MoCl_4-(i-Bu)_2AlOAr体系引发丁二烯聚合的研究

由MoCl_4为主催化剂,(i-Bu)_3Al与酚类反应的产物(i-Bu)_2AlOAr为助催化剂所组成的催化体系,在加氢汽油中引发丁二烯聚合,研究酚类结构对聚合反应的影响。结果表明,带有推电子基团的酚类,可以提高丁二烯岵,聚合速度,其顺序为双酚A>间甲酚间>β-萘酚>苯酚>对氯酚。测定了丁二烯聚合的表现活化能E_α,催化剂利用率α,活性中心浓度[P~*],和活性中心的平均寿期(?)。     

稀土-其它过渡金属混合催化剂用于共轭双烯烃的聚合——Ⅳ.(NdCl3+FeCl3)·nphen-HAI(i-Bu)2体系对异戊二烯的聚合

 本文报道由(NdCl₃+FeCl₃)·nphen-HAl(i-Bu)₂催化体系引发异戊二烯聚合的结果。在适当Nd/Pe比下,该体系对异戊二烯聚合的活性可超过单一钕或铁催化剂的活性,同时随催化剂中钕和铁含量的不同,所得产物的微观结构变化很大,当体系中钕含量由100％→0时,产物的顺-1,4结构含量由94.4％→22.1％,而3,4结构含量由5.6％→77.9％。Al/M(N=Nd+Fe)比、单体浓度和聚合温度不仅对聚合活性有影响,对产物的微观结构影响也较大。事实表明,该聚合体系中存在着两种过渡金属(Nd和Fe)活性中心,它们按各自的机理进行异戊二烯的聚合。     

改型镍体系催化丁二烯顺1,4-聚合活性中心价态的研究

 改型镍系Ni(naph)₂-Al(i-Bu)₂OC₈H₁₇-BF₃·OEt₂的电子顺磁共振谱指出,活性中心主要由Ni(Ⅰ)组成,预混丁二烯能稳定Ni(Ⅰ)和缩短聚合反应的诱导期,但不改变聚合反应的表观活化能。     

CrOx/SiO2催化剂上丙烷在CO2气氛中脱氢反应的研究

采用XRD、UV-vis DRS、ESR和微分吸附量热等技术,考察了铬担载量分别为2.5、5和10wt%的CrO_x/SiO₂催化剂的结构、表面性质和氧化还原性能。结果表明,催化剂表面上存在多种Cr的氧化态和聚集形式。随着Cr担载量从2.5wt%到10wt%的逐渐增大,催化剂表面占主导地位的Cr物种由CrO₃单体转为多聚CrO₃和Cr₂O₃晶相。在CO₂气氛中催化剂对丙烷转化率和丙烯选择性的大小顺序为2.5wt%CrO_x/SiO₂>5wt%CrO_x/SiO₂>10wt%CrO_x/SiO₂,反应过程中的原位ESR和UV-visDRS测定结果表明,催化剂表面的反应活性中心为Cr⁵⁺,Cr⁵⁺可由催化剂预处理过程中Cr³⁺的氧化及丙烷反应过程中CrO₃单体的还原产生,在反应中CO₂可使Cr³⁺重新氧化为Cr⁵⁺.     

α-Ti(HPO4)2微球负载型催化剂的合成及其烯烃聚合催化性能

2种茂金属催化剂及1种后过渡金属催化剂分别被固载于经过甲基铝氧烷处理后的α-Ti（HPO₄）₂微球表面,制备得到3种微球负载型催化剂。在烯烃聚合反应过程中,3种负载型催化剂均表现出比硅胶负载型催化剂更高的催化活性。2种茂金属负载型催化剂在乙烯、丙烯聚合反应中的活性分别高达6.8×10⁷ g_PE·（mol_Zr·h）^-1和5.0×10⁷ g_PP·（mol_Zr·h）^-1,所产生的烯烃聚合产物分子量分布较窄（M_w/M_n<2.3）,表现出良好的单中心催化特性,而且丙烯聚合产物的等规度高达96.5%。负载型后过渡金属催化剂在乙烯聚合反应中的活性稍低,但也能够达到8.3×10⁶ g_PE·（mol_Fe·h）^-1。3种负载型催化剂催化烯烃聚合产物均成微球型,能够很好地复制载体的形貌。     

