Ziegler-Natta催化剂的功能化及聚烯烃高性能化

介绍了Ziegler-Natta催化剂功能化的几种策略,以及其应用于聚烯烃高性能化的研究进展.Ziegler-Natta催化剂/先进聚合助剂复合策略可有效扩展Ziegler-Natta催化剂性能,其中Ziegler-Natta/ω-烯烃甲基二氯硅烷功能催化剂体系在制备长链支化/高熔体强度聚丙烯方面已显示出工业潜力,而Z...     

2,4-戊二醇二苯甲酸酯的质谱研究

在MgCl2为载体的Ziegler-Natta催化剂中必须加入内给电子体化合物,以提高催化剂的定向能力.内给电子体能够避免研磨过程中MgCl2颗粒的重聚集,具有稳定MgCl2初级晶粒、增大比表面积的作用;更重要的是内给电子体还易于吸附在MgCl2的(110)面上,使活性中心TiCl4不易在(110)面上配位,避免无规中心的形成[1-2].因此内给电子体在Z-N催化剂中起着非常重要的作用,其化学结构和在催化剂中的含量对催化剂及聚丙烯的性能影响很大.     

聚烯烃催化剂载体硅胶研发进展

以Ziegler-Natta催化剂和茂金属催化剂为例,介绍了聚烯烃均相催化剂的负载化技术以及载体选择的影响因素,明确了载体的强度、密度、总孔容、孔分布、孔径、粒度和颗粒形状等物理性质是选择载体要考虑的主要因素。综述了聚烯烃催化剂载体硅胶的结构特征和性能特征,并对聚烯烃催化剂载体硅胶的合成机理、影响因素进行了详细介绍。此类载体硅胶比表面积280~320m2/g、堆密度0.28~0.32g/cm3、孔容1.40~1.70cm3/g、平均孔径18~22nm。建议通过开展对不同性能硅胶(如更小粒径、不同元素改性等)的研究开发,以满足不同催化剂对载体硅胶的特殊要求。     

聚丙烯接枝马来酸酐/SiO_2复合载体型钛催化剂制备及表征

可用于负载烯烃聚合催化剂的材料很多,目前无机载体以SiO2和MgCl2最为普遍.但SiO2和MgCl2容易出现团聚现象,特别是由于SiO2表面羟基分布不均匀,会造成载体局部区域的催化剂浓度过大,活性中心过于集中,对烯烃共聚合时共聚单体的分布不利[1].聚合物载体由于表面的官能团分布均匀及分布密度可调,负载后的催化体系对氧、水的稳定性增加.但聚合物载体制备较为复杂,且用研磨法得到的载体颗粒形态及分布不易控制,用于高温聚合时容易破裂.由于无机和有机载体各自具有某些特殊的优点,可以进行互补克服某些不利的因素,因而怎样利用不同类型载体的复配,得到性能优良的复合载体,已成为烯烃催化剂载体化研究的一个重要方向.本文制备了聚丙烯接枝马来酸酐(PMA)/SiO2复合载体,制备了负载化TiCl4烯烃聚合催化剂,其既可以避免由纯无机物为载体而引入过多的无机灰分,又可以避免仅用聚合物为载体而造成的负载率低的缺点,同时保持了无机载体的刚性和聚合物载体官能团的多分布性.     

新型Ti-Co复合负载化催化剂制备支化聚乙烯

以反应法制备了TiCl4、乙酰丙酮改性的TiCl4和Co(acac) 2 为主催化剂 ,SiO2 MgCl2 为载体的复合负载型催化剂 (TiCl4 CH3COCH2 COCH3 Co(acac) 2 SiO2 MgCl2 ) ,以烷基铝作为助催化剂 ,以单一乙烯单体制备了支化聚乙烯 .研究了复合催化剂的组成、烷基铝种类和聚合反应温度等对聚合反应和产物结构性能的影响 .探讨了聚合反应机理 .聚合产物经IR、1 3 C NMR谱分析 ,结果表明Ti Co复合催化剂具有低聚原位共聚功能 ,可制得含有丁基、戊基、己基等各类支链结构的支化聚乙烯 .     

一种复合载体丙烯聚合催化剂的研究

采用SiO2-MgCl2复合载体制备了一种丙烯聚合催化剂,考察了SiO2活化条件、SiO2和MgCl2质量比和催化剂的不同制备工艺对催化剂性能的影响,通过对催化剂的氢调和聚合时间的试验,发现该催化剂用于催化丙烯聚合时,无需加入外给电子化合物就可以使树脂达到较高的等规指数。     

用于丙烯聚合的MgCl2负载Ziegler-Natta催化剂研究进展

综述了用于丙烯聚合的MgCl2负载Ziegler-Natta催化剂研究进展,包括内给电子体的发展及其作用研究,催化剂活性中心的模型,用MgCl2负载的Z-N催化剂制备抗冲聚丙烯合金.     

三乙基铝调控的Ziegler-Natta/茂金属复合催化剂制备聚丙烯催化合金

基于具有"反应器颗粒技术(RGT)"特征的Ziegler-Natta/茂金属复合催化剂(MgCl2/TiCl4/racEt(Ind)2ZrCl2),以三乙基铝(AlEt3,TEA)和烷基铝氧烷(MAO)分别作为Ti和Zr 2种催化剂组分的助催化剂,利用TEA对茂金属Zr中心在丙烯均聚反应中的阻聚作用,以及乙烯对"失活"中心的活性复原,实现了复合催化剂中茂金属Zr中心在聚丙烯催化合金(丙烯均聚+乙烯/丙烯共聚)过程中的"可逆失活".基于这种方法,以MgCl2/TiCl4/rac-Et(Ind)2ZrCl2为催化剂,TEA/MAO为助催化剂,通过一步法(催化剂和助催化剂一次加入)制备了新型聚丙烯催化合金,聚丙烯基体(PP)选择性地由Ti金属中心生成,而乙丙共聚物(EPR)则有相当大的比例由茂金属Zr中心生成.与完全由Ziegler-Natta催化剂所产生的聚丙烯催化合金相比,新型合金中的EPR共聚序列结构更加无规,同时EPR保持在PP基体中均匀分散.     

