wei, LI Lin, SUN Mei-Yue, WANG Tong-Hua. Preparation and Gas Separation Properties of Carbon/Carbon Nanotubes Hybrid Membranes Derived from PMDA-ODA Polyimide. Journal of Inorganic Materials, 2012, 27(9): 923-927 复制到剪切板

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PMDA-ODA型聚酰亚胺炭/碳纳米管杂化膜的制备及气体分离性能研究

宋成文¹, 姜大伟², 李琳², 孙美悦², 王同华²

1. 大连海事大学环境科学与工程学院, 大连116026

2. 大连理工大学化工学院, 精细化工国家重点实验室炭素研究室, 大连116012

王同华, 教授. E-mail:wangth@dlut.edu.cn

宋成文(1975-), 男, 副教授. E-mail:songchengwen_dmu@yahoo.com.cn

基金:国家自然科学基金(20776024, 20836006, 20976021); 国家863项目(2009AA03Z215); 辽宁省教育厅高等学校科研计划项目(2009A098); 中央高校基本科研业务费专项基金(2011QN141); 辽宁省海洋与渔业厅海洋环保专题基金(2012-Inhyhbc-0004, 2012-Inhyhbc-0005);

摘要

针对现有气体分离炭膜存在的渗透速率低等问题, 提出并设计在PMDA-ODA型聚酰亚胺前驱体中掺杂碳纳米管, 经高温热解后制备炭/碳纳米管杂化膜. 分别采用透射电镜(TEM)、X射线衍射分析(XRD)和气体渗透实验对炭/碳纳米管杂化膜的微观结构和分离性能进行表征. 实验结果表明, 在PMDA-ODA型聚酰亚胺前驱体中掺杂碳纳米管后, 碳纳米管与炭基体之间形成明显的“界面间隙”, 打破了原有炭膜中由乱层炭构成的无序微孔结构, 重新构建了杂化炭膜的孔隙结构. 与纯炭膜相比, 杂化炭膜的气体渗透速率大幅增加, 其中O₂的渗透速率增大接近4倍(达到1576 Barrer), 而O₂/N₂的分离选择性仅降低17%.

关键词: 碳纳米管; 聚酰亚胺; 制备; 气体分离

中图分类号:O643 文献标志码:A 文章编号:1000-324X(2012)09-0923-05

Preparation and Gas Separation Properties of Carbon/Carbon Nanotubes Hybrid Membranes Derived from PMDA-ODA Polyimide

SONG Cheng-Wen¹, JIANG Da-Wei², LI Lin², SUN Mei-Yue², WANG Tong-Hua²

1. School of Environment Science and Engineering, Dalian Maritime University, Dalian 116026, China

2. Carbon Research Laboratory and State Key Laboratory of Fine Chemicals, School of Chemical Engineering, Dalian University of Technology, Dalian 116012, China

Fund:National Natural Science Foundation of China (20776024, 20836006, 20976021); National High-tech Research and Development Project of China (2009AA03Z215); Scientific Research Fund of Liaoning Provincial Education Department (2009A098); Fundamental Research Funds for the Central Universities (2011QN141); Special Foundation for Ocean Environmental Protection of Ocean and Fisheries Department of Liaoning Province (2012-Inhyhbc-0004, 2012-Inhyhbc-0005);

Abstract

A convenient and effective strategy was used to develop a novel carbon/carbon nanotubes (C/CNT) hybrid membrane by incorporating multi-walled carbon nanotubes (MWNT) into PMDA-ODA polyimide precursor through controlled pyrolysis process at 600℃. Transmission electron microscope, X-ray diffraction and gas permeation experiments were employed to investigate the microstructural characteristics and gas separation performance of hybrid carbon membrane. Results show that the as-prepared C/CNT hybrid membrane has excellent gas (H₂, CO₂, O₂, N₂ and CH₄) separation properties as compared with pure carbon membrane, and the O₂ permeability of hybrid carbon membrane increases by nearly 4 times reaching 1576 Barrer, while the O₂/N₂ permselectivity decreasing by only 17%. It is believed that carbon membrane doped by MWNT can make effective use of the interfacial gaps formed between MWNT and carbon matrix to reconstruct the pore structure of hybrid carbon membrane, which helps to increase the gas diffusion ability and further improve the gas permeability of hybrid carbon membrane.

