甲醇水蒸气重整制氢CuO/CeO2-ZrO2/SiC整体催化剂的研究

采用浸渍法和溶胶凝胶法制备了CuO/CeO₂-ZrO₂/SiC整体催化剂，并将其用于甲醇水蒸气重整制氢反应中。结果表明，与CuO/CeO₂-ZrO₂颗粒催化剂相比，CuO/CeO₂-ZrO₂/SiC整体催化剂催化活性较好，产氢速率较快且重整气中CO体积分数较低。进一步探究了涂层涂覆量和CuO负载量对催化性能的影响，结果表明，当CeO₂-ZrO₂复合氧化物涂层涂覆量在15%±1%，CuO负载量为5%±1%时，催化性能较好；当反应温度为340℃，水醇物质的量比为1.2，甲醇水蒸气气体空速为4840 h^-1时，甲醇转化率为86.0%，产氢速率为1490.0 L/（m³·s），重整气中CO体积分数为1.55%。最后通过单因素实验法探究了甲醇水蒸气气体空速、水醇物质的量比和反应温度对反应的影响。结果表明，随着气体空速变大，甲醇转化率下降，产氢速率上升，重整气中CO体积分数下降。随着水醇物质的量比增加，甲醇转化率先上升后下降，产氢速率先上升后下降，重整气中CO体积分数下降。随着反应温度的升高，甲醇转化率、产氢速率和重整气中CO体积分数均上升。     

载体焙烧气氛对甲醇水蒸气重整制氢CuO/CeO2催化剂的影响

采用沉淀法和浸渍法制备了具有氧空位的CeO₂纳米材料和甲醇水蒸气重整制氢CuO/CeO₂催化剂,探索不同焙烧气氛对CeO₂纳米材料结构、性质和甲醇水蒸气重整制氢性能的影响。采用SEM、XRD、BET、H₂-TPR、N₂O滴定和XPS等手段对催化剂进行了表征。结果表明,CuO/CeO₂催化剂的催化活性与催化剂的Cu比表面积大小、Cu-Ce的相互作用强弱、表面缺陷和表面氧空位的多少有关。其中,在氢气气氛下焙烧所得的CeO₂负载CuO后的CuO/CeO₂-H催化剂催化活性最佳。在反应温度为250℃,水醇物质的量比为1.2时,甲醇气体空速为800 h^-1,甲醇转化率达到了100%,重整尾气中CO含量为0.87%。     

钙钛矿型甲醇水蒸气重整制氢催化材料的研究

采用溶胶凝胶法合成了钙钛矿复合氧化物, 负载氧化铜后得钙钛矿负载型催化材料, 通过XRD (X射线衍射分析)、BET(比表面积测试)、H₂-TPR(程序升温还原分析)、XPS (X射线光电子能谱)等手段对催化材料进行了表征, 考察了不同种类钙钛矿负载纳米铜催化材料的结构、性质对甲醇水蒸气重整制氢性能的影响. 结果显示, 钙钛矿负载纳米铜催化材料的催化活性主要与催化剂的铜比表面积、表面晶格氧缺位以及活性组分和载体间的相互作用有关. 其中, CuO/LaCrO₃钙钛矿负载型催化材料的表面氧空穴含量较多, 活性组分与载体间相互作用较强, 因此催化甲醇水蒸气重整制氢活性较好. 当反应温度为360 ℃时, CuO/LaCrO₃钙钛矿型催化剂并未出现明显失活现象, 甲醇转化率为98.6%, 产氢速率为694.9 mL•kg_cat ^–1•s ^–1.     

