膦胺铬和双膦铬催化乙烯选择性齐聚研究进展

乙烯选择性齐聚制备线性α-烯烃是在学术界和工业界均受到高度重视,具有目标产物选择性高、产品易分离和经济效益显著等特点。铬系配合物催化剂在催化乙烯选择性齐聚反应中综合性能较好,有良好的发展和应用前景。近年来的研究表明,配体结构对催化剂性能有重要影响;反应体系中通入H 2可以改善齐聚产物的分布并抑制低聚物的生成;开发不以甲基铝氧烷为助催化剂的催化体系可降低催化剂成本;而乙烯选择齐聚机理及金属中心氧化态对催化剂的设计有重要的指导意义。本文主要从以上几个方面介绍了膦胺铬和双膦铬配合物在催化乙烯选择性齐聚中的研究进展,分析了目前乙烯选择性四聚工业化急需解决的问题,展望了该领域未来的发展方向。     

用于乙烯齐聚高选择性制 1-辛烯反应的Cr(Ⅲ)基催化剂体系

将四元催化剂体系(乙酰丙酮铬-膦胺型配体-助催化剂甲基铝氧烷-促进剂六氯乙烷)用于乙烯齐聚制1-辛烯反应,考察了促进剂、助催化剂、Al/Cr摩尔比、反应温度和反应压力等对催化剂的活性和1-辛烯的选择性的影响.结果表明,该四元催化剂体系比三元催化剂体系(铬化合物-膦胺型配体-甲基铝氧烷)对乙烯齐聚反应具有更高的1-辛烯选择性.产物除有1-辛烯外,还有较大量的1-己烯、甲基环戊烷和亚甲基环戊烷.甲基铝氧烷是高选择性生成1-辛烯必不可少的助催化剂.作为促进剂的六氯乙烷可以使乙酰丙酮铬更有利于催化乙烯齐聚反应生成1-辛烯.     

Novel Dendritic PNP Chromium Complexes: Synthesis,Characterization, and Performance on Ethylene Oligomerization

Three dendritic PNP ligands with ethylenediamine, 1,4‐butanediamine, 1,6‐diaminohexane as bridged groups are synthesized in good yields, respectively. Three dendritic PNP chromium complexes ( C1  –  C3 ) are prepared with the ligands and chromium(III ) chloride tetrahydrofuran complex (CrCl₃(THF )₃) as materials. The dendritic PNP ligands and the synthetic chromium complexes are fully characterized by spectroscopic and analytical methods. All chromium complexes activated with methylaluminoxane (MAO ) exhibited moderate activities on ethylene oligomerization (7.90 × 10⁴ – 2.15 × 10⁵ g (mol Cr h)⁻¹] and had better selectivity for C₆ and C₈ oligomer, reaching up to 81%. The chromium complex ( C1 ) activated with diethylaluminium chloride (Et₂AlCl) has higher catalytic activity than the chromium complex C1 activated with MAO , although the chromium complex ( C1 ) activated with Et₂AlCl had lower selectivity for C₆ and C₈ oligomer. The effects of solvent and reaction parameters on ethylene oligomerization are also studied using the chromium complex C1 as pre ‐ catalyst and MAO as co ‐ catalyst. Under optimized conditions ([complex] = 2 μmol, Al/Cr = 500, 25 °C, 0.9 MP a ethylene, 30 min), the catalytic activity of complex C1 in toluene is 2.15 × 10⁵ g (mol Cr h)⁻¹ and the selectivity for C₆ and C₈ oligomer is 36.76%. In addition, the structure of complexes significantly affects both the catalytic activity and the selectivity on ethylene oligomerization.     

新型树枝状PNP铬催化剂的合成及催化性能

以1.0代聚酰胺-胺(PAMAM)为配体骨架,氯代二苯基膦为原料,通过取代反应合成了1种含有较大空间位阻的新型树枝状PNP配体,再以Cr Cl3(THF)3为络合试剂,通过络合反应合成树枝状PNP铬催化剂.采用傅里叶变换红外光谱(FTIR)、紫外-可见分光光度计(UV-Vis)、核磁共振波谱(NMR)、电喷雾电离质谱(ESI-MS)和元素分析等手段证实合成的新型树枝状PNP配体及其铬催化剂的结构与理论设计的结构一致.以甲基铝氧烷(MAO)为助催化剂,对乙烯齐聚反应进行了研究,考察了溶剂种类、反应温度、反应压力及Al/Cr摩尔比对该催化剂活性和选择性的影响.结果表明,以甲苯为溶剂,MAO为助催化剂,当反应温度为25℃,反应压力为0.9 MPa,Al/Cr摩尔比为500时,该催化剂的活性高达2.15×105g/(mol Cr·h),催化剂对乙烯三聚、四聚反应的选择性共达到36.76%.     

