Adsorption separation performance of H2/CH4 on ETS-4 by concentration pulse chromatography

To exploit an effective adsorbent to separate hydrogen and methane, microporous titanium silicate molecular sieve NaETS-4 was synthesized and modified by strontium. The adsorption characteristics and diffusion behaviors of the prepared titanosilicate molecular sieve were studied by concentration pulse chromatography. And the effects of ion-exchange and dehydration temperature on adsorbent structure and gas diffusion were also discussed. The results showed that the thermal stability and Henry's Law constants were enhanced and micropore diffusivity decreased after exchanging Na⁺ with Sr²⁺. With the increase of dehydration temperature, Henry's Law constant and micropore diffusivity of CH₄ decreased in both NaETS-4 and SrETS-4. While for H₂ in SrETS-4, the increase of Henry's Law constant and the decrease of diffusion rate can be attributed to the shrinks of pore diameter resulting from the relocation of Sr²⁺. Correspondingly, the kinetic selectivity of H₂/CH₄ reached 8.91 indicating its potentiality in separating H₂ and CH₄.     

脉冲电晕等离子体作用下CH4/H2反应的机理

本文利用发射光谱技术,对脉冲电晕等离子体作用CH4/H2反应进行了原位诊断,根据等离子体作用下CH4、H2和CH4/H2体系中部分激发态物种的光谱检测数据和有关实验的结果,结合等离子体特性及小分子光化学反应规律,对等离子体作用CH4/H2转化制备C2烃反应的机理进行了讨论。     

La2O3对Ni-Cu/MgSiO催化剂的甲烷部分氧化制氢反应性能的影响

 用等体积浸渍法制备了MgO-SiO2(MgSiO)复合氧化物负载的Ni-Cu双金属催化剂,采用程序升温还原(TPR),X光电子能谱(XPS),红外光谱(IR),程序升温脱附(TPD)及微反技术考察了稀土La2O3的加入对CH4和H2O在Ni-Cu/MgSiO催化剂表面上的吸附及甲烷部分氧化制氢反应性能的影响. 结果表明,加入La2O3使催化剂表面Ni和Cu原子的电子云密度增加,CH4和H2O在催化剂表面上的吸附增强. CH4与O2和H2O在Ni-Cu/MgSiO催化剂上反应的主要产物为H2和CO2. La2O3的加入有利于提高CH4转化率及H2的选择性,并可提高催化剂稳定性及抗积炭能力. 讨论了La2O3的助催化作用机理.     

不同粒径的Ni/SiO2催化剂上CH4和CO2吸附活化的漫反射傅里叶变换红外光谱研究

 采用原位漫反射傅里叶变换红外光谱研究了CH4和CO2在不同粒径的Ni/SiO2催化剂上的吸附及活化. 结果表明,在不同粒径的催化剂上,检测到有CH4解离生成的CHx(x=1～3)物种,以及催化剂表面吸附的CHx物种与表面-OH 作用生成的CHx-O物种. CH4的裂解强烈依赖于催化剂表面Ni颗粒的大小,在粒径8 nm左右的Ni颗粒上, CH4较易解离; CO2难以直接在Ni/SiO2催化剂表面发生解离吸附,但CH4解离生成的吸附H对CO2的解离吸附具有明显的促进作用; CH4与CO2共吸附时,较小粒径的Ni可以促进CO2与表面氧物种发生反应,生成单齿表面碳酸盐物种.     

Quadrupole mass spectrometric study of positive ions from RF plasmas of pure CH4, CH4/H2, and CH4/Ar systems

Quadrupole mass spectrometry has been employed to characterize the ionic species in the discharges of pure CH₄, CH₄/H₂, and CH₄/Ar systems. For pure methane, the major positive ions in the discharge at low pressure (e.g., 0.15 torr) are CH ₃ ⁺ , C₂H ₃ ⁺ , CH ₂ ⁺ , C₂H ₂ ⁺ , CH ₄ ⁺ , C₂H ₄ ⁺ , and C₂H ₅ ⁺ at high pressure (e.g., 0.5 torr) the major ions are CH ₃ ⁺ , C₂H ₃ ⁺ , C₂H ₅ ⁺ , C₃H ₃ ⁺ , C H₃H ₇ ⁺ , C₄H ₇ ⁺ , C₅H ₇ ⁺ , C₆H ₅ ⁺ , and C₇H ₇ ⁺ . The relative abundances of C₁ ions decrease with increasing pressure, whereas those of higher-order ions increase with pressure. For 5% CH₄ + 95% H₂ mixture, in addition to those sampling from the pure methane plasma at the lower pressure, H _n ⁺ ions have also been detected. For 5% CH₄ +95% Ar mixture, the principal ions are CH ₃ ⁺ , CH ₂ ⁺ , CH⁺, CH ₅ ⁺ , Ar⁺, and ArH⁺; the ions containing more than two carbon atoms are negligible. In these discharges, the CH ₃ ⁺ and C₂H ₃ ⁺ are the most important positive ions in C₁ and C₂ ions, respectively. The ions detected are believed to come from the sheath between the electrode and the luminous plasma, and have high kinetic energy. An ion-molecule reaction mechanism is proposed which can well explain the observed main features of ionic products.Died June 1, 1991.     

