助催化剂在Cr催化剂催化乙烯四聚中的作用

主催化剂铬盐与配体、助催化剂组成的三元催化体系能够较高活性的催化乙烯四聚合成1-辛烯。主要研究了助催化剂种类、用量等对催化活性和1-辛烯选择性的影响,采用合适的助催化剂,1-辛烯的选择性达到70.1%,催化活性达到2.62×106 g/(mol Cr)·h。     

乙烯四聚制1-辛烯催化剂研究进展

介绍了传统乙烯齐聚生产1-辛烯工艺,分析了乙烯四聚反应制1-辛烯机理,叙述了乙烯四聚制1-辛烯铬系催化体系中配体、助催化剂和促进剂的国内外最新进展。认为目前研究热点集中在PNP配体上N原子取代和助催化剂及促进剂的筛选等方面,国内急需解决聚乙烯共聚单体1-己烯和1-辛烯的工业化生产问题。     

乙烯选择性四聚制1-辛烯催化剂及工艺技术研究进展

综述了近年来乙烯选择性四聚制1-辛烯技术的发展现状。介绍了乙烯选择性四聚制1-辛烯催化剂研究的最新进展及发展趋势;重点阐述了影响乙烯选择性四聚制1-辛烯催化体系中的两个重要组分,即助催化剂和配体;从技术和经济方面对比了现有技术制1-辛烯的可行性。     

乙烯四聚制1-辛烯的研究

研究了乙烯选择性四聚制1-辛烯的催化剂体系,利用氯化二苯基膦与胺反应生成二苯基膦胺配体,它与乙酰丙酮铬在助催化剂的存在下显示出较高的催化乙烯四聚的活性和较高的1-辛烯选择性;考察了不同溶剂、温度、压力、n(Al)/n(Cr)及第四组分对催化剂体系的影响,确定了适宜的条件,当n(Cr)/n(PNP)/n(Al)为1∶2∶300,反应温度为30℃,压力为3 MPa时,反应时间为30 min,进行乙烯四聚实验,催化剂活性达58.10 kg/(g·h),1-辛烯的选择性接近70%。     

乙烯选择性齐聚取代PNP-Cr催化体系的二维定量构效关系

1-己烯和1-辛烯是制备高性能聚烯烃产品的重要共聚单体,近年来,PNP型铬系乙烯选择性三聚/四聚催化体系成为本领域研究热点。针对实验研究报道的系列氮上取代PNP型铬系催化剂,采用二维定量构效关系（QSPR）方法结合密度泛函理论（DFT）建立了该催化体系1-己烯、1-辛烯选择性的线性回归模型。研究中同时采用了启发式方法和最佳多元线性回归方法,考察了自定义描述符和铬金属活性中心价态（包括一价和二价）对线性回归模型的影响。通过分析发现：基于DFT的自定义描述符的引入能够明显提高模型的相关性和稳定性;基于一价Cr的活性中心模型更适合关联乙烯三聚选择性,二价Cr的活性中心模型更适合关联乙烯四聚选择性;PNP-Cr骨架几何结构尤其是较小的PNP角度是获得较高1-己烯和1-辛烯选择性的关键。最后,根据最佳线性回归模型对新型PNP配体进行了预测,发现了9种新的PNP配体结构可能具有更高的1-辛烯或1-己烯/1-辛烯共选择性,为进一步的实验开发奠定了良好的理论基础。     

带有PNP配体的铬系催化剂在乙烯选择性齐聚中的研究进展

综述了近年来PNP配体铬系催化体系催化乙烯选择性三聚和四聚的最新进展,介绍了PNP配体及其与Cr的配合物的合成方法。列举了P上不同取代基的20种PNP配体结构式,以及N上不同取代基的36种PNP配体结构式,比较了PNP铬配合物的乙烯选择性齐聚催化性能。总结了PNP配体乙烯选择性齐聚催化机理,包括金属环催化机理和双金属催化机理。国内外研究结果表明:PNP配体中P和N上取代基的电子效应和空间位阻是影响其催化性能的主要因素。设计合成新型的配体及催化剂对实现工业化乙烯选择性四聚生产1-辛烯以及实现乙烯选择性齐聚合成其他高碳数α-烯烃至关重要。     

