杂化炭膜的制备及其气体分离应用研究进展

杂化炭膜是一种新型的无机气体分离膜材料,在有效分离气体的应用中有广阔的工业化前景.综述了杂化炭膜制备过程中有机聚合物、掺杂物的选择及采用的涂膜方式和炭化条件对膜分离性能的影响及其在气体分离应用方面的研究进展,并对杂化炭膜的发展方向进行了展望.     

Fe/C杂化炭膜的制备及其气体分离性能

将二茂铁作为有机添加剂引入炭膜前驱体聚酰亚胺,经高温热解制备了Fe/C杂化炭膜。考察了二茂铁的添加量对杂化炭膜气体渗透性能的影响。采用热重、红外、X射线衍射和透射电镜等分析方法对所制备的杂化炭膜进行了表征。结果表明,在前驱体中添加二茂铁能显著提高炭膜的气体渗透性能,随着添加量的增加,膜的气体渗透系数明显增加而分离系数则减小,当二茂铁添加量为15%时,对H₂、O₂、N₂、CO₂、CH₄等纯气体的渗透系数分别为2806、1039、266、31、8 barrer,对O₂/N₂、CO₂/N₂、CO₂/CH₄的分离系数分别为8.6、33.5、129.5。Fe/C杂化炭膜是基于“分子筛分”机理分离气体分子。     

4A沸石填充聚氨酯杂化膜的制备及气体分离性能

两步法制备了4A沸石填充的端羟基聚丁二烯基聚氨酯膜HTPB-PU/4A,并研究了CO2、H2、O2、N2的气体透过性能.结果表明:沸石与膜的相容性较好,添加4A沸石后,膜的热稳定性明显提高,O2渗透性及O2/N2选择性显著改善;随沸石添加时间的增加,膜对各种气体体系的选择性先增加后减小,而渗透性则先增加后趋于稳定;随硬...     

溶胶-凝胶法制备PES-SiO_2气体分离杂化膜及其表征

采用溶胶-凝胶法,利用干/湿相转换法制备PES-SiO_2气体分离杂化膜,探讨了不同二氧化硅的添加量、是否预留空气段以及不同酸作为催化剂对气体分离性能的影响。采用SEM等对膜的结构性能、力学性能进行表征。通过实验发现,用醋酸作为脱水缩合催化剂,不预留空气段,当SiO_2的添加量为2v%时,O_2、N_2、CO_2、CH_4和H_2的通量分别增加471%、596%、181%、181%和232%,O_2/N_2、CO_2/CH_4和H_2/N_2的选择性分别降低到79%、73%和39%,杨氏模量提高为原来的2倍,PES-SiO_2气体分离杂化膜放置16 d后,分离性能趋于稳定。     

溶胶-凝胶法制备PES-SiO_2气体分离杂化膜及其性能

<正>有机/无机杂化材料结合了无机材料的高机械性能、热稳定性、耐压性和有机高分子聚合物材料的延展性、易加工性的优点,两相混合制备气体分离杂化膜已得到广泛的关注[1,2]。由于高分子聚合物气体分离膜渗透通量和分离性能这两个关键参数之间存在着制约关系[3-4],在聚合物中引入无机纳米材料,能够得到高性能的膜材料。本文采用sol-gel法     

炭膜气体分离性能研究

以酚醛树脂为原料制备了炭支撑膜和炭－炭复合膜，研究了其气体分离性能。结果表明：炭支撑膜分离气体和机理包括努森扩散和粘性流；采用浸涂－干燥－炭化的工艺制备的炭－炭复合膜对Ｈ２／ＣＯ２具有较好的分离性能，Ｈ２／ＣＯ２分离系数达５．６，大于理想努森扩散的分离系数３．７。但在高压差时复合膜上ＣＯ２的表面扩散增强，使Ｈ２／ＣＯ２分离系数下降。     

功能化PVI/MOR杂化膜的制备及乙酸脱水分离性能

通过自由基接枝聚合的方法将1-乙烯基咪唑单体接枝到MOR沸石膜的表面,制备出一种新型的亲水性的聚(1-乙烯基咪唑)/丝光沸石(PVI/MOR)杂化膜.并通过扫描电子显微镜(SEM)、X射线衍射(XRD)、傅里叶红外漫反射光谱(DRIFTS)和热重分析等来表征膜的形貌和特性.将膜应用于乙酸脱水分离,考察了不同Ⅵ单体浓度和进料浓度对膜的渗透汽化性能的影响.分析得知以15%的Ⅵ单体浓度制备的PVI/MOR杂化膜具有最好的分离性能,在80℃下和71%～94%的进料浓度范围内均达到理想选择性分离,也就是说在透过侧产品水的含量达到100%.这些实验结果表明将PVI基团接枝到MOR沸石膜层能实现真正意义上的功能化修补膜的缺陷和大大提高膜的分离性能的目的.     