甲烷无氧芳构化反应催化剂Mo/HZSM-5的H2-TPR研究

 采用H2-TPR技术研究了不同方法制备的Mo/HZSM-5催化剂,并借助 1H MAS NMR等表征手段对Mo/HZSM-5催化剂还原过程中可能出现的6个TPR谱峰进行了详细归属,首次指认了分布于分子筛孔道内并与B酸性位相互作用的Mo物种的还原峰. 此外,还考察了各种Mo基催化剂在甲烷无氧芳构化反应中的催化性能. 结果表明,与B酸中心相互作用的Mo物种比其他形式的Mo物种具有更好的活性和稳定性.     

Accurate adsorption energies for small molecules on oxide surfaces: CH4/MgO(001) and C2H6/MgO(001)

A hybrid method is applied that combines second order Møller–Plesset perturbation theory (MP2) for cluster models with density functional theory for periodic (slab) models to obtain structures and energies for methane and ethane molecules adsorbed on the MgO(001) surface. Single point calculations are performed to estimate the effect of increasing the cluster size on the MP2 energies and to evaluate the difference between coupled cluster (CCSD(T)) and MP2 energies. The final estimates of the adsorption energies are 12.9 ± 1.3 and 18.9 ± 1.8 kJ/mol for CH₄ and C₂H₆, respectively. © 2016 Wiley Periodicals, Inc.     

Carbon Dioxide/Methane Separation by Adsorption on Sepiolite

In this work,the use of sepiolite for the removal of carbon dioxide from a carbon diox- ide/methane mixture by a pressure swing adsorption(PSA)process has been researched.Adsorption equilibrium and kinetics have been measured in a fixed-bed,and the adsorption equilibrium parameters of carbon dioxide and methane on sepiolite have been obtained.A model based on the LDF approxima- tion has been employed to simulate the fixed-bed kinetics,using the Langmuir equation to describe the adsorption equilibrium isotherm.The functioning of a PSA cycle for separating carbon dioxide/methane mixtures using sepiolite as adsorbent has also been studied.The experimental results were compared with the ones predicted by the model adapted to a PSA system.Methane with purity higher than 97% can be obtained from feeds containing carbon dioxide with concentrations ranging from 34% to 56% with the proposed PSA cycle.These results suggest that sepiolite is an adsorbent with good properties for its employment in a PSA cycle for carbon dioxide removal from landfill gases.     

ZIF-8材料中CH4/H2吸附与扩散的分子模拟

采用平衡分子动力学和巨正则系综蒙特卡洛模拟方法对多孔沸石咪唑酯骨架材料(ZIF-8)中CH4和H2分子的吸附与扩散特性进行了比较研究.结果表明,采用柔性力场能够很好地复制ZIF-8在不同压力或温度条件下的晶体结构,也能准确地计算不同温度下CH4和H2分子在ZIF-8中的扩散系数,特别是高温下CH4分子因能够摆脱ZIF-8骨架笼口的空间限制而使其扩散系数出现大幅提升.同时,该力场也能粗略地模拟CH4和H2分子在ZIF-8中的等温吸附曲线,通过自编程序得到吸附和扩散平衡时CH4和H2分子在ZIF-8单元晶胞内的几率密度分布数据,并利用VMD软件可视化.结果显示CH4和H2分子在ZIF-8中的优先吸附位置均在大孔中心靠近咪唑环的区域,但CH4分子的优先吸附位置有两个不同层次,而H2分子的优先吸附位置只有一个层次,说明CH4和H2分子在ZIF-8中存在着不同的吸附机理.     

