本文選題：聚酰亞胺　切入點：中空纖維膜　出處：《東華大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：溫室效應(yīng)及能源問題已經(jīng)引起全球廣泛關(guān)注,煙道氣中二氧化碳(CO_2)的控制排放、天然氣及生物沼氣中CO_2的分離等都是亟待解決的混合氣體分離問題。中空纖維分離膜具有能耗低、環(huán)境友好、填充密度高等突出優(yōu)點,對于能源利用和環(huán)境治理都有舉足輕重的作用,已成為最有效的混合氣體分離方法之一。膜材料是膜技術(shù)的核心,聚酰亞胺(polyimide,PI)具有優(yōu)良的機械性能、熱性能和滲透性能,在眾多膜材料中脫穎而出,有望在氣體分離膜領(lǐng)域得到廣泛應(yīng)用。為此,本論文在具有分離特性聚酰亞胺的合成、中空纖維膜的紡絲成形及表面涂層等方面開展研究工作,主要內(nèi)容包括:通過分子結(jié)構(gòu)設(shè)計引入較大自由體積和促進CO_2傳質(zhì)的官能團,分別改善PI的滲透性和選擇性。本文以六氟二酐(6FDA)為二酐單體,4,4'-二氨基二苯醚(ODA)、2,2-雙[4-(4-氨基苯氧基)苯基]丙烷(BAPP)、2,2-雙[4-(4-氨基苯氧基)苯基]六氟丙烷(HFBAPP)、4,4'-雙(4-氨基苯氧基)二苯砜(BAPS)為二胺單體在溶劑N-甲基-2-吡咯烷酮(NMP)中合成不同結(jié)構(gòu)的聚酰亞胺,制備的聚酰亞胺薄膜在常規(guī)有機溶劑中具有極好的溶解性能,具有較好的力學(xué)強度,密度在1.388~1.427 g/cm3之間,自由體積分率在0.144~0.162之間,玻璃化轉(zhuǎn)變溫度在257oC~304oC之間,接觸角在53°~93°之間。其中6FDA-HFBAPP型聚酰亞胺溶解性能最好、自由體積分率最大為0.162、接觸角最大為93°、玻璃化轉(zhuǎn)變溫度最低為257oC,是制備中空纖維氣體分離膜的理想材料。以合成的6FDA-HFBAPP型聚酰胺酸溶液為紡絲液,采用干-濕法及后處理工藝制備了具有致密皮層和多孔支撐層的中空纖維膜,研究了紡絲液的性質(zhì)、內(nèi)外凝固浴組成、內(nèi)凝固浴流速、空氣層高度對中空纖維膜結(jié)構(gòu)和性能的影響。結(jié)果表明,該體系適合采用兩步法紡絲,當(dāng)外凝固浴為純水、內(nèi)凝固組成為VH2OVNMP?=10/90、內(nèi)凝固流速與紡絲液流速之比在0.4~0.6之間、空氣層高度為6 cm時,制備的中空纖維膜的性能最佳,CO_2滲透速率為89 GPU,CH4的滲透速率為75 GPU。為改善所制備的中空纖維膜的分離特性,以制備的聚酰亞胺中空膜為底膜,用PDMS涂層液對底膜進行浸漬涂覆以封堵在干濕法成型過程中致密層產(chǎn)生的缺陷,制備了中空纖維復(fù)合膜。結(jié)果表明,當(dāng)涂層質(zhì)量濃度為5%時,涂覆的效果最佳,經(jīng)涂覆后CO_2的滲透速率為42 GPU,CH4的滲透速率為7.8 GPU,分離系數(shù)為5.4。并采用Henis復(fù)合阻力模型分析了復(fù)合膜的分離機理。
[Abstract]:Greenhouse Effect and energy issues have attracted worldwide attention. The separation of CO_2 from natural gas and biogas is an urgent problem to be solved. The hollow fiber separation membrane has the advantages of low energy consumption, friendly environment, high filling density and so on. Membrane material is the core of membrane technology, and polyimide polyimide (PII) has excellent mechanical, thermal and permeable properties. It is expected to be widely used in the field of gas separation membrane. In this paper, the synthesis of polyimide with separation characteristics, spinning of hollow fiber membrane and surface coating are studied. The main contents include the introduction of large free volume and the promotion of CO_2 mass transfer through the design of molecular structure. The permeability and selectivity of Pi were improved respectively. In this paper, hexafluorodianhydride 6FDAA was used as the monomer of dianhydride 4H 4N -diaminodiphenyl ether (ODAO) 2H 2- BAPPX 2N, BAPPU 2H 2- Bis (4-N 4-Aminophenoxy) phenyl] Hexafluoropropane (HFBAPPU) 4N, Bis 4N, Bis 4N, benzylamino aminophenylamino. Polyimide with different structures was synthesized in the solvent N-methyl-2-pyrrolidone (NMPP) using oxy) diphenyl sulfone (BAPS) as a diamine monomer. The prepared polyimide films have excellent solubility and good mechanical strength in conventional organic solvents. The density is between 1.388g / cm ~ 3 and 1.427 g / cm ~ 3, the free volume integral ratio is 0.144 ~ 0.162, and the glass transition temperature is between 257oC ~ 304oC. The contact angle is between 53 擄and 93 擄. The solubility of 6FDA-HFBAPP polyimide is the best. The maximum free volume integral ratio is 0.162, the contact angle is 93 擄, the glass transition temperature is the lowest 257oC, which is the ideal material for the preparation of hollow fiber gas separation membrane. The synthesized 6FDA-HFBAPP polyamide acid solution is used as spinning solution. Hollow fiber membranes with dense cortex and porous supporting layer were prepared by dry-wet process and post-treatment process. The properties of spinning solution, composition of internal and external coagulation bath, flow rate of internal coagulation bath were studied. Effects of air layer height on the structure and properties of hollow fiber membrane. The results show that the system is suitable for two-step spinning when the external coagulation bath is pure water and the internal solidification composition is VH _ 2O VNMP? 10 / 90, when the ratio of internal solidification velocity to spinning fluid velocity is between 0.4 and 0.6, and the height of air layer is 6 cm, the best permeation rate of CO _ 2 is 89GPUU _ (CH4) and the permeation rate of the prepared hollow fiber membrane is 75GPU. in order to improve the separation characteristics of the prepared hollow fiber membrane, The hollow fiber composite membrane was prepared by impregnating the polyimide hollow membrane with PDMS coating liquid to seal the defects of the dense layer in the process of dry-wet molding. The results showed that the coating concentration was 5. After coating, the permeation rate of CO_2 was 7.8 GPA and the separation coefficient was 5.4. The separation mechanism of the composite membrane was analyzed by using the Henis composite resistance model.
【學(xué)位授予單位】：東華大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TQ051.893

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