PVAm/PAN复合膜的制备及其对CO2/CH4的分离性能

引　言天然气和沼气中含有的大量CO2 将直接影响这些气体的燃烧效果和以这些气体为原料的产品质量 ,并对管线及设备造成腐蚀 ;同时由于CO2 等气体导致的温室效应 ,正引起严重后果 ;再者 ,发展生物技术也对CO2 的分离提出要求 .因此 ,分离CO2 技术已成为目前世界膜界研究的重点[     

含聚乙烯基胺共混固定载体复合膜制备及其 CO2/CH4分离性能

通过溶液共混法制备了聚乙烯基胺（PVAm）/聚乙二醇（PEG）和PVAm/聚N-乙烯基-γ-氨基丁酸钠（PVSA）共混聚合物.分别以这两种共混聚合物为分离层,以聚醚砜超滤膜为支撑层制备了用于分离CO₂的固定载体复合膜.研究了共混组成对膜结构和性能的影响,结果表明共混可以改善固定载体膜的透过分离性能.PEG质量含量为10%的PVAm/PEG共混膜具有整体最优的透过分离性能,当温度为25℃、压力为125kPa时,纯CO₂渗透速率为4.34×10^-9cm³(STP)•cm^-2•s^-1•Pa^-1,CO₂/CH₄理想分离因子为63.5;对PVAm/PVSA共混膜,PVSA质量含量为33.3%的膜具有最高的CO₂/CH₄理想分离因子,而PVSA质量含量为50%的膜具有最高纯CO₂渗透速率.     

用PVP水解物制备CO2固载膜及膜的性能

以自由基聚合合成了聚乙烯基吡咯烷酮（PVP），并用其水解产物聚N-乙烯基-γ-氨基丁酸钠（PVSA）和聚砜（PS）超滤膜制备了PVSA/PS复合膜；用红外光谱、X射线衍射等方法研究了PVP及其水解产物PVSA的结构，证实了PVSA含有可作为CO₂载体的仲胺基与羧基；测试了复合膜的透气性能及对CO₂/CH₄的选择性.结果表明，在26℃，压力为1333Pa时，CO₂渗透速率可达5.46×10^-7 cm³(STP)•cm^-2•s^-1•Pa^-1，CO₂/CH₄的理想分离因子达到212.1.随着进料气压力的增大，CO₂/CH₄的分离因子及CO₂的渗透速率均呈下降趋势.依据膜的渗透通量随压力的变化特性以及不同状态下膜的红外光谱，分析了膜对CO₂的促进传递机理.     

VSA-SA/PS固定载体复合膜的制备及其CO2/CH4分离性能

以自由基共聚合和水解的方法合成了一种新型的CO₂固定载体膜材料N-乙烯基-γ-氨基丁酸钠-丙烯酸钠共聚物 (VSA-SA).以VSA-SA为表层,聚砜超滤膜为支撑体制得复合膜.研究了复合膜对CO₂/CH₄体系的渗透选择性,考察了金属离子交联剂和交联时间以及进料气组成对复合膜性能的影响.本文制得的复合膜运行1周仍能维持良好的分离因子和CO₂渗透速率.     

新型CO_2分离膜的气体吸着性能

引　言石油气和天然气中含有的大量ＣＯ2 直接影响以这些气体为原料的产品质量 ,并对管线和设备造成腐蚀 .同时 ,由于ＣＯ2 等气体导致的温室效应已引起严重后果 .因此 ,如何分离或脱除ＣＯ2 成为人们的研究热点 .采用膜技术分离气体由于具有节约能源、操作简便等优点已得到了很大的发展[1～ 3] .最初用于气体分离的主要膜材料多为普通高分子聚合物 ,如醋酸纤维素、聚酰亚胺等 .至今这些膜材料仍在不断的开发和应用 .但由于Ｒｏｂｅｓｏｎ上限[4 ] 的存在 ,使其很难同时具有高选择性和高透过率 ,研制新型膜材料是解决此问题的一个重要途径 .…     

用PVP水解物制备CO2固载膜及膜的性能

以自由基聚合合成了聚乙烯基吡咯烷酮 (PVP) ,并用其水解产物聚N 乙烯基 γ 氨基丁酸钠 (PVSA)和聚砜 (PS)超滤膜制备了PVSA/PS复合膜 ;用红外光谱、X射线衍射等方法研究了PVP及其水解产物PVSA的结构 ,证实了PVSA含有可作为CO2 载体的仲胺基与羧基 ;测试了复合膜的透气性能及对CO2 /CH4的选择性 .结果表明 ,在 2 6℃ ,压力为 1333Pa时 ,CO2 渗透速率可达 5 4 6× 10 -7cm3 (STP)·cm-2 ·s-1·Pa-1,CO2 /CH4的理想分离因子达到 2 12 1.随着进料气压力的增大 ,CO2 /CH4的分离因子及CO2 的渗透速率均呈下降趋势 .依据膜的渗透通量随压力的变化特性以及不同状态下膜的红外光谱 ,分析了膜对CO2 的促进传递机理     

