Triethylaluminum Research Articles

Optimization of Chloroethane-Promoted Titanium-Catalyzed Ethylene Dimerization Using the Taguchi L16 Design

A five-factor four-level Taguchi L16 orthogonal design was used to determine optimized factors of the [titanium tetrabutoxide (Ti(OC4H9)4)–triethyl aluminum (TEA)] catalyst system with two additives: tetrahydropyran (THP) as an electron donor ligand and chloroethane (CE) as a halide promoter. Tests determined the effects of temperature, pressure, TEA/Ti, THP/Ti, and CE/Ti molar ratios on overall yield of reaction (YR(%)) and weight of polymer (WPE(mg)) and evaluations were investigated by signal to noise (S/N) ratios and their mean. Moreover, analysis of variance (ANOVA) determined that the THP/Ti molar ratio (with 33.42%) and the temperature (38.99%) had the highest contributions in YR and WPE, respectively, for the aforesaid newly introduced four-member system. The confirmation tests showed very good consistency between predicted and actual results. The results show that this previously untested method can efficiently increase YR and decrease WPE and better demonstrates the role of the catalyst. The results can be applied to improve 1-butene production on an industrial scale and minimize polymer fouling that could result in a reactor shutdown.

Improving microisotacticity of Ziegler–Natta catalyzed polypropylene by using triethylaluminum/triisobutylaluminum mixtures as cocatalyst

Propylene was polymerized with TiCl4/Di/MgCl2 catalyst and cocatalysts containing triethylaluminum (TEA) and triisobutylaluminum (TiBA) in the presence of Ph2Si(OMe)2 (external donor) and hydrogen. Chain structure of the formed polypropylene (PP) was characterized by temperature-rise elution fractionation (TREF) combined with DSC and 13C NMR analysis of the main fractions. Increasing the amount of TiBA in cocatalyst leads to decrease of isotactic index of PP, meanwhile the microisotacticity of the main TREF fractions of PP was enhanced. PP produced with the catalyst activated by a 50/50 TEA/TiBA mixture has the same content of highly isotactic chains as PP produced with the TEA activated catalyst, but main TREF fractions of the former has higher microisotacticity than the later. Fast alkyl exchanges in TEA/TiBA mixtures are found by 1H NMR analysis of the mixtures. By analyzing alkanes released from hydrolyzed catalysts that have been treated with the cocatalyst, alkylation power of TEA/TiBA mixture was found to decrease with increasing its TiBA content. The effects of TEA/TiBA mixture in propylene polymerization is explained by the weaker alkylation power and lower Lewis acidity of the mixed alkylaluminums than pure TEA. Decrease in the alkylation power leads to reduction of active centers with the highest stereospecificity, meanwhile decrease in Lewis acidity intensified the role of De in enhancing stereospecificity of different active centers. When the amount of TiBA in TEA/TiBA mixture falls in a suitable range, the later effect becomes dominant, and evident improvement in microisotacticity of PP can be achieved.

Study on propylene polymerization in the presence of phenolic antioxidant (Irganox 1076) and characterization of stabilized polymers

The aim of this study was to investigate different concentrations of Irganox 1076 on Ziegler–Natta catalyst performance during propylene polymerization. Antioxidant masking was conducted by addition of different molar ratio of triethylaluminum (TEAL). Proton nuclear magnetic resonance and Fourier transform infrared spectroscopy spectra confirmed the complete conversion of antioxidant to aluminum aryloxide form. The different concentrations of masked antioxidant with different molar ratio of TEAL were used during polymerization and the catalyst activity was evaluated. Morphology, particle size distribution, melt temperature, crystallization temperature, degree of crystallinity, oxidative induction time, and isotacticity of products in the presence of masked antioxidant were evaluated. Results showed that incomplete masking of OH phenolic antioxidant led to significant catalyst activity reduction. J. VINYL ADDIT. TECHNOL., 21:285–289, 2015. © 2014 Society of Plastics Engineers

“Two-in-One” catalysis of broad/bimodal molecular-weight-distribution polypropylene by a combination of Ziegler–Natta and metallocene catalysts