Keyword: carbon nanotubes; polyimide; preparation; gas separation

Show Figures

膜分离是20世纪60年代后迅速崛起的一门多学科交叉的分离技术. 与传统的分离技术如蒸馏、吸附、深冷分离等相比, 膜分离技术具有高效、节能、设备紧凑、过程易控制等优点, 已广泛应用于能源、电子、石油化工等领域, 成为当今分离科学中最重要的技术手段之一. 目前, 用于气体分离的膜材料主要是聚合物膜^{[ 1, 2]}, 尽管其生产成本较低, 但是由于聚合物膜耐酸、碱和高温、高压的能力较差, 并且聚合物膜的渗透性和分离选择性之间受Robeson 上限制约^{[ 3]}, 因此在很多领域的应用受到了一定的限制.

炭膜是由含碳聚合物在惰性气体氛围或真空条件下, 经过高温热解制备而成的一种新型无机膜材料. 它主要利用聚合物在热解过程中形成的丰富超微孔结构, 对具有不同分子动力学直径的气体进行分离. 近二、三十年来, 炭膜以其优异的气体分离性能, 得到科学家们的广泛关注, 已经成为当前气体分离膜技术的研究热点之一^{[ 4, 5]}. 但到目前为止, 炭膜仍然局限于实验室研究, 这主要是由于目前所制备炭膜的结构属乱层炭结构, 分布于其中的孔隙结构比较致密, 气体的渗透扩散阻力较大, 导致炭膜对气体分子的渗透能力仍然无法满足实际应用的要求^{[ 6]}. 进一步提高炭膜的气体渗透性能已成为实现炭膜产业化应用的关键.

在前驱体中掺杂无机纳米材料重新构建炭膜的孔隙结构, 是打破炭膜原有的无序孔结构, 提高炭膜的气体渗透性能的一种有效方法^{[ 7, 8, 9, 10, 11, 12]}. 碳纳米管(CNT)是日本科学家Iijima发现的准一维管状纳米材料^{[ 13]}, 虽然碳纳米管特殊的力学、电学、热学、磁、储氢性能受到广泛关注^{[ 14, 15]}, 但是基于准一维纳米孔道结构特点方面的应用还有待开发. 针对现有气体分离炭膜存在的问题, 本工作在PMDA- ODA型聚酰亚胺前驱体中掺杂碳纳米管制备成炭/碳纳米管杂化膜, 对现有炭膜的孔结构实现重建, 制备出具有高选择性、高渗透通量的炭膜分离材料.

1 实验部分

1.1 实验原料

杂化炭膜的聚合物前驱体选用天津绝缘材料有限公司生产的PMDA-ODA型聚酰亚胺的预聚体聚酰胺酸(PAA); 多壁碳纳米管(MWNT)是由大连理工大学炭素材料研究室提供.

1.2 炭膜的制备

1.2.1 纯聚酰亚胺炭膜的制备

将聚酰胺酸加入到N, N-二甲基乙酰胺溶剂中, 配成浓度为11%的聚酰胺酸溶液, 搅拌2 h后静置脱泡, 然后倾倒在带有加热器的水平玻璃板上用刮刀展平溶液成膜, 在40℃条件下干燥24 h后, 将膜剪成φ5 cm的圆形膜, 并夹在石墨板间, 放入管式程序升温炭化炉中. 在氩气的保护下, 以2 ℃/min的升温速率升温至100℃、200℃、350℃, 分别恒温1 h, 然后再以2℃/min的升温速率升至600℃, 并恒温2 h. 待其自然冷却至50℃以下时, 将膜取出. 整个炭化过程中保持氩气流速在100 mL/min.

1.2.2 炭/碳纳米管杂化膜的制备

将碳纳米管分散到N, N-二甲基乙酰胺溶剂中, 放入超声波清洗器中利用超声波分散2 h. 将上述碳纳米管与N, N-二甲基乙酰胺混合液加入到聚酰胺酸中, 保证聚酰胺酸浓度为11%, 搅拌2 h后静置脱泡. 然后倾倒在带有加热器的水平玻璃板上用刮刀展平溶液成膜. 在40℃条件下干燥24 h后, 将膜剪成φ5 cm的圆形膜, 并夹在石墨板间, 放入管式程序升温炭化炉中在氩气的保护下, 以3 ℃/min的升温速率升温至100℃、200℃、350℃, 分别恒温 1 h, 然后再以2℃/min的升温速率升至600℃, 并恒温2 h. 待其自然冷却至50℃以下时, 将膜取出, 整个炭化过程中保持氩气流速在100 mL/min.