前驱体和沉淀剂浓度对CuO/ZnO/CeO2-ZrO2甲醇水蒸气重整制氢催化剂性能的影响

采用共沉淀法制备了CuO/ZnO/CeO₂-ZrO₂甲醇水蒸气重整制氢催化剂,探讨了前驱体和沉淀剂浓度对催化剂性能的影响,并采用BET、XRD、H₂-TPR和XPS等手段对催化剂进行了表征。结果表明,前驱体和沉淀剂浓度对催化剂的结构和性能影响很大,当前驱体浓度为0.1mol/L,沉淀剂浓度为0.5mol/L时,所得催化剂CO选择性最小,催化活性最佳。在360h稳定实验中,甲醇最高转化率达100%,重整尾气中H₂含量保持在74.5%以上,CO含量低于0.8%,催化剂稳定性良好。     

水热合成温度对CuO/CeO2催化甲醇水蒸气重整制氢性能的影响

以Ce（NO₃）₃·6H₂O为铈源，尿素为沉淀剂，采用水热法制备纳米CeO₂载体，并通过改变水热合成温度来控制CeO₂载体的微观结构，再通过等体积浸渍法制得CuO/CeO₂催化材料，并将其应用在甲醇水蒸气重整制氢反应（MSR）中进行性能评价。通过低温N2吸附-脱附、XRD、H₂-TPR、XPS等表征，探究了不同水热合成温度对纳米CeO₂载体的微观结构、CuO/CeO₂催化材料结构和甲醇水蒸气重整制氢反应性能的影响。结果表明，在水热合成温度为180℃条件下制备的纳米CeO₂载体具有立方萤石结构，且负载CuO后制备的CuO/CeO₂催化材料中表相CuO的还原温度较低、Cu-Ce间的相互作用较强、催化材料表面氧空穴较多，因此，表现出较好的催化活性。当反应温度为280℃，水醇物质的量比（W/M）为1.2，甲醇水蒸气气体空速（GHSV）为800 h^...     

陈化时间对CuO/ZnO/CeO2/ZrO2甲醇水蒸气重整制氢催化剂性能的影响

采用共沉淀法制备了CuO/ZnO/CeO₂/ZrO₂甲醇水蒸气重整催化剂,探讨了陈化时间对催化剂性能的影响.结果发现,延长陈化时间能增加催化剂的表面铜原子数和改善催化剂的还原性能,但与此同时也降低了催化剂的储放氧性能.延长陈化时间,CuO/ZnO/CeO₂/ZrO₂催化剂的氢产率随表面铜原子数的增加而成线性增长.另一方面,重整尾气中的CO含量也随着储放氧能力的下降而增加.综合考虑产氢率和重整尾气中CO含量,最佳陈化时间为2h,此时,CuO/ZnO/CeO₂/ZrO₂催化剂表现出了最佳性能.     

焙烧温度对甲醇水蒸气重整制氢Ce/Cu/Zn-Al水滑石衍生催化剂的影响

采用原位合成法在γ-Al_2O_3载体表面上合成了Zn-Al水滑石,再采用顺序浸渍法制备了一系列Ce/Cu/Zn-Al催化剂,并采用XRD、BET、H_2-TPR和XPS等手段对催化剂进行了表征,考察了焙烧温度对Ce/Cu/Zn-Al催化剂表面结构及其催化甲醇水蒸气重整制氢性能的影响。结果表明,焙烧温度主要影响了催化剂的Cu比表面积、表面氧空穴含量和Cu-Ce间相互作用。当焙烧温度为500℃时,催化剂Cu的比表面积较大,表面氧空穴含量较多,Cu-Ce间相互作用较强,因此,催化甲醇水蒸气重整制氢活性较好。当焙烧温度升高到700℃时,Cu物种主要以稳定的CuAl_2O_4尖晶石形式存在,不利于甲醇水蒸气重整制氢反应的进行,因此,催化活性较差。     