A strategy for combining Ziegler–Natta and metallocene catalysis to synthesize broad/bimodal molecular-weight-distribution polypropylene (PP) is proposed. The chemistry is centered on a fabrication as well as utilization of a modified MgCl2/TiCl4 Ziegler–Natta catalyst with incorporated C2-symmetric ansa-metallocene catalyst capable of promoting isospecific propylene polymerization. A MgCl2/TiCl4 catalyst is prepared in the presence of a 1,3-diether internal electron donor, 9,9-bis(methoxymethyl)fluorene (BMMF), which, with a porous physical architecture, is able to accommodate MAO-encapsulated and protected rac-[methylene(3-tert-butyl-1-indenyl)2]ZrCl2 (rac-CH2(3-t-Bu-1-Ind)2ZrCl2) without impairing its own composition and structure. Activation of the two-piece catalyst is found to be best conducted by pairing triisobutylaluminium (TIBA) instead of triethylaluminium (TEA) with MAO. Polymerization of propylene with TIBA-MAO-activated modified MgCl2/TiCl4 catalyst containing rac-CH2(3-t-Bu-1-Ind)2ZrCl2 produces broad/bimodal molecular-weight-distribution PP with tunable compositions. Moreover, reactor particles of PP thus produced are ensured with good granular morphology, which is crucial for application in modern PP industry with dominant bulk and gas polymerization processes.

Activation and Deactivation of the Polymerization of Ethylene over rac‐EtInd2ZrCl2 and (nBuCp)2ZrCl2 on an Activating Silica Support

A study is carried out in order to better understand the kinetic behavior of two different metallocene precursors supported on an activating silica support, and, in particular, to attempt to reduce the significance of catalyst deactivation through the use of different alkylating agents. It is observed that it is difficult to prevent the deactivation of the rac‐EtInd2ZrCl2 sites on the activating support, and, furthermore, the deactivation is accompanied by the disa­ppearance of sites producing the highest‐molecular‐weight polymer. On the contrary, with the (nBuCp)2ZrCl2 precursor, it is possible to manipulate the addition of either tri‐isobutylaluminum (TIBA) or triethylaluminum (TEA) to significantly reduce the deactivation of the catalyst on the activating supports. Finally, the molecular‐weight distribution seems to depend much more on the intrinsic properties of the active sites than on how the active sites are treated. image

Observation on different reducing power of cocatalysts on the Ziegler–Natta catalyst containing alkoxide species for ethylene polymerization

ABSTRACTIn this work, the effects of three types of cocatalyst having different alkyl groups, such as triethylaluminium (TEA), triisobutylaluminum (TiBA), and trioctylaluminium (TnOA), and their concentrations on the catalytic activity and polymer properties were investigated for the Ziegler–Natta catalyst containing alkoxide species. The drastic escalation of catalytic activity was observed when the ratio of Al/Ti was increased only for TEA because of its good diffusivity as proven by the electron spin resonance technique. Moreover, it was found that the characteristic of the alkyl group in cocatalyst affected on the chain transfer ability. The chain transfer ability of TnOA was found to be equal to the TiBA in spite of its concentration was higher. By the way, the cocatalyst types and their concentrations did not affect on the variety of active sites as seen in molecular weight distribution of polymer. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40884.

Kinetic studies on the pyrrole–Cr-based Chevron-Phillips ethylene trimerization catalyst system

An extensive experimental kinetic study of ethylene trimerization was carried out over the Chevron-Phillips homogeneous catalyst system [Cr(2-ethylhexanoate)3 (Cr(2-EH)3)/2,5-dimethylpyrrole (DMP)/co-catalyst/halide] in terms of the effects from organic halide additives, type of co-catalysts, temperature, ethylene pressure, Cr concentration, and ligand/Cr molar ratio, etc. Ten kinds of organic halides and four kinds of organometallic co-catalysts were tested in this work. The 1,1,2,2-tetrachloroethane (TCE) and triethylaluminum (TEA) were found to be the best candidates for this catalyst system. The molar ratios of DMP/Cr, TCE/Cr and TEA/Cr showed a strong impact on the catalytic performance of ethylene trimerization. A detailed catalytic kinetic behavior and the kinetic simulation were also performed for the first time over this catalyst system. It could be extrapolated that the dependency of the trimerization reaction rate on ethylene concentration and catalyst concentration is second-order and first-order, respectively. The apparent activation energy of this reaction is 99.1kJ/mol at the temperature range from 65°C to 95°C. And the apparent reaction rate equation is achieved as follows:.R=5.23×1018exp−99.1RTCca1.12Ce1.95.

