聚醚共聚酰胺多层复合气体分离膜的制备及其分离性能

采用浸渍涂覆法,以聚醚共聚酰胺PEBA1074嵌段高分子为选择层膜材料制备具有超薄分离层的PEI/PDMS/PEBA1074/PDMS多层复合气体分离膜,探讨了操作条件对H2、N2、CH4和CO2等在多层复合膜中的渗透性能的影响.多层复合膜对极性气体具有较高的渗透通量,并且对极性/非极性气体分离体系具有较高的选择性.CO2对多层复合膜存在增塑作用,其渗透通量随操作压力的增加而增加;随着操作温度的升高,H2、N2、CH4和CO2在复合膜中的渗透通量显著增大,而CO2/非极性气体(H2、N2和CH4)的分离系数减小.气体渗透通量与温度的关系在PEO链段熔点的上下分别满足不同的Arrhenius方程.当操作温度大于PEO链段熔点温度时,气体的渗透活化能减小.     

苯基修饰微孔SiO2膜的氢气分离和水煤气变换反应性能

通过正硅酸乙酯与苯基三乙氧基硅烷共水解缩聚反应制备苯基修饰SiO2膜,研究膜材料的氢气渗透和分离性能,并将其作为膜反应器的关键材料应用于水煤气变换反应.结果表明,氢气在苯基修饰SiO2膜中的渗透率随着温度的升高而增大,遵循活化扩散机理,300℃下H2渗透率达到4.67×10-7 mol/(m2·s·Pa),理想分离系数H2/CO、H2/CO2和H2/SF6分别达到10.54、10.50、21.16.在300℃,反应物H2O/CO摩尔比为2∶1的条件下进行水煤气变换反应,膜反应器的CO的转化率比传统固定床反应的CO的转化率高约12％,其原因是苯基修饰的SiO2膜对H2具有一定的选择性.     

阴离子功能化超微孔MOF高效选择性捕获低浓度CO2

CO2捕获,尤其低浓度CO2捕获,对人类在限域空间中长时间工作、降低天然气液化过程中CO2腐蚀及冻结效应极为重要.本文首次报道了一种具有一维孔道的ZU-16-Co(TIFSIX-3-Co)材料,该材料孔道中含大量电负性F原子,可实现400–10,000 ppm浓度下CO2的高效捕获.相比同构材料,孔径为3.62?的ZU...     

High temperature oxidation of C2Cl4/CH4 mixtures

Experiments on high temperature oxidation of multi-chlorinated hydrocarbons, tetrachloroethylene (C2Cl4), with hydrocarbon fuels, CH4, were performed in a 15 mm i.d. tubular flow reactor. Temperatures ranged from 700 to 850 degrees C, with the average residence time in the range from 0.3 to 1.5s. Three equivalence ratios, phi=0.87 (fuel-lean (FL)), phi=1 (stoichiometry (S)), and phi=1.3 (fuel-rich (FR)), were studied. The global Arrhenius equations for the decomposition of C(2)Cl(4) for each reactant set ratio are: k(lean)=5.77 x 10(15) exp(-30447/RT), k(stoi)=5.15 x 10(15) exp(-30421/RT), and k(rich)=6.32 x 10(14) exp(-28879/RT). The important reactions for destruction of parent C2Cl4 include: C2Cl4 --> C2Cl3 + Cl, C2Cl4 + H--> C2Cl3 + HCl and C2Cl4 + H --> C2HCl3 + Cl. The resulting reactant loss, and intermediate and final product profiles were determined. C2HCl3, C2Cl2, CO, CO2 and HCl are the major products for the reaction of C2Cl4/CH4/O2 mixtures for these three reaction systems. Minor intermediates include C2H3Cl, C2HCl, COCl2, CH3CHCl2, C2H4, C2H6, CCl2CHCH3 , trans-CHClCHCl, cis-CHClCHCl, trans-ClHC=CClCH(3), C6H6, and Cl2. The experimental data showed that as the oxygen concentration increased, the temperature needed to detect the resulting products decreased.     

