Plasma chemical preparation and characterization of perovskite-type mixed oxides

The microwave plasma enhanced chemical vapour deposition (MPECVD) was applied for the preparation of perovskite-like mixed oxides, using either the metal acetylacetonates or metal nitrates as precursors. The same materials were prepared by the citrate method as reference substances. The obtained mixed oxides were calcined at 1100 °C, tested in the methane oxidation up to 1000 °C and characterized by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), inductive coupled plasma–optical emissions spectroscopy (ICP–OES) and specific surface area (BET) determination. These studies revealed that LaMnO₃ with La³⁺ cation partly substituted by Sr, Ce and Ba cations and La_0.9Sr_0.1Co_0.9Fe_0.1O₃ calcined at 1100 °C seem to be highly active and stable catalysts in methane oxidation. In the case of LaMnO₃ and La_0.9Ce_0.1MnO₃ lowest light-off temperatures were reached with the catalysts prepared by the plasma method.     

1-丁基-3-甲基咪唑醋酸盐和水组成的混合电解液中三价铬电沉积铬的研究

本文在[BMIM]OAc-H₂O电解液中研究了Cr³⁺的电沉积反应. 经循环伏安研究表明,Cr³⁺的还原属于受扩散控制的分步还原过程, 即Cr³⁺ + e →Cr²⁺和Cr²⁺ + 2e → Cr⁰. 在40℃下通过Rendle-Sevcik方程计算得到Cr³⁺的扩散系数为1.2×10^-8 cm²/s. 采用计时电流法探讨了Cr的三维瞬时成核机理. 对沉积的铬镀层进行了XRD、SEM表征, 结果表明经600℃氩气保护下煅烧后的镀层由Cr和Cr₂O₃纳米球状颗粒聚集而成, 其平均粒径为0.48μm. 对40℃,-3.0V条件下所得镀层进行EDX检测,发现Cr与O的能级峰十分明显,其中Cr的质量分数为83.8%. 通过在[BMIM]OAc、[BMIM]BF₄和[BMIM]PF₆三种离子液体体系中电镀得到的Cr镀层质量的比较, 表明OAc-的确有利于Cr的电沉积.     

Surface and catalytic properties of Cu–Ce–O composite oxides prepared by combustion method

Surface and catalytic properties of Cu–Ce–O composite materials prepared by solution combustion method have been investigated. The materials are characterized by X-ray diffraction (XRD), temperature programmed reduction (TPR) and electron paramagnetic resonance spectroscopy (EPR). The results of EPR and TPR show finely dispersed Cu²⁺ species on ceria matrix with low copper content. The Cu²⁺ species exists in the form of dimers and clusters which are not evident in XRD. In addition CuO is also present as small clusters which grow to larger size at higher Cu content. There is no evidence of CuO forming a solid solution with fluorite CeO₂ in combustion method. The Cu²⁺ species mostly appear on surface rather than in the bulk. Hydrogen peroxide decomposition kinetics has been carried out on Cu–Ce–O composite materials to investigate the effect of crystalline and well-dispersed copper oxide phases on CeO₂. From kinetic results, the catalyst materials can be grouped into highly dispersed as well as crystalline CuO phases present on CeO₂ matrix. Two parallel compensating lines for dispersed and crystalline CuO phases on CeO₂ are observed in ln A versus E_a plot indicating the compensation effect in H₂O₂ decomposition. This observation is consistent with XRD and EPR results.     