(二苯甲酰甲烷基)(环戊二烯基)二氯化钛/MgCl2-SiO2/MAO中各组分对乙烯聚合的影响

研究开发了一种新型非茂负载乙烯聚合催化剂 CpTi(dbm)Cl2 MgCl2 SiO2 MAO ,并考察了该催化剂中各组分对乙烯聚合活性的影响 .结果表明 ,SiO2 不仅可以改善催化剂的流动性和分散性 ,还有益于提高催化活性 .MgCl2 对活性中心有一定化学改性作用 ;MgCl2 、SiO2 和CpTi(dbm)Cl2 的比例的变化对载体型催化剂的催化活性有一定影响作用 ;采用适量的MAO对复合载体MgCl2 SiO2 活化 ,能提高催化活性 .用ZnCl2 MAO对SiO2处理制成的复合载体催化剂CpTi(dbm)Cl2 MgCl2 ZnCl2 SiO2 MAO ,可以提高催化活性 ,“锌调”作用明显 ,随着锌化合物含量的增加 ,聚合物相对分子质量下降 ,相对分子质量分布加宽 ,并且其催化活性也增加 .     

原位聚合法制备超疏水的聚乙烯纳米复合材料

采用一种新方法将Ziegler-Natta催化剂组分TiCl4和MgCl2负载到蒙脱土(MMT)的层间,制备了TiCl4/MgCl2/MMT插层型催化剂.利用Ziegler-Natta催化剂特有的"形态复制效应",通过乙烯原位聚合制备出了表面具有花瓣状形态的聚乙烯纳米复合材料.这种聚乙烯纳米复合材料的表面与水的接触角达到(152.2±0.8)°,呈现超疏水性质.     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.     

Copper catalyzed/mediated synthetic methodology for ebselen and related isoselenazolones

Scope of the copper catalyzed/mediated selenium-nitrogen coupling reaction has been studied for the synthesis of isoselenazolones. It is noticed that the 2-chloro, 2-bromo-, and 2-iodo-aryl amides substrates can be exploited in the selenium-nitrogen coupling reaction by employing 25-100 mol % of CuI/1,10-phenanthroline (L) and potassium carbonate as a base in DMF. Furthermore, electron rich 2-chloro-arylamides also underwent selenium-nitrogen coupling reaction to give biologically important selenium-nitrogen heterocycles. Also, copper-catalyzed selenium-nitrogen coupling reaction has been meticulously applied for the synthesis of diaryl diselenides having methoxy, amine, and amide functionality from respective aryl iodides in the presence of stoichiometric amount of succinimide as an external Se-N coupling partner.     

Knoevenagel condensation catalyzed by novel Nmm-based ionic liquids in water

A series of novel N-methyl morpholine (Nmm) based ionic liquids with 1,2-propanediol group were synthesized and used as catalysts for Knoevenagel condensation at room temperature in water. Under the effect of the catalyst, various aldehydes or aliphatic ketones could react with a wide range of activated methylene compounds well, including malononitrile, alkyl cyanoacetate, cyanoacetamide, β-diketone, barbituric acid, 2-arylacetonitrile and thiazolidinedione. Furthermore, most of the products could be separated just by filtrating and washing with water. Additionally, the catalyst is recyclable and applicable for the large-scale synthesis.     

Construction of polyheterocyclic spirotetrahydrothiophene derivatives via sulfa-Michael/aldol cascade reaction

A series of polyheterocyclic spirotetrahydrothiophene derivatives were obtained in moderate to excellent yields via a catalyst-free sulfa-Michael/aldol cascade reaction of chalcones 1 and commercially available 1,4-dithiane-2,5-diol 2 under mild conditions. We also present the first asymmetric sulfa-Michael/aldol cascade reaction of chalcones 1 and commercially available 1,4-dithiane-2,5-diol 2 with moderate to good enantioselectivities catalyzed by readily available chiral phase-transfer catalysts (PTCs).     

Suzuki-Miyaura reactions of the soluble guanylate cyclase inhibitor NS2028: a non-product specific route to C-8 substituted analogues

Both soluble guanylate cyclase (sGC) inhibitors ODQ 1 and NS2028 2 are synthesized via improved protocols. In the former case treating 3,4-dihydroquinoxalin-2(1H)-one oxime 8, which can be prepared in two steps from 1,2-benzenediamine, with 1,1′-carbonyldiimidazole (CDI) gives the dihydro-ODQ 10 that in the presence of KMnO₄ oxidises to give ODQ 1 in an overall yield of 46% starting from 1,2-benzenediamine. In the latter case, the synthesis affords NS2028 2 from 2-amino-4-bromophenol 3 in three steps with an overall yield of 85% and avoids the need for chromatography. Furthermore, Suzuki-Miyaura reaction conditions are described that enable the preparation of 8-aryl and 8-heteroaryl derivatives of NS2028 directly from NS2028 2. Finally, demethylation of the 8-(methoxyphenyl) substituted analogues afforded the 8-(hydroxyphenyl) derivatives 40-42. All new products are fully characterised.