丙烯环氧化反应的高活性钼催化剂

在钼(Ⅵ),钒(Ⅴ)和钛(Ⅳ)等化合物存在下,丙烯与烷基过氧化氢的环氧化反应比传统的氯醇法有很多优点,其中以钼催化剂的性能最优,但目前报道的催化剂在反应过程中因易分解而降低了活性,并且丙烯与烷基过氧化氢的投料比过大(>3:1),丙烯循环次数过多。前文报道了钼烷基醇胺化合物对环已烯的环氧化反应,本文考察了钼烷基醇胺化合物对丙烯与叔丁基过氧化氢环氧化反应的催化性能。     

Ni2（OEt）2／SiO2催化二氧化碳与丙烯直接合成甲基丙烯酸的研究

 采用表面改性法制备了负载型Ni2（OEt）2／SiO2双核金属乙氧基配合物催化剂，利用示差量热、红外光谱和微反技术对催化剂的表面结构、热稳定性、化学吸附性质和催化活性进行了研究．结果表明，负载型双核金属乙氧基配合物Ni2（OEt）2／SiO2中的Ni2＋与载体SiO2表面的O2－以双齿配位形式键合；二氧化碳在催化剂表面存在桥式吸附态和碳酸单乙酯基物种两种吸附态，丙烯则只有一种分子吸附态；在适宜的反应条件下，二氧化碳和丙烯在Ni2（OEt）2／SiO2催化剂上的反应产物主要是甲基丙烯酸．根据实验结果，提出了二氧化碳和丙烯在Ni2（OEt）2／SiO2催化剂表面的反应机理，反应物分子共吸附于催化剂表面同一活性单元上，羧酸根和丙烯解离吸附态的形成是反应顺利进行的关键步骤．     

手性铜催化剂的制备及在环丙烷羧酯酯不对称合成中的应用

３类手性配体ｄ－１０－樟脑磺酸及其衍生物，α－（－）－羟蒎酮及其衍生物，又恶唑啉６衍生物分别与铜（Ⅱ）形成手性铜配合物，催化重氮乙酸酯与１，１－二苯乙烯或异丁烯的环丙烷化加成反应，得到光学活性环丙羧酸酯，不对称诱导最高可达９５％ｅ．ｅ．。     

THE SYNTHESIS OF MODIFIED DIPHENYL OXIDE RESIN

1. INTRODUCTION Poly (diphenyl oxide) (DPO) resins are a series of heat-resisting thermosetting resins. In 1960s, the West House Company applied them to make H class insulting materials and got an extensive use successfully [1]. But due to the three main…     

马来酸酐封端聚碳酸亚丙酯的大分子偶联反应

自从 1 969年井上祥平[1] 发现二氧化碳 (CO2 )可以同环氧化合物直接共聚合成脂肪族聚碳酸酯(APC)以来 ,这一学科领域受到科学家的广泛关注[2～ 8] .这是因为CO2 所产生的温室效应 ,成为使全球变暖的主要因素[9,10 ] .已经确定CO2 使气侯变暖占诸多因素中的 66% .目前大气中CO2 的体积浓度为 345ppmv,由于人类的各类活动每年以 1ppmv的速度递增 .因此 ,降低CO2 排放量已成为全人类共同关注的热点之一 .另一方面 ,CO2 的固定化以及消耗、利用显然是一个应积极鼓励的研究课题 .目前人们已经将CO2 同环氧乙烷 (EO)、环氧丙烷 (PO)、环…     

Heptane-soluble homogeneous zirconocene catalyst: Synthesis of a single diastereomer,polymerization catalysis,and effect of silica supports

