Presence Of Triisobutylaluminum Research Articles

Heterocene-catalyzed ethylene/oct-1-ene copolymerization under MAO-free and low-MAO conditions: The synthesis of highly statistical copolymers and their use in blending with HDPE

Sandwich SiMe2-bridged ansa-complexes of zirconium, containing heterocycle-fused η5-cyclopentadienyls, derivatives of 2,5-dimethyl-7H-cyclopenta[1,2-b:4,3-b']dithiophene (2), 5,10-dihydroindeno[1,2-b]indole (3) and 5,6-dihydroindeno[2,1-b]indole (4) – 'heterocenes' – catalyzed ethylene homopolymerization and ethylene/oct-1-ene (E/O) copolymerization in the presence of triisobutylaluminum (TIBA) without MAO and perfluoroaryl borate activators, the benchmark bis(η5-fluorenyl) complex 1 was virtually inactive under these conditions. In the absence of MAO, E/O copolymerization resulted in a formation of copolymers not containing EOOE fragments even at E/O ratio of 2.4. Addition of 10 eq. of MMAO-12 resulted in increase of both catalytic activities of 2–4 and oct-1-ene incorporation. E/O copolymers POE-05 (obtained on TIBA activated precatalyst 2) and POE-17 (obtained on TIBA/MMAO-12 activated precatalyst 4) were not inferior to the best commercial E/O copolymers in physico-mechanical characteristics at −45 °C. Extrusion blends of POE-05 and POE-17 with high density polyethylene (HDPE) demonstrated high impact strength and frost resistance.

Effect of alkylaluminum cocatalyst on ethylene/1-hexene copolymerization and active center distribution of MgCl2-supported Ziegler-Natta catalyst

Ethylene-1-hexene copolymerization was catalyzed by TiCl4/diester/MgCl2 type Z-N catalyst activated by triethylaluminium (TEA), triisobutylaluminium (TIBA) or TEA/TIBA mixtures. Copolymerization activity decreased with increase of TIBA content in the cocatalyst. Each copolymer sample was fractionated into boiling n-heptane soluble and insoluble fractions. 1-Hexene content of the soluble fraction was 2 ∼ 6 times larger than that of the insoluble fraction. With introduction of TIBA in the cocatalyst, chemical composition distribution of the copolymer was broadened, attributable to increase of 1-hexene in the soluble fraction. Total number of active centers markedly decreased with increasing TIBA in cocatalyst, and active center number in the soluble fraction decreased more than that in the insoluble fraction. Rate constant of ethylene insertion (k pE) in the soluble fraction was much smaller than that of the insoluble fraction. Rate constant of 1-hexene insertion (k pH) of the soluble fraction became far larger than that of the insoluble fraction when TEA/TIBA ratio was lower than 80/20. In the presence of TIBA, only a part of active center precursors with stronger ability of incorporating 1-hexene were effectively activated in the soluble fraction. For the active centers in insoluble fraction, cocatalyst structure exerted more complicated effects on their activation. Active center models were proposed to explain the observed cocatalyst effects.

Effect of the acid–base properties of the support on the catalytic activity of ethylene polymerization using supported catalysts composed of Cp2ZrX2 (X = Cl, Me) and Al2O3(F)

Supported catalysts Al2O3/Cp2ZrX2 and Al2O3(F)/Cp2ZrX2 (X = Me, Cl) for the ethylene polymerization were synthesized by anchoring zirconocene on alumina and alumina, modified with 1–7 wt% fluorine (Al2O3(F)). The study revealed that Al2O3(F)/Cp2ZrMe2 catalysts are active in ethylene polymerization in the absence of organoaluminum cocatalyst, whereas Al2O3(F)/Cp2ZrCl2 catalysts are active in the presence of triisobutylaluminum as a co-catalyst. The metallocene complex was strongly anchored on the support. Active component leaching was not observed during polymerization. The acid–base properties of Al2O3(F) were studied by IR spectroscopy of adsorbed probe molecules: CO, pyridine and CDCl3. A maximum activity of the catalysts was observed in the case of the Al2O3(5%F) support, containing Lewis acid sites with absorption bands (νCO) at 2210–2215 cm−1, Bronsted acid sites with a proton affinity (PA) of 1190 kJ/mol, and weak basic sites with PA 850 and 795 kJ/mol. “Cationic-like” complexes formed on the Lewis acid sites with absorption bands at 2180−2200 cm−1 are inactive at ethylene polymerization.

