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排序方式: 共有300条查询结果,搜索用时 15 毫秒
1.
Qi Dong 《European Polymer Journal》2007,43(8):3442-3451
Using triethylaluminum (TEA), triisobutylaluminum (TIBA) or TEA/TIBA mixtures of molar ratio 75/25, 50/50 and 25/75 as the cocatalyst, five different ethylene-propylene copolymer samples were synthesized by a MgCl2/SiO2/TiCl4/diester type Ziegler-Natta catalyst in a slurry polymerization process. The synthesized copolymers are strongly heterogeneous in chain structure and were fractionated into part of nearly random copolymer and part of segmented copolymer. Both polymerization activity and copolymer structure were found to be markedly changed when the cocatalyst was changed from TEA to TEA/TIBA mixtures or pure TIBA. As the content of TEA in cocatalyst increases, yield of the random part of product increases and the yield of the crystalline segmented copolymer part decreases. There is also a decrease in ethylene content of the whole product with increasing TEA amount. Copolymerization behaviors of the TEA/TIBA mixture activated catalysis systems are not simple superposition of those activated by pure TEA and TIBA. When a 50/50 TEA/TIBA mixture was used as cocatalyst, the copolymerization activity became the highest, and yields of both the random copolymer part and the segmented copolymer part are close to the highest level. On the other hand, both parts of the copolymer produced with a 50/50 TEA/TIBA mixture are relatively more blocky than the products of TEA or TIBA systems, and difference in ethylene content between the random part and the segmented part was the smallest. The segmented copolymer part of three typical samples was further fractionated by temperature-gradient extraction fractionation into fractions of different ethylene content and sequence distribution. Changing TEA content in the cocatalyst exerted strong influences also on the fraction distribution of the segmented part of copolymer. 相似文献
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探讨了有机金属催化剂的组成及其对二氧化碳同环氧丙烷交替共聚产物结构的影响,发现二乙基锌—助剂体系的催化活性按如次顺序递降:二乙基锌—连苯三酚>二乙基锌—间苯二酚>二乙基锌—对苯二胺>二乙基锌—亚乙基脲。若用三异丁基铝代替二乙基锌同连苯三酚构成催化剂,则失去对二氧化碳同环氧丙烷交替共聚反应的活性同时,著者发现二乙基锌—二元芳胺催化体系与二乙基锌—二元酚催化体系的催化活性规律完全不同。 相似文献
6.
双金属氰化物络合物催化环氧烷烃开环聚合的特征 总被引:9,自引:0,他引:9
合成了Co Zn双金属氰化物 (DMC)络合物催化剂 ,以X 射线衍射、元素分析、红外光谱等手段进行了表征 ,考察了该催化体系下环氧丙烷开环聚合的反应特性 ,并初步探讨了聚合反应的机理 .研究发现 ,Co Zn双金属氰化物催化剂具有很高的催化活性 ,适合于中高分子量聚醚的合成 ,但是碱性起始剂起阻聚作用 ;在该催化体系下聚合物分子量可控 ,不饱和度很低 (<0 .0 14meq g) ,分批加料聚合所得到的聚合物分子量分布较窄 (Mn Mw <1.4 ) ,而一步加料聚合所得到的聚合物分子量分布变宽 ;1 3C NMR分析表明聚合物主链具有无规立构分布的特点 ,且链节分布几乎都为头 尾方式 .聚合过程中活性链与非活性链之间可能存在一个交换反应 ;虽然聚合反应有终止 ,但与聚合物链长没有关系 ,聚合物链的终止是可逆的 . 相似文献
7.
Matthias Deppner 《Journal of organometallic chemistry》2005,690(12):2861-2871
The synthesis is described of symmetric alkylidene bridged dinuclear zirconocene complexes. The influence of structural parameters and different cocatalysts such as methylaluminoxane (MAO), triphenyl tetrakis(pentafluorophenyl)borate- or tris(pentafluorophenyl)borane has been investigated for homogeneous propylene polymerization. The dinuclear catalysts show highest polymerization activities by activation with MAO. Activation with triphenyl tetrakis(pentafluorophenyl)borate results in polypropylenes with the highest degree of isotacticity. Compared to the mononuclear reference catalyst the dinuclear MAO activated complex achieved higher propylene polymerization activity and the polypropylene obtained from the dinuclear complex has a higher molecular weight than that one that was produced with the mononuclear complex. 相似文献
8.
A simple high-performance liquid chromatographic method, using photodiode array detection was developed for the determination
of propylene glycol in human plasma and in the fluid retreived after continuous veno-venous hemofiltration. The method entailed
alkaline derivatization with benzoyl chloride and ethylene glycol as internal standard. The separation of the compounds, after
extraction with pentane, was carried out on a Pursuit C8 column with UV-detection at 230 nm. Validation samples were analyzed
with an accuracy between 95 and 105%, and intra- and inter-day coefficients of variation of less than 8%. The calibration
curve was linear over a concentration range of 5–100 mg L−1 with a detection limit of 1 mg L−1. Blood plasma samples of several patients were analysed by using the prescribed method with propylene glycol concentrations
varying from 5 to 98 mg L−1. Compared to previously described LC methods, this method is ten times more sensitive and thus suitable for use in pharmacokinetic
studies of propylene glycol. 相似文献
9.
本文利用流化床反应器研究了多元复合氧化物PMo_(12)Bi_3Fe_(8-x)Ce_xK_(0.1)O_y(x=0-8)中稀土元素铈对丙烯氨氧化的催化作用,并用x-射线衍射、红外光谱、扫描电镜和热重技术表征了催化剂的结构,发现x=2-3时,丙烯腈的收率最高。催化剂中存在Fe_2(MoO_4)_3,Ce_2(MoO_4)_3、α-Bi_2O_3、3MoO_3。这三种物相的互相溶解和凝结形成固溶体和准均相,使活源。份在各物相表面或界面上均匀分布,由此产生的各活性组份的协调作用是催化活性的主要来性组铈能抑制MoO_3升华,稳定活性相结构。 相似文献
10.
Helmut Bahrmann Klaus Bergrath Han -Jerg Kleiner Peter Lappe Christoph Naumann Dieter Peters Dieter Regnat 《Journal of organometallic chemistry》1996,520(1-2):97-100
BINAS is a new, very efficient ligand for propylene hydroformylation. BINAS is made by the sulfonation of NAPHOS. Different synthetic routes to NAPHOS are discussed. A new two step synthesis starting from 2,2′-bis(bromomethyl)-1,1′-binaphthyl is described. 相似文献