α-Ti(HPO4)2微球负载型催化剂的合成及其烯烃聚合催化性能

2种茂金属催化剂及1种后过渡金属催化剂分别被固载于经过甲基铝氧烷处理后的α-Ti（HPO₄）₂微球表面,制备得到3种微球负载型催化剂。在烯烃聚合反应过程中,3种负载型催化剂均表现出比硅胶负载型催化剂更高的催化活性。2种茂金属负载型催化剂在乙烯、丙烯聚合反应中的活性分别高达6.8×10⁷ g_PE·（mol_Zr·h）^-1和5.0×10⁷ g_PP·（mol_Zr·h）^-1,所产生的烯烃聚合产物分子量分布较窄（M_w/M_n<2.3）,表现出良好的单中心催化特性,而且丙烯聚合产物的等规度高达96.5%。负载型后过渡金属催化剂在乙烯聚合反应中的活性稍低,但也能够达到8.3×10⁶ g_PE·（mol_Fe·h）^-1。3种负载型催化剂催化烯烃聚合产物均成微球型,能够很好地复制载体的形貌。     

钼体系催化丁二烯聚合动力学——聚合速度及有关动力学参数的测定

本文研究了MoCl_4OC_8H_(17)-(i-Bu)_2AlO-体系催化丁二烯聚合动力学,考察了影响聚合速度的各种因素,测定了催化剂利用率,活性中心浓度和平均寿命等动力学参数。聚合速度对单体浓度和主催化剂浓度均呈一级关系,表现活化能为17.1千卡/摩尔,催化剂利用率约为4％;活性中心平均寿命与温度和活化能的函数关系可表示为 ?=e~(E_a/RT?/Z_p[Bd]     

用均相的稀土催化剂进行丁二烯-异戊二烯本体共聚合的研究

 本工作用均相的稀土催化体系Nd(naph)₃-Al(i-Bu)₂H-CH₃SiHCl₂进行了丁二烯和异成二烯的本体共聚合,研究了聚合规律和产物的结构性能.结果表明,在适当的催化剂组分比条件下,该催化体系具有较高的催化活性,用DSC测定了共聚物的玻璃化转变温度,¹H-NMR和IR分别测定了共聚物的组成和微观结构,证明共聚物的组成主要决定于单体原料的配料比,共聚物中两种单体单元都具有高顺式结构,生胶和硫化胶的性能测定表明,在丁二烯和异戊二烯两种单体的配料比为30比70时,得到的共聚胶的综合性能较好.     

无溶剂一锅法Al(ClO4)3催化合成α-氨基膦酸酯

以无水高氯酸铝为催化剂, 将芳香醛、芳香胺及亚磷酸酯在无溶剂条件下一锅法反应, 高效地合成了α-氨基膦酸酯, 该催化剂优于其它已发现的催化剂[如Mg(ClO₄)₂, BiCl₃, AlCl₃等], 建立了一种适用于含有钝化基团的芳香胺的α-氨基膦酸酯的新合成方法.     

PdCl2-CuCl2/Al2O3催化剂低温催化CO氧化的失活机理

采用X射线衍射、N₂吸-脱附、X射线光电子能谱分析、氢气-程序升温还原和原位红外漫反射等方法对新鲜和失活的PdCl₂-CuCl₂/Al₂O₃低温催化CO氧化催化剂进行表征,研究了高相对湿度(100%)下催化剂的失活机理.结果表明,催化剂表面沉积的水使得活性铜物种容易从催化剂表面向载体孔道内部迁移,由于Pd、Cu相互作用弱化从而减弱了Pd与Cu物种间的相互作用,使得催化剂的氧化还原性能受到影响,抑制了Pd⁰再氧化为Pd²⁺的过程,从而因CO氧化反应中催化剂氧化还原循环受阻而导致失活.     

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.     

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.     

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.