苯乙烯连续搅拌釜式本体聚合工业过程模拟

采用了机理分析建模法对苯乙烯工业本体预聚过程进行了模型化研究，并通过对流体在反应器中混合模式的分析，表明预聚釜可视作全混流（CSRT）反应器模型，此外对热聚合机理中的引发级数和终止反应进行了考察，利用预聚釜的工业数据确立了三分子引发，同时考虑偶合和歧化终止以及向溶剂链转移的反应机理模型，并选取了合适的动力学参数，然后利用工业装置采集的数据进行了模拟，从宏观转化率，平均分子量和微观分子量分布两个方面对模型进行了验证，模拟结果和工业数据符合得较好，该模型方程不仅能模拟稳态，非稳态预聚过程，同时也为装置开发新产品，改造扩建，优化操作方案等提供了理论基础。     

钼系催化苯乙烯配位聚合

氧配体2,2'-亚甲基双-(4-甲基-6-叔丁基苯酚)(抗氧剂2246,简称O)与Mo Cl5(简称Mo)组成的络合物能够和Al(i-Bu)2OPh CH3(简称Al)组成的二元催化体系催化苯乙烯配位聚合,可制得高转化率的高分子量聚苯乙烯。在O/Mo(摩尔比,下同)为4,Al/Mo为10,Mo/St为4×10-4,80℃下本体聚合9 h的条件下,单体转化率可达到80%。本体聚合所得聚苯乙烯的重均分子量可高达36.5万,分子量分布较窄(Mw/Mn=2.06),红外光谱检测所得的聚苯乙烯均为无规结构。     

Aminolysis of Styrene Oxide Over Heterogeneous Acidic Catalysts

Silica alumina and silica zirconia mixed oxides are shown to be effective and regioselective catalysts for the aminolysis of styrene oxide under very mild experimental conditions, giving the corresponding primary ??-amino-alcohol in good to excellent yield.     

Graft Polymerization of Styrene from Single-Walled Carbon Nanotube using Atom Transfer Radical Polymerization

Summary We grafted polystyrene from the surface of single-walled carbon nanotube (SWNT) via Atom Transfer Radical Polymerization (ATRP). Direct electrophilic addition of chloroform and subsequent hydrolysis introduced hydroxyl groups to the surface of SWNT. ATRP initiators were attached to the SWNT by esterification of 2-chrolopropyl chloride with hydroxyl groups. Subsequent polymerization of styrene with CuCl / N,N,N’,N’,N”-pentamethyldiethylenetriamine catalyst yielded polystyrene grafted SWNT. Transmission electron microscopy analysis clearly showed that approximately 6 nm-thick polystyrene layer was uniformly formed on 1.2 nm diameter SWNT.     

茂钛催化剂合成及苯乙烯间规聚合

介绍了茂钛催化剂ＣｐＴｉ（ＯＰｈ）３（Ｃｐ为环戊二烯基）的合成。使用ＣｐＴｉ（ＯＰｈ）３／ＭＡＯ均相催化体系,研究了工艺条件对苯乙烯间规聚合的影响。初步探讨了以带有反应性功能基团的聚苯乙烯为载体,负载ＣｐＴｉＣｌ３后进行的苯乙烯间规聚合。同时采用了不同配体的ＣｐＴｉ（ＯＲ）３催化剂用于苯乙与乙烯或丙烯共聚合,得到的共聚产物是一类应用前景良好的工程塑料。     

Melamine-Formaldehyde-Supported Titanium-Based Heterogeneous Ziegler-Natta Catalyst for Ethylene Polymerization in Slurry Process

Ethylene was polymerized at 40°C temperature and 1 atm. pressure using melamine-formaldehyde (M-F) supported titanium tetrachloride (TiCl₄) catalyst. Polymer-supported catalysts were prepared with a different weight ratio of TiCl₄/ M-F in hexane. The wt% titanium incorporated in the polymer matrix was determined by UV-visible spectroscopy. In addition, the resulting catalysts were characterized by SEM-EDX, XRD, and TGA. The catalytic productivity is found to be 4721.09 g PE/g Ti/h. The productivity of the catalysts also depends on the titanium content in the polymer matrix. The catalyst with titanium content 3.5 wt% showed maximum activity. These catalysts also showed good storability.     