甲醇水蒸气重整制氢CuO/CeO2-ZrO2/SiC整体催化剂的研究

采用浸渍法和溶胶凝胶法制备了CuO/CeO2-ZrO2/SiC整体催化剂,并将其用于甲醇水蒸气重整制氢反应中。结果表明,与CuO/CeO2-ZrO2颗粒催化剂相比,CuO/CeO2-ZrO2/SiC整体催化剂催化活性较好,产氢速率较快且重整气中CO体积分数较低。进一步探究了涂层涂覆量和CuO负载量对催化性能的影响,结果表明,当CeO2-ZrO2复合氧化物涂层涂覆量在15%±1%,CuO负载量为5%±1%时,催化性能较好;当反应温度为340℃,水醇物质的量比为1. 2,甲醇水蒸气气体空速为4840 h-1时,甲醇转化率为86. 0%,产氢速率为1490. 0 L/(m3·s),重整气中CO体积分数为1. 55%。最后通过单因素实验法探究了甲醇水蒸气气体空速、水醇物质的量比和反应温度对反应的影响。结果表明,随着气体空速变大,甲醇转化率下降,产氢速率上升,重整气中CO体积分数下降。随着水醇物质的量比增加,甲醇转化率先上升后下降,产氢速率先上升后下降,重整气中CO体积分数下降。随着反应温度的升高,甲醇转化率、产氢速率和重整气中CO体积分数均上升。     

甲醇水蒸气重整制氢反应条件的优化

对共沉淀法制备的CuO/ZnO/CeO₂-ZrO₂催化剂在甲醇水蒸气重整制氢反应体系中的性能进行了考察,并利用统计学实验设计方法对该反应的反应条件进行了优化。选择反应温度、水醇比和甲醇气体空速为独立要因,利用全因子实验设计方法,得到反应温度对两个响应值(甲醇转化率和重整气中CO物质的量分数)的影响最为显著,甲醇气体空速对重整气中CO物质的量分数的影响最小。固定甲醇气体空速为300 h^-1,利用中心旋转组合设计实验方法对反应温度和水醇比进行优化,得出当反应温度在249~258℃、水醇比在1.76~2.00时,甲醇能全部转化,重整气中CO物质的量分数小于0.5%。此模型的计算值与实验结果较为接近,表明采用统计学实验设计方法得出的结论对甲醇水蒸气重整制氢反应条件的优化具有指导意义。     

甲醇水蒸气重整制氢的高效碳纳米管改性Cu/ZnO/Al2O3催化剂

以碳纳米管为助剂,制备用于甲醇水蒸气重整制氢的新型高效Cu/ZnO/Al₂O₃催化剂,并与传统Cu/ZnO/Al₂O₃催化剂在相同条件下的催化性能进行了比较.结果表明,添加适量碳纳米管可显著提高催化剂的低温催化活性和选择性,在大幅度提高产氢速率的同时有效降低了重整产气中CO的含量.SEM和XRD分析证实适量碳纳米管的添加有效促进了Cu/ZnO/Al₂O₃催化剂结构特性的改善,有利于活性铜物种的分散,从而显著提高了催化剂的低温催化性能.     

The preparation of NbH5(Me2PCH2CH2Me2)2 and NbHL2(Me2PCH2CH2PMe2)2 (L = CO or C2H4)

MMe₅(dmpe) (M = Nb or Ta, dmpe = Me₂PCH₂CH₂PMe₂) reacts with H₂ (500 atm) and dmpe in THF at 60°C to give MH₅(dmpe)_2? NbH₅(dmpe)₂ readily reacts with two mol of CO or ethylene (L) to give NbHL₂(dmpe)₂. The exchange of the hydride ligand with the ethylene protons in NbH(C₂H₄)₂(dmpe)₂ is not rapid on the ¹H NMR time scale (60 MHz) at 95°C.     

Li2O-TiO2-SiO2-P2O5和Li2O-TiO2-Al2O3-P2O5体系锂离子固体电解质的制备及性能研究

一些具有NASICON型网格结构的固体电解质具有高的电导率和好的稳定性,NASICON的意思是Na Super Ionic Conductor[1]。当NaZr2(PO4)3中P5 被Si4 部分取代时便可以得到具有NASICON结构的Na1 xZr2SixP3-xO12体系,其具有高的钠离子电导率。然而有相同结构的Li1 xZr2SixP3-xO12体系的离子电导率却很低,这是因为Li 半径太小,而NASICON三维网格结构的离子通道太大,两者不匹配而使电导率下降[2]。但当LiZr2(PO4)3中Zr4 被离子半径小些的Ti4 取代,所得LiTi2(PO4)3的通道就与Li 半径相匹配,适合于锂离子的迁移,从而使其电导率…     

