Synthesis of a novel triple-site diphosphinoamine （PNP） ligand and its applications in ethylene tetramerization

A novel triple-site diphosphinoamine （PNP） ligand was synthesized and characterized. In combination with Cr（Ⅲ） and methylaluminoxane （MAO）, it generated active catalytic systems for ethylene tetramerization toward 1-octene with high catalytic activity and long lifetime. The effects of reaction temperature, molar ratio of AI/Cr and molar ratio of ligand/Cr on catalytic activity and selectivity to 1-octene were studied with reaction kinetics of the catalytic system for ethylene tetramerization described. At the AI/Cr molar ratio of 100, the catalytic activity is up to 2.29×10^6 g· mol^-1 （Cr）· h^-1 and the selectivity to 1-octene is 49.65 wt%.     

Boron- and silicon-bridged bis（diphenylphosphino）-type ligands for chromium-catalyzed ethylene oligomerization

PNP-type ligands showed very good property in the catalytic systems of PNP/Cr(Ⅲ)/methylaluminoxane(MAO)for ethylene selective tetramerization toward1-octene.In this research,two PNP analogues bis(diphenylphosphino)phenylborane and bis(diphenylphosphino)dimethylsilane have been synthesized and characterized.In combination with CrCl3(THF)3as active center and MAO as cocatalyst,these ligands produced a new catalytic systems for ethylene oligomerization to linear α-olefins with catalytic activities of up to 3.07 9 106g mol-1(cat)h-1.Herein,we report the effects of the reaction temperature,ethylene pressure,and the molar ratio of Al/Cr on the catalyst activities and product selectivities.     

Preparation of 1-octene by ethylene tetramerization with high selectivity

Two novel PNP ligands have been synthesized and characterized by ^1H-NMR, elemental analysis, and mass spectra. In combination with Cr（Ⅲ） and cocatalyst MAO, they generate active catalytic systems that tetramerize ethylene with both high catalytic activity and high selectivity to produce 1-octene. The results show that these catalyst systems are able to catalyze ethylene tetramerization, with high catalytic activity up to 0.89×10^6 g/mol Cr.h, and the selectivity of C8 in products is 72.52%, and the percentage of 1-olefins in the C8 cut is 97.87%.     

Mesoporous zeolite SBA-15 supported nickel diimine catalysts for ethylene polymerization

The novel mesoporous zeolite SBA-15 is successfully used as the support to immobilize late-transition metal nickel diimine catalyst, both in physical and chemical methods, EA, ICP, FT-IR and XRD are applied to characterizing these supported catalysts. The results of ethylene polymerization reveal that these supported catalysts have high catalytic activity as their homogenous counterpart does,moreover, polyethylene with a fibrous morphology is produced due to the channel effect of support, and both the molecular weight and molecular weight distributions of polymers are increased greatly.     

Research on Influence Factors of Surfactivity of Polyester Polyether Block Copolymer

Polyester polyether block copolymer （PPBC） was synthesized by ester-exchange and polycondensation reactions using dimethyl terephthalate （DMT）, ethylene glycol （EG） and polyethylene glycol （PEG） as monomer. The effects of PEG molecular weight, mol ratio of DMT to PEG （nDMT/nPEG）, temperature and time of polycondensation reaction and vacuum degree in the reaction system on the surface tension and critical micelle concentration （CMC） of PPBC aqueous solution were studied. It was found that both the molecular weight and the concentration of PEG can affect PPBC＇s surface activity obviously, and the optimum synthesis condition of PPBC used as surfactant is as follows： PEG molecular weight is 1 500, tool ratio of DMT to PEG is 3, temperature and time of polycondensation reaction is 260℃ × 1 h, vacuum degree of condensation reaction is 0.03-0.05 MPa. It was proved by surface tension measurement of PPBC aqueous solution that the PPBC synthesized in this condition is a good surfactant with excellent surfactivity.     

Synthesis of a new meso／microporous composite molecular sieve of MCM-41／mordenite

An MCM-41/mordenite composite with twofold porous structure and stepwise-distributed acidity was prepared for the first time by using zeolite mordenite as the silica-alumina source. The composite molecular sieve has been investigated and compared with a mechanical mixture of mordenite and MCM-41 for their structure, acidity and catalytic activity by means of XRD, N2 adsorption and desorption, HRTEM, DTG, NH3-TPD and catalytic reaction. The characterization results show that the structure and property of the composite molecular sieve are quite different from those of the mechanical mixture, which might be ascribed to the incorporation of secondary building units characteristic of zeolite mordenite into the mesoporous walls of the composite which gives rise to the thicker mesoporous walls, the higher hydrothermal stability and more strong acid sites. Furthermore, the new strategy could be used as a new general method for the preparation of catalysts for the reaction system with multifold large molecules, and the results were well confirmed by the dealkylation of C10^ aromatic hydrocarbon.     

