α-纤维素膜气体分离性能

制备了α-纤维素膜并对其气体分离性能进行了研究.测定了水溶胀下，CO₂、H₂、CH₄、N₂、O₂等气体在α-纤维素膜内的气体渗透速率.通过比较研究醋酸纤维素膜、苯甲酰化纤维素膜和聚砜膜在干态和湿态下的气体渗透性能，揭示了水对α-纤维素膜气体渗透性能的作用规律.     

6FDA型聚酰亚胺中气体溶解行为的分子模拟

用分子模拟方法对6FDA-durene、6FDA-pPDA及其共聚物6FDA-durene/pPDA的链间距及自由体积进行了模拟计算,结果与文献实验值一致;采用巨正则Monte Carlo(GCMC)方法模拟了O₂、N₂、CH₄和CO₂在聚酰亚胺中的溶解,计算结果表明：COMPASS力场能较准确地描述O₂、N₂和CH₄在聚酰亚胺中的吸附溶解,O₂、N₂、CH₄的溶解系数模拟结果与实验数据吻合较好。CO₂的溶解系数计算值与实验值偏差较大(约50％),主要原因可能在于模拟过程中未考虑体积溶胀效应以及COMPASS力场不能精确描述CO₂与—CF₃基团的相互作用。同一聚合物中,计算所得气体溶解系数的大小顺序为CO₂>CH₄>O₂>N₂,与气体凝聚性趋势一致,同种气体在6FDA型聚酰亚胺中的溶解系数与其自由体积分数变化趋势一致。3种聚合物对CO₂/CH₄的溶解选择性高于O₂/N₂,共聚物与均聚物相比,气体溶解选择性没有明显提高。     

O2/N2、O2/CO2和O2/CO2/NO气氛下煤粉燃烧NOx排放特性

利用滴管炉研究了O₂/N₂、O₂/CO₂和O₂/CO₂/NO气氛下煤燃烧过程中NO_x的排放特性。实验结果表明,在O₂/N₂和O₂/CO₂气氛下,高温或高O₂浓度均使NO排放量增加。O₂/CO₂气氛下NO排放量比O₂/N₂气氛下NO排放量低大约30%～40%。在O₂/CO₂/NO气氛下,温度不同时,O₂浓度变化对NO排放量的影响规律不同,对循环NO降解的影响规律也不同。高温不利于循环NO降解。随停留时间的延长NO排放量出现两个峰值。     

甲基丙烯酸二甲氨基乙酯-丙烯腈共聚物膜的制备及其气体渗透性能

采用水溶液沉淀法合成了甲基丙烯酸二甲氨基乙酯（DM）和丙烯腈（AN）的共聚物，用红外光谱、黏度法和X射线衍射分析了聚合物的结构.实验考察了反应条件对共聚物结构的影响.在此基础上，通过溶液浇注法制备了甲基丙烯酸二甲氨基乙酯（DM）和丙烯腈（AN）的共聚物膜，研究了聚合物膜的CO₂、CH₄渗透性能.结果表明，由于共聚物中含有能与CO₂进行可逆反应的叔胺基，共聚物膜表现出较好的CO₂渗透性和CO₂/CH₄选择性，如在25℃、压力为1140 Pa时，CO₂的渗透速率可达 3.53×10^-12 cm³(STP)•cm^-2•s^-1•Pa^-1 ， CO₂/CH₄ 的理想分离因子达到104.5.利用膜吸附CO₂和CH₄后红外光谱的变化，分析了膜对CO₂的促进传递机理.     