Neue Verbindungen im System CaO/SiO2/CaCl2/H2O

New Compounds in the System CaO/SiO₂/CaCl₂/H₂O The hydrothermal formation of novel calcium silicate hydrates of compositions 5 CaO · 2 SiO₂ · CaCl₂ · 4 H₂O, 5 CaO · 2 SiO₂ · CaCl₂ · 2 H₂O and 4 CaO · 2 SiO₂ · CaCl₂ · H₂O from Ca₃SiO₅ and mixtures of CaO and SiO₂, respectively, in presence of calciumchloride at 200°–350 °C is described. From molybdate-reaction, ²⁹Si MAS NMR, DTA and TG measurements it is concluded that these compounds are based on disilicate anions and are to be interpreted as calcium hydroxide disilicate chlorides.     

Formation of [Cp2TiSbMe2]2, [Cp2TiSb(SiMe3)2]2 and [Cp2TiCl]2·2Mes4Sb2

Reactions of [Cp₂Ti(btmsa)] (btmsa = bis(trimethylsilyl)acetylene) with R₄Sb₂ (R = Me, Me₃Si) give [Cp₂TiSbMe₂]₂ (1) or [Cp₂TiSb(SiMe₃)₂]₂ (2) respectively. [Cp₂TiCl]₂·2Mes₄Sb₂ (3) is serendipitously formed from [Cp₂Ti(btmsa)] and Mes₂SbH containing NH₄Cl traces.     

Conversion of NO in NO/N2, NO/O2/N2, NO/C2H4/N2 and NO/C2H4/O2/N2 Systems by Dielectric Barrier Discharge Plasmas

An experimental study on the conversion of NO in the NO/N₂, NO/O₂/N₂, NO/C₂H₄/N₂ and NO/C₂H₄/O₂/N₂ systems has been carried out using dielectric barrier discharge (DBD) plasmas at atmospheric pressure. In the NO/N₂ system, NO decomposition to N₂ and O₂ is the dominating reaction; NO conversion to NO₂ is less significant. O₂ produced from NO decomposition was detected by an on-line mass spectrometer. With the increase of NO initial concentration, the concentration of O₂ produced decreases at 298 K, but slightly increases at 523 K. In the NO/O₂/N₂ system, NO is mainly oxidized to NO₂, but NO conversion becomes very low at 523 K and over 1.6% of O₂. In the NO/C₂H₄/N₂ system, NO is reduced to N₂ with about the same NO conversion as that in the NO/N₂ system but without NO₂ formation. In the NO/C₂H₄/O₂/N₂ system, the oxidation of NO to NO₂ is dramatically promoted. At 523 K, with the increase of the energy density, NO conversion increases rapidly first, and then almost stabilizes at 93–91% of NO conversion with 61–55% of NO₂ selectivity in the energy density range of 317–550 J L⁻¹. It finally decreases gradually at high energy density. A negligible amount of N₂O is formed in the above four systems. Of the four systems studied, NO conversion and NO₂ selectivity of the NO/C₂H₄/O₂/N₂ system are the highest, and NO/O₂/C₂H₄/N₂ system has the lowest electrical energy consumption per NO molecule converted.     

KCl-KBO2-K2CO3, K2MoO4-KBO2-K2CO3, and K2WO4-KBO2-K2CO3 ternary systems

phase diagrams of KCl-KBO₂-K₂CO₃, K₂MoO₄-KBO₂-K₂CO₃, and K₂WO₄-KBO₂-K₂CO₃ ternary systems were studied by a calculation-experimental method and differential thermal analysis (DTA). The coordinates of ternary eutectics were determined to be E ₁: 622°C, 8.5 mol % KBO₂, 56.5 mol % KCl, and 35 mol % K₂CO₃; E ₂: 710°C, 23 mol % KBO₂, 43 mol % K₂CO₃, and 34 mol % K₂MoO₄; E ₃: 710°C, 23 mol % KBO₂, 43 mol % K₂CO₃, and 34 mol % K₂WO₄. The specific heats of melting of the eutectics were determined.     