Phosphazene/triisobutylaluminum-promoted anionic ring-opening polymerization of 1,2-epoxybutane initiated by secondary carbamates

The deprotonation of secondary carbamates bytBuP2in the presence of a Lewis acid allowed initiating the polymerization of 1,2-epoxybutane.

Alkylation of toluene with dichloromethane in the presence of triisobutylaluminum and perfluorophenylborates

1H NMR method showed that in systems based on triisobutylaluminum (TIBA) and triphenylcyclopropenylium [Ph3C3]+[B(C6F5)4]–(CPB) or triphenylmethylium [Ph3C]+[B(C6F5)4]–(TB) perfluorophenylborates in a toluene–dichloromethane mixture the Friedel–Crafts process occurs with the formation of ditolylmethane (DTM) accompanied by the complete decomposition of TIBA to form isobutane. 19F NMR spectroscopy showed that the [B(C6F5)4]–anion decomposes in the systems to form B(C6F5)3 and HC6F5. The short-living [AlBu2 i]+ cation formed in the reaction of perfluorophenylborates with TIBA is assumed to be the species initiating the process. It has been shown that CPB is less reactive than TB. The addition of a stoichiometric amount of Ph2CCpFluHfMe2 exerts no effect on the process with the CPB-containing system but inhibits the reaction in the case of TB.

Study of triisobutylaluminum as cocatalyst and processing parameters on ethylene polymerization performance of α-diimine nickel(II) complex by response surface method

In this research work, 1,4-bis(2,6-diisopropylphenyl)-acenaphthenediimine-diboromonickel(II) (1) complex was synthesized and its ethylene polymerization in the presence of triisobutylaluminum (TIBA) as activator was studied. The effects of three critical factors [polymerization temperature (T), cocatalyst to catalyst ratio (CC) and pressure (P)] on the average molecular weight and crystallinity of the final polymers and also reaction yields as the response variables were evaluated with the help of empirical statistical models and visualized with the response surface method. The results show that activity of 1 as well as M w and crystallinity of the resulting polymers are influenced strongly by the polymerization factors. The activity of TIBA-activated catalyst 1 reaches a maximum at 10 °C after raising pressure and CC to 7 bar and 3,000, respectively. This activity is much higher than previously reported activity for this catalyst. Furthermore, a polymerization condition for reaching desirable responses is predicted and experimentally verified.

A Convenient Triisobutylaluminium (TIBAL)-Promoted Johnson-Claisen Approach to γ,δ-Unsaturated Alcohols

Mixed ortho esters derived from allylic alcohols undergo methanol elimination in the presence of triisobutylaluminium (TIBAL) at room temperature to form mixed ketene acetals. TIBAL then promotes immediate Claisen rearrangement of these intermediates, and subsequent reduction of the ester products, to give unsaturated γ,δ-primary alcohols in a convenient, one-pot procedure.

Novel supported catalysts for ethylene polymerization based on aluminohydride-zirconocene complexes

Ethylene polymerization using catalysts derived from activation of zirconocene aluminohydride complexes, supported on silica, pretreated with methylaluminoxane (MAO), is described. The novel catalyst compositions were compared to those using conventional zirconocene dichloride complexes and characterized by SEM/EDX and DRIFT spectroscopy. Supported catalysts were prepared which featured various surface Al:Zr ratios. When using excess MAO as both activator and scavenger, the catalysts containing the most Zr per g of support gave rise to the most active formulations; the high activities in the presence of excess MAO are due, in part, to catalyst leaching prior to and/or during polymerization. When tri-isobutylaluminum (TIBAL) was used as scavenger, the supported catalysts that featured a higher surface Al:Zr ratio had higher activity than those prepared at the lower Al:Zr ratios. The activity of the aluminohydride complexes was significantly higher than that of the corresponding dichloride complexes, when activated by MAO while the in the presence of TIBAL, there was little difference in performance between the two catalyst precursors.