Cr负载V2O5-WO3/TiO2催化剂的低温NH3-SCR脱硝活性

采用浸渍法制备了一系列不同Cr负载量的CrO_x-V₂O₅-WO₃/TiO₂催化剂, 研究了Cr改性对该催化剂脱硝活性及抗硫性能的影响. 结果表明, Cr的引入使V₂O₅-WO₃/TiO₂催化剂的低温NO_x去除效果和抗硫性能显著提升. Cr的负载量为3%(以Cr₂O₃计算质量分数)时, 催化剂具有最佳的低温脱硝活性和N₂选择性. 结构表征结果表明, 改性催化剂中Cr元素主要以Cr³⁺形式存在, Cr的引入使催化剂的氧化性能明显提升, 并使表面弱酸位点、 强酸位点和催化剂表面吸附氧数量增多. XPS分析结果表明, Cr能使催化剂中V⁵⁺/V⁴⁺比例降低, 促进催化剂中自由电子的迁移. In situ DRIFTs表征结果显示, Cr的引入能促进NO与吸附在Brönsted酸位点上的NH₃在低温条件下反应, 从而使催化剂具有更好的低温脱硝活性. UV-Vis光谱分析结果表明, CrO_x负载量提高会显著增加高价态Cr的烧结聚集. 同时, 提出了一种选择性催化还原(SCR)反应中Cr-V协同催化的机理.     

Synthesis of binaphthols over mesoporous molecular sieves

Mesoporous aluminosilicates (Al-containing NaMCM-41) were applied as catalyst supports for oxidative coupling of β-naphthol and substituted β-naphthols due to their remarkable features such as surface area, ordered mesopores and high thermal stability. The NaMCM-41 supported copper catalysts prepared by impregnation method, and Cu-NaMCM-41 was prepared by incorporating copper during synthesis. Oxidative coupling of β-naphthol reaction was studied using molecular oxygen as oxidant. The copper supported NaMCM-41 catalysts were prepared with different Si/Al ratios and calcined from 120 to 420 °C were observed to show varied product selectivity. The NaMCM-41 supported copper catalysts and Cu-NaMCM-41 were more active than the corresponding Cu/Fe supported on NaY zeolite. The catalysts were characterized by X-ray diffraction (XRD), temperature programmed reduction (TPR), UV–DRS, ICPMS and BET surface area techniques and the reaction products were confirmed by ¹H-NMR, FTIR and HRMS. An attempt has been made to explain the product selectivity of the catalysts discussed with the above techniques. The high dispersion of Cu⁺² species observed in the catalysts having high Si/Al ratios in NaMCM-41 support and catalysts that are calcined at low temperatures, i.e. less than 420 °C, yielded an unexpected product perylene diol. A comparatively low dispersion of Cu⁺² species, noticed in catalysts having low Si/Al ratios and calcined at high temperatures, yielded binapthol as the coupled product. The effect of the variation of catalyst and the solvent are also studied.     

β-Ga2O3∶Cr3+近红外长余辉纳米颗粒的制备及发光性能

以三乙二醇为表面配体, 利用沉淀法制备了β-Ga₂O₃∶Cr³⁺近红外(NIR)长余辉纳米颗粒. 考察了反应条件对β-Ga₂O₃∶Cr³⁺的发光性能和晶体结构的影响, 并初步探讨了其NIR余辉发光机理. 结果表明, 当溶液的pH值为7, 煅烧温度为700 ℃时, 可获得高纯度的β-Ga₂O₃∶Cr³⁺纳米颗粒, 其平均粒径为30 nm, 最大余辉发射波长可调控为750 nm, NIR余辉发光时间长于384 h. 本方法得到的β-Ga₂O₃∶Cr³⁺长余辉纳米颗粒不仅尺寸小, 而且NIR余辉时间长, 发射波长可调控, 在低背景噪音的深组织活体成像中具有潜在的应用前景.     

A Rhodamine-based fluorescent sensor for chromium ions and its application in bioimaging

A rhodamine-based sensor (1) has been developed for the detection of chromium ions. Cr³⁺-induced opening of the rhodamine spirocycle in sensor (1) led to the distinct colorimetric and fluorescence responses. Among all the tested ions, only Cr³⁺ generated a significant fluorescence enhancement of up to 13-fold, which indicated the high selectivity of 1. Sensor (1) was successfully applied in the in vivo fluorescence imaging of Cr³⁺ in C. elegans. The results provided solid evidences for the future estimation of Cr³⁺ in environmental applications and tobacco samples.     