几种HQDEA型聚醚酰亚胺的透气性能

合成了四种双醚二酐(HQDEA)型聚醚酰亚胺,研究了它们对H_2、CO_2、O_2、N_2和CH_4五种气体的透过性能。结果表明,这类聚醚酰亚胺的分子结构,特别是取代基的位置对透气性和透气选择性有很大的影响。酰亚胺键邻位甲基取代聚醚酰亚胺(HQDEA-DMMDAI)兼具有高的透气性和透气选择性。     

KOH活化法制备气体分离用炭分子筛膜

选用KOH为活化剂,利用化学活化法制备炭分子筛膜,考察在热塑性酚醛树脂(PFNR)涂膜液中添加不同质量分数的KOH对炭分子筛膜的影响.结果表明,在炭化过程中,KOH的加入可促进炭分子筛膜孔径的均匀分布,使炭分子筛膜具有发达的孔隙结构.当KOH在PFNR中的添加量从0％增加到4％时,H2的渗透速率由23.68×10-10 mol·m-2·s-1·pa-1提高到28.6×10-10 mol·m-2·s-1·Pa-1;但H2/N2和H2/CH4的分离系数明显下降,分别从471.3下降到147.5、540下降到270.CO2/CH4和O2/N2的分离系数只有轻微下降.     

溶胶-凝胶法载银SiO2杂化膜的制备及性能研究

采用溶胶-凝胶法,在甲基化改性的SiO2溶胶中掺杂硝酸银,制备Ag/M-SiO2杂化膜。通过XRD、XPS、紫外-可见吸收谱、N2吸附-脱附以及气体渗透性能测试等方法,考察了银掺杂对杂化膜结构和性能的影响。结果表明,Ag/M-SiO2膜中的银元素完全为纳米金属银,具有面心立方结构。金属银的掺杂对Ag/M-SiO2膜的化学结构基本没有影响,但使其孔径和总孔体积略微增大。与未载银的SiO2膜相比,Ag/M-SiO2膜具有更大的H2渗透速率和更好的H2/CO2选择性。金属银的引入增强了H2的表面扩散作用,促进了H2在膜中的传递,提高了SiO2膜的水汽稳定性。     

Synthesis of ultrasmooth nanostructured diamond films by microwave plasma chemical vapor deposition using a He/H(2)/CH(4)/N(2) gas mixture

Ultrasmooth nanostructured diamond (USND) films were synthesized on Ti-6Al-4V medical grade substrates by adding helium in H(2)/CH(4)/N(2) plasma and changing the N(2)/CH(4) gas flow from 0 to 0.6. We were able to deposit diamond films as smooth as 6 nm (root-mean-square), as measured by an atomic force microscopy (AFM) scan area of 2 μm(2). Grain size was 4-5 nm at 71% He in (H(2) + He) and N(2)/CH(4) gas flow ratio of 0.4 without deteriorating the hardness (~50-60 GPa). The characterization of the films was performed with AFM, scanning electron microscopy, x-ray diffraction (XRD), Raman spectroscopy, and nanoindentation techniques. XRD and Raman results showed the nanocrystalline nature of the diamond films. The plasma species during deposition were monitored by optical emission spectroscopy. With increasing N(2)/CH(4) feedgas ratio (CH(4) was fixed) in He/H(2)/CH(4)/N(2) plasma, a substantial increase of CN radical (normalized by Balmer H(α) line) was observed along with a drop in surface roughness up to a critical N(2)/CH(4) ratio of 0.4. The CN radical concentration in the plasma was thus correlated to the formation of ultrasmooth nanostructured diamond films.     

木质包装废弃物热化学反应转化特性研究

采用热重红外联用分析和热解气质联用分析技术,考察了红橡木材包装废弃物的热分解、气相组分生成及分布规律。研究表明:在800℃终温和10℃/min的升温速率条件下,红橡木材包装废弃物的主要热解阶段集中在220～385℃,失重率为78.99%;高温区热解活化能明显低于低温区,说明随着温度的升高较容易发生热解反应;热解初期主要是水分和部分酸类、醛类物质的析出,主要热解阶段为H2O,CO2,CO,CH4和酸类、醛类、酯类等的大量析出,在热解后期主要为CO2和CH4的析出;热解析出的气体主要为含氧官能团的有机化合物,包括酸类(19.29%)、醛类(15.14%)、酯类(9.97%)、酮类(9.00%)、糖类(8.59%)、酚类(5.29%)、醇类(3.63%)等。     