Ethylene oligomerization by novel iron(Ⅱ) diimine complexes/MAO

Two novel Fe(Ⅱ) diimine complexes have been synthesized. In combination with MAO, they generate active catalytic systems that oligomerize ethylene with both high catalytic activity and high selectivity for α-olefins. The effects of substituents on the aryl ring, reaction temperatures and molar ratios of Al/Fe on catalytic activity and product distribution are studied.     

Half-sandwich β-diketonato complexes of zirconium and their application as catalysts to ethylene polymerization

The bis(β-diketonato) Zr complexes CpZr(acac)2Cl (acac = acetylacetonato) (1) and Cp*Zr(acac)2Cl (2) can be synthesized by the reac-tion of Cp′ZrCl3(Cp′ = Cp or Cp*) with 2 equiv of lith-ium acetylacetonate. CpZr(acac)2Cl (1) can be quan-titatively prepared by treatment of Cp2ZrCl2 with ex-cess acetylacetone. The tris(β-diketonato) Zr com-plex CpZr(tfac)3 (tfac = trisfluoroacetylacetonato) (3) has been prepared by treatment of CpZrCl3 with so-dium trisfluoroacetylacetonate. The replacement of both chlorine atoms and one Cp group from zir-conocene dichloride by nonfluorinated diketone,acetylacetone,readily occurs at room temperature in triethylamine medium,offering the tris(β-diketonato) Zr complex CpZr(acac)3 (4). The complexes were characterized by 1H NMR spectroscopic methods. In addition,the molecular structures of complexes 3 and 4 have been determined by X-ray diffraction methods. When activated by excess methylaluminoxane (MAO),these complexes were active for ethylene polymerization,offering polyethylenes with high mo-lecular weights and narrow molecular weight distribu-tions. Complex 4 showed a very high ethylene po-lymerization activity of up to 7100 kg PE/mol Zr·h at 5 atm. Complexes 1 and 2 were also active for ethyl-ene/1-hexene copolymerization.     

LLDPE/TiO2 nanocomposites produced from different crystallite sizes of TiO2 via in situ polymerization

Nano-TiO2 particles with a range of crystallite sizes were synthesized by a conventional sol-gel method,and then used as nanoparticle substrates in the synthesis of LLDPE/TiO2 nanocomposites via in situ polymerization of ethylene/1-hexene with zirconocene/MMAO catalyst.It was found that the size of the nano-TiO2 crystallite nanoparticles can influence the catalytic activity in the polymerization system.The larger nano-TiO2 crystallites provided better catalytic activity in the polymerization system due to more space for monomer attack.In addition,by thermo-gravimetric analysis,it can be seen that the larger nano-TiO2 crystallites also exhibited lower interaction with available MMAO.Consequently,the MMAO reacted more efficiently with the zirconocene catalyst during the activation process,and enhanced polymerization catalysis.All the polymer nanocomposites products did not have well defined melting temperature indicating non-crystalline polymers.This is due to the high amount of hexene incorporation(based on 13C NMR).The difference in crystallite sizes of the nano-TiO2 also affected how 1-hexene became incorporated into the polymer nanocomposites.The smaller crystallite size of nano-TiO2 allowed greater 1-hexene incorporation due to depression of the reactivity of the ethylene.The contribution of this work helps develop a better understanding of the role of nano-TiO2 in the catalytic activity of the polymerization system and in the microstructure of the polymer composite product.However,this study only considers work on the laboratory scale,so for commercial application of these results,it is necessary to scale up the polymerization process.It is only at this stage,that other physical properties,such as the mechanical properties of these materials can be sensibly determined.     

Synthesis of higher molecular weight PAN and its copolymers for carbon fibers

Higher molecular weight polyacrylonitrile (PAN) was obtained by the free-radical suspension copolymerization of itaconic acid (IA) and acrylonitrile (AN) which was carried out in DMSO/H₂O using 2,2'-azodiisobutyronitrile (AIBN) as the initiator. The effects of polymerization parameters, such as IA monomer concentration and DMSO/H₂O ratio, on the conversion of polymerization and number-average molecular weight are specially described. The copolymerization reaction rate and the number-average molecular weight of the resultant copolymers decrease with the result of high chain transfer constant of DMSO. For the copolymerization of AN and IA, with the inclusion of the good solvent DMSO, the solution degree of AN in DMSO/H₂O is higher than that in water, as a result, the resulting copolymer pellets range from soft bulk to solid grain, as characterized by the use of SEM. Higher molecular weight P(AN-co-IA) copolymers have a lower initiation of exothermal reaction temperature and wider DSC exothermal peaks compared with PAN homopolymers, which corresponds with the results of an IR study.     