1.3 炭膜的渗透性能测试

复合炭膜的气体渗透性能采用恒压变体积法测定^{[ 16]}. 气体的渗透系数( P)及分离系数( α₁₂)计算公式如下:

(1)

(2)

式中 F 为气体渗透通量; 是膜上下游的压差; A是气体透过膜的有效面积; l是膜的厚度.

1.4 炭膜结构性能表征

采用Philips Tecanai GZ20型高倍透射电镜观察炭膜及分散其中的碳纳米管的微观形貌. 取微量样品粉末溶入乙醇, 超声分散20 min后, 取几滴样品液滴在铜网上, 吹风机吹干后置入分析仪器中, 脱气后进行观察.

采用日本理学D/Max-2400型X 射线衍射仪对样品的微晶结构进行表征, 实验采用Cu靶辐射源, 石墨单色器, 管压40 kV, 管流100 mA, 扫描范围5º~80º, 扫描速率0.6º/min, X光波长λ=0.154055 nm, 步长为0.02º.

2 结果与讨论

2.1 炭/碳纳米管杂化膜的微观结构分析

用于制备杂化膜的碳纳米管微观形貌如图1 (a)所示, TEM分析显示, 碳纳米管呈一维束状结构, 管直径约为10 nm, 比较均一, 部分碳纳米管顶端呈“开孔”状态. 为了进一步考察掺杂碳纳米管后制备的炭/碳纳米管杂化膜的微观形貌特征以及碳纳米管在其中的分散情况, 对杂化膜也进行了TEM观察和分析, 其结果如图1(b),(c)所示. 从图1(b,c)可以看出, 部分碳纳米管以单根形式分散在炭基体中. 碳纳米管管壁是由高度有序的石墨炭层构成, 而杂化膜的基体为聚酰亚胺经高温热解而成的, 由无数小颗粒的微晶组成的乱层炭结构, 各微晶颗粒间的空隙以及微晶层片间距便是炭膜中起分离作用的纳米孔道^{[ 16]}. 从透射电镜照片还可看出, 碳纳米管与炭基体之间存在明显的间隙, 说明并未形成C-C化学键. 碳纳米管与无定型炭基体间的“相界面”为杂化膜进行气体分离创造了更多有利于气体分子扩散的空隙.

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	图1 (a)碳纳米管, (b)炭/碳纳米管复合膜和(c)炭基体与碳纳米管形成的“界面间隙”透射电镜照片Fig. 1 TEM images of (a) CNT, (b) C/CNT membrane and (c) interlayer gap between carbon matrix and CNT

对于掺杂碳纳米管后炭膜的微结构特征, 还结合XRD进行了分析. 如图2所示, 对于纯炭膜而言, 存在较宽的(002)及(100)衍射峰, 表明采用聚酰亚胺为前驱体经高温热解后制备的纯炭膜主要是由无数小颗粒的微晶组成的乱层炭结构^{[ 17]}. 而对于炭/碳纳米管杂化膜, 可以明显看出(002)和(100)衍射峰变得比较尖锐, 这表明杂化膜中有石墨化炭层存在, 而这主要是由于杂化炭膜中掺杂的碳纳米管管壁的石墨层片所致.