MFI型沸石膜的渗透分离性能及应用

综述了ＭＦＩ型沸石分子筛的渗透分离性能,探讨了其可能的分离机理,并介绍了包括膜分离与经在内的前沿进展。     

填充型有机-无机杂化分离膜研究进展

根据有机、无机组分间相互作用类型对有机-无机杂化膜进行了分类,重点论述了无机粒子填充型有机-无机杂化膜的最新研究进展,归纳了此类杂化膜的优异性能,总结了无机粒子的物理化学性能、含量、尺寸及其与聚合物的相容性等因素对此类杂化膜结构和性能的主要影响。最后提出了目前研究中存在的一些问题,并对其发展做出了简要的述评。     

有机-无机杂化气体分离膜研究

介绍气体的分离机理及杂化膜的主要制备方法;并对杂化膜的改性进行详细地阐述;为获得气体分离性能优异的有机一无机杂化气体分离膜奠定理论基础。     

Gas Separation Properties of Polyimide-Zeolite Mixed Matrix Membranes

Mixed matrix membranes (MMMs) of polyimide (PI) and zeolite 13X, ZSM-5 and 4A were prepared by a solution-casting procedure. The effect of zeolite loading, pore size, and hydrophilicity/hydrophobicity of zeolite on the gas separation properties of these mixed matrix membranes were studied. Experimental results indicate that permeability of He, H₂, CO₂, and N₂ increased with zeolite loadings. Selectivity of H₂/N₂ shows a slight improvement for low loadings of zeolites 13X and ZSM-5 but has a decreasing trend for zeolite 4A and high loadings of zeolites 13X and ZSM-5. In addition, selectivity of H₂/CO₂ remains low (1–3) while selectivity of CO₂/N₂ is significantly improved with the incorporation of the three zeolites in the polyimide membrane. Experimental permeabilities are higher than those predicted by the Maxwell model except for H₂ and N₂ permeabilities of the PI-4A system which are consistent with the predicted permeabilities. The proposed modified Maxwell model is capable of predicting the permeabilities of polyimide-zeolite 4A MMMs, but fails to simulate the permeability increase induced by interface voids in the polyimide-zeolite 13X and ZSM-5 systems.     

Simulations of Membrane Gas Separation: Chemical Solvent Absorption Hybrid Plants for Pre- and Post-Combustion Carbon Capture

Solvent absorption and membrane gas separation are two carbon capture technologies that show great potential for reducing emissions from stationary sources such as power plants. Here, plants combining chemical solvent absorption and membrane gas separation are considered for post-combustion capture as well as pre-combustion capture. In all ASPEN HYSYS simulations the membrane stage initially concentrates CO₂ into either the permeate or the retentate stream, which is then passed to a monoethanolamine (MEA) based solvent absorption process. In particular, post-combustion capture scenarios examined a membrane that is selective for CO₂ against N₂, while for the pre-combustion scenario a H₂-selective membrane was studied. It was found the energy demand of the combined hybrid plant was always more than that of a stand alone MEA solvent process. This was mainly due to the need to generate a pressure driving force upstream of the membrane in the post-combustion scenario or to recompress downstream gas streams in the pre-combustion scenarios. For both scenarios concentrating the CO₂ in the feed to the solvent system reduced the absorber column height and diameter, which could represent a CAPEX saving for the hybrid plant, dependent upon the membrane price. The use of a hydrogen selective membrane downstream of an oxygen fired gasifier was identified as the most prospective scenario, as it led to significant reductions in absorber size, for a relatively small membrane area and energy penalty.     

Separation of CO2/N2 Gas Mixture through Carbon Membranes: Monte Carlo Simulation

Abstract

Monte Carlo simulation method is employed to investigate separation behavior of gas mixture composed of carbon dioxide and nitrogen through a model carbon membrane under the different conditions. The simulation gives insight into the separation mechanism to a certain extent, which is based on the loading and diffusion of carbon dioxide and nitrogen in the carbon membrane with different pore size. The simulation results indicate that the carbon dioxide can be adsorbed on the surface of membrane wall more strongly, whereas the diffusion rate of nitrogen is more prominent. When the separation condition alters, the influence of the two main factors mentioned above on transport of gas molecules in membranes becomes different. Therefore, the equilibrium selectivity of nitrogen and carbon dioxide changes correspondingly.     