Long-lived photoinduced charge separation in carbazole–pyrene–viologen system incorporated in Langmuir–Blodgett films of substituted diazacrown ethers

Diaza-18-crown-6 ethers appending two pyrenyl (Py) or two carbazolyl (Cz) groups were synthesized. These macrocyclic compounds form 1:1 host–guest complexes with methyl viologen chloride (MV²⁺), and these complexes were assembled into monolayers by Langmuir–Blodgett technique. The generated assembly involves the general structure of donor–sensitizer–acceptor (Cz–Py–MV²⁺) in space, although any of the photo- and redox-active components are not covalently bonded. Photoirradiation of the pyrenyl group resulted in the charge-separated pair Cz√⁺–Py–MV√⁺ which survived up to hours in a well anaerobic atmosphere. An electrode was fabricated by transferring the L–B film on an ITO glass. The photoinduced voltage of this electrode was measured with a saturated calomel reference electrode in hydroquinone (H₂Q) solution to be ca. 168 mV when the light intensity was 218 mW/cm². This electrode was also used as the light electrode to construct a photogalvanic cell with a platinum electrode as the dark electrode. Irradiation of the light electrode with visible light results in anodic photocurrent, and there is no net chemical change associated with the function of the cell which converts light to electricity.     

Vapor–liquid equilibria and excess properties for methyl tert-butyl ether (MTBE) containing binary systems

Methyl tert-butyl ether (MTBE) is recently widely used in the chemical and petrochemical industry as a non-polluting octane booster for gasoline and as an organic solvent. The isobaric or isothermal vapor–liquid equilibria (VLE) were determined directly for MTBE+C₁–C₄ alcohols. The excess enthalpy (H^E) for butane+MTBE or isobutene+MTBE and excess volume (V^E) for MTBE+C₃–C₄ alcohols were also determined. Besides, the infinite dilute activity coefficient, partial molar excess enthalpies and volumes at infinite dilution (γ^∞, H^E,∞, V^E,∞) were calculated from measured data. Each experimental data were correlated with various g^E models or empirical polynomial.     

Identification of chromium and nickel sites in zinc phosphate glasses

Optical and EPR investigations of chromium and nickel doped zinc phosphate glasses are carried out at room temperature to evaluate crystal field, spin-Hamiltonian and bonding parameters. For Cr³⁺ ion, the site symmetry is ascribed to a distorted octahedron, whereas the Ni²⁺ ion is located in a near octahedral site. In addition, the bonding parameters suggest covalent nature for Cr³⁺ and a moderate covalent nature for Ni²⁺ in the zinc phosphate glasses.     

硫酸盐体系三价铬沉积机理及镀层表征

在新研发的硫酸盐三价铬镀厚铬的镀液体系中, 运用线性扫描伏安法(LSV)和循环伏安法(CV)对三价铬在铜电极表面的电沉积过程进行研究, 并运用X射线荧光测厚仪、扫描电子显微镜(SEM)、X射线能量色散谱(EDS)、X射线衍射仪(XRD)、显微硬度计和Tafel曲线表征铬镀层厚度、形貌、组成、结构、显微硬度及在3.5wt% NaCl溶液中的耐蚀性. 结果表明, 在该体系中三价铬的沉积过程分两步进行(Cr³⁺ + e →Cr²⁺ , Cr²⁺ + 2e → Cr), 第一步得到1个电子, 受电化学过程和扩散过程共同控制, 第二步得到2个电子, 为扩散控制下的不可逆过程; 该镀层为瘤状纳米晶结构, 镀层中含有少量的铁元素(1.10 wt%), 显微硬度达到789.2 Hv, 镀层在3.5wt% NaCl溶液中的腐蚀电位(E_corr)为-0.29 V, 腐蚀电流密度(j_corr)为9.26×10^-5 A·dm^-2.     