A series of novel bisphosphinoamine ligands: Synthesis,characterization and application in ethylene tetramerization

A series of novel N-halogen-substituted-aryl bisphosphinoamine ligands were synthesized and characterized by elemental analysis, ¹H NMR and mass spectrometry. The combination of these ligands with Cr(III) and activation by methylaluminoxane leads to highly active catalytic systems for the tetramerization of ethylene to form 1-octene. The catalytic activities and product selectivities depend on the aryl ring substituents and the reaction conditions. We found that the location and size of the substituents are important in determining the catalytic activity and selectivity toward 1-octene. This trend is similar to that observed for their alkyl-substituted analogues.     

Preparation of PE/MMT nanocomposite by monomer intercalation and <Emphasis Type="Italic">in situ</Emphasis> copolymerization

The catalyst [(2-ArN=C(Me))₂C₅H₃N]FeCl₂ (Ar = 2-C₆H₄(i-Pr)) with methylaluminoxane (MAO) as cocatalyst was intercalated between layers of montmorillonite (MMT) for ethylene oligomerization. Metallocene catalyst Me₂Si(Ind)₂ZrCl₂ and MAO was then added to form a dual functional catalytic system. A PE/MMT nanocomposite was prepared by copolymerization of ethylene with α-olefins produced in situ from ethylene over the dual functional catalytic system. The catalytic system was of high polymeric activity. The resultant PE/MMT nanocomposites were stable and got increases in tensile strength and temperature of maximum weight loss (T_onset).     

Preparation of PE/MMT nanocomposite by monomer intercalation and in situ copolymerization

The catalyst {[(2-ArN == C(Me)(2C5H3N]FeCl2} (Ar = 2-C6H4(i-Pr)) with methylaluminoxane (MAO) as cocatalyst was intercalated between layers of montmorillonite (MMT) for ethylene oligomerization. Metallocene catalyst Me2Si(Ind)2ZrCl2 and MAO was then added to form a dual functional catalytic system. A PE/MMT nanocomposite was prepared by copolymerization of ethylene with α-olefins produced in situ from ethylene over the dual functional catalytic system. The catalytic system was of high polymeric activity. The resultant PE/MMT nanocomposites were stable and got increases in tensile strength and temperature of maximum weight loss (Tonset).     

Synthesis, structure and ethylene polymerization behavior of titanium complexes [C3H6（N = CH-Ar-O）2]TiCl2

Early transition metal catalysts containing twophenoxy-imine ligands, called FI catalysts which havevery high potential to become a new generation of olefinpolymerization catalysts, are new-type catalysts whichhave attracted much attention in recent years[1—3]. Many ofthem display activities comparable to those of the metal-locene catalysts and, in some cases, behave as living po-lymerization catalysts of α-olefins. Brookhart and Gibsonet al.[4,5] recently reported separately series of Schi…     

改性Ziegler-Natta体系催化乙烯/1-辛烯共聚合反应

采用改性Ziegler-Natta(Z-N)催化体系(n-BuO)TiCl₃/MgCl₂/AlEt₃催化乙烯/1-辛烯共聚合。考察了聚合温度、Al/Ti物质的量比、单体投料比及乙烯压力对聚合行为的影响,并与传统Z-N催化体系TiCl₄/MgCl₂/AlEt₃催化乙烯/1-辛烯共聚合行为进行了对比研究。采用GPC,DSC,¹³C-NMR,SEM对共聚物的结构、形态及性能进行了表征。结果表明,改性Z-N催化体系催化乙烯/1-辛烯共聚合时,1-辛烯的共聚能力明显高于传统Z-N催化体系,在共聚物中1-辛烯的插入量达2.26%（摩尔分数）,而传统Z-N催化剂1-辛烯的插入量仅为0.34%（摩尔分数）;Al/Ti物质的量比及单体投料比对催化剂的活性、1-辛烯的插入量、共聚物的分子量与分子量分布及共聚物的微观结构有明显的影响;根据¹³C-NMR结果计算了单体的竞聚率:r_E=55.00,r_O=0.023,其乘积r_E· r_O=1.27,表明该聚合物为无规共聚物。     

SBA-15负载二氯二茂锆催化剂的制备及催化乙烯聚合反应

以介孔分子筛SBA-15为载体负载二氯二茂锆配合物制备了SBA-15负载二氯二茂锆催化剂,在助催化剂MMAO作用下,该负载催化剂常压下可高活性催化乙烯聚合,通过XRD、TEM、DSC表征了SBA-15负载催化剂和所得聚乙烯,结果发现:因载体的孔道效应而生成了纤维状聚乙烯.考察了反应温度、Al/Zr摩尔比对乙烯聚合活性的影响.     

Ethylene polymerization by novel highly active iron/acetyl（imino）pyridyl complex

In recent years, significant developments have oc- curred in olefin polymerization with late-transition- metal catalyst systems, in particular, the discovery of exceptionally active catalysts based on penta- coordi- nate iron and cobalt bearing bis(imino)pyridyl triden- tate ligands with substituted aryl groups, reported in- dependently by the groups of Brookhart[1] and Gibson[2]. Following this discovery, a considerable amount of efforts have been dedicated to investigate the nature of the ac…