醚类给电子体对Cr/PNP乙烯选择性齐聚体系催化反应性能的影响

采用实验和DFT计算相结合的方法,研究了4种醚类给电子体对Cr/PNP乙烯齐聚催化体系的影响.实验结果表明,C₆+C₈选择性和聚乙烯的选择性受给电子体种类影响各异.DFT计算表明,添加乙醚、甲缩醛、二噁烷和乙二醇二甲醚给电子体后,反应的速率决定步骤均从两分子乙烯氧化偶联成金属五元环转移到第四分子乙烯插入铬金属七元环.给电子体乙二醇二甲醚和甲缩醛的两个氧原子与铬中心在反应过程中发生单/双配位交替变化,其环状结构的大小和稳定性影响乙烯分子插入难易程度,从而影响反应选择性和活性.醚类给电子体对乙烯齐聚反应的影响是电子效应和位阻效应的协同作用,但位阻效应更加明显.另外,在甲基环己烷和甲苯两种溶剂下,乙烯齐聚体系能垒差小于1.5 kJ·mol^-1,在本体系中可以忽略甲基铝氧烷（MAO）中微量甲苯对反应性能的影响.     

超支化双吡啶亚胺铬催化剂的合成及催化乙烯齐聚性能

以1.0代(G)超支化大分子(C₃₈H₅₁N₉O₂)为配体骨架,2-氯-4-甲基吡啶和CrCl₃(THF)₃为原料,依次经过取代和配合反应合成了一种超支化双吡啶亚胺配体及其铬催化剂。 利用紫外-可见光谱(UV-Vis)、傅里叶变换红外光谱(FT-IR)、电喷雾电离质谱(ESI-MS)、核磁共振氢谱(¹H NMR)和元素分析等方法对其进行表征。 结果与理论设计预期一致。 考察了反应温度、乙烯压力、Al与Cr摩尔比(n(Al)/n(Cr))、溶剂及助催化剂种类等因素对催化剂催化乙烯齐聚性能的影响。 结果表明,以甲苯为溶剂,甲基铝氧烷(MAO)为助催化剂,当反应温度为45 ℃,乙烯压力为4 MPa,n(Al)/n(Cr)=300,催化剂用量为7 μmol时,活性可达1.32×10⁵ g/(mol(Cr)·h),C₆和C₈的选择性为59.30%。     

超支化铬系催化剂的合成及乙烯齐聚性能研究

以正辛胺和十二胺为原料,分别制备了两种超支化PNP配体,通过引入金属铬活性位点的方法合成了具有不同烷基链长度的超支化PNP铬系催化剂.采用红外光谱(IR)、核磁共振磷谱(~(31)P-NMR)、核磁共振氢谱(~1H-NMR)、紫外光谱(UV)和质谱(MS)等表征方法证明合成催化剂的结构与理论结构预测相符.详细考察了催化剂用量、溶剂种类、反应条件以及配合物结构对乙烯齐聚性能的影响.实验结果显示,超支化PNP铬系催化剂在甲苯作溶剂,甲基铝氧烷(MAO)做助催化剂时表现出良好的催化乙烯齐聚性能,产物主要为低碳烯烃.在最佳条件下,催化活性最高可达到1.69×10~5 g·(mol Cr·h)~(-1),己烯和辛烯的选择性为43.3%以上.相同聚合条件下,其催化活性随着端基烷基链长度的增加而下降.     

Synthesis and application of chromium complexes bearing hyperbranched PNP ligands in the ethylene oligomerization

