N_2优先渗透ZIF-8复合膜的制备及其CO_2捕集

为了获得经济节能的烟道气CO_2回收方法,制备了一种新型的N_2优先渗透ZIF-8复合膜。以柔性聚砜(PSf)多孔膜为支撑层,采用Zn~(2+)与壳聚糖的交联溶液对聚砜支撑层表面改性,使Zn~(2+)固定在PSf膜表面;然后与2-甲基咪唑(Hmim)配位得到ZIF-8晶种层;最后通过界面聚合法二次生长制得ZIF-8复合膜。采用FTIR、XRD及SEM对ZIF-8复合膜的形貌结构进行表征,结果显示成功制备了致密的ZIF-8复合膜。在进料气为纯气条件下,探究了二次生长时间、Zn~(2+)溶液的浓度、测试时间及测试压力对ZIF-8复合膜N_2/CO_2分离性能的影响,阐明其N_2优先渗透机理;并进一步考察了混合气分离性能。结果表明:在25℃和0.1 MPa下,最优ZIF-8复合膜的N_2渗透性为523 GPU,N_2/CO_2选择性为19;同条件下混合气的N_2渗透性和N_2/CO_2选择性分别为517 GPU和18。所制备的ZIF-8复合膜可以使N_2优先渗透,实现烟道气中高浓度N_2渗透,低浓度CO_2截留在膜的上游侧。原因主要是ZIF-8复合膜含有较多的CO_2强吸附位点,使CO_2被吸附在膜内不易从膜的下游侧脱附,渗透性小,而N_2优先渗透,这为N_2优先渗透膜的制备提供了一种新思路。     

含有MCM-41分子筛的混合基质复合膜用于CO2分离

为了提高CO₂分离膜的性能,将接枝了氨基的MCM-41分子筛(MCM-NH₂)添加到聚乙烯基胺(PVAm)水溶液中配制涂膜液,并将PVAm-MCM-NH₂涂膜液涂覆到聚砜(PSf)超滤膜上制备PVAm-MCM-NH₂/PSf混合基质复合膜。复合膜分离层较薄,有利于CO₂渗透速率的提高。接枝的胺基提高了分子筛与聚合物的相容性和膜内胺基含量,有利于膜渗透选择性能的提高。使用CO₂/N₂混合气(15% CO₂ + 85% N₂,体积分数)考察了不同MCM-NH₂添加量的PVAm-MCM-NH₂/PSf膜的渗透选择性能。当涂膜液中m_MCM-NH2/m_PVAm为0.2、湿涂层厚度为50 μm,测试温度为22℃ 、进料气压力为0.11 MPa时,膜的CO₂渗透速率可达4.66×10^-7 mol·m^-2·s^-1·Pa^-1,CO₂/N₂分离因子可达150。较高的CO₂/N₂分离性能表明PVAm-MCM-NH₂/PSf膜在烟道气碳捕集领域具有良好的应用前景。此外,考察了湿涂层厚度、热处理、添加小分子胺等条件对膜渗透选择性能的影响。     

聚乙烯胺/埃洛石纳米管混合基质膜的制备及其CO2/N2分离

制备高性能的气体分离膜,是实现CO₂高效回收的关键。为了提高CO₂分离膜的性能,将中空管状结构的埃洛石纳米管（HNTs）添加到聚乙烯胺（PVAm）中配制涂膜液,并将PVAm-HNTs涂膜液涂覆到聚砜（PSf）超滤膜上制备PVAm-HNTs/PSf混合基质膜。其中PSf超滤膜作为支撑层,PVAm-HNTs致密涂层作为功能层,功能层结构与形态对CO₂分离具有关键作用。采用XRD、SEM对HNTs的结构与形态进行表征,并借助FTIR和SEM对膜的形态与结构进行分析。在进料气为纯气条件下,系统地研究了HNTs添加量、进料压力、PVAm-HNTs涂层厚度对PVAm-HNTs/PSf膜的CO₂分离性能影响,并考察了混合基质膜的CO₂/N₂混合气分离性能。结果显示：在水溶液中显示正电性的PVAm与负电性的HNTs具有较好的界面相容性。HNTs添加量为1%（质量）、PVAm-HNTs湿涂层厚度为50 μm的混合基质膜,表现出最优的CO₂分离性能。在进料气压力为0.1 MPa、测试温度为25℃、CO₂/N₂（15/85,体积比）混合气进料的条件下,膜的CO₂渗透速率为178 GPU,CO₂/N₂选择性为83;该膜具有较好的稳定性,经过120 h运行后,渗透性和选择性仍能保持稳定。     