Effect of Raw Multi-Wall Carbon Nanotubes on Morphology and Separation Properties of Polyimide Membranes

Raw multi wall carbon nanotubes (r-MWCNTs) were embedded as fillers inside the polyimide (PI) matrix and PI/r-MWCNTs mixed matrix membranes were fabricated by the phase inversion method. The TEM images and permeation results using helium as test gas showed that r-MWCNTs were generally closed ended and acted as impermeable nano particles. Gas permeation tests using CO₂ and CH₄ showed that the addition of r-MWCNTs into the dope solution increased the CO₂/CH₄ separation factor while decreasing the carbon dioxide and methane permeances. When the r-MWCNTs content was increased from 0% to 6 wt.%, permeance of CO₂ in the flat sheet mixed matrix membranes decreased from 9.15 GPU to 5.49 GPU and CO₂/CH₄ separation factor increased from 19.05 to 45.75. Identical to flat sheet mixed matrix membranes, the addition of 2 wt.% r-MWCNTs into a spinning dope increased the CO₂/CH₄ separation factor from 46.61 to 72.20. The glass transition temperature of the mixed matrix flat sheet membranes increased with an increase in the r-MWCNTs content. This implies a good segmental-level attachment between the two phases that forms a rigidified polymer region at the polymer/r–MWCNTs interface. FESEM images showed well dispersed r-MWCNTs in the polymer matrix at a loading of 2 wt% r-MWCNTs.     

气体透过碳膜的非平衡动力学模拟研究

The permeation of various pure gas （H2, He, Ne, CH4 and At） through carbon membranes is investigated using a dual control volume grand canonical molecular dynamics method. A two-dimensional slit pore is employed instead of the one-dimensional pore. Compared with the experiments, simulation results show that the improvement of pore model is very necessary. The effects of membrane thickness, pore width and temperature on gas permeance and ideal separation factor are also discussed. Results show that gas permeates through membrane according to Knudsen diffusion in large pore, while Knudsen diffusion is accompanied by molecular sieving in small pore. Moreover, methane is easily adsorbed on the membrane surface due to strong attractive interactions of membrane and shows higher permeance than that of Knudsen flow. In addition, it is noted that when membrane thickness is thin enough the permeance of gas does not decrease with the increase of membrane thickness due to the strong adsorption until membrane resistance becomes dominant.     

富含二氧化碳的天然气分离及其利用

论述了国内外对富含二氧化碳的天然气分离技术的研究进展,包括：膜分离法、变压吸附（PSA）法、物理吸收法和化学吸收法等,并分析了天然气资源的深加工利用及其产品开发前景。     

Ionic Liquids‐Based Membranes for Carbon Dioxide Separation

Ionic liquids (ILs) have gained wide‐spread focus owing to its negligible vapor pressure, low heat capacity, high thermal stability, and structural diversity. The solubility and selectivity toward carbon dioxide has made ILs a unique platform that possess the potential in gas separations. In particularly, combining functional ILs with membranes and porous supports is an efficient way to design task‐specific materials for CO₂ separations. This minireview summarizes the developments and advances of ionic liquids‐based membranes for CO₂ separations in recent three years, with an emphasis on the strategy of incorporating ionic liquids and CO₂ separation performance.     

Sequential Template Decomposition to Adjust the Performance of Imperfect Zeolite BEA Membranes

Zeolite membranes offer superior thermal, chemical, and mechanical stability compared to polymeric membranes. However, it is still a challenge to prepare completely defect‐free membranes without any intercrystalline voids, which is necessary for gas separation processes. In this study zeolite beta (*BEA) membranes on stainless‐steel supports were prepared by applying the multiple in situ crystallization technique. The membranes were used as a model system to systematically study the decomposition of the organic structure directing agent tetraethylammoniumhydroxide (TEA‐OH). It was evaluated if the organic decomposition products of TEA‐OH can be used for enhancing the membranes selectivity. Post‐treatment experiments have been carried out to adjust surface properties and pore size dimensions in the zeolitic membrane layer. The results show that membranes calcined at lower temperatures exhibit a higher gas selectivity.     

Novel Composite Membranes for Gas Separation: Preparation and Performance

High performance composite membranes based on molecular sieving silica (MSS) were synthesized using sols containing silicon co-polymers (methyltriethoxysilane and tetraethylorthosilicate). Alpha alumina supports were treated with hydrochloric acid prior to sol deposition. Permselectivity of CO2 over CH4 as high as 16.68 was achieved whilst permeability of CO2 up to 36.7 GPU (10–6 cm3 (STP) cm–2 · s–1 · cm Hg–1) was measured. The best membrane's permeability was finger printed during various stages of the synthesis process showing an increase in CO2/CH4 permselectivity by over 25 times from initial support condition (no membrane film) to the completion of pore structure tailoring. Transport measurement results indicate that the membrane pretreated with HCl has highest permselectivity and permeation rate. In particular, there is a definite cut-off pore size between 3.3 and 3.4 angstroms which is just below the kinetic diameters of Ar and CH4. This demonstrates that the mechanism for the separation in the prepared composite membrane is molecular sieving (activated diffusion), rather than Knudsen diffusion.     

气体分离膜材料研究进展

介绍了高分子材料、无机材料、有机－无机杂化材料三类气体分离膜材料，主要包括聚酰亚胺、聚砜、聚二甲基硅氧烷、聚[1-(三甲基硅氧烷）－1－丙炔]等高分子材料，以及致密无机膜和多孔无机膜材料，并且对有机－无机杂化材料作了简要概述。在评价了各种膜材料性能的基础上，展望了气体分离膜材料的发展前景。