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	图2 纯炭膜和炭/碳纳米管膜的XRD图谱Fig. 2 XRD patterns of pure carbon membrane and C/CNT membrane

2.2 炭/碳纳米管杂化炭膜的气体分离性能

掺杂碳纳米管前后, 炭膜的气体渗透性的变化分别如图3(a)所示. 对于纯炭膜, 其孔结构主要是由聚酰亚胺前驱体发生热分解反应产生的超微孔孔隙组成^{[ 18]}, 气体的渗透速率仍遵循着H₂>CO₂>O₂> N₂>CH₄的变化顺序, 即随着分子动力学直径的递增(H₂: 0.289 nm, CO₂: 0.33 nm, O₂: 0.346 nm、N₂: 0.364 nm, CH₄: 0.38 nm)呈现逐渐降低的趋势, 说明纯炭膜进行气体分离时所遵循的分离机理是“分子筛分机理”. 当掺杂碳纳米管后, 由于碳纳米管的介入使得在碳纳米管与炭基体间产生明显的“界面间隙”. 与纯炭膜相比, 由于这种“界面间隙”结构的存在, 大大增加了杂化炭膜的自由体积, 降低了气体分子在杂化炭膜中的渗透扩散阻力, 从而使杂化炭膜表现出较高的渗透速率^{[ 19]}. 可见, 在现有炭膜中掺杂碳纳米管可以有效地利用碳纳米管与炭基体之间形成的“界面间隙”, 打破纯炭膜所具有的由单纯乱层炭堆积形成的致密超微孔结构, 重新构建具有高分离性能的杂化炭膜的孔结构. 另外, 值得注意的是, CO₂气体的渗透速率在所有气体分子中增幅最大, 而且超过了比其分子动力学直径还要小的H₂, 这主要是由于由相界面间隙所构成的较大微孔结构提高了CO₂的“表面扩散”作用, 从而大大提高了CO₂的渗透速率^{[ 4, 7]}.

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	图3 纯炭膜和炭/碳纳米管膜的气体渗透性能(a)和气体分离选择性(b)Fig. 3 Gas permeability (a) and permselectivity (b) of pure carbon membrane and C/CNT membrane

图3(b)给出了掺杂碳纳米管后杂化膜对O₂/N₂、CO₂/N₂、CO₂/CH₄、CO₂/H₂的气体分离选择性的变化. 由图3(b)可知, 掺杂碳纳米管后, O₂/N₂、CO₂/N₂、CO₂/CH₄的分离选择系数均下降, 但降幅并不太大, 这主要是由于掺杂的碳纳米管与炭基体间形成的相界面增大了杂化膜的平均孔径, 削弱了杂化炭膜的“分子筛分”作用, 从而使其选择性降低. 而对于CO₂/H₂, 其分离选择系数则稍有增加,这主要是由于CO₂ 的“表面扩散”作用增强使得CO₂气体的渗透速率超过H₂渗透速率而引起的特殊现象. 由图3(b)还可以看出, 主要标识杂化膜气体分离性能的O₂/N₂分离系数下降并不显著, 结合图3(a)可知, 掺杂碳纳米管后O₂和N₂的渗透速率都得到了成倍的提高, 因此, 在聚酰亚胺前驱体中掺杂碳纳米管后制备的炭/碳纳米管杂化膜可以有效地提高炭膜的气体分离性能.

3 结论

在PMDA-ODA型聚酰亚胺中掺杂多壁碳纳米管, 经高温热解后制备出炭/碳纳米管杂化膜. 掺杂后的碳纳米管能够均匀地分散在炭基体中, 使得在碳纳米管与炭基体之间产生明显的“界面间隙”, 改变了纯炭膜所具有的由单纯乱层炭堆积形成的致密超微孔结构, 增强了气体分子在杂化炭膜中的扩散能力, 与纯炭膜相比, 杂化炭膜的气体渗透速率大幅增加. 但是, 由于碳纳米管与炭基体间形成的“界面间隙”的存在也在一定程度上削弱了杂化炭膜的“分子筛分”作用, 从而使其选择性稍有下降.

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[18]	SONG Cheng-Wen, WANG Tong-Hua, WANG Xiu-Yue. Preparation and O₂/N₂ separation performance of carbon molecular sieve membranes derived from poly(furfuryl alcohol). Acta Polymerica Sinica, 2010, 1(5): 609-612. [本文引用:1] [JCR: 0.677] [CJCR: 0.963]
[19]	Tseng H, Kumar I A, Weng T, et al. Preparation and characterization of carbon molecular sieve membranes for gas separation-the effect of incorporated multi-wall carbon nanotubes. Desalination, 2009, 240(1/2/3): 40-45. [本文引用:1] [JCR: 3.041]

2008

4.093

0.0

... 目前, 用于气体分离的膜材料主要是聚合物膜^[1,2], 尽管其生产成本较低, 但是由于聚合物膜耐酸、碱和高温、高压的能力较差, 并且聚合物膜的渗透性和分离选择性之间受Robeson 上限制约^[3], 因此在很多领域的应用受到了一定的限制 ...

