發(fā)布時間：2018-03-15 18:23

  本文選題：氣體分離　切入點：CO_2捕集　出處：《大連理工大學》2017年博士論文　論文類型：學位論文

【摘要】：進入21世紀以來,化石能源在全球范圍內(nèi)的消耗逐年增高,溫室氣體減排和能源氣體凈化成為CO_2捕集的兩個重要組成部分,其中代表性分離體系為煙道氣(CO_2/N_2)和天然氣(CO_2/CH_4)。膜分離作為一種節(jié)能高效、清潔環(huán)保的新型分離技術,應用于CO_2分離有良好前景�；旌匣|(zhì)膜由聚合物基體和分散于其中的無機填料共同構成,結合了聚合物膜易加工和無機膜分離性能高的優(yōu)點,是高性能氣體分離膜的重要發(fā)展方向。金屬有機骨架(MOF)是一種具有規(guī)整孔道結構的新型晶體材料,由過渡金屬離子與有機配體經(jīng)共價鍵或配位鍵橋接而成。與傳統(tǒng)無機填料相比,MOF具有合成條件溫和、易功能化等優(yōu)點,因此,MOF混合基質(zhì)膜成為當前研究的熱點。然而,目前文獻報道的MOF混合基質(zhì)膜多為通過澆鑄得到,對具有薄選擇層MOF混合基質(zhì)膜研究較少。此外,MOF混合基質(zhì)膜還存在相界面易產(chǎn)生缺陷、MOF柔性骨架削弱選擇性等問題。本論文基于三種對CO_2具有選擇性的MOF(ZIF-7、ZIF-8和Cu-BTC),利用MOF在聚合物溶液中原位合成實現(xiàn)具有薄選擇層的MOF混合基質(zhì)膜的制備,并通過離子液體在MOF中預先負載強化MOF/聚合物界面相容性,從而提高混合基質(zhì)膜的分離性能。首先,基于非對稱膜的傳統(tǒng)制備工藝(浸沒沉淀相轉化法,NIPS),采用直接共混和微波輔助分別制備了具有超薄皮層的ZIF-7/PES和MW-ZIF-7/PES非對稱膜,ZIF-7的加入可同時提高膜對H2和CO_2的滲透速率和選擇性。MW-ZIF-7/PES膜在經(jīng)PDMS堵孔后,其H2和CO_2滲透速率高于PES膜,然而選擇性下降明顯。這是因為NIPS法對鑄膜液組成要求較高,該方法用于制備表面無缺陷非對稱MOF混合基質(zhì)膜時,制備窗口較窄。其次,為拓寬MOF在聚合物溶液中的原位合成范圍,開發(fā)出Cu-BTC前驅(qū)體和PES在DMSO中的穩(wěn)定相容體系,在高溫下,鑄膜液熱致相分離(TIPS)和Cu-BTC合成同時發(fā)生,得到非對稱的Cu-BTC/PES膜,首次實現(xiàn)了非對稱MOF混合基質(zhì)膜的一步制備。該方法制備的Cu-BTC/PES膜具有典型的非對稱結構,由致密的皮層和多孔支撐層構成,制備得到的Cu-BTC/PES膜可通過乙醇與DMSO的置換成功活化。Cu-BTC在膜中的含量可以通過Cu(NO_3)_2的投加量調(diào)節(jié),且隨Cu(NO_3)_2用量的提高,Cu-BTC/PES膜致密層厚度降低,膜滲透速率得到明顯提高。當Cu-BTC含量從7.5 wt%提高到21.0 wt%,膜的H2和CO_2滲透速率提高了接近20倍,CO_2/N_2選擇性保持在20左右。進一步通過纖維素醚類聚合物(EC)與Cu(NO_3)_2的絡合作用實現(xiàn)了 Cu-BTC/EC混合基質(zhì)膜的常溫原位制備。EC起到降低溶液中前驅(qū)體擴散速率、促進Cu-BTC合成的作用。在Cu-BTC含量為26 wt%,Cu-BTC/EC膜氣體分離性能最好,其CO_2滲透系數(shù)相對于純EC膜提高了 69%,而CO_2/CH_4選擇性僅從10.7下降到9.9。通過考察Cu-BTC/EC膜的熱性能、機械性能及不同溫度壓力下的氣體滲透性能,發(fā)現(xiàn)在Cu-BTC含量較低時,Cu-BTC/EC界面相容性較好,Cu-BTC可以提高聚合物相的耐CO_2塑化能力。最后,為強化混合基質(zhì)膜中MOF與聚合物(Pebax)界面相容性,將具有高CO_2選擇性和聚合物親和性的離子液體[bmim][Tf2N]引入到ZIF-8孔道中,制備了 IL@ZIF-8材料及IL@ZIF-8/Pebax膜。IL@ZIF-8的水洗處理可有效限制[bmim][Tf2N]向Pebax基體中擴散。測試了 IL@ZIF-8/Pebax膜的機械性能和氣體分離性能,結果表明IL@ZIF-8同時提高了 Pebax膜的機械性能和CO_2分離性能,添加量為15 wt%時,膜的CO_2滲透系數(shù)為104.0 Barrer,CO_2/N_2選擇性為83.9,CO_2/CH_4選擇性為34.8,相對于原膜分別提高了 45%、74%和92%,超過了 2008年Robeson上限。通過膜的SEM和DSC表征及Maxwell傳遞模型對比,確認了 IL@ZIF-8對Pebax膜機械性能和氣體分離性能的增強主要源于離子液體對ZIF-8/Pebax界面相容性的強化。
[Abstract]:Since twenty-first Century, the consumption of fossil energy in the global scope increased year by year, greenhouse gas emission reduction and energy gas purification become the two important parts of CO_2 capture, the representative system for flue gas separation (CO_2/N_2) and natural gas (CO_2/CH_4). The membrane separation as a new energy efficient and clean separation technology the application of CO_2 in environmental protection, has a good prospect. The separation of mixed matrix membranes composed of polymer matrix and inorganic filler dispersed therein, with the advantages of easy processing of polymer membrane and inorganic membrane separation performance is high, high performance is an important development direction of gas separation membrane. The metal organic framework (MOF) is a new type of crystal materials with ordered pore structures, by transition metal ions and organic ligands through covalent bond or coordination bond bridging. Compared with traditional inorganic filler, MOF has mild synthesis conditions and easy functionalization The advantages, therefore, MOF mixed matrix membranes become the focus of current research. However, the current MOF mixed matrix membranes reported in the literature were obtained by casting with thin layer MOF, mixed matrix membrane research. In addition, MOF also has a mixed matrix membrane interface defects, MOF flexible framework and other issues. Selective weakening this thesis is based on three kinds of selectivity to CO_2 MOF (ZIF-7, ZIF-8, and Cu-BTC) in the polymer solution in situ synthesis with a thin layer of the choice of MOF mixed matrix membranes were prepared by the MOF, and the ionic liquid in MOF pre load strengthening MOF/ polymer interface compatibility, so as to improve the separation performance of mixed matrix membranes at first, the asymmetric membrane based on the traditional preparation process (immersion precipitation phase inversion method, NIPS), microwave assisted by direct blending were prepared with thin cortex ZIF-7/PES and MW-ZIF-7/PES on That film, the addition of ZIF-7 can also improve the permeation rate and selectivity of.MW-ZIF-7/PES membrane of H2 and CO_2 in the PDMS H2 and the plug hole, the permeation rate of CO_2 is higher than that of PES film, but the selectivity decreased. This is because the NIPS method requires high casting solution, the method for preparation of surface defects asymmetric MOF mixed matrix membrane, preparation of the window is narrow. Secondly, to broaden the scope of in situ synthesis of MOF in polymer solution, developed the Cu-BTC precursor and PES DMSO in the stable compatible system under high temperature, casting solution of thermally induced phase separation (TIPS) and Cu-BTC synthesis occurred at the same time, Cu-BTC/PES the asymmetric membrane, for the first time to achieve a step of preparing asymmetric MOF mixed matrix membrane. The method of the Cu-BTC/PES film prepared with the asymmetric structure, composed of dense cortex and a porous support layer, the Cu-BTC/PES film prepared by ethanol With the DMSO content in the film is the successful replacement of activated.Cu-BTC Cu (NO_3) by adjusting the dosage of _2, and Cu (NO_3) _2 with the increased amount of dense Cu-BTC/PES film thickness decreased, the membrane permeation rate was improved obviously. When the content of Cu-BTC increased from 7.5 wt% to 21 wt%, increased to 20 times the penetration rate of membrane H2 and CO_2, CO_2/N_2 selectivity remained at around 20. The cellulose ether polymer (EC) and Cu (NO_3) _2 complexation achieved Cu-BTC/EC mixed matrix membranes at room temperature in situ preparation of.EC precursor solution to reduce the diffusion rate, promote Cu-BTC synthesis. The content of Cu-BTC is 26 wt%, the separation performance of Cu-BTC/EC membrane gas permeability coefficient CO_2 the best, relative to the pure EC film is increased by 69%, while the selectivity of CO_2/CH_4 only decreased from 10.7 to 9.9. by thermal performance investigation of Cu-BTC/EC films, the mechanical properties of different temperature and pressure The gas permeability, found in Cu-BTC is low, Cu-BTC/EC interface has good compatibility, Cu-BTC can improve the resistance of CO_2 phase polymer plasticizing capacity. Finally, in order to strengthen the MOF and polymer in mixed matrix membrane (Pebax) interface compatibility, high CO_2 selectivity and affinity polymer ionic liquid into [bmim][Tf2N] the channel of ZIF-8, IL@ZIF-8 and IL@ZIF-8/Pebax membrane materials.IL@ZIF-8 were prepared by washing treatment can effectively limit the [bmim][Tf2N] to the Pebax matrix diffusion. The mechanical properties and gas separation performance of IL@ZIF-8/Pebax membrane were tested, the results show that IL@ZIF-8 improves the mechanical properties of Pebax membrane and CO_2 separation performance, when adding 15 wt% film CO_2 the permeability coefficient is 104 Barrer, the CO_2/N_2 selectivity was 83.9, the selectivity of CO_2/CH_4 was 34.8, compared with the original film were increased by 45%, 74% and 92%, more than 2008 Robes On upper limit. Through the comparison of SEM and DSC characterization and Maxwell transfer model, it is confirmed that the enhancement of IL@ZIF-8 on mechanical properties and gas separation performance of Pebax film is mainly due to the enhancement of ionic liquid's compatibility to ZIF-8/Pebax interface.

【學位授予單位】：大連理工大學
【學位級別】：博士
【學位授予年份】：2017
【分類號】：TQ051.893

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本文編號：1616414