CGC/i-Bu_3Al/Ph_3C~+B(C_6F_5)_4~-催化乙烯均聚及乙烯与1-辛烯共聚行为

研究了限制几何构型催化剂二甲硅基(N-叔丁胺基)(四甲基环戊二烯基)二氯化钛/三异丁基铝(i-Bu_3Al)/硼酸盐[CGC-Ti/i-Bu_3Al/Ph_3C~+B(C_6F_5)_4~-]催化乙烯均聚及乙烯与1-辛烯共聚行为。乙烯均聚结果表明:随着i-Bu3Al用量的增加,聚合活性先升高后降低;在低乙烯浓度时,乙烯均聚相对于乙烯浓度为二级反应。乙烯与1-辛烯共聚结果表明:随着1-辛烯初始浓度升高,聚合活性先升高后平稳;改变1-辛烯的初始浓度可以实现对共聚单体插入率及共聚物热性能的调控;在共聚体系内加入氢气,能够提高且稳定聚合活性,降低聚合物的相对分子质量,使相对分子质量分布变宽。     

石化院两成果获发明专利

<正>日前,中国石油石油化工研究院两项科研成果获得国家发明专利授权。这两项专利成果分别是一种乙烯齐聚的催化剂组合物及其用途、一种聚烯烃类成核剂及其制备和应用。1-辛烯、1-己烯等线性α-烯烃是重要的化工产品和中间体,尽管1-辛烯、1-己烯在化学工业中具有重要的应用价值,但目前还没有乙烯齐聚高选择性合成1-辛烯和1-己烯的技术。传统的乙烯齐聚技术得到的齐聚产物中的1-辛烯和1-己烯含量不高。为此,石化院科研人员开发了一种乙烯齐聚的铬系催化剂体系,通过选用两种配体使1-辛烯和1-己烯的选择性提高,催化剂活性     

乙烯选择性齐聚催化体系的研究进展

综述了近年来乙烯选择性二聚、三聚、四聚等催化体系的最新进展。研究表明:乙烯选择性齐聚催化剂中配体的配位原子上取代基的空间位阻效应和配位原子的电子效应是影响目标产物的选择性和催化活性的主要因素,设计合成新型的配体对提高乙烯选择性催化体系活性和1-辛烯选择性工业化的生产至关重要。     

乙烯四聚催化体系双膦胺配体的结构与性能

简述了乙烯四聚反应制备1-辛烯催化体系的最新研究进展.指出乙烯四聚制1-辛烯催化体系中配体的结构和电子性是影响催化体系的活性和目的产物1-辛烯的选择性的主要因素.PNP配体中N取代基和P取代基的空间位阻和给电子效应都会对催化体系的活性和1-辛烯选择性产生影响.分析了由于取代基空间体积的增大和电负性的增强均使乙烯的进一步...     

Performance of various aluminoxane activators in ethylene tetramerization based on PNP/Cr(III) catalyst system

Ethylene tetramerization with PNP/Cr(III)/aluminoxanes was investigated. By comparing catalytic activity, selectivity to 1-octene and selectivity to methylenecyclopentane in ethylene tetramers, the effects of various aluminoxanes on ethylene tetramerization were discussed. The results showed that MMAO(TMA-depleted), MAO and EAO were all effective cocatalyst for ethylene tetramerization toward 1-octene. PNP/Cr(III)/MMAO catalytic systems afford the highest catalytic activity and the highest selectivity to 1-octene. The selectivities to methylenecyclopentane was decreased by using i-BAO and EAO as cocatalyst, which indicated that different mechanism for ethylene tetramerization has been occurred in such cases.     

N-substituted diphosphinoamines: Toward rational ligand design for the efficient tetramerization of ethylene

Bis(diphenylphosphino)amine (PNP) ligands with different alkyl and cycloalkyl substituents attached to the N atom of the ligand backbone were synthesised and tested together with chromium as ethylene tetramerization catalysts. On activation with a methylaluminoxane-based activator, the catalysts displayed good activity and selectivity toward 1-octene and 1-hexene, with the best ligand systems containing cyclopentyl or cyclohexyl moieties. In addition, it was established that substitution at the 2 position of the cyclohexyl skeleton and, more importantly, an increase in steric bulk at that point, led to a drastic reduction of side product formation (i.e., methyl- and methylenecyclopentane). Interestingly, additional methyl substitution in the 6 position of the cyclohexyl ring changed the selectivity of the catalyst from predominantly tetramerization to a 1:1 mixture of 1-hexene and 1-octene. Structurally similar ligands, such as cyclohexylmethyl and cyclohexylethyl PNP, were also tested and were also found to yield efficient tetramerization catalysts. It was concluded that structural fine tuning of the N-alkyl moiety of the PNP ligand is essential for obtaining efficient tetramerization catalysts, with the best systems achieving combined selectivities as high as 88% (1-octene and 1-hexene) with exceptionally high activities exceeding 2,000,000 g/(g-Cr h).     

