论文总字数：21694字

摘 要

类石墨相氮化碳（g-C₃N₄）具有良好的化学稳定性，且可剥离为单层结构，同时其表面分布均匀微孔，可用于制备高性能分离膜。本文以g-C₃N₄为研究对象，表征分析其物化性质，考察g-C₃N₄纳米片的制备条件，并选用聚醚嵌段聚酰胺（Pebax）制备C₃N₄/ Pebax混合基质膜，考察了旋涂次数、C₃N₄掺杂量对膜结构和气体分离性能的影响。

通过SEM、XRD、AFM、BET比表面积、紫外分光光度法等表征C₃N₄的物化性质。结果表明，经过烧结以及热腐蚀后的粉体，在体积比为1:1的异丙醇和水混合溶剂中分散良好，成功剥离后的纳米片片层厚度在1-7 nm。通过SEM表征分析形貌得到热腐蚀的最优处理条件。XRD表征表明成功烧结制得C₃N₄前驱体，且热腐蚀后的粉体图谱与文献报道一致。通过BET比表面积测试表明成功剥离后的C₃N₄纳米片具有比块状C₃N₄粉体更大的比表面积，有利于提高膜的气体分离性能。

采用旋涂制膜的方法，考察C₃N₄掺杂量对混合基质膜性能的影响。通过旋涂次数控制膜层结构，并通过气体分离性能测试检测膜的CO₂/N₂分离性能。实验表明，随着旋涂层数的增加，CO₂渗透率逐渐降低，而CO₂/N₂选择性则增加至约70。当旋涂次数达到7次时，CO₂/N₂选择性有所下降。这主要是因为旋涂次数的增加会导致膜层中C₃N₄的增加，而C₃N₄的大量团聚降低了膜对CO₂气体的吸附量。通过性能对比，确定最佳旋涂层数为3次。随着C₃N₄掺杂量的增加，膜的通量继续增加，但气体选择性先上升然后下降，原因主要是C₃N₄过多将破坏膜层中的气体分子传输通道。通过对比实验确定最佳掺杂量为1wt％。

关键词：类石墨相氮化碳 CO₂分离 混合基质膜 聚醚嵌段聚酰胺

Exfoliation of noval two-dimensional material g-C₃N₄

and preparation of gas separation membrane

Abstract

Graphite-like phase carbon nitride (g- C₃N₄) has good chemical stability and can be exfoliated into a single-layer structure, and its surface is uniformly distributed with micropores, which can be used to prepare high-performance separation membranes. Herein, g-C₃N₄ was chosen to characterize and analyze its physicochemical properties. The C₃N₄/ Pebax mixed matrix membrane was prepared by introducing polyether block polyamide (Pebax). The preparation conditions of g-C₃N₄ nanosheets, times of spin coatings, effect of C₃N₄ doping amount on membrane structure and gas separation performance were investigated.

The physicochemical properties of C₃N₄ were characterized by SEM, XRD, AFM, BET specific surface area, ultraviolet spectrophotometry. The results showed that the powder after sintering and thermal etching is well dispersed in a mixed solvent of isopropyl alcohol and water with a volume ratio of 1:1, and the thickness of the nanosheet layer after successful exfoliation is 1-7 nm. The morphological analysis by SEM was carried out to obtain the optimal processing conditions for thermal etching. XRD characterization showed that the C₃N₄ precursor was successfully sintered, and the powder phase after thermal etching was consistent with the literature. The BET specific surface area test showed that the C₃N₄ nanosheets after successful exfoliation have a larger specific surface area than the bulk powder.

The effect of C₃N₄ loading on mixed matrix membrane was investigated by spin coating method. The membrane structure was controlled by the times of spin coatings, and the CO₂/N₂ separation performance of membranes was examined by gas separation performance test. The CO₂ permeance gradually decreased with the increase of the number of spin coatings. The CO₂/N₂ selectivity increased to about 70 and then dropped at 7 spin-coating times. Therefore, the optimum number of spin coatings was determined to be 3 times. The results showed that as the loading of C₃N₄ increases, the flux of the membrane continues to rise, but the gas selectivity first rose and then fell, and finally the optimal loading is determined to be 1 wt%.

Key words: Graphite-like phase carbon nitride；CO₂ separation；Mixed matrix membrane；Polyether block polyamide（Pebax）

目 录

摘 要 Ⅰ

Abstract Ⅱ

第一章 文献综述 1

1.1背景 1

1.2气体分离膜的性能评价 2

1.3 C₃N₄材料在膜分离领域的研究进展 3

1.4本课题研究意义及内容 6

1.4.1研究意义 6

1.4.2研究内容 6

第二章 C₃N₄纳米片的制备及表征 7

2.1引言 7

2.2实验部分 7

2.2.1实验试剂和仪器设备 7

2.2.2 C₃N₄前驱体的烧结 8

2.2.3 C₃N₄热腐蚀条件的考察 10

2.2.4 C₃N₄纳米片的液相剥离 11

2.2.5 C₃N₄纳米片的物化性质表征 12

2.3 本章小结 15

第三章 C₃N₄/Pebax混合基质膜的制备与表征 16

3.1引言 16

3.2实验部分 16

3.2.1实验试剂和仪器设备 16

3.2.2 C₃N₄/Pebax混合基质膜的制备 17

3.2.3 C₃N₄/Pebax混合基质膜的表征 18

3.3本章小结 18

第四章 C₃N₄/Pebax混合基质膜的气体分离性能测试 19

4.1引言 19

4.2实验部分 19

4.2.1旋涂次数对C₃N₄/Pebax混合基质膜性能的影响 19

4.2.2 C₃N₄掺杂量对C₃N₄/Pebax混合基质膜性能的影响 20

4.3本章小结 21

第五章 结论与展望 22

参考文献 23

致谢 26

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