界面聚合法制备用于脱氮提纯CH4的N2优先渗透ZIF-90/聚酰胺混合基质膜

作为一种高效的分离方法,膜法分离非常规天然气具有较理想的应用前景。相较CH₄优先渗透膜,N₂优先渗透膜优势在于分离N₂/CH₄混合气后CH₄处于高压侧,利于后续处理。以均苯三甲酰氯为油相单体,间苯二胺为水相单体,采用界面聚合法在聚砜基膜上制备致密超薄聚酰胺分离层,并通过向其中引入孔径可允许N₂分子通过而不允许CH₄分子通过的纳米颗粒ZIF-90,在膜内形成固定的N₂传递通道,成功制备了用于脱氮提纯CH₄的N₂优先渗透混合基质膜。膜渗透选择性能测试结果显示当混合基质膜中纳米颗粒掺杂量为0.30 g·L^-1时,2 bar（1 bar=0.1 MPa）进料压力下,N₂渗透速率达1.16×10^-9 mol·m^-2·s^-1·Pa^-1,N₂/CH₄分离因子达16.6,分离因子比未掺杂ZIF-90的聚酰胺膜提高46.5%,具有一定的处理非常规天然气脱氮提纯甲烷的应用潜力。     

界面聚合法制备用于脱氮提纯CH4的N2优先渗透ZIF-90/聚酰胺混合基质膜

作为一种高效的分离方法,膜法分离非常规天然气具有较理想的应用前景。相较CH₄优先渗透膜,N₂优先渗透膜优势在于分离N₂/CH₄混合气后CH₄处于高压侧,利于后续处理。以均苯三甲酰氯为油相单体,间苯二胺为水相单体,采用界面聚合法在聚砜基膜上制备致密超薄聚酰胺分离层,并通过向其中引入孔径可允许N₂分子通过而不允许CH₄分子通过的纳米颗粒ZIF-90,在膜内形成固定的N₂传递通道,成功制备了用于脱氮提纯CH₄的N₂优先渗透混合基质膜。膜渗透选择性能测试结果显示当混合基质膜中纳米颗粒掺杂量为0.30 g·L^-1时,2 bar（1 bar=0.1 MPa）进料压力下,N₂渗透速率达1.16×10^-9 mol·m^-2·s^-1·Pa^-1,N₂/CH₄分离因子达16.6,分离因子比未掺杂ZIF-90的聚酰胺膜提高46.5%,具有一定的处理非常规天然气脱氮提纯甲烷的应用潜力。     

机械化学法合成小尺寸MOF填料助力高性能CO2分离

利用金属-有机骨架UTSA-280具有特定刚性尺寸的一维孔道可以筛分CO₂、CH₄、N₂的特性,采用机械化学研磨法减小其颗粒尺寸,将UTSA-280掺入聚砜（PSf）中制备MOF基混合基质膜,用于天然气提纯和烟道气CO₂捕获。结果表明,在PSf中掺入UTSA-280不仅可以增加聚合物的CO₂渗透通量而且提高了气体分离选择性。当UTSA-280掺杂量为30%（质量）时,混合基质膜对CO₂/CH₄、CO₂/N₂的分离因子分别为56.39和53.17,CO₂的渗透通量为18.61 Barrer,相对于PSf纯膜,选择性分别提高了47.3%和63.5%,CO₂渗透通量提高了128.9%,打破了“trade-off”效应。该工作通过引进具有分子筛分效应的MOF填料,能够增加气体通量的同时提高混合基质膜对含CO₂气体的分离性能,对天然气的提纯以及烟道气的CO₂的捕获有重要意义。     