Equilibrium and kinetic analysis of CO2-N2 adsorption separation by concentration pulse chromatography

CO2 and N(2) adsorption kinetics and equilibrium behaviours have been studied with silicalite, NaY and 13X by using concentration pulse chromatography for the separation of these gases in the present study. Adsorption Henry's Law constants, the heat of adsorption values, micropore diffusion coefficients and corresponding activation energies are determined experimentally and the three different mass transfer mechanisms are discussed. From the equilibrium data, the corresponding separation factors are obtained for the adsorption separation processes. The heat of adsorption values as well as the Henry's Law adsorption equilibrium constants of CO(2) are much higher than those of N(2) for all the adsorbents studied. 13X, NaY and silicalite all have good separation factors for CO(2)/N(2) system based on equilibrium processes. The order of the equilibrium separation factors is 13X (Ceca)>13X (Zeochem)>NaY (UOP)>silicalite (UOP). Equilibrium selectivity favours CO(2) over N(2). Micropore diffusion resistance is the definite dominant mass transfer mechanism for CO(2) with silicalite and NaY.     

A型沸石/活性炭复合材料的制备及甲烷/氮气吸附分离性能

以沥青和煤矸石为原料,经炭化、活化后获得型体活性炭材料(AC),并在此基础上进行水热晶化,研究晶化时间对复合材料中4A沸石的形成、孔结构和甲烷、氮气吸附性能的影响。通过X射线衍射(XRD)、扫描电子显微镜(SEM)、77 K下的氮气吸附-脱附以及273 K下的CO_2吸附等温线对样品进行表征,结果表明水热晶化后,复合材料中的硅铝形成立方结构的4A沸石,出现了0.45~0.6 nm的微孔,微孔孔容增加,并伴有少量的中孔和大孔。复合材料在298 K下的甲烷(CH_4)和氮气(N_2)吸附等温线的结果表明,晶化时间6 h的复合材料AC-2的甲烷吸附量被提高至10.8 m L/g,并保持较高的CH4/N2平衡分离比(3.7)。     

环孢素A在反相液相色谱中的吸附行为及分离纯化北大核心CSCD

环孢素A(cyclosporine A,CsA)是由11个氨基酸组成的中性环状多肽,是临床拮抗器官和组织移植后排异反应的首选药物。高效液相色谱法广泛应用于CsA的分离分析,开展CsA色谱行为的研究是使用制备高效液相色谱纯化CsA的关键。该文首先在C18固定相上比较了CsA在甲醇-水和乙腈-水两种流动相体系中的保留行为,结果表明其保留时间对有机相比例变化比较敏感。控制甲醇比例在84%~88%,或者乙腈比例在75%~85%,CsA的保留因子(k)在3~7范围内。考察了上样量对CsA峰形的影响。随着上样量增加,在两种流动相体系中,CsA的峰形都由对称开始变得拖尾,保留时间前移。因此在进行CsA纯化时,需要特别注意前杂的去除情况。然后采用吸附等温线描述CsA的保留行为,当流动相中CsA的质量浓度较低时,有机相比例对溶质在固定相上的吸附量影响并不明显。随着溶质的质量浓度增加至0.5 g/L以上,有机相比例降低有助于提高CsA在固定相上的吸附量。和甲醇-水体系相比,在乙腈-水体系中固定相对溶质有更大的吸附容量。用模型对CsA的等温吸附曲线拟合,在甲醇-水体系中符合Langmuir模型,在乙腈-水体系中为Moreau模型。由模型参数可知在两种体系下,CsA在C18固定相上均为单层吸附,区别在于乙腈-水体系中CsA会产生较大的分子间作用力。最后,实验采用0~60 min 65%~75%乙腈、60~80 min 75%乙腈的条件开展了环孢素A纯化的探索实验,可将CsA的杂质控制在0.2%以下。本研究结果对采用制备高效液相色谱纯化CsA具有指导意义。     

Chiral separation of N-(trans-4-isopropylcyclohexylcarbonyl)-D,L-phenylalanine isomers by high performance liquid chromatography

Summary A high-performance liquid chromatographic method was developed for the chiral separation of a new anti-diabetic agent, N-(trans-4-isopropylcyclohexylcarbonyl)-D-phenylalanine, and its L-enantiomer. The separation was performed on a Sumichiral OA-3300 column. Optimized mobile phase was 0.025 mol.L⁻¹ ammonium acetate in methanol solution. UV detection was at 210 nm. Baseline chiral separation was obtained within 12 minutes. The detection limits are 80 pg for the D-enantiomer and 120 pg for the L-enantiomer. RSD of the method was below 1% (n=5).     

