Internal Electron Donor Research Articles

MgCl2‐supported TiCl4catalysts containing diethyl norbornene‐2,3‐dicarboxylate internal electron donor for 1‐butene polymerization: Effects of internal electron donor configuration

ABSTRACTThree isomeric 5‐norbornene‐2,3‐dicarboxylic acid diethyl ester (NDDE) withendo‐,exo‐, andtrans‐configuration have been synthesized and employed as internal electron donors (IED) in 1‐butene polymerization over magnesium chloride supported Ziegler–Natta catalysts. It was found that the configuration of NDDE plays a key role in tuning the catalyst activity, stereospecificity, molecular weight (MW), and polydispersity index (PDI) of resulting poly(1‐butene). The type of catalyst withcis‐5‐norbornene‐endo‐2,3‐dicarboxylic acid diethyl ester as IED shows the highest catalyst activity, while catalyst withtrans‐NDDE as IED yields the poly(1‐butene) with the highest MW and the most broad PDI. IR results showed that the NDDE withendo‐,exo‐, andtrans‐configuration have different coordination way to MgCl2, subsequently affecting the catalysts performance. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci.2014,131, 40758.

9-Fluorenemethanol: an internal electron donor to fine tune olefin polymerization activity

A new MgCl2 based molecular adduct has been synthesized with 9-fluorenemethanol (9FM) as a novel internal electron donor (IED), along with ethanol (EtOH) (MgCl2·n9FM·xEtOH). The above molecular adduct has been subjected to a variety of structural, spectroscopic and morphological characterization techniques. The results of the solid state (13)C CPMAS NMR technique suggests the coordination of 9FM to MgCl2. Observation of a low angle diffraction peak at 2θ = 5.7° (d = 15.5 Å) underscores the coordination of 9FM along the z-axis, and ethanol in the molecular adduct. Active Ziegler-Natta catalysts were prepared by two different synthesis methods; the conventional method to obtain a high surface area active catalyst, and other one with 9FM as an integral part of the active catalyst in order to study the influence of 9FM as an IED over the active sites. The active catalysts were also characterized thoroughly with different analytical tools. The XRD results show (003) facets of δ-MgCl2 (α-MgCl2) for the conventional (non-conventional) titanated catalyst. Results of the ethylene polymerization activity study reveals that the conventionally prepared highly porous active catalyst shows 1.7-2.5 times higher activity than the non-conventional prepared catalyst; however, the latter shows a low molecular weight distribution and confirms the role of the Lewis base as an IED.

Adsorption of TiCl4 and electron donor on defective MgCl2 surfaces and propylene polymerization over Ziegler-Natta catalyst: A DFT study

The formations of defective MgCl2 surfaces, and subsequent adsorption of Ti species and electron donor, as well as propylene polymerization over the Ziegler-Natta catalyst have been investigated using density functional theory (DFT) method. Twelve possible support models of regular and defective MgCl2 (110) and (100) surfaces were built. The individual adsorptions of titanium chlorides as mononuclear or dinuclear, and ethyl benzoate (EB) as electron donor, on these models were evaluated. The analysis of energies presented the cases of EB adsorption were generally more stable than titanium chlorides on both surfaces. Thus, EB as internal electron donor mainly prevented TiCl4 from coordinating on the MgCl2 surfaces where mostly non-stereospecific active sites could be formed. Exceptionally, A5 the site model with terminal Cl-vacancy on the MgCl2 support, presented stronger adsorption of TiCl4 than that of EB on (110) surface. Since the TiCl4 and ethyl benzoate (EB) would compete to adsorb on the support surface, it seems reasonable to assume that TiCl4 might predominately occupy this site, which can act as the most plausible active site for propylene polymerization. The first insertion of propylene monomer into the A5 active site model showed that it exhibited good regioselectivity but poor stereospecificity in the absence of electron donor.

Copolymerization of ethylene and 1-hexene with TiCl4/MgCl2 catalysts modified by 2,6-diisopropylphenol

A supported TiCl4/MgCl2 catalyst without internal electron donor (O-cat) was prepared firstly. Then it was modified by 2,6-diisopropylphenol to make a novel modified catalyst (M-cat). These two catalysts were used to catalyze ethylene/1-hexene copolymerization and 1-hexene homopolymerization. The influence of cocatalyst and hydrogen on the catalytic behavior of these two catalysts was investigated. In ethylene/1-hexene copolymerization, the introduction of 2,6- i Pr2C6H3O- groups did not deactivate the supported TiCl4/MgCl2 catalyst. Although the 1-hexene incorporation in ethylene/1-hexene copolymer prepared by M-cat was lower than that prepared by O-cat, the composition distribution of the former was narrower than that of the latter. Methylaluminoxane (MAO) was a more effective activator for M-cat than triisobutylaluminium (TIBA). MAO led to higher yield and more uniform chain structure. In 1-hexene homopolymerization, the presence of 2,6- i Pr2C6H3O- groups lowered the propagation rate constants. Two types of active centers with a chemically bonded 2,6- i Pr2C6H3O- group were proposed to explain the observed phenomena in M-cat.