Heterogeneous catalysts immobilizing α-diimine nickel complexes into fluorotetrasilicic mica interlayers to prepare branched polyethylene from only ethylene

Abstract The α-diimine nickel (II) complexes immobilized into the clay mineral interlayer were prepared by the reaction of the Ni2+ ion-exchanged fluorotetrasilicic mica and the α-diimine ligand. These procatalysts showed a high catalytic activity for the slurry polymerization of ethylene in the presence of methylalumoxane, triethylaluminum or triisobutylaluminum. The activity was strongly affected by the solvent used in the preparation and the steric bulk of the ligand. A high activity (2313 kg-PE mol-Ni−1 h−1) was obtained by the polymerization at 50 °C in the presence of triisobutylaluminum using the procatalyst prepared with the [Ar–N C(CH3)C(CH3) N–Ar (Ar = 2,6-C6H3(CH3)2)] ligand in acetonitrile.

Controlled High-Speed Anionic Polymerization of Propylene Oxide Initiated by Onium Salts in the Presence of Triisobutylaluminum

The conventional anionic polymerization of propylene oxide (POx) proceeds at a very slow rate in low polar media and is characterized by an important transfer reaction to monomer. This only allows the formation of poly(propylene oxide) oligomers. A new polymerization strategy allowing the fast and controlled anionic polymerization of POx has been developed. It is based on the formation of complexes with both the anionic initiator and the monomer. The influences of alkali metal alkoxides (i-PrONa), ammonium salts (NBu4Cl and NOct4Br), and phosphonium salts (PBu4Cl) as initiators, in combination with triisobutylaluminum, have been investigated in terms of reactivity, molar mass control, livingness, and polymerization mechanism. PPOx with narrow polydispersities and controlled molar masses, up to 150 000 g/mol, have been obtained in hydrocarbon media, at low temperature, and in short reaction times.

Ethylene polymerization over zirconocenes supported on alumina- and titania-based acidic oxides

Ethylene polymerization was performed using bis( n-butylcyclopentadienyl)zirconium dichloride (( n-BuCp) 2ZrCl 2) supported on alumina- and titania-based acidic oxides (Al 2O 3, TiO 2, AlPO 4, TiO 2–Al 2O 3, SiO 2–Al 2O 3, TiO 2–SiO 2 and H–Y zeolite) in the presence of triisobutylaluminum. These oxides were also tested in an isopropylbenzene cracking reaction to determine their acid properties. Among the catalysts, AlPO 4-supported ( n-BuCp) 2ZrCl 2 showed the highest polyethylene productivity, but AlPO 4 was inactive in the cracking reaction. FT-IR spectra of pyridine-adsorbed AlPO 4 and Al 2O 3 indicated that the acid sites do not participate in active-site formation. It is possible that the metallocene is activated on sites formed by the reaction of characteristic OH groups of AlPO 4 with triisobutylaluminum.

Stereospecific polymerization of propylene with group 4 ansa-fluorenylamidodimethyl complexes

Group 4 [η 1:η 3- tert-butyl(dimethylfluorenylsilyl)amido]dimethyl complexes [ t-BuNSiMe 2Flu]MMe 2 (M = Ti, 1; Zr, 2; Hf, 3) were synthesized in a one-pot synthesis starting from the ligand, MeLi and MCl 4 (M = Ti, Zr, Hf), respectively. The structures of these complexes were determined by X-ray crystallography and the results obtained revealed that the fluorenyl ligand coordinates to center metal in a η 3-manner irrespective of center metal employed. Propylene polymerization was conducted at 0 or 20 °C in toluene by 1– 3 combined with dried methylaluminoxane (MAO), which was prepared from the toluene solutions of MAO by removing free trialkylaluminiums, and HNMe 2PhB(C 6F 5) 4 in the presence of triisobutylaluminium. The 1–dried MAO system gave the polymer with syndiotactic triad (rr) of 63% at 0 °C, whereas 2 and 3 did not give any polymer in the same conditions. The 2–dried MAO system gave the polymer with the highest syndiotacticity (rr = 97%) at 20 °C, although the activity was low. The 3–dried MAO system did not give any polymer even at 20 °C. When HNMe 2PhB(C 6F 5) 4 was used in place of dried MAO at 20 °C, 1 gave almost atactic polymer, while 2 and 3 gave highly syndiotactic one (rr > 90%). These results indicate that the catalytic performance strongly depended on the center metal of the ansa-fluorenylamidodimethyl complexes as well as cocatalysts employed.