2006

4.093

0.0

1999

5.438

0.0

2001

4.093

0.0

... 近二、三十年来, 炭膜以其优异的气体分离性能, 得到科学家们的广泛关注, 已经成为当前气体分离膜技术的研究热点之一^[4,5] ...

... 作用, 从而大大提高了CO₂的渗透速率^[4,7] ...

2004

5.868

0.0

Carbon. 2004, 42(2):241-259 DOI:10.1016/j.carbon.2003.10.022

Fabrication of carbon membranes for gas separation--a review

Abstract

Carbon membrane materials are becoming more important in the new era of membrane technology for gas separation due to their higher selectivity, permeability and stability in corrosive and high temperature operations. Carbon membranes can be produced by pyrolysis of a suitable polymeric precursor under controlled conditions. This paper reviews the fabrication aspects of carbon membranes, which can be divided into six steps: precursor selection, polymeric membrane preparation, pretreatment of the precursor, pyrolysis process, post-treatment of pyrolyzed membranes and module construction. The manipulation of the pretreatment variables, pyrolysis process parameters and post-treatment conditions were shown to provide an opportunity to enhance the separation performance of carbon membranes in the future. By understanding the available methods, one can choose and optimize the best technique during the fabrication of carbon membranes. Furthermore, areas of future potential in carbon membrane research for gas separation were also briefly identified.

... 近二、三十年来, 炭膜以其优异的气体分离性能, 得到科学家们的广泛关注, 已经成为当前气体分离膜技术的研究热点之一^[4,5] ...

2010

0.531

1.106

Journal of Inorganic Materials. 2010, 25(5):449-456 DOI:10.3724/SP.J.1077.2010.00449

Physical design, preparation and functionalization of carbon membranes for gas separation

1.Carbon Research Laboratory, State Key Laboratory of Fine Chemicals, Department of Materials Science and Chemical Engineering, School of Chemical Engineering, Dalian University of Technology, Dalian 116012, China; 2.Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China

Two challenges faced by carbon membrane for application on commercial scale are its low permeability and poor mechanical strength. And it is attributed to the vermiform pore structures and special characteristics of carbon membranes. In order to solve these problems, methods such as choosing the precursors with suitable chemical structure and space mould, incorporating nanosize functional groups into precursors are employed to effectively change and improve the vermiform pore structures of carbon membranes and enhance the gas permeabilities of carbon membranes. The results indicate that the gas permeabilities of hybridized function carbon membranes are increased by 2 orders in magnitude without reducing the gas selectivity obviously. Besides, some functional carbon membranes have also revealed higher gas selectivity for some gases such as CO₂. The coalbased composite carbon membranes with high gas permselectivity are developed by dipcoating the precursors on the cheap coalbased supports invented by ourselves to improve the mechanical strength of carbon membranes.

气体渗透性低、机械强度差是炭膜产业化道路上的两大难题.研究发现，根源在于炭膜的蠕虫状孔道结构与均质炭膜的特有性质.为了解决炭膜渗透性低的问题，通过选择适宜的聚合物前驱体的分子结构与空间构型结合填充纳米粒子为功能基团等手段，实现对炭膜蠕虫状孔结构有效地调控与重新构建.在保证高选择性的条件下，不仅使炭膜的气体渗透性能提高了2个数量级以上，而且还使炭膜对某些气体具有较高分离选择性的功能化效果.为了改善炭膜的机械强度，将自主研发的廉价煤基炭膜支撑体与前驱体相复合，采用简单的制膜工艺，制备得到复合性能好、气体分离性能高的复合炭膜.

... 但到目前为止, 炭膜仍然局限于实验室研究, 这主要是由于目前所制备炭膜的结构属乱层炭结构, 分布于其中的孔隙结构比较致密, 气体的渗透扩散阻力较大, 导致炭膜对气体分子的渗透能力仍然无法满足实际应用的要求^[6] ...