工艺条件对Ni/Al2O3和Ni/CeO2-Al2O3催化剂在甲烷自热重整制氢反应中催化性能的影响

采用共沉淀法制备γ-Al₂O₃载体和不同Ce添加量的CeO₂-Al₂O₃载体,然后用浸渍法制备Ni负载质量分数10%的Ni/γ-Al₂O₃和Ni/CeO₂-Al₂O₃催化剂。在固定床微反装置中考察了反应温度、原料气配比和CH₄空速等工艺条件对Ni/γ-Al₂O₃和Ni/Ce₃₀Al₇₀O_δ催化剂在甲烷自热重整制氢反应中催化性能的影响。结果表明,添加Ce的催化剂催化性能有较大提高,在Ni/Ce₃₀Al₇₀O_δ催化剂上,反应温度750 ℃时, CH₄转化率94.3％,与Ni/Al₂O₃催化剂相比,提高20％。Ni/γ-Al₂O₃和Ni/CeO₂-Al₂O₃催化剂的CH₄转化率均随反应温度的升高而增大。原料气中n(O₂)∶n(CH₄)和n(H₂O)∶n(CH₄)的增加均能提高各催化剂的CH₄转化率。但n(O₂)∶n(CH₄)和n(H₂O)∶n(CH₄)的变化对各催化剂的催化性能的影响不同。随着n(O₂)∶n(CH₄)的增大,产物中n（H₂）∶n（CO）降低,n（CO₂）∶n(CO＋CO₂)升高;而n(H₂O)∶n(CH₄)增大时,产物中n（H₂）∶n（CO）和n（CO₂）∶n(CO＋CO₂)均升高。随着CH₄空速的增加,Ni/Al₂O₃催化剂上CH₄转化率、n（H₂）∶n（CO）和n（CO₂）∶n(CO＋CO₂)均较大程度下降;而在Ni/Ce₃₀Al₇₀O_δ催化剂上,随着CH₄空速的增加,CH₄转化率、n（H₂）∶n（CO）和n(CO₂）∶n(CO＋CO₂)变化不大。     

气体与煤表面吸附作用的量子化学研究

选用褐煤、次烟煤、高挥发分烟煤、低挥发分烟煤和无烟煤5种煤表面结构模型,采用量子化学半经验方法INDO,从分子水平描述了CO、O₂、H₂O(g)、CO₂、CH₄和H₂等6种气体在煤表面的吸附作用,计算了气体在煤表面的吸附能、吸附距离、吸附作用键级和净电荷变化等微观参数,用Morse函数拟合了气体与煤表面的结合能曲线,得到了气体吸附作用强弱次序为：CO和O₂最强,H₂O和CO₂次之,CH₄和H₂最弱。     

O2/CO2气氛下煤燃烧SO2/NO析出特性

在水平管式炉上研究了O₂浓度、CO₂浓度、温度及石灰石添加等各参数对O₂/CO₂气氛下徐州烟煤和龙岩无烟煤燃烧过程中SO₂/NO排放特性的影响。结果发现,O₂/CO₂气氛下,烟煤和无烟煤燃烧SO₂/NO的析出规律与空气气氛下不同,同等O₂浓度下析出量比空气气氛下小。O₂/CO₂气氛下,随着O₂浓度的提高,烟煤和无烟煤SO₂/NO排放量均增大;随着CO₂浓度的升高, SO₂/NO排放量均减小。O₂/CO₂气氛下,石灰石添加对SO₂排放的抑制作用低于空气气氛下;石灰石添加对NO的排放有一定减排作用。对煤灰的元素分析显示O₂/CO₂燃烧对SO₂的抑制主要是由于煤灰的自固硫能力增强,而对NO的减排作用则是促进燃料N向其他含N气体的转换。     

Y型沸石/炭杂化膜的制备及其气体分离性能

以聚酰胺酸为前驱体,Y型沸石为掺杂物,经高温炭化制备了Y型沸石/炭杂化膜.通过纯组分气体(H2,CO2,O2,N2)的渗透实验对杂化膜的气体渗透性能进行测定,并使用透射电镜,X射线衍射对杂化膜的微结构进行表征.研究了沸石的含量以及炭化温度对杂化炭膜的气体渗透性能和微结构的影响.结果表明,随着膜内沸石含量的提高,Y型沸石/炭杂化膜的气体渗透性能明显提高,而随着炭化温度的升高,Y型沸石/炭杂化膜的渗透系数降低,选择性提高.与纯炭膜相比,Y型沸石/炭杂化膜在保持高O2N2选择性的前提下,其渗透性能显著提高.炭化温度为700℃,沸石含量为15%,Y型沸石/炭杂化膜O2的气体渗透系数为501 bareer,O2/N2选择性为15.6.当炭化温度超过800℃以后,杂化膜中的沸石晶体结构被破坏,其气体渗透系数接近纯炭膜的气体渗透系数.因此,保持沸石孔道结构的完整是制备高性能沸石/炭杂化膜的关键因素之一.     

O2/CO2气氛下煤燃烧SO2/NO析出特性

在水平管式炉上研究了O₂浓度、CO₂浓度、温度及石灰石添加等各参数对O₂/CO₂气氛下徐州烟煤和龙岩无烟煤燃烧过程中SO₂/NO排放特性的影响。结果发现,O₂/CO₂气氛下,烟煤和无烟煤燃烧SO₂/NO的析出规律与空气气氛下不同,同等O₂浓度下析出量比空气气氛下小。O₂/CO₂气氛下,随着O₂浓度的提高,烟煤和无烟煤SO₂/NO排放量均增大;随着CO₂浓度的升高, SO₂/NO排放量均减小。O₂/CO₂气氛下,石灰石添加对SO₂排放的抑制作用低于空气气氛下;石灰石添加对NO的排放有一定减排作用。对煤灰的元素分析显示O₂/CO₂燃烧对SO₂的抑制主要是由于煤灰的自固硫能力增强,而对NO的减排作用则是促进燃料N向其他含N气体的转换。     

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.     