EPR study of ceria–silica and ceria–alumina catalysts: Localization of superoxide radical anions

Oxygen adsorption experiments were performed on evacuated and prereduced CeO₂/SiO₂ and CeO₂/Al₂O₃ catalysts with and without platinum. Considerable amounts of the superoxide radical ions were stabilized on all the samples. Signal parameters suggest Ce⁴⁺–O₂⁻ positioning for all detectable superoxide species. Physisorbed oxygen broadens O₂⁻ signal beyond detection for all the alumina-based samples, while the same procedure for all the silica-based samples did not change signal shape of O₂⁻ species. Detectable O₂⁻ species are localized in the bulk of ceria and the nature of support (silica or alumina) determines the number of oxygen vacancies and the rate of electron transfer. XRD data suggest that for alumina-based samples small and/or thin islands of ceria dominate, while comparatively large ceria particles are stabilized on the surface of silica-based samples with the same ceria content. Average size of ceria crystallites is still not determining factor and cannot account for the observed differences. Higher concentrations of paramagnetic species may be stabilized on alumina-based samples and thus, sensor-like behavior towards gaseous oxygen at room temperature was detected for them—oxygen admission reversibly changes superoxide lineshape. For silica samples, only minor changes of O₂⁻ lineshapes were typical upon the change of the partial pressure of oxygen at ambient and low temperatures. Addition of platinum has little effect on parameters of the O₂⁻ signal, except an enhancement of the superoxide decay in the reducing media. Possible site for O₂⁻ stabilization inside the lattice of CeO₂ was proposed and relevance of the observed effects to the redox catalysis discussed.     

Preparation of Al2O3–ZrO2 mixed supports; their characteristics and hydrothermal stability

Al₂O₃–ZrO₂ mixed supports have been synthesised using a colloidal solution of ZrO(OH)₂ or a Zr(IV) propoxide solution in organic medium. Zirconia content in these samples was about 10% (36% of the theoretic monolayer). The hydrothermal stability (alumina→boehmite transformation at 230 °C, about 10 bar pressure, in the presence of water vapour) of these supports was then investigated by XRD. The presence of the zirconia over the alumina decrease the quantity of boehmite formed after the hydrothermal treatment. The dispersion of zirconia and the stability in hydrothermal conditions of the final support are function of the preparation method.     

Pd-Cu/羟磷灰石的制备及常温常湿CO催化氧化性能

通过溶胶-凝胶法(SG)和水热法(HT)合成了羟磷灰石载体(HAP-SG, HAP-HT), 以浸渍法制备负载型Pd-Cu/HAP催化剂(PC-SG, PC-HT), 并考察其常温常湿条件下CO催化氧化反应性能. 采用电感耦合等离子体发射光谱(ICP-OES)、 N₂物理吸附-脱附、 X射线衍射(XRD)、 傅里叶变换红外光谱(FTIR)、 H₂程序升温还原(H₂-TPR)、 CO₂程序升温脱附(CO₂-TPD)、 X射线光电子能谱(XPS)和CO原位漫反射傅里叶变换红外光谱(in-situ DRIFTS)等手段对Pd-Cu/HAP催化剂进行了表征. 结果表明, 相比于PC-SG, PC-HT具有较大比表面积和孔容, 含有较多的Cu₂Cl(OH)₃物种且与Pd物种和载体直接产生了较强的相互作用; 而且PC-HT表面含有较强CO活化能力的Pd⁺物种和更多具有较强氧化还原性质的Cu⁺物种, 以及较少数量和较低强度的碱性位点, 因而表现出更加优异的常温常湿条件下CO催化氧化性能.     

New approaches in the design of ceramic and hybrid membranes

This paper describes approaches developed for the preparation and also the characterization of innovative inorganic or hybrid membrane materials. Soft chemistry routes, sol–gel methods and plasma-enhanced chemical vapour deposition (PECVD) are used to get tailor-made layers with different architectures. The infiltrated composite membranes are first examined. They exhibit a good thermo-mechanical resistance, a low sensitivity to the presence of defects, a relatively high flow resistance and are attractive for catalytic contactor applications. Preliminary results on supported ceramic membranes with a hierarchical porosity are then presented. Finally, examples are given to illustrate the interest of the PECVD route and of plasma post-treatments for preparing very thin hybrid separative layers.     

W/O型微乳状液迁移和富集痕量金属离子Cd2+、Cr3+的研究

利用各种分离技术分离和富集金属离子,无论是在环境保护还是在湿法冶金方面都具有重要的意义.油包水型微乳状液因具有独特的物理化学性质,已越来越广泛地应用于金属离子的萃取分离上.     