Removal of NO in NO/N2, NO/N2/O2, NO/CH4/N2, and NO/CH4/O2/N2 systems by flowing microwave discharges

In this paper, continuing previous work, we report on experiments carried out to investigate the removal of NO from simulated flue gas in nonthermal plasmas. The plasma-induced decomposition of small concentrations of NO in N2 used as the carrier gas and O2 and CH4 as minority components has been studied in a surface wave discharge induced with a surfatron launcher. The reaction products and efficiency have been monitored by mass spectrometry as a function of the composition of the mixture. NO is effectively decomposed into N2 and O2 even in the presence of O2, provided always that enough CH4 is also present in the mixture. Other majority products of the plasma reactions under these conditions are NH3, CO, and H2. In the absence of O2, decomposition of NO also occurs, although in that case HCN accompanies the other reaction products as a majority component. The plasma for the different reaction mixtures has been characterized by optical emission spectroscopy. Intermediate excited species of NO*, C*, CN*, NH*, and CH* have been monitored depending on the gas mixture. The type of species detected and their evolution with the gas composition are in agreement with the reaction products detected in each case. The observations by mass spectrometry and optical emission spectroscopy are in agreement with the kinetic reaction models available in literature for simple plasma reactions in simple reaction mixtures.     

Formation of nano-crystalline quartz crystals from ZnO/MgO/Al2O3/TiO2/ZrO2/SiO2 glasses

Glasses with the compositions 50.9 SiO₂ · 20.8 Al₂O₃ · (20.8 ? x) MgO· × ZnO · 3.7 TiO₂ · 3.7 ZrO₂ with x = 0, 2.3, 4.6 and 9.3 were annealed at temperatures in the range from 850 to 1100 °C. Depending on temperature, high- or low-quartz solid solutions, magnesium aluminosilicate, mullit and spinel precipitated. These glass–ceramics exhibit excellent mechanical properties and are potential candidates for applications in micromechanics or as hard disc substrate.The larger the ZnO concentration, the lower is the glass transition temperature. Also microhardnesses and Young’s moduli increased with increasing ZnO concentration. The nucleation temperature was of minor importance. To achieve good mechanical properties, the initially formed high-quartz phase must transform to the corresponding low-quartz phase. This occurs if the quartz phase contains only minor MgO or ZnO concentrations, which can be achieved by increasing the annealing times or temperature. Then MgO, ZnO and Al₂O₃ occur as separate spinel or gahnite phase.     

Synthesis and characterization of inorganic solid electrolytes of Li2O-SiO2-P2O5 and Li2O-TiO2-SiO2-P2O5 systems

The lithium-ion-conducting inorganic solid electrolytes in the oxide systems Li₂O-SiO₂-P₂O₅ and Li₂O-TiO₂-SiO₂-P₂O₅ were prepared by the solid-state reaction, and the electrolyte pellet made by cold-pressing method had diameter of 13 mm and was about 1 mm thick. Phase identification and surface morphology of the products were carried out by X-ray diffraction and scanning electron microscopy. Ionic conductivity of the pellets was investigated through ac impedance. The results show that the adding of other cations can improve the ionic conductivity of the solid electrolyte, and the sintering temperature and duration can influence the ionic conductivity. The maximum ionic conductivity in the samples is 9.9 × 10⁻⁴ S/cm in the Li₂O-TiO₂-SiO₂-P₂O₅ system. Original Russian Text ? W. Li, M. Wang, Z.H. Li, X.F. Shang, H. Wang, Y.W. Wang, Y.B. Xu, 2007, published in Elektrokhimiya, 2007, Vol. 43, No. 11, pp. 1341–1345.     

Solubility in the Na2Cr2O7-(NH4)2Cr2O7-K2Cr2O7-H2O system

Solubility in the Na₂Cr₂O₇-(NH₄)₂Cr₂O₇-K₂Cr₂O₇-H₂O four-component water-salt system at 25, 50, and 75°C was studied for the first time. Phase field boundaries for individual salts and potassium and ammonium dichromate solid solutions, monovariant lines, and invariant points were determined. Experimental data were used to optimize the looped isohydric process of potassium dichromate preparation involving additional salts.