A high CO2 permselective mesoporous silica/carbon composite membrane for CO2 separation

Ordered mesoporous silica/carbon composite membranes with a high CO₂ permeability and selectivity were designed and prepared by incorporating SBA-15 or MCM-48 particles into polymeric precursors followed by heat treatment. The as-made composite membranes were characterized by high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and N₂ adsorption, of which the gas separation performance in terms of gas permeability and selectivity were evaluated using the single gas (CO₂, N₂, CH₄) and gas mixtures (CO₂/N₂ and CO₂/CH₄, 50/50 mol.%). In comparison to the pure carbon membranes and microporous zeolite/C composite membranes, the as-made mesoporous silica/C composite membranes, and the MCM-48/C composite membrane in particular, exhibit an outstanding CO₂ gas permeability and selectivity for the separation of CO₂/CH₄ and CO₂/N₂ gas pairs owing to the smaller gas diffusive resistance through the membrane and additional gas permeation channels created by the incorporation of mesoporous silicas in carbon membrane matrix. The channel shape and dimension of mesoporous silicas are key parameters for governing the gas permeability of the as-made composite membranes. The gas separation mechanism and the functions of porous materials incorporated inside the composite membranes are addressed.     

Controlled synthesis of high performance carbon/zeolite T composite membrane materials for gas separation

A simple approach has been developed to synthesize the carbon/zeolite T composite membrane materials with the high gas separation performance. The precursors of the composite membrane are composed of polyimide matrix and dispersed zeolite T particles. The composite membranes prepared by pyrolysis at 973 K show excellent gas (H₂, CO₂, O₂, N₂, and CH₄) permeability and selectivity (O₂/N₂, CO₂/CH₄) for both single gas and mixed-gas. The gas separation performance of the composite membranes can be controlled in a wide range by only changing the zeolite T particle size. The maximum selectivity of O₂ over N₂ (21/79 mol%) for the composite membranes with the least zeolite T particle (0.5 μm) is 15 with an O₂ permeability of 347 Barrers (1 Barrer = 7.5 × 10⁻¹⁸ m² s⁻¹ Pa⁻¹) and the selectivity of CO₂ over CH₄ (50/50 mol%) reaches a value of 179 with a CO₂ permeability of 1532 Barrers. It is believed that the increase of gas permeability is attributed to the ordered microchannels in the zeolite and the interfacial gaps formed between zeolite and carbon matrix in the composite membranes. And the gas selectivity is tuned by the size of interfacial gaps which are varied with the zeolite particle size. This technique will provide a simple and convenient route to efficiently improve the trade-off relationship between the permeability and the selectivity and enable the construction of carbon-based composite materials with novel functionalities in membrane science.     

Physical and Gas Transport Properties of Novel Hyperbranched Polyimide – Silica Hybrid Membranes

Summary Physical and gas transport properties of novel hyperbranched polyimide – silica hybrid membranes were investigated. Hyperbranched polyamic acid as a precursor was prepared by polycondensation of a triamine monomer, 1,3,5-tris(4-aminophenoxy)benzene (TAPOB), and a dianhydride monomer, 4,4-(hexafluoro-isopropylidene)diphthalic anhydride (6FDA), and subsequently modified the end groups by 3-aminopropyltrimethoxysilane (APTrMOS). The hyperbranched polyimide – silica hybrid membranes were prepared using the polyamic acid, water, and tetramethoxysilane (TMOS) via a sol-gel technique. 5 % weight-loss temperature and glass transition temperature of the hyperbranched polyimide – silica hybrid membranes determined by TG-DTA measurement considerably increased with increasing silica content, indicating effective cross-linking at polymer – silica interface mediated by APTrMOS moiety. CO₂, O₂, and N₂ permeability coefficients of the hybrid membranes increased with increasing silica content. It was pointed out that the increased gas permeabilities are mainly attributed to increase in the gas solubilities. On the contrary, CH₄ permeability of the hybrid membranes decreased with increasing silica content because of decrease in the CH₄ diffusivity and, as a result, CO₂/CH₄ selectivity of the hybrid membranes remarkably increased. It was concluded that the 6FDA-TAPOB hyperbranched polyimide – silica hybrid membranes have high thermal stability and excellent gas selectivity, and are expected to apply to a high-performance gas separation membrane.     