Coordination polymerization at very low amounts of methylaluminoxane as cocatalyst

The effect of very low amounts of methylaluminoxane as an activating cocatalyst in the coordination polymerization has been investigated in the syndiospecific polymerization of styrene with a half-sandwich metallocene catalyst in the presence of triisobutylaluminum at molar ratios of methylaluminoxane/transition metal from 0/1 to about 20/1 in comparison to the polymerization behavior at high molar methylaluminoxane (MAO)/metal ratios. As a result, there cannot be observed any polymerization reaction below a true molar ratio MAO/Ti of 6:1. At higher molar ratios until about 20, the polymerization conversion is increasing significantly with the MAO/Ti molar ratio. These observations and the results of the determination of the kinetic reaction order can be explained with Barron’s tert-butyl aluminoxane based model of MAO as a cage of six monomeric MAO units (AlOMe) 6 in contrast to Sinn’s MAO model of a cage of twelve monomeric units (AlOMe) 12 and are discussed with the results received at usually applied much higher MAO/transition metal ratios leading to a first-order dependence of the polymerization rate on the MAO concentration. From the thermal behavior of the syndiotactic polystyrenes synthesized it can be concluded, that the stereospecificity of the polymerization reaction is not affected by MAO at low MAO concentrations.

Copolymerization of Propylene and Polar Allyl Monomer with Zirconocene/Methylaluminoxane Catalyst: Catalytic Synthesis of Amino-Terminated Isotactic Polypropylene

The copolymerizations of propylene with allyl monomers carrying alcohol or amine were conducted by the rac-dimethylsilylbis(1-indenyl)zirconium dichloride/methylaluminoxane catalyst system. The allyl monomers were pretreated by alkylaluminum before the polymerization. Although the efficiency of the introduction of allyl alcohol-based comonomer was extraordinary low (0.04−0.08 mol % in polymer), the trimethylaluminum-treated allylamine was found to be introduced more effectively (0.65 mol % in polymer). The 13C NMR study indicated that the position of allylamine unit in the copolymer was influenced by the kind of alkylaluminum used at the polymerization. In the presence of trimethylaluminum, the terminally aminated polypropylene was obtained ([amino end polymer]/[whole polymer] = 0.83). In the presence of triisobutylaluminum, however, the allylamine unit is located both on the main chain and at the chain end. The end-aminated polymer was probably obtained due to the formation of dormant species after the i...

A Hyperbranched Polysilane-Based, Borane Cocatalyst for the Metallocene-Catalyzed Polymerization of Propylene

The synthesis of a vinyl-terminated, hyperbranched polysilane and the additional hydroboration with bis(pentafluorophenyl) borohydride are reported. Quantitative transformation was proved by 1H NMR and FT-IR analysis. The polymeric borane was tested as cocatalyst in the metallocene-catalyzed polymerization of propylene. The corresponding catalyst system comprising rac-[1-(9-η5-fluorenyl)-2-(5,6-cyclopenta-2-methyl-1-η5-indenyl)ethane]zirconocene dichloride and the polymeric borane was activated in situ in the presence of triisobutylaluminum (TIBA). Polymerizations were performed at temperatures of 30 and 50 °C with a propylene concentration of 3 mol/L in toluene solution using various cocatalyst:catalyst ratios (10:1, 50:1, and 100:1). This polymer-supported catalyst system produces polypropylenes with excellent activities and good molecular weights. These results were compared with an additional set of polymerization experiments using molecular dispersed B(C6F5)3 as cocatalyst, resulting in significantly...

Linked cyclopentadienyl-amido titanium catalysts supported on pyridylethylsilane-modified silica for heterogeneous ethylene homo- and copolymerization

Linked cyclopentadienyl-amido titanium dimethyl and dichloro complexes, Ti(η 5:η 1-C 5Me 4SiMe 2N t Bu)X 2 (X=Me, Cl), were reacted with trityl tetrakis(pentafluorophenyl)borate (TB), Ph 3C +[B(C 6F 5) 4] −, and methylaluminoxane (MAO), followed by treatment with toluene suspension of pyridylethylsilane-modified silica, to give two new supported-type titanium catalysts, PySTiTB and PySTiMAO. PySTiTB polymerized ethylene in the presence of triisobutylaluminum (TIBA) in hexane at 60 °C and 5 bar with slightly higher activity than the corresponding homogeneous system under the same conditions. PySTiMAO showed relatively high activity even without any use of alkylaluminum compound. The activity could be improved to reach the value comparable with that of the corresponding homogeneous system, when TIBA and modified MAO (MMAO) were employed as external aluminum compounds. Polyethylenes obtained with PySTiTB were found to have molecular weights ( M w) slightly above 10 6 and narrow molecular weight distributions (MWDs), M w/ M n=1.8–3.0. Polyethylenes obtained with PySTiMAO have M w ranging from 1.5×10 5 to 1.2×10 6 and narrow MWDs when combined with TIBA, but very broad MWDs ( M w/ M n=5.0–13.4), when MMAO was used instead of TIBA. Both new supported titanium catalysts also showed modest activities in random copolymerization of ethylene with 1-octene. The present supported catalysts produced copolymers with lower 1-octene contents compared to the corresponding homogeneous systems. PySTiMAO, when combined with MMAO, gave copolymers with highest 1-octene contents, and the MWDs of the resulting copolymers were found to be in a wide range varying from 3.0 up to as broad as 25.