串级催化聚合制备线性低密度聚乙烯/聚烯烃热塑性弹性体

通过齐聚催化剂和共聚催化剂的有机结合和相互协同,可实现以乙烯为唯一单体的串级催化聚合,合成乙烯与α-烯烃共聚的线性低密度聚乙烯和聚烯烃热塑性弹性体,但开发高选择性、高共聚能力、适合高温聚合的串级聚合催化体系仍极具挑战。本文围绕不同类型的乙烯齐聚/聚合反应,评述了乙烯二聚、三聚、四聚及聚烯烃大单体合成技术及其相应的串级催化聚合的研究进展。迄今,大部分串级催化聚合是在较低的聚合反应温度下进行的,有限的串级催化体系适合高温聚合;乙烯二聚和三聚串级催化聚合可合成短支链较均一的乙烯与α-烯烃共聚物,但在乙烯四聚串级催化聚合中1-辛烯的选择性亟待提高;此外,通过聚烯烃大单体的串级催化聚合,可为具有特殊链拓扑结构的高性能聚烯烃热塑性弹性体的开发开拓新途径。     

Chromium catalysts supported on mesoporous silica for ethylene tetramerization: Effect of the porous structure of the supports

Supported chromium catalysts were prepared by loading Cr(acac)₃ and N-isopropyl bis(diphenylphosphino)amine (PNP) onto methylaluminoxane-modified MCM-41 and SBA-15. The structure of supported catalysts was characterized and the influence of the pore structure of supports on the reactivity for ethylene tetramerization was investigated. The results revealed that the chromium was immobilized on the mesoporous silica in different supported patterns, which was affected by the pore size of the supports and affected catalyst performance. The highest selectivity toward 1-octene was provided by the SBA-15-supported Cr(acac)₃/PNP catalyst, and this value was higher than that of the homogeneous analogs.     

序列分布导向的CGC催化乙烯与1-辛烯共聚过程建模

限制几何构型催化剂(constrained geometry catalyst,CGC)特别适用于乙烯与α-烯烃溶液聚合法制备高性能聚烯烃弹性体POE(polyolefin elastomer)。基于CGC催化乙烯与1-辛烯共聚反应机理,建立了乙烯与1-辛烯共聚反应动力学模型并确定了动力学参数。采用前期实验获得的乙烯消耗速率曲线与催化剂平均活性验证了动力学模型的准确性。基于动力学模型和面向序列结构的共聚机理,建立了乙烯与1-辛烯共聚过程序列分布模型。模型可准确预测序列分布与短支链含量及其随反应条件的变化趋势。结果表明,随着1-辛烯浓度的增加,乙烯序列长度逐渐减小,其平均序列长度线性降低,而1-辛烯平均序列平均长度呈线性增加的趋势。所建模型可为从聚合过程角度调控POE链结构提供理论参考。     

Synthesis of linear low density polyethylene with a nano-sized silica supported Cp2ZrCl2/MAO catalyst

A nano-sized silica supported Cp₂ZrCl₂/MAO catalyst was used to catalyze the copolymerization of ethylene/1-hexene and ethylene/1-octene to produce linear low-density polyethylene (LLDPE) in a batch reactor. Under identical reaction conditions, the nano-sized catalyst exhibited significantly higher polymerization activity, and produced copolymer with greater molecular weight and smaller polydispersity index than a corresponding micro-sized catalyst, which was ascribed to the much lower internal diffusion resistance of the nano-sized catalyst. Copolymer density decreased with the increase of polymerization temperature, probably due to the decrease of reactivity ratio r ₁ and ethylene solubility with increasing temperature. Polymerization activity of the nano-sized catalyst increased rapidly with increasing comonomer concentration. Ethylene/1-octene exhibited higher polymerization activity and had a stronger comonomer effect than ethylene/1-hexene.     

Homo- and copolymerizations of ethylene and α-olefins in <Emphasis Type="Italic">n</Emphasis>-hexane catalyzed by Ni(ii)-α-diimine catalyst

Ni(II)-α-diimine catalyst [(2,6-i-Pr)₂C₆H₃-DAB(An)]NiBr₂ plus methylaluminoxane was successfully used in the homopolymerization of ethylene, 1-hexene, and 1-octene and the copolymerization of ethylene with 1-hexene and 1-octene in n-hexane. The polymerization of 1-octene was conducted in a controlled manner with a narrow molecular weight distribution (M _w/M _n = 1.2–1.5) and with the weight-average molecular weight increasing linearly with the monomer conversion. The molecular weights, T _g, T _m, branching degree, and density of the obtained (co)polymers were greatly controlled by ethylene pressure and polymerization temperature. Compared with that of ethylene homopolymer, the branching degree of the copolymers prepared by the copolymerization of ethylene with 1-hexene or 1-octene increased, whereas the molecular weight, density, T _m, and catalyst activity decreased. However, compared with those of the homopolymer of 1-hexene or 1-octene, the copolymer density, T _m, and catalyst activity increased, whereas the branching degree declined.