6FDA-TAPOB hyperbranched polyimide-silica hybrids for gas separation membranes

Physical and gas transport properties of hyperbranched polyimide-silica hybrid membranes were investigated. Hyperbranched polyamic acid as a precursor was prepared by polycondensation of a triamine, 1,3,5-tris(4-aminophenoxy) benzene (TAPOB), and a dianhydride, 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), and subsequently modified a part of end groups by 3-aminopropyltrimethoxysilane (APTrMOS). The hyperbranched polyimide-silica hybrid membranes were prepared by sol–gel reaction using the polyamic acid, water, and alkoxysilanes. 5% weight-loss temperature of the hybrid membranes increased with increasing silica content, indicating effective crosslinking at polymer-silica interface mediated by APTrMOS moiety. On the other hand, glass transition temperature of the hybrid membranes prepared with methyltrimethoxysilane (MTMS) showed a minimum value at low silica content region, suggesting insufficient formation of three-dimensional Si O Si network compared to the hybrid membranes prepared with tetramethoxysilane (TMOS). CO₂, O₂, N₂, and CH₄ permeability coefficients of the hybrid membranes increased with increasing silica content. Especially for TMOS/MTMS combined system, the hybrid membranes showed simultaneous enhancements of gas permeability and CO₂/CH₄ separation ability. It was concluded that the 6FDA-TAPOB hyperbranched polyimide-silica hybrid membranes have high thermal stability and excellent CO₂/CH₄ selectivity and are expected to apply to high-performance gas separation membranes. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

The morphology and gas‐separation performance of membranes comprising multiwalled carbon nanotubes/polysulfone–Kapton

The development of desirable chemical structures and properties in nanocomposite membranes involve steps that need to be carefully designed and controlled. This study investigates the effect of adding multiwalled nanotubes (MWNT) on a Kapton–polysulfone composite membrane on the separation of various gas pairs. Data from Fourier transform infrared spectroscopy and scanning electron microscopy confirm that some studies on the Kapton–polysulfone blends are miscible on the molecular level. In fact, the results indicate that the chemical structure of the blend components, the Kapton–polysulfone blend compositions, and the carbon nanotubes play important roles in the transport properties of the resulting membranes. The results of gas permeability tests for the synthesized membranes specify that using a higher percentage of polysulfone (PSF) in blends resulted in membranes with higher ideal selectivity and permeability. Although the addition of nanotubes can increase the permeability of gases, it decreases gas pair selectivity. Furthermore, these outcomes suggest that Kapton–PSF membranes with higher PSF are special candidates for CO₂/CH₄ separation compared to CO₂/N₂ and O₂/N₂ separation. High CH₄, CO₂, N₂, and O₂ permeabilities of 0.35, 6.2, 0.34, and 1.15 bar, respectively, are obtained for the developed Kapton–PSF membranes (25/75%) with the highest percentage of carbon nanotubes (8%), whose values are the highest among all the resultant membranes. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43839.     

Effect of coating method on gas separation by PDMS/PES membrane

In this study, polydimethylsiloxane (PDMS)‐coated polyethersulfone (PES) composite membrane was prepared for gas separation. “Film casting” and “dip‐coating” techniques were used for producing selective PDMS layer on the surface of the PES support. The effects of coating technique and conditions including coating solution concentration and curing temperature on permselectivity of CO₂, CH₄, and N₂ were investigated. The prepared PES support did not provide any selectivity to the gases. When the concentration of PDMS coating solution was increased, initially permeability of CO₂ was rapidly dropped and then gradually reached to an almost constant value. The optimum concentration of coating solution was 5 wt%. Curing temperature showed no pronounced effect on the CO₂ permeability and selectivity. In “film casting” method, double coating showed superior permeability and selectivity. However, triple “dip‐coating” was promising. The selectivity of composite membrane prepared by “dip‐coating” was higher than “film casting” method. CO₂/N₂ and CO₂/CH₄ selectivity of five sequential dip‐coated composite membranes was 45.5 and 9.3, respectively. POLYM. ENG. SCI., 2013. © 2013 Society of Plastics Engineers     

Reducing the crystallinity of high molecular weight poly (ethylene oxide) using ultraviolet cross-linking for preparation of gas separation membranes