Bis(1-indenyl)-di[1′S, 2′R, 5′S)-methoxy]silane ( 1 ) was converted into a mixture of corresponding ansa-diastereomeric zirconocenes. Further purification afforded a single dia-stereomer, di[(1′S, 2′R, 5′S)-methoxy] silylene-bis[η⁵-1(R, R)-(+)-indenyl] dichlorozirconium ( 2 ), which is optically active and hydrocarbon soluble. Extremely rapid ethylene, propylene, and ethylene-hexene polymerizations were observed both in toluene and n-heptane solutions; for instance, at 50°C, activity for ethylene polymerization reaches ～ 1.5×10¹⁰ (g of PE/((mol of Zr) · [C₂H₄] · h). The “bare” zirconocenium ion generated from 2/TIBA/Ph₃CB(C₆F₅)₄ exhibits unusual polymerization behaviors; the polymerization activity increases monotonically with temperature of polymerization (T_p) up to a conventional polymerization condition (50–70°C), and the ¹³C NMR study shows that the isotactic poly-propylene obtained has fairly high [mmmm] methyl pentad distributions at high T_p (?25°C with [mmmm] ～ 0.93–0.75) and a perfect stereoregularity at low T_p (?0°C with [mmmm] > 0.99). The catalyst precursors 2 and Et(Ind)₂ZrCl₂ ( 3 ) supported on silica by different approaches produced poly(olefins) of different molecular weights and stereoregularities, and a methylaluminokane and Ph₃CB(C₆F₅)₄ free silica-supported zirconocene system was found to be activated by triisobutylaluminum. © 1995 John Wiley & Sons, Inc.     

Silver(I) Complexes with Nitrogen-Containing Noncyclic, Macrocyclic, and Macrobicyclic Ligands in Propylene Carbonate

Stability constants and thermodynamic data for complex formation of silver(I) with noncyclic, macrocyclic, and macrobicyclic ligands have been measured in propylene carbonate using potentiometric and calorimetric methods. All ligands containing two nitrogen donor atoms form extremely stable complexes. Only if substituents reduce the basicity of the nitrogen donor atoms, the stability of the complexes decreases drastically. However, the cryptand (221) forms the most stable complex of all ligands examined. In this case, the dimensions of the ligand cavity and of the cation are nearly identical.     

丙烯环氧化反应中TS-1催化剂失活研究

采用丙烯气相进料，在预混段中先与双氧水的甲醇溶液混合后进入固定床反应器，考察了进料液中pH值、丙二醇单甲醚、乙硫醇以及铁锈等对丙烯环氧化连续反应中TS-1分子筛催化剂性能的影响。结果表明，进料液体pH值对催化剂的催化性能有影响，适宜的进料液体pH值在7左右；副产物丙二醇单甲醚含量的增加不会对催化剂性能产生影响；乙硫醇量的增加使环氧丙烷选择性下降，但不会引起催化剂的失活；而进料液体中铁锈的引入会导致催化剂中部分孔堵塞，使催化剂部分失活。当进料液中的pH值用0.1mol/L的氨水调节为7左右，在反应温度55℃,反应压力0.7MPa，TS-1催化剂具有较好的稳定性，经130h的连续试验考察，双氧水的转化率和环氧丙烷的选择性约为90%。     

Analysis of compounds of environmental concern: II. Diphenyl ethers

Nineteen halogenated and/or nitrated diphenyl ethers (currently listed in EPA Method 8111) have been separated on a DB-5/ DB-1701 column pair connected to an inlet splitter and separate electron capture detectors. Retention times are included for 10 additional compounds evaluated for their suitability as internal standards or surrogate compounds for incorporation into Method 8111. Method reproducibility and linearity are discussed, and results are presented for extracts of two real samples spiked with the 19 diphenyl ethers and analyzed using the dual-column dual-detector arrangement.     

Morphology, crystallization behavior and properties of impact-modified polypropylene copolymer with or without sodium benzoate as a nucleating agent

 The morphology, crystallization behavior, and properties of an impact-modified polypropylene (PP) copolymer with or without sodium benzoate were investigated. The contents of ethylene–propylene rubber (EPR) in the reactor-made PP copolymer is about 15 wt%. For comparison, blends of PP and EPR containing the same EPR composition were prepared by melt-mixing. Morphological studies by scanning probe microscopy indicated that the impact-modified copolymer consists of three different phases, i.e., polyethylene, PP, and EPR phases, which is considerably different from the morphology of the conventional PP/EPR blend of the corresponding composition. The impact-modified PP copolymer exhibited a higher crystallization rate in terms of the lower crystallization half-time and thus higher thermal and mechanical properties, such as impact strength and hardness, than the PP/EPR blend did. The addition of sodium benzoate as a nucleating agent to the copolymer increased the crystallization rate and the mechanical properties. Received: 4 June 2001 Accepted: 31 October 2001