Synthesis of (co-)polyethylene with broad molecular weight distribution by the heterogenous Ziegler–Natta catalysts via one-pot strategy

A new method was presented for preparing (co-)polyethylene with broad molecular weight distribution (MWD) and high molecular weight employed by the novel heterogeneous Ziegler–Natta catalysts via one-pot strategy. The preparation of these catalysts involved the introduction of alkoxy silane compounds as electron donors. The influences of the electron donors structure, as well as polymerization conditions such as temperature, molar ratio of Al/Ti, ethylene pressure and the concentration of 1-hexene in feed on the polymerization performance for ethylene (co-)polymerization, were investigated. The morphology of the catalyst particles was characterized by SEM and Ti content of these catalysts was characterized by ICP. The GPC results showed that the obtained homopolyethylene and ethylene/1-hexene copolymer had the widest molecular weight distribution up to ca 50 when diethoxy-isopropoxy-(t–butoxy)-silane (ED3) was used as internal electron donor. The 13C NMR and FT-IR analysis indicated that these catalysts efficiently catalyzed the copolymerization of ethylene with 1-hexene.

Physiological and biochemical responses of transgenic potato plants with altered expression of PSII manganese stabilizing protein

Manganese-stabilizing protein (MSP) represents a key component of the oxygen-evolving complex (OEC). Transgenic potato plants with both enhanced (sense) and reduced (anti-sense) MSP expression levels were generated to investigate the possible physiological role of MSP in overall plant growth, particularly in tuber development. MSP antisense plants exhibited both higher tuberization frequency and higher tuber yield with increased total soluble carbohydrates. The photosynthetic efficiencies of the plants were examined using the OJIP kinetics; MSP-antisense plants were photosynthetically more active than the MSP-sense and UT (untransformed) control plants. The oxygen measurements indicated that the relative oxygen evolution was directly proportional to the MSP expression, as MSP-antisense plants showed much lower oxygen evolution compared to MSP-sense as well as UT plants. MSP-sense plants behaved like the UT plants with respect to morphology, tuber yield, and photosynthetic performance. Chlorophyll a fluorescence analyses indicate a possible lack of intact Oxygen Evolving Complexes (OECs) in MSP antisense plants, which allow access to internal non-water electron donors (e.g., ascorbate and proline) and consequently increase the Photosystem II (PSII) activity of those plants. These findings further indicate that this altered photosynthetic machinery may be associated with early tuberization and increased tuberization frequency.

Enhancement of Photoresponse Properties of Conjugated Polymers/Inorganic Semiconductor Nanocomposites by Internal Micro‐Magnetic Field

In this paper, the effect of the internal micro-magnetic field (IMMF) on the photocurrent property of conjugated polymer/inorganic semiconductor nanocomposites is reported and analyzed. By using the redox reaction, magnetic Fe(3)O(4) nanoparticles were coated on the surface of highly active nanorods of conjugated polyaniline (PANI), forming an internal micro-magnetic electron donor (i.e., Fe(3)O(4)@PANI). After subsequent incorporation of CdS nanoparticles (serving as electron acceptors), the power conversion efficiency (PCE) of the system (Fe(3)O(4)@PANI-CdS) was found to be as high as 3.563%, contrasting sharply with the value (1.135%) of the hybrid without Fe(3)O(4) (PANI-CdS). This obvious enhancement originated from the fact that the IMMF increased the number of singlet polaron pairs through field-dependent intersystem crossing (ISC), giving a positive contribution to the photocurrent generation. Additionally, the dependence of the photocurrent on the remnant magnetization of the Fe(3)O(4)@PANI-CdS nanocomposites was investigated. A percolation behavior was observed, which was due to the appearance of interpenetrating networks consisting of donor and acceptor phases, leading to the recombination of charge carriers through trapping. The outcomes of the present work might help to produce a new family of conjugated organic/inorganic semiconductor nanocomposites with designed optoelectronic performances.