Ultraselective Carbon Molecular Sieve Membranes with Tailored Synergistic Sorption Selective Properties

Membrane‐based separations can reduce the energy consumption and the CO₂ footprint of large‐scale fluid separations, which are traditionally practiced by energy‐intensive thermally driven processes. Here, a new type of membrane structure based on nanoporous carbon is reported, which, according to this study, is best referred to as carbon/carbon mixed‐matrix (CCMM) membranes. The CCMM membranes are formed by high‐temperature (up to 900 °C) pyrolysis of polyimide precursor hollow‐fiber membranes. Unprecedentedly high permselectivities are seen in CCMM membranes for CO₂/CH₄, N₂/CH₄, He/CH₄, and H₂/CH₄ separations. Analysis of permeation data suggests that the ultrahigh selectivities result from substantially increased sorption selectivities, which is hypothetically owing to the formation of ultraselective micropores that selectively exclude the bulkier CH₄ molecules. With tunable sorption selectivities, the CCMM membranes outperform flexible polymer membranes and traditional rigid molecular‐sieve membranes. The capability to increase sorption selectivities is a powerful tool to leverage diffusion selectivities, and has opened the door to many challenging and economically important fluid separations that require ultrafine differentiation of closely sized molecules.     

The Experimental Study of Temperature Dependence of Binary Diffusion Coefficients of Gases at Different Pressures

An experimental study of the temperature dependence of the binary diffusion coefficients (BDCs) was conducted for five binary mixtures of gases: $\mathrm{H}_{2}{-}\mathrm{N}_{2}, \mathrm{H}_{2}{-}\mathrm{CO}, \mathrm{H}_{2}{-}\mathrm{CH}_{4}, \mathrm{H}_{2}{-}\mathrm{C}_{2}\mathrm{H}_{6}$ , and $\mathrm{H}_{2}{-}\mathrm{C}_{3}\mathrm{H}_{8}$ . Measurements were carried out with the use of a steady-flow method in the temperature range from 250 K to 900 K and the pressure range from 0.1 MPa to 15 MPa. The determination of the BDCs is based on analysis of the volume fraction of the diffusing gas in the gas flow. The experimental data were compared with the results of calculations by the proposed formula evaluated within the framework of the elementary kinetic theory. The obtained results exhibit considerably good agreement with the experimental data within the experimental error. The results of investigations of the temperature dependence of the BDCs show that this dependence can be fitted with a power law only at atmospheric pressure.     

Ultra-smooth nanostructured diamond films deposited from He/H2/CH4/N2 microwave plasmas

Addition of He to a high CH4 content (10.7 vol%) H2/CH4/N2 feedgas mixture for microwave plasma chemical vapor deposition produced hard (58-72 GPa), ultra-smooth nanostructured diamond films on Ti-6AI-4V alloy substrates. Upon increase in He content up to 71 vol%, root mean squared (RMS) surface roughness of the film decreased to 9-10 nm and average diamond grain size to 5-6 nm. Our studies show that increased nanocrystallinity with He addition in plasma is related to plasma dilution, enhanced fragmentation of carbon containing species, and enhanced formation of CN radical.     

Fluorophilic ionophores for potentiometric pH determinations with fluorous membranes of exceptional selectivity