Synthesis and CO2/CH4 separation performance of Bio-MOF-1 membranes

Herein we present the preparation of continuous and reproducible Bio-MOF-1 membranes supported on porous stainless steel tubes. These membranes displayed high CO(2) permeances for equimolar mixtures of CO(2) and CH(4). The observed CO(2)/CH(4) selectivities above one indicate that the separation is promoted by competitive adsorption.     

Adsorption of a H2-Ne binary mixture on NaA zeolite

Co-adsorption of hydrogen and neon on NaA zeolite was studied volumetrically at 40 K, 50 K, and 90 K over the pressure range 3–65 kPa. As the adsorption of hydrogen increases at constant pressure, the adsorption of neon linearly decreases through the entire temperature range. The coefficients of displacement of components from the sorption volume were determined. The adsorption selectivity coefficient of H₂ () in the H₂-Ne-NaA system was calculated over the temperature range 35–100 K. The increase in a by a factor of 5 while the temperature decreases by 30 K makes it possible to remove the microimpurities of H₂ from Ne by a cryoadsorption method.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 840–842, May, 1993.     

Dynamic Adsorption of H2S onto a Goethite-Based Material

The use of adsorption technology to remove H₂S from synthetic gas (H₂S and N₂) using a goethite-based adsorbent was investigated. The influence of the H₂S feed concentration (150–600 mg), the adsorbent dosage (1–4 g), and the gas flow rate (210–540 cm³/min) on the breakthrough curves and H₂S adsorption on the adsorbent at the breakthrough point was investigated. Dynamic column experiments were performed to provide data for the theoretical models and to verify the performance of the system in the adsorption process. The theoretical models used in the present work were found to predict the adsorption breakthrough performance reasonably well.     

不同吸附模式对As(V)在TiO2颗粒上亚稳态吸附的影响

通过对比As(V)在TiO₂颗粒上的柱(column)吸附和静态(batch)吸附行为, 研究了柱吸附和静态吸附两种反应模式对该体系亚稳态吸附的影响. 在相同热力学条件下, 将总量一定的As(V)溶液分别加入柱吸附和静态吸附体系中. 结果表明, 随着吸附模式的改变, 静态吸附体系比柱吸附体系更快达到吸附平衡, 静态吸附体系平衡吸附量(0.42 mg·g^-1)明显高于柱吸附体系平衡吸附量(0.25 mg·g^-1), 且静态吸附体系的吸附不可逆性弱于柱吸附体系的吸附不可逆性. 说明溶质吸附模式(动力学条件)的改变使得相同热力学条件下的吸附反应达到了不同的平衡状态. 柱吸附和静态吸附实验中, As(V)在TiO₂颗粒上的液膜扩散系数、总传质系数及吸附平衡后形成的微观吸附状态均不同, 共同导致了两种反应宏观吸附行为上的差异.     

BNiAl_2O_3催化剂上用脉冲反应研究CO_2的活化及其与CH_4的反应(英文)

用脉冲微反应系统研究了１０２３Ｋ下，ＣＯ２在Ｎｉ／Ａｌ２Ｏ３上的裂解及其与ＣＨ４的反应，发现ＣＯ２裂解吸附产生Ｏ（ａｄ）和ＣＯ，该反应步骤较慢。产生的ＣＯ会进一步在Ｎｉ表面裂解，而由ＣＨ４裂解产生的活性碳物种与Ｏ（ａｄ）的反应是一较快步骤。     

无氧下低浓度硫化氢在浸渍活性炭上的吸附研究

为了考察常温、无氧下浸渍Na2CO3改性、原料气相对湿度对活性炭吸附硫化氢的促进作用,用动态吸附法分别测试了不同湿度下原活性炭和浸渍活性炭对低浓度硫化氢的吸附,同时考察了温度对该吸附过程的影响。结果表明,吸附平衡数据均符合Freundlich吸附等温方程。与原活性炭相比,浸渍活性炭的孔容和比表面积略有降低,但对硫化氢的吸附能力却显著提高,说明硫化氢与浸渍剂在活性炭表面上发生了化学反应。相对湿度增加,活性炭和浸渍活性炭对H2S的吸附能力均显著增强。温度升高,平衡吸附量均略有下降。