Series of hyperbranched PNP ligands ( L1 – L3 ) were prepared using three low-generation hyperbranched molecules with the same branching chains and functional groups but different alkyl chain length as backbones in a mixed solvent of acetonitrile and dichloromethane. The chromium complexes ( Cr1 – Cr3 ) were obtained by reacting with CrCl₃(THF)₃ and the corresponding ligands ( L1 – L3 ). Both L1 – L3 and Cr1 – Cr3 were characterized by elemental analysis, Fourier transform infrared and electrospray ionization–mass spectrometry as well as ¹H nuclear magnetic resonance (NMR) and ³¹P NMR measurements in the case of the ligands. When activated with different aluminum co-catalysts, all three chromium complexes were able to catalyze the ethylene oligomerization, but the products of the ethylene oligomerization were mainly dependent on ethylene pressure, co-catalyst and ligand backbone. Upon activation with methylaluminoxane, the catalytic activity and the selectivity of C8 olefin increased with increasing of ethylene pressure for Cr1 , the catalytic activity was 13.83 × 10⁵ g·(mol Cr·h)⁻¹ and the main product was C8 olefin (50.68%) at the ethylene pressure of 4.0 MPa. When activated with diethylaluminium chloride, ethylaluminium dichloride and ethylaluminum sesquichloride, Cr1 showed the lower catalytic activity and the higher selectivity of C4 olefin in toluene. An increase in the length of alkyl chain in the hyperbranched PNP ligand backbone caused a decrease in the catalytic activity and an increase in the selectivity of C8 + olefin. The PNP chromium complexes exhibited higher selectivity for higher carbon number olefins compared with the dendritic PNP chromium complex ( Cr5 ).     

超支化铬系催化剂的合成及乙烯齐聚性能研究

以不同端基烷基链长度的1.0G超支化大分子为桥联基,通过对其端基氨基进行催化功能改性,合成了系列具有不同桥联基长度的超支化PNP铬系催化剂。采用红外光谱(IR)、核磁共振氢谱(1H-NMR)、核磁共振磷谱(31P-NMR)、紫外光谱(UV)和质谱(MS)等表征方法证明合成催化剂的结构与理论结构相符。详细考察了溶剂种类、反应温度、Al/Cr摩尔比、反应压力、催化剂用量和催化剂结构对催化剂乙烯齐聚性能的影响。实验结果表明,当以甲苯为溶剂,甲基铝氧烷(MAO)为助催化剂时,超支化PNP铬系催化剂表现出良好的催化乙烯齐聚性能,产物以低碳烯烃为主。最佳条件下,催化活性最高可达到1.69×105g/mol Cr·h,己烯和辛烯的选择性为43.3%以上。相同聚合条件下,其催化活性随着端基烷基链长度的增加而下降。     

Styrene‐ethylene co‐oligomerization with bis‐(diphenylphosphino)‐amine/chromium catalysts and the use of the co‐oligomerization products in copolymerization reactions with metallocenes

Ethylene‐styrene (or 4‐methylstyrene) co‐oligomerization using various bis(diphenylphoshino)amine ligands in combination with chromium is discussed. GC analysis of the reaction mixture shows that various phenyl‐hexene and phenyl‐octene isomers are formed either through cotrimerization or cotetramerization. It seems that the more bulky ligands display lower selectivity to co‐oligomerization and favor ethylene homo‐oligomerization. Subsequent copolymerization of the oligomerization reaction mixture using a metallocene polymerization catalyst results in a copolymer with a branched structure as indicated by Crystaf and ¹³C NMR analysis. Assignments of the ¹³C NMR spectrum are proposed from an APT NMR experiment combined with calculated NMR chemical shift data using additivity rules. An indication of the ability of the different co‐oligomerization products to copolymerize into the polyethylene chain could be established from these assignments. Unreacted styrene and the more bulky isomers, 3‐phenyl‐1‐hexene and 3‐phenyl‐1‐octene, are not readily incorporated while branches resulting from the other isomers present in the co‐oligomerization reaction mixture are detected in the NMR spectrum. © 2008 Wiley Periodicals, Inc. JPolym Sci Part A: Polym Chem 46: 1488–1501, 2008     

Selective ethylene oligomerization bearing hyperbranched bispyridylamine chromium catalyst

Two new hyperbranched bispyridylamine ligands and multinuclear chromium complexes were synthesized with 1.0?G hyperbranched macromolecules, 2-chloropyridine, 2-chloro-4-methylpyridine and CrCl₃(THF)₃ as raw materials. The structures of hyperbranched ligands and chromium complexes were characterized by UV, FT-IR, ¹H NMR, ESI-MS, and elemental analysis. These hyperbranched chromium complexes were evaluated as catalyst precursors by using MAO as activator in the oligomerization of ethylene. Effects of reaction temperature, reaction pressure, Al/Cr molar ratio, concentration of catalyst, solvent, and the structure of catalysts on the catalytic activity and product selectivity were investigated. The oligomerization results showed that with increase of reaction temperature, reaction pressure, and Al/Cr molar ratio, the catalytic activity increased and then decreased; the catalytic activity continuously decreased as the amount of catalyst increased. The products were mainly based on C₆ and C₈. Under optimized conditions, the catalytic system of hyperbranched NNN/Cr(III)/MAO led to activity of 1.26?×?10⁵ g/(mol·Cr·h) and 63.34% selectivity for C₆ and C₈.     