二次生长法制备ZIF-8膜及其对CO2/N2的分离性能

采用二次生长法在α-Al₂O₃载体上制备超薄型ZIF-8膜,研究了多种轻分子气体以及混合气体CO₂/N₂的渗透分离性能。通过SEM和XRD表征了ZIF-8晶种层的晶种涂布状态,以及ZIF-8晶体膜的生长覆盖度和晶膜厚度。研究结果表明：采用低浓度的晶种悬浮液通过浸润式连续多次涂布法,有利于获得晶种层厚度均匀且覆盖度高的超薄均匀ZIF-8晶种层,经过二次生长后所得ZIF-8膜的覆盖度高、厚度均匀且较薄,仅约为8.8 μm;在所测试范围内的CO₂/N₂混合气体中,此ZIF-8膜对CO₂具有优先选择透过性,其对CO₂/N₂的渗透分离因子随温度的升高而降低,随渗透压力的增加而增加,在298 K、406 kPa和CO₂组分含量为50%时,该分离因子能达到6,显著超过Knudsen扩散的分离系数。     

聚乙烯胺/Cu3（BTC）2-MMT-NH2混合基质膜的制备及气体传递性能

采用阳离子交换与Cu₃(BTC)₂原位合成相结合制备Cu₃(BTC)₂-MMT,同时,借助3-氨基丙基三乙氧基硅烷(KH550)氨基功能化制备Cu₃(BTC)₂-MMT-NH₂杂化材料。然后,将杂化材料添加到聚乙烯胺(PVAm)基质中作为选择性涂层涂覆到聚砜(PSf)支撑体上,制备了PVAm/Cu₃(BTC)₂-MMT-NH₂混合基质膜。通过XRD和FTIR对杂化材料的晶态结构和化学结构进行了表征,同时采用ATR-FTIR证实了Cu₃(BTC)₂-MMT-NH₂杂化材料与PVAm基质之间存在氢键相互作用。系统性研究了PVAm/Cu₃(BTC)₂-MMT-NH₂混合基质膜中MMT阳离子交换量、Cu₃(BTC)₂-MMT与KH550的质量比、Cu₃(BTC)₂-MMT-NH₂的负载量、操作压力、湿膜厚度、操作温度以及混合气作为原料气对膜CO₂渗透性、CO₂/N₂选择性的影响。结果表明：在纯气气氛,操作温度为25℃、操作压力为1 bar(1 bar=0.1 MPa)的条件下,当Cu₃(BTC)₂-MMT-NH₂负载量为3%(质量)时,膜的气体分离性能最优,CO₂渗透率为203 GPU(1GPU=10^-6 cm³·cm^-2·s^-1·cmHg^-1,1 cmHg=1333.22 Pa),CO₂/N₂选择性为100.7,远高于添加MMT、Cu₃(BTC)₂和MMT/Cu₃(BTC)₂混合物的混合基质膜。这是由于Cu₃(BTC)₂-MMT-NH₂具有层间快速传递通道且与聚合物基质有良好的相容性。此外,混合气测试条件下,混合基质膜运行360 h,仍能保持优异的CO₂分离性能稳定性。     