Zeolite MCM-22 Supported Heterogeneous Chromium Catalyst for Ethylene Polymerization

The chromium alkyl complex Cp*Cr(py)Me₂ (Cp* = ⁵-pentamethylcyclopentadienyl, py = pyridine, Me = methyl) has been affixed to the surface of zeolite MCM-22 via methane elimination. The resulting composite material has been characterized by a variety of physical methods. The results are consistent with the presence of isolated organometallic fragments linked to the solid support by a covalent chromium–oxygen bond. Activation of this material with methylaluminoxane (MAO) yielded a highly active catalyst for the polymerization of ethylene. The polyethylene thus formed featured high molecular weights (M_w 4 × 10⁶) and narrow molecular weight distributions (M_w/M_n 3.5).     

稀土催化苯乙烯本体聚合机理与动力学

The bulk polymerization of styrene catalyzed by Nd(P204)3/MgBu2/HMPA (hexamethyl phospho-ramide) was carried out in capped glass tubes. The effects of reaction conditions on polymerization conversion and molecular weight in the range of high conversion were investigated. The molecular weight of the resultant polymers is dramatically high and its distribution is relatively narrow. The polymerization process demonstrates the feature of living polymerization and auto-acceleration phenomenon. The auto-acceleration phenomenon is attributed to the non-instantaneous formation of the active species. The experimental data suggest that chain transfer to MgBu2 is one of the factors governing the molecular weight development. A mechanism of polymerization is presented with the chain transfer process incorporated.     

苯乙烯分散聚合反应

苯乙烯在乙醇／水混合溶液介质中,在偶氮二异丁腈引发作用下,以聚乙烯基吡咯烷酮为稳定剂进行分散聚合反应,采用溴加成双键分析方法研究了苯乙烯分散聚合反应过程中单体转化率的变化,并讨论了引发剂浓度和反应温度对单体转化率的影响。     

苯乙烯间规空间定向聚合

综述国外近年来苯乙烯间规定向聚合的进展,包括高活性催化剂和聚合规律的研究;介绍间规聚苯乙烯(s-PS)主要特性、应用和结构表征情况。     

Enantioselective Hydrogenation in Water Over Chiral Modified Heterogeneous Catalyst Admixed With Organic Solvent

Hydrogenation of α,β-unsaturated acid over cinchonidine-modified Pd/C results in poor enantioselectivity in water, but the selectivity becomes much higher when Pd/C is admixed with a small amount of a hydrophobic water-insoluble organic solvent. With the admixed catalyst, the product is easily removed by separation of the aqueous phase under the hydrogen atmosphere and the remaining catalyst can be reused.     

Selective Hydrogenation of Benzene to Cyclohexene Over Colloidal Ruthenium Catalyst Stabilized by Silica

A colloidal ruthenium catalyst stabilized by silica was prepared through microemulsion processing. Ruthenium colloids with particle size about 4 nm are highly dispersed in silica. The selective hydrogenation of benzene to cyclohexene was studied over the catalyst. Much higher activity and selectivity was obtained compared with its supported counterparts.     

Hydrogenation of l-Arabinose and d-Galactose Mixtures Over a Heterogeneous Ru/C Catalyst

Complete hydrogenation of d-galactose and l-arabinose mixtures on a Ru/C catalyst was achieved with excellent selectivities exceeding 95?%. No unexpected effects of temperature and pressure were observed. A detailed kinetic model was derived to describe the simultaneous hydrogenation of the monomeric sugars.     

Au/Pt Bimetallic Nanoparticle Decorated Microparticle Hybrid Catalyst System for Heterogeneous Hydrogenation of Styrene

Catalysis Letters - Poly(methacryloyloxy quinoline) microparticles were synthesized and used as reducing and stabilizing agents to prepare Au/Pt bimetallic nanoparticle (NP) decorated microparticle...     