树枝状吡啶亚胺铬催化剂的合成及其催化性能研究

以1. 0代聚酰胺-胺树枝状大分子为配体骨架、吡啶二甲醛为原料,合成了一种新型树枝状吡啶亚胺(DPI)配体,再以CrCl_3·6H_2O为络合试剂,制备DPI-Cr催化剂。采用IR、UV-Vis、MS、元素分析等确证了产物结构。考察溶剂种类、助催化剂种类、反应温度、乙烯压力以及Al/Cr摩尔比对DPI-Cr催化乙烯齐聚性能的影响。结果表明,DPI-Cr催化剂表现出良好的催化活性和烯烃选择性,优化反应条件下,催化效率可达4. 91×10~4g/mol Cr·h,C_6和C_8选择性为73. 90%。     

Ethylene tetramerization: a new route to produce 1-octene in exceptionally high selectivities

Linear alpha-olefins, such as 1-hexene and 1-octene, are important comonomers in the production of linear low-density polyethylene (LLDPE). The conventional method of producing 1-hexene and 1-octene is by oligomerization of ethylene, which yields a wide spectrum of linear alpha-olefins (LAOs). While there exists several processes for producing 1-hexene via ethylene trimerization, a similar route for the selective production of 1-octene has so far been elusive. We now, for the first time, report an unprecedented ethylene tetramerization reaction that produces 1-octene in selectivities exceeding 70%, using an aluminoxane-activated chromium/((R2)2P)2NR1 catalyst system.     

Experimental evidence for large ring metallacycle intermediates in polyethylene chain growth using homogeneous chromium catalysts

Deuterio-ethylene labeling studies on two homogeneous chromium ethylene oligomerization catalysts show that chain propagation proceeds via metallacyclic intermediates; reactions performed in the presence of 1-nonene show no incorporation of the higher olefin, strongly implicating the involvement of large ring metallacycles.     

Selective ethylene oligomerization with in‐situ‐generated chromium catalysts supported by trifluoromethyl‐containing ligands

A series of pyrrole‐containing diarylphosphine and diarylphosphine oxide ligands were prepared. The catalytic activity of the corresponding in‐situ‐generated chromium catalysts was investigated during selective ethylene oligomerization reactions. Variations in the ligand system were introduced by modifying the diarylphosphine and pyrrole moieties that affect the steric and electronic properties. Minor changes in the ligand structure and the composition of activators significantly changed the catalytic activity, selectivity toward linear alpha‐olefins (LAO) versus polyethylene (PE), and the distribution of oligomeric products. The presence of trifluoromethyl groups on the diphenyl rings in ligand 3 promoted oxidation to form the corresponding phosphine oxide structure, 3o , which dramatically enhanced the catalytic activity of ethylene trimerization. The in‐situ‐generated chromium complex based on 3o activated by DMAO (dry methylaluminoxane)/TIBA (triisobutylaluminum) was used to achieve activity of about 1250 g (mmol of Cr)⁻¹ h⁻¹ with 98.5 mol % 1‐hexene, along with a negligible amount of PE side product. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 444–450     

改性三氧化二铬催化1,1,3,3-四氯丙烯氟化高选择性合成反式-1-氯-3,3,3-三氟丙烯研究

反式-1-氯-3, 3, 3-三氟丙烯 (HCFO-1233zd (E))是近年来正在研发的第四代发泡剂,其大气臭氧消耗潜能值为0.00024,温室效应潜能值为7.0,毒性低,常态下不燃,使用安全;它也是合成含氟精细化工品的中间体,以及合成氟树脂和氟弹性体的单体。本论文制备了Al,Zn,Co改性的Cr2O3催化剂,将其成功应用于1, 1, 3, 3-四氯丙烯（HCC-1230za）与氟化氢反应中,高选择性地合成HCFO-1233zd (E),复合催化剂Zn / Cr2O3显示高稳定性,其中HCC-1230za转化率高达99.4％,HCFO-1233zd（E）的选择性高达98.2％。反应条件诸如反应物HF / HCC-1230za 的摩尔比和反应温度等对产物分布有显着影响。在相对较低的温度（200?C）和较大的HF / HCC-1230za 摩尔比（10：1）下,对HCFO-1233zd（E）的选择性有利。通过XRD,XPS,BET和V70吡啶吸附红外光谱技术对复合催化剂Zn / Cr2O3进行了表征。 XRD结果表明,催化剂中大多数无定形Cr2O3和高度分散微晶相Cr2O3共同导致催化剂的高活性和高稳定性。HCC-1230za的转化率与预氟化处理催化剂Zn / Cr2O3的比表面积有关,催化剂的比表面积越高,催化活性越高。XPS光谱表明,在预氟化过程中,表面铬氧化物可能与F原子强烈相互作用,从而导致Cr原子的化学环境发生广泛变化。V70吡啶吸附红外光谱和氨-程序升温脱附技术结果证明尚未失活的催化剂Lewis 酸和Br?nsted酸中心的数目和强度与新制备的催化剂相比明显提高。     