聚乙烯胺/Cu3（BTC）2-MMT-NH2混合基质膜的制备及气体传递性能

采用阳离子交换与Cu₃(BTC)₂原位合成相结合制备Cu₃(BTC)₂-MMT,同时,借助3-氨基丙基三乙氧基硅烷(KH550)氨基功能化制备Cu₃(BTC)₂-MMT-NH₂杂化材料。然后,将杂化材料添加到聚乙烯胺(PVAm)基质中作为选择性涂层涂覆到聚砜(PSf)支撑体上,制备了PVAm/Cu₃(BTC)₂-MMT-NH₂混合基质膜。通过XRD和FTIR对杂化材料的晶态结构和化学结构进行了表征,同时采用ATR-FTIR证实了Cu₃(BTC)₂-MMT-NH₂杂化材料与PVAm基质之间存在氢键相互作用。系统性研究了PVAm/Cu₃(BTC)₂-MMT-NH₂混合基质膜中MMT阳离子交换量、Cu₃(BTC)₂-MMT与KH550的质量比、Cu₃(BTC)₂-MMT-NH₂的负载量、操作压力、湿膜厚度、操作温度以及混合气作为原料气对膜CO₂渗透性、CO₂/N₂选择性的影响。结果表明：在纯气气氛,操作温度为25℃、操作压力为1 bar(1 bar=0.1 MPa)的条件下,当Cu₃(BTC)₂-MMT-NH₂负载量为3%(质量)时,膜的气体分离性能最优,CO₂渗透率为203 GPU(1GPU=10^-6 cm³·cm^-2·s^-1·cmHg^-1,1 cmHg=1333.22 Pa),CO₂/N₂选择性为100.7,远高于添加MMT、Cu₃(BTC)₂和MMT/Cu₃(BTC)₂混合物的混合基质膜。这是由于Cu₃(BTC)₂-MMT-NH₂具有层间快速传递通道且与聚合物基质有良好的相容性。此外,混合气测试条件下,混合基质膜运行360 h,仍能保持优异的CO₂分离性能稳定性。     

SPEEK/PSI半互穿网络共混膜的制备及其CO2分离研究

为了获得高性能的气体分离膜，实现烟道气中CO₂/N₂高效分离回收，以磺化聚醚醚酮（SPEEK）和聚琥珀酰亚胺（PSI）为原料，己二胺为交联剂，原位交联反应制备富含氨基的半互穿网络共混膜，在膜内构建CO₂传递通道和亲和位点，并采用红外光谱对共混膜的结构进行表征。研究水含量、PSI用量和进料气压力对膜气体分离性能的影响，在混合气条件下考察其气体分离性能和长时间运行稳定性。研究结果表明：SPEEK与PSI两相界面相容性较好，它们之间存在较强的相互作用，且呈半互穿网络微结构；PSI含量为60%（质量）时，纯气和混合气条件下CO₂渗透性分别为652和601 Barrer，对应的CO₂/N₂选择性为67.6和60.3，优于纯SPEEK膜，且超过2008年的Robeson上限；共混膜运行360 h后，CO₂渗透性和CO₂/N₂选择性仍然稳定。这主要是因为SPEEK与PSI形成富含氨基的半互穿网络微结构后，一方面提供了CO₂促进传递载体；另一方面，增强了共混膜的保水性能，形成大量CO₂传递水通道。     

Covalent organic frameworks-incorporated thin film composite membranes prepared by interfacial polymerization for efficient CO2 separation

Thin film composite (TFC) membranes with nanofillers additives for CO₂ separation show promising applications in energy and environment-related fields. However, the poor compatibility between nanofillers and polymers in TFC membranes is the main problem. In this work, covalent organic frameworks (COFs, TpPa-1) with rich —NH— groups were incorporated into polyamide (PA) segment via in situ interfacial polymerization to prepare defect-free TFC membranes for CO₂/N₂ separation. The formed covalent bonds between TpPa-1 and PA strengthen the interaction between nanofillers and polymers, thereby enhancing compatibility. Besides, the incorporated COFs disturb the rigid structure of the PA layer, and provide fast CO₂ transfer channels. The incorporated COFs also increase the content of effective carriers, which enhances the CO₂ facilitated transport. Consequently, in CO₂/N₂ mixed gas separation test, the optimal TFC (TpPa_0.025-PIP-TMC/mPSf) membrane exhibits high CO₂ permeance of 854 GPU and high CO₂/N₂ selectivity of 148 at 0.15 MPa, CO₂ permeance of 456 GPU (gas permeation unit) and CO₂/N₂ selectivity of 92 at 0.5 MPa. In addition, the TpPa_0.025-PIP-TMC/mPSf membrane also achieves high permselectivty in CO₂/CH₄ mixed gas separation test. Finally, the optimal TFC membrane showes good stability in the simulated flue gas test, revealing the application potential for CO₂ capture from flue gas.     

