CeO_2/Ni/Mo/SBA-15甲烷二氧化碳重整催化剂的表征和催化性能(英文)

考察了CeO2修饰及未修饰的Ni/Mo/SBA-15催化剂在CH4-CO2重整上的催化性能并采用N2吸脱附、CO2程序升温脱附、H2程序升温还原、傅里叶红外光谱、X射线衍射、扫描电子显微镜和X射线光电子能谱对催化剂进行了表征.结果表明,在常压,800oC条件下,经过100h在线评价后,Ni/Mo/SBA-15和CeO2/Ni/Mo/SBA-15催化剂仍具有高的反应活性和规整的六方介孔结构,其中CeO2修饰的CeO2/Ni/Mo/SBA-15催化剂表面没有积炭形成,表明CeO2的加入促进了Ni物种在SBA-15介孔分子筛表面的分散,从而阻止了Ce/Ni/Mo/SBA-15催化剂上Ni的烧结和积炭.     

Ni2P/SiO2 和Ni/SiO2 催化剂甘油氢解反应性能比较:催化剂活性及产物选择性影响因素的探讨（英文）

采用浸渍法及程序升温还原法制备了Ni2P/SiO2和Ni/SiO2催化剂,利用N2吸附-脱附、X射线衍射、X射线荧光、CO化学吸附、氢气程序升温脱附及氨气程序升温脱附等手段对催化剂进行了表征并用于甘油氢解反应.结果表明,Ni2P/SiO2和Ni/SiO2具有相近的表面Ni密度,但前者表面酸中心和表面氢物种(包括吸附氢和溢流氢)密度明显更高,且在甘油氢解反应中的活性也更高,这与其酸性中心与金属中心之间的协同作用有关.Ni2P/SiO2催化剂上主要产物为1,2-丙二醇及1-丙醇,而Ni/SiO2催化剂上主要产物为1,2-丙二醇、乙二醇和乙醇.提高反应温度和H2压力不能促进Ni2P/SiO2上乙醇和乙二醇的生成,但促进了1,2-丙二醇进一步氢解转化为1-丙醇.由此可见,Ni2P/SiO2具有较强的C-O键断裂活性及较弱的C-C键断裂活性,这可能分别与其较多酸性中心和电子及几何结构性质密切相关.     

SO_4~(2-)/SnO_2/SBA-15固体酸催化剂的制备及其在环酮缩合反应中的应用

采用等体积浸渍法制备了不同负载量的固体酸催化剂SO42-/SnO2/SBA-15,利用X射线粉末衍射、N2吸附-脱附和透射电镜等手段对样品进行了表征,并考察了催化剂对4-叔丁基环己酮与乙二醇缩合反应的催化性能.结果表明,SO42-/SnO2催化剂负载于SBA-15后其催化性能明显改善.研究了SO42-/20%SnO2/SBA-15催化剂上部分酮类化合物与乙二醇及1,2-丙二醇的缩合反应,并考察了反应时间和催化剂用量等因素对反应性能的影响.在适宜的温和条件下,一些环酮类底物如环己酮、4-甲基环己酮和4-叔丁基环己酮等均可反应得到相应的缩醛化产物,且催化剂至少可循环使用4次.     

Ni_2P/SiO_2 和Ni/SiO_2 催化剂甘油氢解反应性能比较:催化剂活性及产物选择性影响因素的探讨(英文)

采用浸渍法及程序升温还原法制备了Ni2P/SiO2和Ni/SiO2催化剂,利用N2吸附-脱附、X射线衍射、X射线荧光、CO化学吸附、氢气程序升温脱附及氨气程序升温脱附等手段对催化剂进行了表征并用于甘油氢解反应.结果表明,Ni2P/SiO2和Ni/SiO2具有相近的表面Ni密度,但前者表面酸中心和表面氢物种(包括吸附氢和溢流氢)密度明显更高,且在甘油氢解反应中的活性也更高,这与其酸性中心与金属中心之间的协同作用有关.Ni2P/SiO2催化剂上主要产物为1,2-丙二醇及1-丙醇,而Ni/SiO2催化剂上主要产物为1,2-丙二醇、乙二醇和乙醇.提高反应温度和H2压力不能促进Ni2P/SiO2上乙醇和乙二醇的生成,但促进了1,2-丙二醇进一步氢解转化为1-丙醇.由此可见,Ni2P/SiO2具有较强的C-O键断裂活性及较弱的C-C键断裂活性,这可能分别与其较多酸性中心和电子及几何结构性质密切相关.     