1,3‐butadiene polymerization using Co/Nd‐based Ziegler/Natta catalyst: Microstructures and properties of butadiene rubber

Among Ziegler‐Natta catalysts used for 1,3‐butadiene (1,3‐BD) polymerization, the advantage of a neodymium (Nd)‐based catalyst is that it provides butadiene rubber (BR) with a high content of cis−1,4 configuration and a low amount of vinyl−1,2 units. Whereas, a cobalt (Co)‐based catalyst can produce BR with a low content of trans−1,4 configuration. Thus, this research was aimed to prepare BR containing a high content of cis−1,4 configuration with low amounts of both trans−1,4 and vinyl−1,2 units using a combination of Nd‐ and Co‐based Ziegler/Natta catalysts with triethyl aluminum (TEAL) and diethyl aluminum chloride (DEAC) acting as a co‐catalyst and a chlorinating agent, respectively. The effects of the molar Co/Nd ratio, TEAL concentration, DEAC loading, 1,3‐BD content, solvent type, and reaction temperature on % conversion, microstructures, molecular weight, and molecular weight distribution of the obtained BR (Co/Nd‐BR) were evaluated. The Co/Nd‐BR having >97% of cis−1,4 configuration, <2% of trans−1,4 structure, and <1% of vinyl−1,2 unit with >80% conversion was achieved when 3.01 M of 1,3‐BD concentration was treated in a toluene/cyclohexane mixture (7/3 [w/w]). The Co/Nd‐BR exhibited no gel formation with high mechanical performance, which was equivalent to commercial BR produced from a Nd‐based catalyst system. POLYM. ENG. SCI., 55:14–21, 2015. © 2014 Society of Plastics Engineers

Thermochemical Analysis of Hypergolic Propellants Based on Triethylaluminum/Nitrous Oxide

The vacuum specific impulse, density vacuum specific impulse, and solid exhaust products were examined for several propellant formulations based on the pyrophoric material triethylaluminum (TEA) using CEA thermodynamics code. Evaluation of TEA neat and mixed with hydrocarbon fuels with LOX, N2O, N2O4, liquefied air, and HNO3were performed at stoichiometry. The vacuum specific impulse of neat TEA with N2O is comparable to that of nitric acid with the same, but the N2O formulation will produce slightly less solid products during combustion. Additionally, N2O-TEA propellants have vacuum specific impulses and density vacuum specific impulses within 92.9% and 86.7% of traditional hydrazine propellant formulations under stoichiometric conditions.

Preparation and Properties of Ball-Milled MgH<sub>2</sub>/Al Nanocomposites for Hydrogen Storage

For reversible hydrogen storage properties of 17MgH2 + 12Al § Mg17Al12 + 17H2, MgH2/Al nanocomposites (I)­(IV) synthesized by ball milling of MgH2 and Al (or AlH3) were studied in connection with milling conditions. The milling processes consisting of two steps were effective to improve the hydrogen storage behavior; MgH2 was first milled with solutions of triethylaluminium (TEA) in hexane, followed by addition of Al and TEA solutions. The mixtures were further milled to yield the nanocomposite (III). In preparing the nanocomposite (IV), AlH3 was used instead of Al. For the nanocomposites (III) and (IV), it was proved by XRD, TDS, DSC and PCI that such ball-milling led to high dispersion of nanocrystalline MgH2 in Al and/or AlH3 matrix in the resulting nanocomposites. In DSC measured under a 0.1MPa hydrogen atmosphere, the nanocomposites (III) and (IV) exhibited reversible H2 absorption and desorption at 493­503 and 573­593K, respectively. [doi:10.2320/matertrans.M2013368]

