Mechanistic Studies of Ethylene and α-Olefin Co-Oligomerization Catalyzed by Chromium–PNP Complexes
作者:Loi H. Do、Jay A. Labinger、John E. Bercaw
DOI:10.1021/om300492r
日期:2012.7.23
chromatographic and massspectrometric analyses, strongly support a mechanism that involves five- and seven-membered metallacyclic intermediates comprised of ethylene and LAO units. Using 1-heptene as a mechanistic probe, it was established that 1-hexene formation from ethylene is competitive with formation of ethylene/LAO cotrimers and that cotrimers derived from one ethylene and two LAO molecules
为了探索从乙烯作为化学原料生产窄分布的中长链烃的可能性,使用先前报道的铬络合物 [CrCl 3 (PNP OMe )]( 1,其中 PNP OMe = N,N-双(双(邻-甲氧基苯基)膦基)甲胺)。在乙烯和 1-己烯存在下,通过用改性甲基铝氧烷 (MMAO) 处理活化1,主要提供 C 6和 C 10烯烃产物。C 10的身份通过详细的气相色谱和质谱分析指定的异构体强烈支持涉及由乙烯和 LAO 单元组成的五元和七元金属环中间体的机制。使用 1-庚烯作为机制探针,确定由乙烯形成的 1-己烯与乙烯/LAO 共三聚体的形成具有竞争性,并且还生成了衍生自一个乙烯和两个 LAO 分子的共三聚体。Complex 1/ MMAO 也能够将 1-己烯转化为 C 12二聚体和 C 18三聚体,尽管效率很低。讨论了这些研究的机械意义,并与之前的烯烃共三聚报道进行了比较。
Elongation and branching of α-olefins by two ethylene molecules
作者:Thomas Dietel、Fabian Lukas、Winfried P. Kretschmer、Rhett Kempe
DOI:10.1126/science.abm5281
日期:2022.3.4
α-Olefins are important starting materials for the production of plastics, pharmaceuticals, and fine and bulk chemicals. However, the selective synthesis of α-olefins from ethylene, a highly abundant and inexpensive feedstock, is restricted, and thus a broadly applicable selective α-olefin synthesis using ethylene is highly desirable. Here, we report the catalytic reaction of an α-olefin with two ethylene
Cr catalyst based on a PCCP ligand shows high activity in ethylene oligomerization, giving 1-hexene and considerable C10 fraction. DFT calculation results are consistent with the experimental observations on the distribution of C10 isomers.
Elongation and branching of α-olefins by ethylene employing an easily accessible Zr catalyst
作者:Christian Heber、Thomas Dietel、Isabelle Haas、Winfried P. Kretschmer、Rhett Kempe
DOI:10.1016/j.jcat.2024.115503
日期:2024.6
Selective co-oligomerizations between α-olefins and ethylene are of high interest since they allow to extend the α-olefin scope employing inexpensive and abundantly available ethylene. Here we report on an easily accessible zirconium catalyst that permits the co-oligomerization of 1-hexene and ethylene with an activity of 2200 kg/mol h bar and a co-oligomer selectivity of 65 mol%. In more detail, we
α-烯烃和乙烯之间的选择性共低聚化反应非常受关注,因为它们允许使用廉价且可用的乙烯来扩展α-烯烃的范围。在这里,我们报道了一种易于接近的锆催化剂,它允许 1-己烯和乙烯的共低聚化,活性为 2200 kg/mol h bar,共低聚物选择性为 65 mol%。更详细地,我们报告了六种新型 Zr 预催化剂的合成和结构、它们的乙烯均聚化行为以及六种预催化剂中最有前途的共低聚化。标准是活性和选择性 (α 值)。这里介绍的一些 Zr 催化剂系统在乙烯均聚化中显示出极高的活性,最高可达 96,600 kg/mol h bar。
Decene formation in ethylene trimerization reaction catalyzed by Cr–pyrrole system
作者:Timur M. Zilbershtein、Vladislav A. Kardash、Vladlena V. Suvorova、Anatoly K. Golovko
DOI:10.1016/j.apcata.2014.01.051
日期:2014.4
Decene formation in the ethylene trimerization reaction was studied using a chromium(III) 2-ethylhexanoate/2,5-dimethylpyrrole/triethylaluminum/diethylaluminum chloride catalyst system. Kinetic investigations revealed that some decene formation reactions did not depend on 1-hexene concentration, because 1-hexene and catalyst may react with ethylene before dissociation of 1-hexene-catalyst complex after 1-hexene formation. The results demonstrated that decene formation is an intrinsic part of the trimerization reaction mechanism. It was also shown that a stepwise elimination mechanism for the decomposition of the chromacycloheptane intermediate cannot explain the observed product distribution. The dependencies found allow selection of appropriate conditions for low or high decene formation in the ethylene trimerization reaction. (C) 2014 Elsevier B.V. All rights reserved.