Ceramic Supported PDMS and PEGDA Composite Membranes for CO2 Separation

Composite membranes have attracted increasing attentions owing to their potential applications for CO2 separation. In this work, ceramic supported polydimethylsiloxane （PDMS） and poly （ethylene glycol） diacrylate （PEGDA） composite membranes were prepared. The microstructure and physicochemical properties of the compos- ite membranes were characterized. Preparation conditions were systematically optimized. The gas separation performance of the as-prepared membranes was studied by pure gas and binary gas permeation measurement of CO〉 N2 and H〉 Experiments showed that PDMS, as silicone rubber, exhibited larger permeance and lower separation factors. Conversely, PEGDA composite membrane presented smaller gas permeance but higher ideal selectivity for CO2/N2. Compared to the performance of those membranes using polymeric supports or freestanding membranes, the two kinds of ceramic supported composite membranes exhibited higher gas permeance and acceptable selectivity. Therefore, the ceramic supported composite membrane can be expected as a candidate for CO2 separation from light gases.     

界面聚合制备含丙烯氧基团的复合膜用于CO2分离

含有醚氧基团的膜与CO₂分子具有较强的极性作用,可以实现对CO₂/N₂物系的高效分离.其中,含丙烯氧(PO)基团的聚合物链段自由体积较大且不易结晶,是一类具有发展潜力的溶解选择性膜材料.以均苯三甲酰氯为油相单体,含PO基团的多胺为水相单体,通过界面聚合,成功制备了含PO基团的复合膜.分别采用聚醚胺D400、D230及T403为多胺水相单体,考察了膜内PO基团数量和交联度对复合膜分离性能的影响.结果表明,采用D400所制的复合膜由于具有最高的PO基团含量及较低的交联度,因此具有最高的CO₂渗透速率和CO₂/N₂分离因子.之后,考察了单体浓度、酸吸收剂种类以及水相溶液pH对复合膜分离性能的影响.通过优化这些制膜条件,制备出了CO₂/N₂分离性能较好的复合膜.     

High-performance SSZ-13 membranes prepared using ball-milled nanosized seeds for carbon dioxide and nitrogen separations from methane

SSZ-13 membranes with high separation performances were prepared using ball-milled nanosized seeds by once hydrothermal synthesis. Separation performances of SSZ-13 membranes in CO_2/CH_4 and N_2/CH_4 mixtures were enhanced after synthesis modification. Single-gas permeances of CO_2, N_2 and CH_4 and ideal selectivities were recorded through SSZ-13 membranes. The effects of temperature, pressure, feed flow rate and humidity on separation performance of the membranes were discussed. Three membranes prepared after synthesis modifications had an average CO_2 permeance of 1.16 × 10~(-6) mol·(m~2· s·Pa)~(-1)(equal to 3554 GPU) with an average CO_2/CH_4 selectivity of 213 in a 50 vol%/50 vol% CO_2/CH_4 mixture. It suggests that membrane synthesis has a good reproducible. The membrane also displayed a N_2 permeance of 1.07 × 10~(-7) mol·(m~2·s·Pa)~(-1)(equal to 320 GPU) with a N_2/CH_4 selectivity of 13 for a 50 vol%/50 vol% N_2/CH_4 mixture. SSZ-13 membrane displayed stable and good separation performance in the wet CO_2/CH_4 mixture for a long test period over 100 h at 348 K. The current SSZ-13 membranes show great potentials for the simultaneous removals of CO_2 and N_2 in natural gas purification as a facile process suitable for industrial application.     

Separation and enrichment of carbon dioxide by capillary membrane module with permeation of carrier solution