超声吸附制备均匀分散在SBA-15的S2O82--Fe2O3纳米粒子:增强S2O82--Fe2O3本体催化活性

酸催化剂在化学反应和化工生产中具有重要的作用.传统无机酸,如H2SO4,H3PO4和对甲苯磺酸等具有较高的催化活性,但是存在污染大、设备腐蚀严重以及催化剂不能重复使用等问题.固体酸具有酸性强、易分离、环境友好以及稳定性和重复使用性好等特点因而近年来越来越引起人们的关注.其中,SO42--MxOy固体超强酸(如SO42--ZrO2,SO42--TiO2和SO42--SnO2等)因具有很好的催化性能而备受关注.相比SO42--MxOy,S2O82--MxOy具有更强的酸性和稳定性而成为研究的重点.如何克服固体超强酸本体的低比表面积和孔容,增加其比表面积和催化活性是固体超强酸研究的热点.超声吸附法可保证所制介孔固体酸活性组分均匀分散,以及大的比表面积和更多的酸性位点.因此采用超声吸附法制备了一种新型介孔固体酸S2O82--Fe2O3/SBA-15.相比S2O82--Fe2O3本体、B酸和文献报道催化剂,负载30%Fe2O3的S2O82--Fe2O3/SBA-15在环氧苯乙烷甲醇醇解的探针反应中显示出很高的催化活性,反应收率为100%.S2O82--Fe2O3纳米粒子的纳米效应和SBA-15介孔结构的协同作用使S2O82--Fe2O3/SBA-15具有高催化活性.相比S2O82--Fe2O3本体,采用超声分散技术制备的S2O82--Fe2O3/SBA-15固体超强酸具有典型的介孔结构、大的比表面和孔容,并且表面富含酸性位点.并且吡啶红外分析S2O82--Fe2O3/SBA-15表面富含L酸和B酸.环氧苯乙烷甲醇醇解探针反应表明,Fe2O3负载量为30%时,S2O82--Fe2O3/SBA-15的催化活性最高,优于S2O82--Fe2O3本体和已报道的布朗酸和路易斯酸等催化剂,将醇底物拓展(ROHs,R = C2H5-C4H9),S2O82--Fe2O3/SBA-15的催化活性也优于S2O82--Fe2O3本体.同时,S2O82--Fe2O3/SBA-15具有很好的重复使用性能,连续使用七次,反应收率在84.1%以上.总之,具有高催化活性、好的稳定性和经济性的S2O82--Fe2O3/SBA-15具有广阔的应用前景.     

连续流微反应器中微纤结构化的Nafion/SiO2固体酸催化苯硝化反应

采用溶胶-凝胶组装方法制备了Nafion/SiO2胶体, 并涂附于烧结的316L不锈钢(SS-316L)金属微纤网络, 形成了空隙率为60%-75%(φ, 体积分数)的整体式微纤结构化的Nafion/SiO2固体酸催化剂. 使用傅里叶变换红外光谱(FT-IR), 热重分析(TGA), 扫描电子显微镜(SEM)及NH3吸附法对微纤结构化的Nafion/SiO2催化剂进行了表征. 结果显示, 溶胶-凝胶组装方法可以明显促进Nafion的分散, 导致酸性中心的暴露量显著增加; 结构化的Nafion/SiO2催化剂以200-400 nm颗粒堆积而成的多孔涂层形式存在. 在一种集换热、混合、催化(反应)功能于一体的微反应器中, 考察了整体式微纤结构化的Nafion/SiO2固体酸催化剂催化苯硝化的反应性能. Nafion在SiO2中的组装量为20%(w, 质量分数), 金属微纤网络上Nafion/SiO2担载量为36.3%(w)的优化催化剂上, 75 ℃时苯转化率为44.7%, 硝基苯选择性可达99.9%. 相近转化率下, Nafion/SiO2固体酸单位酸中心的催化效能约为硫酸的600倍.     