Ionophore-doped sensor membranes exhibit greater selectivities and wider measuring ranges when they are prepared with noncoordinating matrixes. Since fluorous phases are the least polar and least polarizable liquid phases known, a fluorous phase was used for this work as the membrane matrix for a series of ionophore-based sensors to explore the ultimate limit of selectivity. Fluorous pH electrode membranes, each comprised of perfluoroperhydrophenanthrene, sodium tetrakis[3,5-bis(perfluorohexyl)phenyl]borate, and one of four fluorophilic H(+)-selective ionophores were prepared. All the ionophores are highly fluorinated trialkylamines containing three electron withdrawing perfluoroalkyl groups shielded from the central nitrogen by alkyl spacers of varying lengths: [CF(3)(CF(2))(7)(CH(2))(3)](2)[CF(3)(CF(2))(6)CH(2)]N, [CF(3)(CF(2))(7)(CH(2))(3)](2)(CF(3)CH(2))N, [CF(3)(CF(2))(7)(CH(2))(3)](3)N, and [CF(3)(CF(2))(7)(CH(2))(5)](3)N. Their pKa values in the fluorous matrix are as high as 15.4 +/- 0.3, and the corresponding electrodes exhibit logarithmic selectivity coefficients for H(+) over K(+) as low as <-12.8. The pKa and selectivity follow the trends expected from the degree of shielding and the length of the perfluoroalkyl chains of the ionophores. These electrodes are the first fluorous ionophore-based sensors described in the literature. The selectivities of the sensor containing [CF(3)(CF(2))(7)(CH(2))(5)](3)N are not only greater than those of analogous sensors with nonfluorous membranes but were of the same magnitude as the best ionophore-based pH sensors ever reported.     

基于Matlab的燃气锅炉尾气气体状态计算

以甲烷、氢气、一氧化碳这三种气体的混合气体燃烧产生的尾气为研究对象,利用Matlab编写了计算软件。因为压力和温度较便于测量,所以程序是以三种气体的质量分数和混合气体的总压力和温度为输入参数,计算气体的比体积,并且计算混合气体两种状态间的焓差。     

A gas chromatographic separation for the h and C stable isotope ratio determination of coal compounds

A new, completely automated gas chromatography technique has been developed to separate the different gaseous compounds produced during underground coal gasification for their (13)C/(12)C and D/H isotope ratio measurements. The technique was designed for separation and collection of H(2), CO, CO(2), H(2)O, H(2)S, CH(4), and heavier hydrocarbons. These gaseous compounds are perfectly separated by the gas-phase chromatograph and quantitatively sent to seven combustion and collection lines. H(2), CO, CH(4), and heavier hydrocarbons are quantitatively oxidized to CO(2) and/or H(2)O. The isotopic analyses are performed by the sealed-tube method. The zinc method is used for reduction of both water and H(2)S to hydrogen for D/H analysis. Including all preparation steps, the reproducibility of isotope abundance values, for a quantity higher than or equal to 0.1 mL of individual components in a mixture (5 mL of gases being initially injected in the gas chromatograph), is ±0.1‰ for δ(13)C(PDB) and ±6‰ for δD(SMOW).     

Mobile Fourier-transform infrared spectroscopy monitoring of air pollution

Fourier transform infrared spectroscopy is an efficient technique for the detection and quantification of molecules in gas mixtures. Measurement results from a mobile laboratory for ambient air analysis and for remote sensing of plume emission with the commercially available K300 spectrometer are reported. CO, CO(2), NO, NO(2), N(2)O, NH(3), CH(4), SO(2), H(2)O, HCl, and HCHO concentrations have been determined with good agreement with in situ results. The on-line multicomponent analysis software is based on line-by-line retrieval and least-squares fitting procedures, including the effects of multiple aerosol scattering and cloud and rain influences.     

加热和光照条件下Ru/TiO2催化二氧化碳甲烷化研究

本研究利用浸渍法制备了Ru/TiO₂催化剂, 并在光照和加热两种条件下考察了其催化二氧化碳与氢的反应, 发现催化剂在两种条件下均可引发显著的甲烷化反应(CO₂ + 4H₂ → CH₄ + 2H₂O)。结果显示, 在光照和加热(150~350℃)条件下, CH₄为唯一含C产物。而在更高温度的加热条件下(>400℃)除了生成CH₄外, 还产生少量CO副产物, 表明反应温度对产物选择性有显著影响。随着反应温度由150℃升高到550℃, 对于不同负载量的担载Ru催化剂, CO₂转化率均先增加后降低, 其中在Ru担载量为1.5wt%Ru/TiO₂催化剂上CO₂转化率在350℃时达到最高, 为77.58%。而在温度>400℃条件下, CO的选择性也随反应温度的升高而逐渐增加。综合反应结果和XRD、XPS和N₂吸附-脱附等表征结果, 发现二氧化碳与氢在光照和加热条件下(150~550℃)反应机制不同。在光照条件下, 光激发电子首先被金属Ru捕获, 进而将吸附在金属Ru上的二氧化碳还原, 活性物种经由RuC中间体形成CH₄。而加热条件下(150~550℃), H₂先被Ru活化成氢原子, 氢原子还原吸附在催化剂表面的CO₂形成RuC中间体, 最后RuC中间体进一步加氢生成CH₄。虽然在两种反应条件下经历相同的中间体, 但是中间体的形成路径不同, 即反应物CO₂被活化的方式不同, 因而产物选择性不同。     