乙烯选择性三聚/四聚铬系催化剂及其齐聚机理研究进展

线性α-烯烃是一类重要的有机化工原料和中间体,其下游市场包括聚乙烯、合成润滑油、表面活性剂等,其中C4~C8 组分的消费量占全球线性α-烯烃消费量的一半以上。采用1-己烯和1-辛烯作为共聚单体生产的线性低密度聚乙烯（LLDPE）和高密度聚乙烯（HDPE）产品具有优异的性能,被广泛用于薄膜、管材等领域。为了提高原子经济性,学术界和工业界一直致力于乙烯选择性三聚/四聚催化剂的设计与开发,而铬系催化剂是其中研究最广泛、最深入的体系。本文从配体、铬源、助催化剂、反应条件等方面综述了典型的铬系乙烯选择性三聚/四聚催化体系,包括雪佛龙菲利普斯乙烯三聚催化体系,Cr/PNP催化体系,以及其他N、P、Si配体等催化体系。在本文第二部分综述了乙烯选择性齐聚的相关机理提案,包括经典的Cossee-Arlman机理、单核金属环机理、双核金属环机理、双配位机理、及其他机理提案。     

Hyperbranched bisphosphinoamine ligands: synthesis,characterization and application in ethylene oligomerization

Two hyperbranched bisphosphinoamine (PNP) ligands and chromium complexes were synthesized in good yield with 1.0 generation (1.0 G) hyperbranched macromolecules, chlorodiphenylphosphine (Ph₂PCl) and CrCl₃(THF)₃ as raw materials. The hyperbranched PNP ligands and chromium complexes were characterized by FT-IR, ¹H NMR, ³¹P NMR, UV and ESI-MS. Comparing with the chromium complexes, the hyperbranched PNP ligands, in combination with Cr(III), and activation by methylaluminoxane (MAO) in situ generated species with better catalytic performance for ethylene oligomerization. The effect of solvent, chromium source, ligand/Cr molar ratio, reaction temperature, Al/Cr molar ratio and reaction pressure on the catalytic activity and product selectivity were studied. The results showed that with increase of ligand/Cr molar ratio, reaction temperature and Al/Cr molar ratio, the catalytic activity increased at first and then decreased. However, the catalytic activity continuously increased with increase of reaction pressure. Under the optimized conditions, the catalytic system of hyperbranched PNP/Cr(III)/MAO led to catalytic activity of 2.68 × 10⁵ g/(mol Cr·h) and 37.71% selectivity for C₆ and C₈.     

Hydrogenation of cinnamaldehyde in liquid phase in the presence of copper supported catalysts

Copper supported on zirconia is rather selective to cinnamic alcohol. The addition of chromium to such catalysts appreciably increased the activity while preserving a significant cinnamic alcohol selectivity.     

Mechanism of selective oxidation of organic sulfides with Oxo(salen)chromium(V) complexes

The selective oxidation of organic sulfides to sulfoxides by oxo(salen)chromium(V) complexes in acetonitrile is overall second-order, first-order each in the oxidant and the substrate. The rate constant, k(2), values of several para-substituted phenyl methyl sulfides correlate linearly with Hammett sigma constants and the rho values are in the range of -1.3 to -2.7 with different substituted oxo(salen)chromium(V) complexes. The reactivity of different alkyl sulfides is in accordance with Taft's steric substituent constant, E(S). A mechanism involving direct oxygen atom transfer from the oxidant to the substrate rather than electron transfer is envisaged. Correlation analyses show the presence of an inverse relationship between reactivity and selectivity in the reaction of various sulfides with a given oxo(salen)chromium(V) complex and vice versa. Mathematical treatment of the results shows that this redox system falls under strong reactivity-selectivity principle (RSP).