微波加热法快速制备COFs及其复合膜的气体分离性能研究

本文以间苯二甲醛和三聚氰胺为原料,二甲基亚砜(DMSO)为溶剂,通过微波加热法成功快速制备了具有三维多孔结构的聚合物N-COF。由核磁共振图谱(NMR)和电子显微镜(SEM)确定了其化学结构和表面多孔形貌。将N-COF与聚砜树脂(PSF)进行共混,成功制备了N-COF/PSF复合薄膜。并对其进行CO_2/N_2气体分离和热重分析测试。CO_2/N_2分离系数(PCO_2/PN_2)高达97.6。     

淀粉基多孔碳材料的制备及其吸附CO2/CH4性能

以淀粉为原料,使用水热法将其碳化后用活化剂KOH对其活化,制备了淀粉基多孔碳材料,并对其进行结构表征和CO₂/CH₄的吸附性能测试,计算吸附热以及材料对CO₂/CH₄的吸附选择性,讨论了碳材料结构对其吸附性能的影响。结果表明：在制备过程中,随着活化剂KOH用量比例的增大,所制得的材料其比表面积和孔容增大,其孔径分布也就越宽。所制得的碳材料其比表面积可达2972 m²·g^-1。这些淀粉基多孔碳材料对水蒸气的吸附等温线呈现出Ⅳ类等温线。所制备材料对CO₂吸附容量主要取决于其孔径小于0.8 nm的累积孔容（Vd < 0.8 nm）。材料的超微孔的孔容越大,其对CO₂吸附容量也越大。所制备的C-KOH-1材料在101325 Pa和298 K条件下,对CO₂的吸附量达到4.2 mmol·g^-1,其对CO₂的吸附热明显高于其对CH₄吸附热,其对CO₂/CH₄吸附选择性为3.7～4.26,同时本文通过对材料的水蒸气吸附等温线进行测试,结果表明所得材料主要表现为中等憎水性,这对材料在实际工况的应用奠定了基础。     

电场辅助制备多壁碳纳米管/聚苯乙烯复合膜的气体分离性能

采用溶液浇铸法制备了不同含量多壁碳纳米管（MWCNTs）和聚苯乙烯（PS）掺杂的气体分离复合膜,成膜过程中在垂直于铸膜液平面的方向上施加场强为2000 V·cm^-1,频率为1 Hz的交变电场,直至溶剂挥发完全。采用荧光分光光度计、体式显微镜和数字万用表考察了膜的荧光特性,铸膜液中MWCNTs对水平电场的响应,MWCNTs在膜中的分散情况以及膜的垂直向电阻率,测定了复合膜对CO₂、CH₄的渗透系数。结果表明电场作用不仅可以实现MWCNTs在膜中的定向排布,还能够使MWCNTs在膜中分散得更均匀,定向复合膜CO₂和CH₄的透过性和选择性都优于非定向复合膜。     

热处理条件对PVA/PAN和PPVA/PAN渗透汽化复合膜分离性能的影响

制备了以聚乙烯醇（PVA）、磷酸酯化聚乙烯醇（PPVA）和活性分离层的PVA／PAN、PPVA／PAN渗透汽化复合膜并用于乙醇－水恒沸混合物的分离。考察了热处理条件对复合膜分离性能及吸附性能的影响。结果表明,复合膜的分离性能主要是由热处理温度决定的,并且,PPVA／PAN复合膜比PVA／PAN复合膜具有更好的分离性能。确定了最佳的热处理条件,对于PVA／PAN复合膜：在403K下,热处理时间不小于4h,对于PPAV／PAN复合膜：在423K下,热处理时间不小于2h。     

聚乙烯醇陶瓷复合膜的制备与性能研究

以大孔径廉价的陶瓷粗滤膜（SiO2）作为基质膜,以亲水性的聚乙烯醇为原料、戊二醛作交联剂,采用涂敷的方法制备了聚乙烯醇陶瓷复合膜。考察了基质膜的孔径大小、聚乙烯醇的浓度、交联时间等对复合膜性能的影响。在膜反应器中膜通量的变化及有机污染物的去除效果表明：复合膜具有较好的耐污染特,陛及较高的COD去除率。     

CO2固定载体膜过程中物质间相互作用及其影响

采用自由基聚合合成了聚乙烯基吡咯烷酮，经水解得到了聚N-乙烯基-γ氨基丁酸钠(PVSA).该聚合物含有能与CO₂进行可逆反应的仲胺基和羧基.以PVSA为表层，以微孔膜为支撑体，制备了新型CO₂固定载体复合膜.以CO₂/CH₄体系为分离对象，研究了CO₂、CH₄、PVSA、水、膜中小分子杂质和支撑膜等相互之间的作用，同时探讨了这些相互作用对膜结构和性能的影响.     