催化剂Ce-SO2-4/SBA-15的固相合成及其催化性能

以介孔分子筛SBA-15为载体,采用固相研磨法将Ce和SO2-4 同时掺杂在SBA-15中,合成了Ce-SO2-4/SBA-15负载型催化剂(Cat).用IR, XRD, TEM,低温N2吸附-脱附,TG和NH3-TPD等方法对Cat的结构性质及其表面酸性进行了研究.结果表明,Cat保持高度有序的一维六方介孔结构,且具有弱酸中心和中强酸中心.用Hammett指示剂法测得其表面酸强度为0.99～1.80,表明Cat为固体酸.将Cat用于催化合成乙酸正丁酯,正交实验结果表明:在冰乙酸0.126 mol, n(冰乙酸): n(正丁醇)=1.0 : 1.2, Cat 375 mg,回流反应140 min的较佳反应条件下,酯化率达97.45%.     

H5PMo10V2O40/SBA-15催化剂的制备及其催化性能

以Keggin型杂多酸H5PMo10V2O40为主体,SBA-15介孔分子筛为载体,利用溶胶-凝胶法制备了不同负载量的H5PM10V2O40/SBA-15负载型催化剂,通过XRD、FTIR、TEM、H2-TPR和N2吸脱附法对样品进行了分析和表征,并将制得的负载型催化剂应用于苯氧化苯酚的反应中,研究了不同条件(温度、时间和催化剂用量等)下的催化性能.研究结果表明:H5PMo10V2O40杂多酸能均匀地分散于SBA-15孔道中且SBA-15的六方介孔结构并未发生改变:较好地解决了活性组分大量溶脱的问题;与H5PMo10V2O40杂多酸相比,H5PMo10V2O40/SBA-15催化剂在苯氧化为苯酚的反应中具有更高的转化率和更好的选择性,当反应温度为70℃,催化剂的使用量为0.25 g,反应时间为2 h和H5PMo10V2O40负载量为60%时苯酚的选择性达到了82.53%.     

硬脂酸法制备SO42-/Fe2O3-SiO2固体酸及其催化性能的初步探讨

首次用硬脂酸法制备了Fe2O3-SiO2混合氧化物,经浸渍H2SO4后再焙烧得SO2-4/Fe2O3-SiO2固体酸催化剂.用TEM,XRD,N2吸附/脱附和TG-DTA等手段对其进行了表征,结果显示制得的Fe2O3-SiO2混合氧化物具有多孔结构.且随着Si含量的增大,其比表面积明显增大,但孔径减小.用乙酸/丁醇酯化催化反应评估了该固体酸的催化性能.     

Ni/γ-Al2O3催化剂的2-MF气相加氢合成2-MTHF性能研究

2-甲基四氢呋喃(2-MTHF)是极具市场潜力的生物燃料、绿色溶剂和化学中间体.采用浸渍法制备Ni/γ-Al2O3催化剂,在固定床反应器评价其2-甲基呋喃(2-MF)气相加氢合成2-甲基四氢呋喃(2-MTHF)反应性能.通过XRD、N2等温吸附-脱附、H2-TPR、NH3-TPD、TEM、H2吸附和XPS对催化剂结构和表面性质进行表征,研究Ni负载量、焙烧温度和反应条件对催化剂性能的影响规律.结果表明:Ni/γ-Al2O3催化剂的Ni金属面积、晶粒尺寸、反应温度和压力都会影响2-MF的转化率;孔结构、酸量和反应温度是影响2-MTHF选择性的主要原因,平均孔径大、酸量大和适宜的反应温度有利于提高2-MTHF选择性. 400℃焙烧的负载量为15%的Ni/γ-Al2O3催化剂, Ni金属面积大、晶粒尺寸小、总酸量多,催化剂表面的金属活性中心与酸性中心协同作用促进了2-MF呋喃环上C=C加氢生成2-MTHF,性能较优.在2 MPa、100℃、WHSV=2.7 h-1、H2/2-MF=6.4的条件下,该催化剂上2-MF转化率为99.8%, 2-MTHF选择性为98.0%,催化剂可以稳定运行40 h.     

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.     

Phase relations in the K2W2O7-K2WO4-KPO3-Bi2O3 system and structure of K6.5Bi2.5W4P6O34