A novel facilitated transport membrane for gas separation using a capillary membrane module is proposed in which a carrier solution is forced to permeate the membrane. Both a feed gas and a carrier solution are supplied to the lumen side (high pressure side, feed side) of the capillary ultrafiltration membrane and flow upward. Most of the carrier solution which contains dissolved solute gas, CO₂ in the present case, permeates the membrane to the permeate side (low pressure side, shell side), where the solution liberates dissolved gas to form a lean solution. The lean solution is circulated to the lumen side. This type of capillary membrane module was applied to the separation of CO₂ from model flue gases consisting of CO₂ and N₂. Monoethanolamine (MEA), diethanolamine (DEA) and 2-amino-2-methyl-1-propanol (AMP) were used as carriers or absorbents of CO₂. The feed side pressure was atmospheric and the permeate side was evacuated at about 10 kPa. CO₂ in the feed gas was successfully concentrated from 5–15% to more than 98%. The CO₂ permeance was as high as 2.7×10⁻⁴ mol m⁻² s⁻¹ kPa⁻¹ (8.0×10⁻⁴ cm³ cm⁻² s⁻¹ cmHg⁻¹) when the CO₂ mole fraction in the feed was 0.1 and temperature was 333 K. The selectivity of CO₂ over N₂ was in the range from 430 to 1790. The membrane was very stable over a discontinuous one-month testing period.     

一步法制备含氨基化合物的非对称CO2分离膜

采用一步相分离法,制备以聚醚砜（PES）为主体材料,二乙醇胺（DEA）为添加剂和氨基载体的膜,用于CO₂分离。考察了PES浓度、DEA浓度、膜厚度对CO₂/N₂分离性能的影响,同时考察了膜性能的长时间稳定性。当涂膜液中DEA/PES的质量比为12/26、刮刀与无纺布的距离为300 μm、进料气压力为0.11 MPa（表压）时,膜的CO₂渗透速率可达274 GPU,CO₂/N₂分离因子可达50。测试温度低于40℃时,DEA/PES膜的CO₂渗透速率和CO₂/N₂分离因子保持稳定。另外,对CO₂/N₂分离性能较好的DEA/PES膜（质量比为12/27）进行CO₂/CH₄分离性能测试,在1 MPa（表压）下性能优于商品膜。上述结果表明,本文研制的DEA/PES膜制备步骤简单,易于规模化制备,性能较优,在CO₂分离领域具有良好的应用前景。     

Strain-controlled graphdiyne membrane for CO2/CH4 separation: Firstprinciple and molecular dynamic simulation

Tensile strain of porous membrane materials can broaden their capacity in gas separation. In this work, using van der Waals corrected density functional theory(DFT) and molecular dynamics(MD) simulations, the performance and mechanism of CO_2/CH_4 separation through strain-oriented graphdiyne(GDY) monolayer were studied by applying lateral strain. It is demonstrated that the CO_2 permeance peaks at 1.29 × 10~6 gas permeation units(GPU) accompanied with CO_2/CH_4 selectivity of 5.27 × 10~3 under ultimate strain, both of which are far beyond the Robeson's limit. Furthermore, the GDY membrane exhibited a decreasing gas diffusion energy barrier and increasing permeance with the increase of applied tensile strain. CO_2 molecule tends to reoriented itself vertically to permeate the membrane. Finally, the CO_2 permeability decreases with the increase of the temperature from300 K to 500 K due to conserving of rotational freedom, suggesting an abnormal permeance of CO_2 in relation to temperature. Our theoretical results suggest that the stretchable GDY monolayer holds great promise to be an excellent candidate for CO_2/CH_4 separation, owing to its extremely high selectivity and permeability of CO_2.     

ZnO修饰的不锈钢网支撑体上ZIF-8膜的制备

ZIF-8因具有0.34 nm的孔道直径而被认为是最具应用前景的气体分离膜材料之一。不锈钢网（SSN）作为分离膜的支撑体具有价格低廉、易于裁剪、厚度薄等优点。采用水热法在SSN表面生长ZnO缓冲层,以ZnO修饰的SSN（ZnO/SSN）为支撑体制备ZIF-8膜。采用X射线衍射（XRD）和扫描电子显微镜（SEM）对合成的ZIF-8膜进行表征,并进行了气体渗透性能测试,结果表明,在ZnO颗粒修饰后的SSN支撑体上无需活化可制备出单一物相、无缺陷的ZIF-8膜;在室温（298 K）下,ZIF-8膜的H₂/CO₂、H₂/N₂、H₂/CH₄的理想分离系数分别为7.3、9.2、12.4;在150℃,ZIF-8膜的渗透性能稳定。