PREPARATION AND TESTING OF CARBON/SILICALITE-1 COMPOSITE MEMBRANES

Methods for preparation of carbon/silicalite-1 composite membranes have been developed. First, silicalite-1 membranes were prepared by in-situ hydrothermal synthesis on both porous alumina and metal disks. Preparation of the carbon/silicalite-1 composite membranes was accomplished by polymerizing furfuryl alcohol on the surface of the silicalite-1 membrane, followed by carbonizing the polymer layer in an inert atmosphere at 773 K. The pure silicalite-1 membrane showed no selectivity for single gases, indicating the presence of intercrystalline diffusion and viscous flow as the dominant transport mechanism. The carbon/zeolite composite membrane exhibited ideal selectivities for He/N₂, CO₂/N₂, and N₂/CH₄ of 11.99, 17.12, and 3.58 at room temperature. No permeation of n-butane and i-butane for the composite membrane was detected up to temperatures of 453 K, indicating that the pore size for the composite membrane was approximately 0.4 nm. By carefully oxidizing the carbon layer in air at 623 K, the pore size of the composite membrane was adjusted such that n-butane permeation could be detected. No permeation of i-butane was apparent, suggesting that the pore size of the composite membrane had been enlarged to approximately 0.5 nm. Further oxidation of the carbon layer produced a finite n-/i-C₄H₄ ideal selectivity, indicating that the pore size of the membrane was now larger than 0.55 nm. Therefore, selective oxidation of the carbon layer can be used to control the pore size of the composite membrane.     

PREPARATION AND TESTING OF CARBON/SILICALITE-1 COMPOSITE MEMBRANES

Methods for preparation of carbon/silicalite-1 composite membranes have been developed. First, silicalite-1 membranes were prepared by in-situ hydrothermal synthesis on both porous alumina and metal disks. Preparation of the carbon/silicalite-1 composite membranes was accomplished by polymerizing furfuryl alcohol on the surface of the silicalite-1 membrane, followed by carbonizing the polymer layer in an inert atmosphere at 773 K. The pure silicalite-1 membrane showed no selectivity for single gases, indicating the presence of intercrystalline diffusion and viscous flow as the dominant transport mechanism. The carbon/zeolite composite membrane exhibited ideal selectivities for He/N₂, CO₂/N₂, and N₂/CH₄ of 11.99, 17.12, and 3.58 at room temperature. No permeation of n-butane and i-butane for the composite membrane was detected up to temperatures of 453 K, indicating that the pore size for the composite membrane was approximately 0.4 nm. By carefully oxidizing the carbon layer in air at 623 K, the pore size of the composite membrane was adjusted such that n-butane permeation could be detected. No permeation of i-butane was apparent, suggesting that the pore size of the composite membrane had been enlarged to approximately 0.5 nm. Further oxidation of the carbon layer produced a finite n-/i-C₄H₄ ideal selectivity, indicating that the pore size of the membrane was now larger than 0.55 nm. Therefore, selective oxidation of the carbon layer can be used to control the pore size of the composite membrane.     

CO2通过合成聚合物膜的促进传递

Two kinds of fixed carrier membrane materials containing secondary amine and carboxyl groups whichcan be used as carriers of CO2 were prepared. One was poly(N-vinyl-γ-sodium aminobutyrate)(PVSA), whichwas obtained through the hydrolysis of polyvinylpyrrolidone (PVP) synthesized with N-vinylpyrrolidone(NVP) byradical polymerization. The other was poly(N-vinyl-γ-sodium aminobutyrate-co-sodium acrylate)(VSA-SA), whichwas obtained through the hydrolysis of copolymer of N-vinylpyrrolidone and acrylamide(AAm) (NVP-AAm). Thecomposite membranes were developed with PVSA or VSA-SA as active layer and polysulfone (PS) as supportmembranes. The permeation rates of pure CO2 and CH4 gas as well as binary mixtures of CO2/CH4 throughthe composite membranes were measured. The results show that the composite membranes present better CO2permeation rates than other fixed carrier membranes do reported in literature. For example, at 26℃, 1330 Pa of CO2pressure, the PVSA/PS composite membrane displays a CO2 permeation rate of 5.95 × 10-7 cm3.cm-2.s-1.pa-1with CO2/CH4 ideal separation factor of 212.1. At 20℃, 6400Pa of CO2 pressure, the VSA-SA/PS compositemembrane displays a CO2 permeation rate of 4.24 × 10-8 cm3@cm-2.s-1.Pa-1 with CO2/CH4 ideal separationfactor of 429.7. The results with the gas mixtures are not as good as those obtained with pure gas because ofthe coupling effects between CO2 and CH4. The heat cross-linked membrane shows good separation factor due todensification of the polymer.     

超临界CO2萃取精馏制取高纯度EPA乙酯和DHA乙酯

Fish oil ethyl esters complexed with aqueous silver nitrate solution were extracted and rectified by supercritical CO₂ to obtain DHA ester and EPA ester with high purity. The effects of some independent variables,such as extraction pressure, temperature gradient of rectifying column and programmed pressure,on rectification were investigated.The results showed that programmed pressure is suitable for purification of EPA and DHA esters. Increase of column temperature gradient from bottom to top is one of the key elements in rectification. Furthermore, higher temperature gradient leads to better separation effect.