2009

3.365

0.0

... 在前驱体中掺杂无机纳米材料重新构建炭膜的孔隙结构, 是打破炭膜原有的无序孔结构, 提高炭膜的气体渗透性能的一种有效方法^{[7,8,9,10,11,12]} ...

... 作用, 从而大大提高了CO₂的渗透速率^[4,7] ...

2002

8.238

0.0

... 在前驱体中掺杂无机纳米材料重新构建炭膜的孔隙结构, 是打破炭膜原有的无序孔结构, 提高炭膜的气体渗透性能的一种有效方法^{[7,8,9,10,11,12]} ...

2004

8.238

0.0

... 在前驱体中掺杂无机纳米材料重新构建炭膜的孔隙结构, 是打破炭膜原有的无序孔结构, 提高炭膜的气体渗透性能的一种有效方法^{[7,8,9,10,11,12]} ...

2005

5.868

0.0

Carbon. 2005, 43(12):2600-2607 DOI:10.1016/j.carbon.2005.05.018

Carbon membranes from cellulose and metal loaded cellulose

Abstract

The focus of this work was to find a low-cost precursor for carbon molecular sieve (CMS) membranes, and a simple way of producing them. In addition, several ways of modifying a carbon material are described. The modification method used in this study was metal doping of carbon. CMS membranes were formed by vacuum carbonization of cellulose and metal loaded cellulose. Metal additives include oxides of Ca, Mg, Fe(III) and Si, and nitrates of Ag, Cu and Fe(III).

The carbon membrane containing Fe-nitrate has promising separation performance for the gas pairs O₂/N₂ and CO₂/CH₄. Carbon containing nitrates of Cu or Ag show high selectivity, but reduced O₂ and CO₂ permeability compared to carbon with Fe-nitrate. Element analysis indicates that Cu migrates to the carbon surface, creating an extra layer resistance to gas transport. A silver mirror is also seen on the surface of Ag-nitrate-containing carbon. However, the Ag- and Cu-containing membranes show a high H₂ permeability. Adding metal oxides makes the carbon membranes retard the transport of easily condensable gases (e.g. CO₂). This can be exploited for enhanced H₂/CO₂ separation efficiency.

... 在前驱体中掺杂无机纳米材料重新构建炭膜的孔隙结构, 是打破炭膜原有的无序孔结构, 提高炭膜的气体渗透性能的一种有效方法^{[7,8,9,10,11,12]} ...

2010

0.531

1.106

Journal of Inorganic Materials. 2010, 25(1):47-52 DOI:10.3724/SP.J.1077.2010.00047

Polymide/ Fe₃O₄-carbonized membranes for gas separation

(1.Carbon Research Laboratory, State Key Laboratory of Fine Chemicals, Department of Materials Science and Chemical Engineering, School of Chemical Engineering, Dalian University of Technology, Dalian 116012, China; 2.Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China)

Novel functional carbon membranes for gas separation were designed and prepared by incorporating Fe₃O₄ nanoparticles into carbon membranes precursor polyimide. The assynthesized membranes were characterized by TEM, XRD and VSM. The effects of Fe₃O₄addition and the final pyrolysis temperature on the gas permeability were investigated. The results show that Fe₃O₄ nanoparticles transformed into other phase morphologies are helpful to form the graphite-like layers during the pyrolysis process, which make the membrane with two types of carbon structure : amorphous carbon and graphite-like layers. All the functional carbon membranes exhibit magnetism. Single gas permeation test results show that the assynthesized membranes exhibit an outstanding molecular sieving capability together with high gas permeability. The gas permeability of H₂ is 61 times higher than the pure carbon membrane and the H₂/CO₂ selectivity is also improved. Fe₃O₄ addition and the final pyrolysis temperature siginificantly impair the gas permeability. When the Fe₃O₄ content is 20wt%, the permeabilities of pure gas H₂, CO₂, O₂, N₂, CH₄ in the functional carbon membrane are 15476, 4385, 1565, 193 and 114 Barrers (1Barrer=1×10^-10 cm³ (STP) ·cm/(cm²·s·cmHg)), respecticvely. The final pyrolysis temperature also has a remarkable effect on the gas separation performance.