Cr~(3+)改性NaY分子筛的吸附脱氮性能

对Cr~(3+)离子改性NaY分子筛的实验条件进行了研究,通过XRD、FT-IR、N_2吸附-脱附等方法对改性后的CrY分子筛进行表征,确定最佳改性条件为温度40℃,Cr~(3+)浓度0.5 mol/L,改性两次。FT-IR谱图表明,CrY分子筛波数1 147 cm~(-1)处峰明显消失,且波数1 024 cm~(-1)峰与标准的NaY分子筛相比发生了蓝移现象,可以判定Cr~(3+)交换到分子筛骨架上。考察了吸附时间和温度对CrY分子筛吸附脱除模拟燃料中喹啉的影响。结果表明,吸附温度对吸附影响不大,可在室温下进行。CrY对喹啉的吸附主要为化学吸附,且吸附类型为配位吸附和π络合吸附,最佳吸附时间为30 min,吸附等温线线性回归表明,CrY分子筛对喹啉吸附动力学模型为L型和F型混合吸附。     

玻璃基片上纳米碳管电极的集成

利用微波等离子体化学气相沉积法在玻璃孔穴中定位生长纳米碳管电极, 分析了负偏压对纳米碳管电极生长的影响. 该电极对铜离子的电化学检测性能分析结果表明, 所制备的纳米碳管电极具有良好的电化学检测性能, 位于－0.0100 V附近的铜离子的还原峰峰形良好, 其电流在铜离子浓度为0.01~0.30 mmol•L^-1时, 与Cu²⁺浓度呈良好的线性关系, 相关系数为0.9975, 且具有较好的长期稳定性和重现性.     

Ion-exchange properties of hypercrosslinked polystyrene impregnated with methyl orange

A novel bipolar stationary phase (HCPS–MO) was prepared by impregnation of hypercrosslinked polystyrene (HCPS) with methyl orange (MO; 4-dimethylamino-4′-sulfoazobenzene) and its ion-exchange properties were studied. Simultaneous separation of cations and anions on HCPS–MO is possible, although it behaves preferentially as a cation-exchanger. Unusual selectivity of HCPS-MO for alkali and alkaline-earth metal cations: Na⁺+K⁺+4⁺+ and Mg²⁺2+2+2+ was observed. The effect of temperature on retention of alkali and alkaline-earth metal cations was studied. Separation of Na⁺, K⁺, Rb⁺, NH₄⁺, Cs⁺, Mg²⁺ and Ca²⁺ on HCPS–MO with diluted cerium(III) nitrate solution as an eluent in single run is presented.     

Capillary electrochromatographic separation of metal ion species with on-line detection by inductively coupled plasma mass spectrometry

A bonded phase capillary column containing macrocyclic polyamine, [28]ane-N₆O₂ functional groups was used for the electrophoretic separation of arsenic, chromium and selenium species. A simple device interfacing this capillary electrochromatography (CEC) systems to an inductively coupled plasma mass spectrometer (ICPMS) is described. The dimension of the capillary column was 160 cm×100 μm i.d. To accommodate this electrophoretic separation, an auxiliary capillary was used with nitric acid (0.05 M) as makeup liquid. With the electrokinetic method at –20 kV, 20 s and a nebulizer gas flow rate of 1 l min⁻¹, the sample injected was analyzed with an applied potential of −20 kV. The background electrolyte buffer for the separation of CrO₄²⁻–Cr³⁺ was phosphate (20 mM, pH 6.5). That for HAsO₄²⁻–Ph₄As⁺ was pyromellitate (20 mM, pH 6.0) and for SeO₄²⁻–SeO₃²⁻ was acetate (20 mM, pH 6.0). The role of the buffer’s anion was also discussed. The separation efficiency of the bonded phase was compared with the bare fused silica. Concentration detection limits for these metal ions were in the low ppb range. In addition, the matrix effect of the established system with the bonded phase was found smaller than that with the bare fused silica.