Experimental studies for semi-cryo engine development

Development of Cryogenic engine is essential requirement in order to improve the pay load capability of rocket launching systems. Cryogenic stage is more suitable for the upper stage of the launch vehicle mainly due to the high specific impulse and relatively low structural weight. As the pay load increases a high thrust booster engine is also required for the launch vehicle. Semi cryogenic propulsion is ideally suitable for booster engine, in terms of higher density impulse and low cost and easy handling. LPSC has undertaken the development of Semi Cryo Engine to power the booster stages of India's future launch vehicles. The Engine works on Oxidizer rich staged combustion cycle, using LOX and Isrosene propellant combination. Preburner (PB) and Thrust Chamber (TC) are the major subsystems of the engine. PB produces the hot gases at lower temperature for driving the turbo pump which raises the propellant pressure and TC produces hot gas in the chamber at high temperature which expands through the nozzle for generating thrust. Design of injector and arrangement of injector are critical in the design of pre burner and Thrust chamber so as to admit and meter the propellants into the chamber with proper mixture to ensure complete and stable combustion. The propellants require ignition source for initiating ignition. A mixture of Tri-ethyl Aluminium and Tri-ethyl Boron (TEA/TEB) is used as a source of ignition which is hypergolic with oxygen. In order to understand the behavior of the different systems and technology involved, it is planned to design and realize injector and evaluate the characteristics of its performance during cold flow as well as hot test. The development programme is planned in two phases. Initially Single element pre burner and thrust chamber hardware are realized, cold flow test are carried out and hot test are being done. It is also planned to realize subscale thrust chamber and pre burner as a phase-2 activity to study the behavior of multi element interaction and its performance. A lot of critical technologies are to be developed and demonstrated prior to the development of full scale engine. The characterization of injector elements, performance validation at near operating conditions, Ignition characteristics of hypergolic liquid, validation of material, evaluation of different coating are set for the objectives of the initial phase of tests. This paper discuss the different experimental studies carried out, experimental results and features of hardware, design aspects, cold flow characteristics, hot test result for the initial phase of development and also future plan of action.

Process parameter optimization through Design of Experiments in synthesis of high cis-polybutadiene rubber

The neodymium octanoate (Nd), diethylaluminum chloride (DEAC) and triethylaluminum (TEAL)-based catalyst system was studied for polymerization of 1,3-butadiene (BD). The present paper deals with the identification of linear, square and interaction effects of the process parameters on conversion, molecular weight and microstructure of the polybutadiene rubber and consequently the optimization of polymerization process using statistical tool, Design of Experiments. The process comprises of two steps: (1) active catalyst formulation and (2) polymerization of BD. Both steps were optimized sequentially using Box–Behnken design (BBD) and each BBD has three independent variables. In both designs and models, the proposed correlations represent the experimental data adequately for response variables viz. conversion, molecular weight and cis-content. Optimum catalyst formulation was observed to be BD/Nd, DEAC/Nd and TEAL/Nd molar ratio of 902.88, 1.74 and 27.51, respectively. Optimum polymerization conditions were monomer concentration 22%, reaction time 3.3h and reaction temperature 42°C for the said catalyst system.

실리카 나노기공내 담지된 알루미늄계 유기금속화합물을 이용한 L-lactide 중합

In this study, the bulk polymerizations of L-lactide were carried out with triethylaluminium (TEAL), which was supported inside of the nanopore of silica. The feed amount of TEAL in the feed, the immobilization time and temperature were changed to observe the effect of immobilization condition on the polymerization performance with the silica- supported TEAL. As the feed amount of TEAL increased, the conversion of polymerization increased. The highest molecular weight (MW) was achieved at 8 mmol/g-silica of TEAL. Hexane and toluene as solvents were employed to investigate the effect of temperature on the immobilization. Hexane showed better efficiency of immobilization TEAL and the immobilization temperature at showed the highest conversion and MW.

Influence of the aluminum alkyl co-catalyst type in Ziegler-Natta ethene polymerization on the formation of active sites, polymerization rate, and molecular weight

The influence of the concentration of the co-catalysts triethylaluminium (TEAL), tri-iso-butylaluminium (TIBAL), tri-n-octylaluminium on the polymerization rate for standard Ziegler-Natta catalyst systems was studied. By comparing the influence of monomeric TIBAL with TEAL co-catalyst on the polymerization activity, the effect of TEAL dimerization was described. The use of the Eley-Ridealadsorption model instead of Langmuir-Hinselwood model is proposed for the absorption of monomeric aluminiumalkyl species and for the formation of active centers C*. It is further proposed that steric hindrance from different co-catalysts, which results in a higher molecular weight (MW) of polymers, is caused by active centers with reduced space for chain transfer reactions.