Influence of Ni Catalyst Layer and TiN Diffusion Barrier on Carbon Nanotube Growth Rate

Dense, vertically aligned multiwall carbon nanotubes were synthesized on TiN electrode layers for infrared sensing applications. Microwave plasma-enhanced chemical vapor deposition and Ni catalyst were used for the nanotubes synthesis. The resultant nanotubes were characterized by SEM, AFM, and TEM. Since the length of the nanotubes influences sensor characteristics, we study in details the effects of changing Ni and TiN thickness on the physical properties of the nanotubes. In this paper, we report the observation of a threshold Ni thickness of about 4 nm, when the average CNT growth rate switches from an increasing to a decreasing function of increasing Ni thickness, for a process temperature of 700°C. This behavior is likely related to a transition in the growth mode from a predominantly “base growth” to that of a “tip growth.” For Ni layer greater than 9 nm the growth rate, as well as the CNT diameter, variations become insignificant. We have also observed that a TiN barrier layer appears to favor the growth of thinner CNTs compared to a SiO₂ layer.     

无外加表面活性剂的苯乙烯悬浮聚合

针对传统悬浮聚合制备聚苯乙烯颗粒粒径分布宽、有效粒子收率低的问题,采用过硫酸铵/磷酸钙复合分散剂体系,在无外加表面活性剂情况进行苯乙烯悬浮聚合,制备了聚苯乙烯珠粒。通过对聚合稳定性、聚苯乙烯珠粒粒径及分布的测定与分析,考察了磷酸钙、过硫酸铵的用量及比例对悬浮聚合的影响,并分析了过硫酸胺对悬浮聚合的分散稳定机理。结果表明,当过硫酸铵和磷酸钙的用量分别为单体质量的0.01%和1.00%时,悬浮聚合体系稳定,得到的粒子透明性好,平均粒径为1.35 mm,粒径分布窄;通过改变过硫酸铵和磷酸钙的用量,可以调节聚苯乙烯珠粒的平均粒径。     

间规聚苯乙烯的合成与工业化研究

本文评述了间规聚苯乙烯（ｓＰＳ）的联合机理与工业化研究,介绍了茂金属催化剂和聚合反应器。强调要实现ｓＰＳ的工业化,尚需加强以聚合反应工艺和反应器开发为目标的聚合反应工程研究。     

Catalytic Etherification of Glycerol to Diglycerol Over Heterogeneous Calcium-Based Mixed-Oxide Catalyst: Reusability and Stability

The activities of different heterogeneous alkaline-earth metal oxide catalysts and mixed-metal oxide catalysts were investigated. Glycerol etherification was carried out at 250°C in a three-necked glass reactor vessel at atmospheric pressure. In a typical experiment, 50 g of anhydrous glycerol was loaded into the reactor. Then, 2 wt.% of catalyst was added to the reactor. The reactor was then heated to the appropriate reaction temperature in nitrogen atmosphere under continuous stirring. The heterogeneous CaO catalyst showed the highest catalytic conversion (72%) compared with other alkaline-earth metal oxides, with a diglycerol yield of 19%. The highest glycerol conversion of 96% and diglycerol yield of 52% were observed for the mixed-metal oxide catalyst (Ca_1.6Al_0.4La_0.6O₃). Reusability and stability of this catalyst were tested. The ICP-AES analysis was performed to confirm the leaching of the metal species in the liquid phase of the reaction mixture.     

Multi-Directional Growth of Aligned Carbon Nanotubes Over Catalyst Film Prepared by Atomic Layer Deposition

The structure of vertically aligned carbon nanotubes (CNTs) severely depends on the properties of pre-prepared catalyst films. Aiming for the preparation of precisely controlled catalyst film, atomic layer deposition (ALD) was employed to deposit uniform Fe₂O₃ film for the growth of CNT arrays on planar substrate surfaces as well as the curved ones. Iron acetylacetonate and ozone were introduced into the reactor alternately as precursors to realize the formation of catalyst films. By varying the deposition cycles, uniform and smooth Fe₂O₃ catalyst films with different thicknesses were obtained on Si/SiO₂ substrate, which supported the growth of highly oriented few-walled CNT arrays. Utilizing the advantage of ALD process in coating non-planar surfaces, uniform catalyst films can also be successfully deposited onto quartz fibers. Aligned few-walled CNTs can be grafted on the quartz fibers, and they self-organized into a leaf-shaped structure due to the curved surface morphology. The growth of aligned CNTs on non-planar surfaces holds promise in constructing hierarchical CNT architectures in future.