Decomposition of benzene in the RF plasma environment. Part I. Formation of gaseous products and carbon depositions

This study employed radio-frequency (RF) plasma for decomposing benzene (C6H6) gas, and examined both gaseous products and solid depositions after reaction. The reactants and products were analyzed mainly by using both an on-line Fourier transform infrared (FT-IR) spectrometer and a gas chromatography. The analyses for solid deposition included electron spectroscopy for chemical analysis (ESCA), element analysis and heat value analysis. The C2H2, C2H4, C2H6, CH4, CO2 and CO were detected and discussed. The analytical results demonstrate that in the C6H6/Ar plasma, C2H2 is the sole gaseous product being detected. The fraction of total carbon input converted into C2H2 YC2H2 increased with increasing C6H6 feed concentration, but decreased with increasing input power. In the C6H6/H2/Ar system, besides C2H2, CH4, C2H4 and C2H6 were also detected, and their yields increased with increasing H2/C6H6 ratio. The above results indicated that the addition of H2 (auxiliary gas) achieves the benefit of creating hydrogen-rich species like CH4, C2H4 and C2H6. In the C6H6/O2/Ar system, C6H6 could be totally oxidized into CO2, CO and H2O, and no measurable phenol was found. Analyses of solid depositions revealed that the carbon depositions were similar to those of Anthracite. The carbon deposition has a heat value of 7000 kcal/kg. Additionally, the possible reaction pathways were also built up and discussed.     

Preparation and Gas-sensing Characteristics of Na~+-doped ZnO Single Crystals

ZnO single crystals were grown by vapor phase reaction of Zno powder with active carbon powdei at an elevated temperature The typical crystals were colorless and transparent with maximum size o4 0.1 mm in diameter and 25 mm in length, The gas-sensing characteristics of Na+-doped anc undoped single crystals were investigated in 1 %H2. Co and CH, in air between 1 50 and 600℃. It was found that the undoped ZnO single crystals showed little gas sensitivity in air. and Na+-doping can greatly enhance the senstivity by increasing the resistivities. The maximum sensitivity of the samples is 22 (Ra/ Rg) for H2. 1 2 for CO and 4 for CH4     

Auto-ignition hazard of mixtures of ammonia,hydrogen, methane and air in a urea plant

The auto-ignition of NH(3)/CH(4)/H(2)/air mixtures constitutes a hazard that is of much concern in urea plants. In this study, the auto-ignition behaviour of NH(3)/CH(4)/H(2)/air mixtures is investigated experimentally for pressures up to 7500 kPa. The experiments were carried out in a closed spherical vessel with a volume of 8 dm(3). The concentration and the pressure dependence of the auto-ignition temperature (AIT) were determined for four types of mixtures: NH(3)/air, NH(3)/CH(4)/air, NH(3)/H(2)/air and NH(3)/CH(4)/H(2)/air. The most ignitable NH(3)/air mixtures were situated between stoichiometry and the upper flammability limit. Small amounts of methane and hydrogen decrease the AIT of NH(3)/air mixtures to a large extent. The pressure dependence of the AIT could be correlated by a Semenov relationship. For the multi-fuel mixtures, a distinct deviation from the Semenov correlation was observed at the lowest temperatures. With respect to the explosion hazard in urea plants, the experimental results were used to assess realistic AIT values in the pool reactor and the ammonia scrubber, operating at a pressure of 15,000 kPa.