The phase relations in the cross-section of the K₂W₂O₇-K₂WO₄-KPO₃ containing 15 mol% Bi₂O₃ were undertaken using flux method. Crystallization fields of K_6.5Bi_2.5W₄P₆O₃₄, K₂Bi(PO₄)(WO₄), Bi₂WO₆, KBi(WO₄)₂ and their cocrystallization areas were identified. Novel phase K_6.5Bi_2.5W₄P₆O₃₄ was characterized by single-crystal X-ray diffraction: sp. gr. P−1, a=9.4170(5), b=9.7166(4), c=17.6050(7) Å, α=90.052(5)°, β=103.880(5)° and γ=90.125(5)°. It has a layered structure, which contains {K₇Bi₅W₈P₁₂O₆₈}_∞ layers stacked parallel to ab plane and sheets composed by potassium atoms separating these layers. Sandwich-like {K₇Bi₅W₈P₁₂O₆₈}_∞ layers are assembled from [W₂P₂O₁₃]_∞ and [BiPO₄]_∞ building units, and are penetrated by tunnels with K/Bi atoms inside. FTIR-spectra of K₂Bi(PO₄)(WO₄) and K_6.5Bi_2.5W₄P₆O₃₄ were discussed on the basis of factor group theory.     

Sol-gel synthesis of K3InF6 and structural characterization of K2InC10O10H6F9, K3InC12O14H4F18 and K3InC12O12F18

K₃InF₆ is synthesized by a sol-gel route starting from indium and potassium acetates dissolved in isopropanol in the stoichiometry 1:3, with trifluoroacetic acid as fluorinating agent. The crystal structures of the organic precursors were solved by X-ray diffraction methods on single crystals. Three organic compounds were isolated and identified: K₂InC₁₀O₁₀H₆F₉, K₃InC₁₂O₁₄H₄F₁₈ and K₃InC₁₂O₁₂F₁₈. The first one, deficient in potassium in comparison with the initial stoichiometry, is unstable. In its crystal structure, acetate as well as trifluoroacetate anions are coordinated to the indium atom. The two other precursors are obtained, respectively, by quick and slow evaporation of the solution. They correspond to the final organic compounds, which give K₃InF₆ by decomposition at high temperature. The crystal structure of K₃InC₁₂O₁₄H₄F₁₈ is characterized by complex anions [In(CF₃COO)₄(OH_x)₂]^(5−2x)− and isolated [CF₃COOH_2−x]^(x−1)− molecules with x=2 or 1, surrounded by K⁺ cations. The crystal structure of K₃InC₁₂O₁₂F₁₈ is only constituted by complex anions [In(CF₃COO)₆]³⁻ and K⁺ cations. For all these compounds, potassium cations ensure only the electroneutrality of the structure. IR spectra of K₂InC₁₀O₁₀H₆F₉ and K₃InC₁₂O₁₂F₁₈ were also performed at room temperature on pulverized crystals.     

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.     

NaBO2-NaCl-Na2CO3, NaBO2- Na2CO3-NaMoO4, NaBO2- Na2CO3-NaWO4, and NaBO2-NaCl-Na2WO4 ternary systems

The phase diagrams of the NaBO₂-NaCl-Na₂CO₃, NaBO₂-Na₂CO₃-Na₂MoO₄, NaBO₂- Na₂CO₃-Na₂WO₄, and NaBO₂-NaCl-Na₂WO₄ ternary systems were studied by a calculation-experimental method and differential thermal analysis. The coordinates of ternary eutectics were determined: E ₁: 612°C, 16 mol % NaBO₂, 42 mol % NaCl, and 42 mol % Na₂CO₃; E ₂: 568°C, 12 mol % NaBO₂, 28 mol % Na₂CO₃, and 60 mol % Na₂MoO₄; E ₃: 575°C, 12 mol % NaBO₂, 32 mol % Na₂CO₃, and 56 mol % Na₂WO₄; E ₄: 628°C, 8 mol % NaBO₂, 20 mol % NaCl, and 72 mol % Na₂WO₄; and E ₅: 655°C, 9 mol % NaBO₂, 53 mol % NaCl, and 38 mol % Na₂WO₄.     

Li2SO4-Na2SO4-H2O和Li2SO4- K2SO4-H2O溶液的体积性质

本文用高精度数字式振荡管密度计测定了288K至318K温度范围内Li₂SO₄ + Na₂SO₄ + H₂O和 Li₂SO₄ + K₂SO₄ + H₂O三元体系的密度。混合溶液的离子强度范围从0.1到4.5 mol.kg_–1,混合溶液中Na₂SO₄和K₂SO₄的离子强度分数为0.2,0.4,0.6和0.8。用密度实验值拟合得到了不同温度下Pitzer离子相互作用模型混合参数θ_V和 ψ_V,模型的计算值与实验值的偏差在±0.002 g.cm_–3以内。用Pitzer模型计算了不同离子强度下三元体系的混合体积。     

Extension of the La7Mo7O30 structural type with La7Nb3W4O30 and La7Ta3W4O30 compounds

Two compounds of formula La₇A₃W₄O₃₀ (with A=Nb and Ta) were prepared by solid-state reaction at 1450 and 1490 °C. They crystallize in the rhombohedric space group R-3 (No. 148), with the hexagonal parameters: , and , . The structure of the materials was analyzed from X-ray, neutron and electronic diffraction. These oxides are isostructural of the reduced molybdenum compound La₇Mo₇O₃₀, which are formed of perovskite rod along [111]. An order between (Nb, Ta) and W is observed.     