CO₂-selective cross-linked poly (ethylene oxide) (PEO) membranes were prepared by the UV irradiation of high molecular weight PEO in the presence of benzophenone as photo-initiator, which act as a hydrogen-abstracting agent. The main goal was to study the effects of the cross-linking process on the structural properties of hydrogel films intended for the gas separation applications. It was found that the gel fraction, and cross-link density enhanced, and the crystallinity, and the size of spherulites decreased by the cross-linking process. Moreover, the permeation performances for N₂, O₂, CH₄, and CO₂ and the relationship between the gas permeation performances and physical properties were investigated. The results indicated that the degree of cross-linking and crystallinity could be controlled by changing the initiator concentration, as by increasing the initiator content, the crystallinity percent and gas permeability of the membranes decreased, and the gas pair ideal selectivity of CO₂/N₂, CO₂/CH₄, CH₄/N₂, and O₂/N₂ increased.     

PVAm/PAN复合膜的制备及其对CO2/CH4的分离性能

New polymeric membrane materials——polyvinyl amine (PVAm) with different primary amine contents were synthesized.By covering polyacrylonitrile(PAN) ultrafiltration membranes with PVAm, the PVAm/PAN composite membranes for CO₂/CH₄ separation were prepared. The composite membranes containing more primary amino groups have higher selectivity for CO₂/CH₄.The cross-linking of acid or glutaradehyde could improve the gas permselectivity of the composite membranes. With decreasing CO₂ content in the feed gas, the CO₂/CH₄ separation factor increased.When the feed gas was 25%(vol) CO₂ and 75%(vol) CH₄, the CO₂ permeation rate was 4.1×10^-9cm³(STP) •cm^-2•Pa^-1•s^-1, and the CO₂/CH₄ separation factor was 180.     

Etching and acidifying graphene oxide membranes to increase gas permeance while retaining molecular sieving ability

Graphene oxide (GO) nanosheets stacked in parallel with subnanometer channels can exhibit an excellent size-sieving ability for membrane-based gas separation. However, gas molecules have to diffuse through the tortuous nanochannels, leading to low permeability. Herein we demonstrate two versatile approaches to modify the GO (before membrane fabrication by vacuum-filtration) to collectively increase gas permeability, etching using hydrogen peroxide to generate in-plane nanopores and acidifying using hydrochloric acid. For example, a membrane prepared at a pH of 5.0 using the 4-h-etched GO (HGO-4h) shows He permeability of 5.3 Barrer and He/CH₄ selectivity of 800, which are 5 times and 1.5 times those of the GO membranes, respectively. Decreasing the pH from 5.0 to 2.0 for HGO-4h enhances He permeability to 57 Barrer and He/CH₄ selectivity to 1,800. The HGO-4h prepared at the pH of 2.0 exhibits separation properties of H₂/CO₂, H₂/N₂, He/N₂, and He/CH₄ surpassing their corresponding upper bounds.     

Fabrication and modification of cellulose acetate based mixed matrix membrane: Gas separation and physical properties

[Cellulose acetate (CA)-blend-multi walled carbon nano tubes (MWCNTs)] mixed matrix membranes (MMMs), [CA/polyethylene glycol (PEG)/MWCNTs] and [CA/styrene butadiene rubber (SBR)/MWCNTs] blend MMMs were prepared by solution casting method for gas separation applications using Tetrahydrofuran (THF) as solvent. Both raw-MWCNTs (R-MWCNTs) and functionalized carboxylic-MWCNTs (C-MWCNTs) were used in membrane preparation. The MWCNTs loading ratio and pressure effects on the gas separation performance of prepared membranes were investigated for pure He, N₂, CH₄ and CO₂ gases. Results indicated that utilizing C-MWCNT instead of R-MWCNTs in membrane fabrication has better performance and (CO₂/CH₄) and (CO₂/N₂) selectivity reached to 21.81 and 13.74 from 13.41 and 9.33 at 0.65 wt% of MWCNTs loading respectively. The effects of PEG and SBR on the gas transport performance and mechanical properties were also investigated. The highest CO₂/CH₄ selectivity at 2 bar pressure was reached to 53.98 for [CA/PEG/C-MWCNT] and 43.91 for [CA/SBR/C-MWCNT] blend MMMs at 0.5 wt% and 2 wt% MWCNTs loading ratio respectively. Moreover, increase of feed pressure led to membrane gas permeability and gas pair selectivity improvement for almost all prepared membranes. The mechanical properties analysis exhibited tensile modules improvement with increasing MWCNTs loading ratio and utilizing polymer blending.