采用共混法在聚酰亚胺前驱体中引入Fe₃O₄纳米粒子, 经高温热解炭化制备了杂化功能炭膜. 采用XRD、TEM和VSM等分析方法对所制备的功能炭膜进行表征, 并探讨了Fe₃O₄纳米粒子的掺杂量及炭化终温对功能炭膜气体分离性能的影响. 结果表明, Fe₃O₄纳米粒子在热解炭化过程中发生了物相形态的改变, 并对前驱体起到了催化石墨化的作用, 使功能炭膜具有类石墨片层和乱层炭的两种炭结构形态, 同时具有磁性. 气体渗透实验表明, 掺杂Fe₃O₄纳米粒子使所制备的功能炭膜具有“分子筛分”的分离特征, 提高了炭膜的气体渗透性能, 特别是对小分子气体H₂的渗透性提高了61倍, H₂/CO₂的分离选择性也明显得到改善. Fe₃O₄的掺杂量和炭化终温对炭膜的气体分离性能有显著影响. Fe₃O₄添加量为20wt%的功能炭膜对H₂、CO₂、O₂、N₂和CH₄等纯气体的渗透系数分别为15476、4385、1565、193和114Barrers ［1Barrer =1×10^-10cm³(STP)·cm/(cm²·s·cmHg)］.

... 在前驱体中掺杂无机纳米材料重新构建炭膜的孔隙结构, 是打破炭膜原有的无序孔结构, 提高炭膜的气体渗透性能的一种有效方法^{[7,8,9,10,11,12]} ...

2011

0.531

1.106

Journal of Inorganic Materials. 2011, 26(2):165-169 DOI:10.3724/SP.J.1077.2011.00165

Effect of different drying methods on PPESK carbon membrane

1. Carbon Material Research Lab, State Key Lab of Fine Chemicals, College of Chemical Engineering, Dalian University of Technology, Dalian 116012, China; 2. Dalian Instituteof Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China

The carbon membranesderived from the PPESK precursor in CHCl₃solvent for gas separation wereprepared with freezing and refrigeration drying methods. The influences ofdrying methods on the structure and gas separation performance of PPESK carbonmembranes were investigated. FTIR, TG, XRD and gas permeation tests were used to characterize thechange of chemical and carbon structure and gas separation properties of carbonmembranes prepared with different drying methods. The result indicated that theeffects of drying methods on the structure and performance of PPESK carbonmembranes are to promote the precursor to form a polymeric membrane with thedifferent chemical structure during the drying and make the chemical structureof derived polymeric membranes change in different ways during the laterpreoxidation and carbonization. Compared with refrigeration drying, thefreezing drying weakened decomposition reaction and promoted condensationreaction during preoxidation and carbonization. As a result, the frozenmembrane exhibited a better gas separation performance with a good flexilitydue to its dense microstructure. The freezing drying was the optimum way toprepare PPESK carbon membranes using CHCl₃ as solvent.

以PPESK为前驱体, CHCl₃为溶剂, 分别采用冷冻干燥法和冷藏干燥法制备气体分离炭膜, 借助于红外光谱、热重分析、X射线衍射和气体渗透等测试手段, 研究探讨了干燥方式对聚醚砜酮(PPESK)基炭膜的化学结构、炭微结构及气体分离性能的影响. 结果表明, 干燥方式对炭膜结构性能的影响主要体现在促使前驱体在干燥过程中形成具有不同化学结构的聚合物膜, 使它们在以后的预氧化和低温热解炭化过程中表现出不同的演变规律与冷藏干燥相比, 冷冻干燥得到的聚合物膜在预氧化和炭化过程中分解反应程度较弱, 但芳香缩合反应却很深刻, 使形成的炭膜微结构尺寸较小, 气体分离性能较高, 并具有良好的表观柔韧性. 所以, 采用CHCl₃为溶剂制备PPESK炭膜, 冷冻干燥将是首选干燥方式.

... 在前驱体中掺杂无机纳米材料重新构建炭膜的孔隙结构, 是打破炭膜原有的无序孔结构, 提高炭膜的气体渗透性能的一种有效方法^{[7,8,9,10,11,12]} ...

1991

38.597

0.0

... 碳纳米管(CNT)是日本科学家Iijima发现的准一维管状纳米材料^[13], 虽然碳纳米管特殊的力学、电学、热学、磁、储氢性能受到广泛关注^[14,15], 但是基于准一维纳米孔道结构特点方面的应用还有待开发 ...