SnSbBiS4-SnS and SnSbBiS4-Sn2Sb6S11 sections of the SnS-Sb2S3-Bi2S3 ternary system

SnSbBiS₄-SnS and SnSbBiS₄-Sn₂Sb₆S₁₁ sections were studied by physicochemical methods (DTA, X-ray powder diffraction, microstructure observation, and microhardness measurements). These sections were found to be eutectic quasi-binary sections of the SnS-Sb₂S₃-Bi₂S₃ ternary system. Solid solution regions based on the initial components were found on either side of the sections. Alloys in the solid solution region are p-type semiconductors.     

Theoretical study of polyoxide clusters B20O30, Al20O30, V20O50, Si20O30H20, and Si20O30F20

The structural, electronic, and vibrational characteristics and energies of the isolated polyoxide clusters B₂₀O₃₀, Al₂₀O₃₀, V₂₀O₅₀, Si₂₀O₃₀H₂₀, and Si₂₀O₃₀F₂₀ and their complexes with the H⁻ ion and ammonia complexes Al₂₀O₃₀ · nNH₃ have been calculated by the density functional theory B3LYP method with different basis sets. The computation results show that the symmetric closo structure I _h with oxygen bridges located above the centers of the faces of an empty [M₂₀] dodecahedron is more favorable for V₂₀O₅₀, Si₂₀O₃₀H₂₀, and Si₂₀O₃₀F₂₀. For B₂₀O₃₀, the cage closo isomer is also more favorable than the other isomers, but its structure is severely distorted as compared to a dodecahedron and has a symmetry close to C ₃ . For Al₂₀O₃₀, the I _h structure corresponds to a high-lying local minimum of the potential energy surface. For Al₂₀O₃₀, a set of unusual puckshaped isomers of symmetry C _i , with different numbers of four-coordinate atoms ^IVAl and three-coordinate atoms ^IIIO, was localized; these structures are more than 90 kcal/mol more favorable than the dodecahedron I _h . The most favorable isomer of Al₂₀O₃₀ contains twelve four-coordinate atoms ^IVAl and four five-coordinate atoms ^VAl. The energies of dissociation of the most favorable M₂₀O₃₀ clusters into the M₂O₃ (C _2v ) and M₄O₆ (T _d ) fragments and, in the case of Al₂₀O₃₀, also into the Al₈O₁₂ (O _h ) and Al₁₂O₁₈ (D _3d ) fragments, have been estimated. The conclusion has been drawn that these clusters can, in principle, exist and can be experimentally detected in the isolated state. Analogous calculations have been performed for ammonia complexes Al₂₀O₃₀ · nNH₃ with n varying from 1 to 20. The effect of solvation on the relative stability of the dodecahedral and puckshaped isomers of the Al₂₀O₃₀ cluster is observed. The isomers with ammonia molecules in their first coordination sphere become much closer to one another on the energy scale; however, the dodecahedron remains a considerably less favorable intermediate. Original Russian Text ? O.P. Charkin, N.M. Klimenko, D.O. Charkin, 2008, published in Zhurnal Neorganicheskoi Khimii, 2008, Vol. 53, No. 4, pp. 624–635.     

Structural chemistry of Sr3Cr2WO9, Ca3Cr2WO9, and Ba3Cr2WO9

We have studied the preparation and crystallographic structure of three perovskite-type compounds: Sr₃Cr₂WO₉, cubic, the lattice parameter of which is a = 7.812Å; Ca₃Cr₂WO₉, tetragonal, the lattice parameters of which are a = 5.408 Å and c = 7.635Å; and Ba₃Cr₂WO₉, hexagonal, the lattice parameters of which are a = 5.691 Å and c = 13.957Å. We have compared these three structures and shown the relationship between the dimensions of the alkaline-earth metal and the existence of the different structures.