Ethylene Polymerization with “Constrained-Geometry” Titanium Catalysts over Borate-Modified Silica Supports

Two different mesoporous silica materials, Sylopol® 948 and MPS5, were used as substrates for the preparation of silica-bound trityl tris(pentafluorophenyl)- borate activators. The borate-modified silica supports, B- Sylopol and B-MPS5, were characterized by solid-state NMR spectroscopy and ICP mass spectrometry, and applied as activators for slurry polymerization of ethylene using constrained-geometry titanium complexes of the formula Ti(η 5 :η 1 -C 5 Me 4 SiMe 2 NR)X 2 (R = Me, i Pr, t Bu; X = Me, Bz, Cl) in the presence of triisobutylaluminium (TIBA). The activity of the B-Sylopol system was higher than that of the corresponding homogeneous catalysts Ti(η 5 :η 1 -C 5 Me 4 SiMe 2 NR)X 2 /Ph 3 C + [B(C 6 F 5 ) 4 ] - , whereas that of the B-MPS5 system was lower. These supported catalysts produced polyethylenes with higher molecular weights (M w in the range of 10 6 ), narrower molecular weight distributions (M w /M n = 1.5-2.3) and higher bulk densities (up to 0.4 g/cm 3 ) compared to those of polyethylenes obtained with the homogeneous system. The resulting polyethylenes were found to replicate the shapes of the supported borate activators. Fine polyethylene particles due to the cracking of the support were observed with the B-Sylopol system, while well-shaped polyethylene spheres were formed with the B-MPS5 system.

Copolymerization of ethylene and 1-hexene with Et(Ind)2ZrCl2 in hexane

Copolymerizations of ethylene and 1-hexene were carried out in hexane at 60°C by using ethylenebis(indenyl)zirconium dichloride as catalyst and methylaluminoxane (MAO) as cocatalyst in presence of triisobutylaluminum (TIBA). The influence of the alkylaluminum concentration and AlTOTAL/Zr molar ratio on the catalyst activity and comonomer incorporation are evaluated. Increasing the TIBA concentration, the MAO solubility augments in the polymerization milieu, as well as the catalyst activity and the comonomer incorporation. Increasing the AlTOTAL/Zr molar ratio, catalyst activity becomes higher, while comonomer incorporation remained constant at around 8wt% for molar ratios between 0 and 5000. For AlTOTAL/Zr molar ratios higher than 5,000 comonomer incorporation increased gradually. Under the same experimental conditions dimethylsilylbis(indenyl)zirconium dichloride showed higher thermal stability and led to higher comonomer incorporation.

Application of a cationic activated metallocene catalyst system in the copolymerization of ethylene and 1-butene under high pressure

The activation of metallocene catalyst by a cationic activator in the presence of triisobutylaluminium was examined in the copolymerization of ethylene and 1-butene under high pressure of 150 MPa and temperatures of 463 to 473 K. A continuously operated micro-pilot plant unit equipped with a stirred autoclave was used. The catalyst productivity determined from the amount of polymer and the catalyst feed was in the range of 100 to 300 kg polymer/g zirconium. The resulting copolymers were analyzed for their physical properties and the amount of 1-butene incorporated. The results of the polymerization with the metallocene/cationic activator system were compared to the data obtained earlier using methyl aluminoxane as the activator.

ChemInform Abstract: Oligomerization of Trimethylsilylacetylene in the Presence of Catalytic Systems Based on Halides of Group III ‐ VI Transition Metals.

AbstractOligomerization of trimethylsilylacetylene (I) in the presence of triisobutylaluminum (II) gives the linear products (III) and (IV) and/or the cyclic trimer (V).