2008

10.677

0.0

2008

10.677

0.0

2008

2.894

0.0

... 3 炭膜的渗透性能测试复合炭膜的气体渗透性能采用恒压变体积法测定^[16] ...

... 碳纳米管管壁是由高度有序的石墨炭层构成, 而杂化膜的基体为聚酰亚胺经高温热解而成的, 由无数小颗粒的微晶组成的乱层炭结构, 各微晶颗粒间的空隙以及微晶层片间距便是炭膜中起分离作用的纳米孔道^[16] ...

2010

4.093

0.0

... 如图2所示, 对于纯炭膜而言, 存在较宽的(002)及(100)衍射峰, 表明采用聚酰亚胺为前驱体经高温热解后制备的纯炭膜主要是由无数小颗粒的微晶组成的乱层炭结构^[17] ...

2010

0.677

0.963

Acta Polymerica Sinica. 2010, 1(5):609-612 DOI:10.3724/SP.J.1105.2010.09176

Preparation and O₂/N₂ separation performance of carbon molecular sieve membranes derived from poly(furfuryl alcohol)

1 Environmental Information Institute, School of Environment Science and Engineering, Dalian Maritime University, Dalian116026; 2 Carbon Research Laboratory and State Key Laboratory of Fine Chemicals, School of Chemical Engineering, Dalian University of Technology, Dalian116012

A convenient and effective approach has been developed to prepare carbon molecular sieve (CMS) membranes derived from poly(furfuryl alcohol) with high O₂/N₂ separation performance in this paper.The CMS membranes is formed by coating a thin layer of viscous poly(furfuryl alcohol) liquid,which was synthesized by polymerization of furfuryl alcohol by oxalic acid catalyst,on a porous coal-based tubular support followed by controlled pyrolysis.TGA,XRD,SEM and gas permeation experiments are employed to give an insight into pyrolysis process,morphological characteristics and separation performance of CMS membranes.The results show that the CMS membranes with a continuous defect-free coating exhibit an excellent O₂/N₂ separation performance.The increase in the final pyrolysis temperature from 600℃ to 900℃ results in a decrease in the d-spacing of the interlayers of graphitic carbon planes and the shrinkage in size of ultramicropores,which leads to the reduction in permeabilities of O₂ and N₂ and improvement in O₂/N₂ permselectivity.It can also be found that the correlation points for all CMS membranes prepared in the present work fall above the Robeson’s upper bound limit that is uncommon for polymeric membranes.These results indicate that poly(furfuryl alcohol)based CMS membranes obtained from the novel method are of great potential for O₂and N₂ separation.

以草酸为催化剂将糠醇单体直接聚合成所需黏度的聚糠醇液体作为涂膜液，仅需一步涂覆便可在价格低廉的煤基炭管支撑体上制备出高性能的聚糠醇炭分子筛膜.聚糠醇炭分子筛膜的热解过程、微观形貌和分离性能分别采用热重分析、扫描电镜以及O₂、N₂渗透实验进行表征.实验结果表明制备出的聚糠醇炭分子筛膜表面均匀且无缺陷.聚糠醇在热解过程中最终转化成具有超微孔的乱层石墨微晶结构.热解温度升高导致了起分离作用的有效超微孔尺寸的减小，进而表现出O₂、N₂的渗透速率逐渐降低，O₂/N₂的选择性逐渐增大的趋势.不同热解温度下制备的炭分子筛膜的O₂渗透性和O₂/N₂选择性之间关系均超出了传统聚合物膜的Robeson上限.

... 对于纯炭膜, 其孔结构主要是由聚酰亚胺前驱体发生热分解反应产生的超微孔孔隙组成^[18], 气体的渗透速率仍遵循着H₂>CO₂>O₂> N₂>CH₄的变化顺序, 即随着分子动力学直径的递增(H₂: 0 ...

2009

3.041

0.0

... 结构的存在, 大大增加了杂化炭膜的自由体积, 降低了气体分子在杂化炭膜中的渗透扩散阻力, 从而使杂化炭膜表现出较高的渗透速率^[19] ...