The Effect of Substituents in PNPNH Ligands on Activity and Selectivity of a Chromium-Based Catalyst System for Highly Selective Ethylene Trimerization

The influence of ligand substituents on a highly selective homogeneous catalyst system for the trimerization of ethylene to 1-hexene consisting of chromium(III) acetylacetonate, a ligand with a PNPNH backbone, tetraphenylphosphonium chloride as chlorine source, and triethyl aluminum as activator was investigated. These N-modified and P-modified ligands, which differ strongly in their electronic and steric properties of the substituents, were tested in the ethylene trimerization at three temperatures (50, 70, and 90 °C). Interestingly, the substituents at the N atoms of the PNPNH-backbone had only little effect on the catalytic activity, on 1-hexene selectivity, and on thermal stability of the catalyst system, whereas the substituents at the P atoms significantly influenced the efficiency of the system. This is even more surprising as the PNP ligand from SASOL for ethylene tetramerization is much more sensitive against substituent variation at its N atom.

Effect of the Combined External Electron Donors on the Structure and Properties of Polypropylene/Poly(ethylene-co-propylene) In-Reactor Alloys Prepared by High-Efficiency Industrial Ziegler–Natta Catalyst

In this work, a series of isotactic polypropylene/ethylene–propylene rubber (iPP/EPR) in-reactor alloys were prepared by high-efficiency industrial Ziegler–Natta catalyst with diphenyldimethoxysilane/dicyclopentyldimethoxysilane (DDS/D-donor) mixtures as external electron donors. The effects of the external electron donor on the structure and mechanical properties of the iPP/EPR in-reactor alloys were studied. According to the characterization results, the iPP/EPR in-reactor alloys were mainly composed of random poly(ethylene-co-propylene), multiblock poly(ethylene-co-propylene), and highly isotactic PP. For DDS/D-donor mixtures as external electron donors and triethylaluminum (TEA) as the cocatalyst, as the amount of D-donor in DDS/D-donor mixtures increased, the molecular weight of polypropylene homopolymer and the structural uniformity of multiblock poly(ethylene-co-propylene) increased, whereas when D-donor alone was used as the external electron donor, they decreased. However, the isotacticity of pol...

Formation of [Cr(CO)x(Ph2PN(iPr)PPh2)]+ Structural Isomers by Reaction of Triethylaluminum with a Chromium N,N-Bis(diarylphosphino)amine Complex [Cr(CO)4(Ph2PN(iPr)PPh2)]+: An EPR and DFT Investigation

The interaction of triethylaluminum (TEA) with a solution of the paramagnetic Cr(I) bis(phosphine) complex [Cr(CO)41][Al(OC(CF3)3)4] (1 = Ph2PN(iPr)PPh2) has been studied using EPR and DFT. It was found that the TEA is responsible for the complete removal of all CO groups from the [Cr(CO)41]+ complex, producing the [Cr(1-bis-η6-arene)]+, and this reaction occurs via a dominant pathway involving a series of [Cr(CO)x1]+ (x < 4) intermediates, consistently including the cis-[Cr(CO)31]+ complex (species A) and the “piano-stool”-type [Cr(CO)21]+ complex (species C). A further [Cr(CO)21]+ intermediate complex (labeled species D, which is a structural isomer of species C) was also identified experimentally, suggesting a second pathway for TEA activation may also be operative. All of these paramagnetic complexes have been characterized by CW EPR, and the spin Hamiltonian parameters were verified using DFT. The distribution and type of [Cr(CO)x1]+ intermediates formed were found to be very sensitive to the experimental conditions, including the quantity and manner of TEA addition, the temperature of activation, and the aging time of the solution.

New aluminum 2,2′-methylenebis(4-chloro-3-methyl-6-(isopropyl)phenoxides): Structural characterization of an unusual ionic aluminum bisphenoxide [Al(THF)4(Cl)2]+[Al(mcmip)2]−·x THF

Abstract The synthesis and X-ray structure determination of an uncommon ionic aluminum bisphenoxide [Al(THF)4(Cl)2]+[Al(mcmip)2]−·1.1 THF (1) and its neutral analogue (mcmip)Al(CH2CH3)(THF) (2) are reported (mcmipH2: 2,2′-methylenebis(4-chloro-3-methyl-6-(isopropyl)phenol). The ligand was reacted in THF with diethyl aluminum chloride, respectively triethyl aluminum, under liberation of ethane to yield crystalline aluminum bisphenoxides. Compound 2 exhibits the usual structural features found in neutral THF-aluminum bisphenoxides adducts whereas the ionic compound 1 consists of a cationic octahedral aluminum dichloride moiety, [Al(THF)4(Cl)2], and an anionic di-bisphenoxide aluminate fragment [Al(mcmip)2] containing two 2,2′-methylenebis(4-chloro-3-methyl-6-(isopropyl)phenol) ligands. Both aluminum bisphenoxides were tested as catalysts in the copolymerization of cyclohexene oxide with CO2 and displayed similar good catalytic activities although the carbonate amounts present in the copolymer remain low.

Mesoporous Polystyrenes via Lamellar Block Copolymer Assembly

Block copolymers (BCPs) are well-known to self-assemble into a variety of nanostructures, such as spherical, cylindrical, gyroid-like, and lamellar morphologies, depending on the volume fraction of the block and/or the chain architecture. Organic mesoporous materials applicable to separations, sensors, etc., could be one of the interesting fields using block copolymers. To prepare organic mesoporous materials, block copolymers should consist of chemically inert and labile blocks. A polystyrene-block-polylactide (PS-b-PLA) system is a representative example. The PS block is mechanically and chemically robust, while the PLA block is easily hydrolyzed under basic conditions. In a given morphology, PLA domain structures determine the resulting pore morphology. Among possible pore architectures, one-dimensional cylindrical pores have been intensively studied, perhaps because the morphology exists over a wide range of volume fraction, and also because it consists of confined pores. Recently, a three-dimensionally connected mesoporous structure from a gyroid morphology was also reported. On the other hand, due to its wide volume fraction range near 0.5, a lamellar morphology can be obtained as readily as a cylindrical morphology. Nevertheless, a lamellar morphology has rarely been utilized for preparing organic mesoporous materials. With this in mind, it would be interesting to prepare lamellar mesoporous materials using a lamellar BCP. In this paper, we report a mesoporous material, consisting of PS layers, by a chemical etching of sacrificial PLA layers in a lamellar structure. To obtain the porous material, we first synthesized a block copolymer (PS-b-PLA) using a click reaction of individually prepared PS and PLA blocks. The PS was prepared by the anionic polymerization of styrene. The PS end was functionalized with a hydroxyl group, which was converted into an alkynyl group for the next click coupling (Scheme S1(b)). From the H NMR data, the number average molecular weight (Mn) of the obtained PS was determined to be 14,400 g/mol. The other PLA block was synthesized by a ring opening polymerization (ROP) of D,L-lactide using triethyl aluminum as the catalyst (Scheme S1(c)). For the click coupling with the PS block, the ROP initiator contained an azide end. From the H NMR analysis, the Mn was estimated to be 10,500 g/mol, and the GPC data showed the polydispersity (Mw/Mn) to be 1.06. The click coupling was carried out using Cu(I)Br/PMDETA as the catalyst (Scheme 1). The obtained block copolymer showed a triazolyl hydrogen at 7.39 ppm in the H NMR spectrum (Figure S1), and the polydispersity was 1.04, indicative of its narrow molecular weight distribution (Figure S2). The volume fraction ( f ) of the PS block was calculated to be 0.60. The differential scanning calorimetry (DSC) data of the block copolymer displayed two glass transitions at 51.4 C

Ring-opening polymerization behavior of l-lactide catalyzed by aluminum alkyl catalysts

The l-lactide polymerization using trimethylaluminum (TMA), triethylaluminum (TEAL), trioctylaluminum (TOA), triisobutylaluminum (TIBA), and aluminum isopropoxide (Al(O-i-Pr)3) were studied to produce a PLA. The conversion, turnover frequency (TOF), and molecular weight of TIBA were higher than those of Al(O-i-Pr)3 with the polymerization time of 5min. In the case of 15min, the conversion of aluminum alkyls was lower than that of Al(O-i-Pr)3, but the molecular weight of PLA produced by aluminum alkyl was relatively high in comparison with the catalytic activity of Al(O-i-Pr)3. TMA, TEAL, and TIBA seemed to have lower propagation rates and much lower termination rates than Al(O-i-Pr)3.