Propylene polymerization over MgCl2-supported TiCl4 catalysts bearing different amounts of a diether internal electron donor: Extrapolation to the role of internal electron donor on active site

In this work, the composition of MgCl2-supported Ziegler-Natta (ZN) catalysts bearing different amounts of 9,9-bis(methoxymethyl)fluorine (BMMF) and the propylene polymerization over these catalysts are investigated. Based on the experimental results, the models of active sites suitable for ZN catalysts with/without internal donor BMMF are established, and they can be described as follows: atactic site (I)—isolated TiCl4 monomeric species on the (110) lateral cut (around which there is no complexes), weakly isospecific site (II)—semi-isolated and surrounded TiCl4 monomeric species on the (110) lateral cut (in the vicinity of which BMMF or other TiCl4 is adsorbed), and highly isospecific site (III)—dimeric TiCl4 species (Ti2Cl8) on the (104) lateral cut. Meanwhile, the mechanism underlying the role of BMMF on active sites is revealed (i) convert atactic sites (I) to weakly isospecific site (II) by occupying either or both of L1 or/and L2 vacancies around site; (ii) improve the isotacticity of weakly isospecific site (II) in donor-free ZN catalyst by adsorbing at L2 vacancy or/and replacing the Cl for TiCl4 at L1; and (iii) replace highly isospecific site (III). In addition, these roles of BMMF are successively achieved according to the amount of BMMF added. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Highly filled clay polypropylene nanocomposites prepared by in situ polymerization with clay-supported magnesium/titanium catalysts

Ziegler-Natta catalysts based on TiCl 4 supported on clay/MgCl 2 were obtained and tested in propylene polymerization. Two types of clay: the sodium clay Gelmax 400 and the organophylic one Cloisite 30B were employed. The catalysts preparation involved the treatment of the clays with an alcohol adduct of MgCl 2 followed by treatments with TiCl 4 and triethylaluminium (dealcoholation), optionally using ethyl benzoate as internal electron donor. The catalyst performance showed to be markedly influenced by the clay type and synthesis conditions. Dealcoholation was the main factor that affected the catalyst activity. Impregnation of clay/MgCl 2 supports with Ti generated catalysts with about 5 wt.% of titanium and crystalline structure with different families of lamellar structures, evidenced by low intensity peaks at different (0 0 1) plane 2 θ position in the X-ray diffraction curves of the clay-supported catalysts. The catalysts were used in the polymerization of propylene producing polypropylenes with significant isotacticity and crystallinity. Among the catalysts, that prepared using the sodium clay as support without internal donor showed the higher catalytic activity (6433 g PP/g Ti). Due to different catalyst activity, polypropylenes with different contents of clay were obtained. The residual clay acts as filler, PP nanocomposites, were obtained by this in situ method, some of them highly filled. The degradation behavior of these highly filled nanocomposites was highly improved with increasing of the on set and maximum degradation temperatures in the range of 200 °C. The shape of the polymer particles was very similar to those of catalyst particles due to the replica phenomenon, also observed for these catalyst systems.

Toward an Understanding of the Molecular Level Properties of Ziegler−Natta Catalyst Support with and without the Internal Electron Donor

Two Ziegler−Natta catalysts supported on molecularadducts, namely, MgCl2·6EtOH (ME) and MgCl2·5EtOH·EtOOCPh (Est-ME), have been prepared. A systematic effort has been made to unravel the molecular level structure−property relationships of the catalysts and adducts. Ethylbenzoate is an internal electron donor, and its in situ formation through EtOH + PhCOCl coupling is successfully achieved. The above adduct has been treated with TiCl4, and the resultant catalyst (Ti/Est-ME) is evaluated for ethylene polymerization activity. IR and 13C CP/MAS NMR of Est-ME (Ti/Est-ME) show carbonyl features at 1730 (1680) cm−1 and 169 (170) δ, respectively, providing direct support for the presence of ester as an integral part. In spite of low surface area, Ti/Est-ME gives higher yield for ethylene polymerization than the one derived from ME. The results indicate that electronic environment is more important than surface area or any other single factor in determining the polymerization activity.

Dependence of comonomer effect and hydrogen effect on internal donor in ethylene/1-hexene copolymerizations with MgCl2-supported catalysts

AbstractEthylene homopolymerization and copolymerizations with 1-hexene by three types of MgCl2-supported catalysts were compared. Cat-1 contains no internal electron donor (ID), Cat-2 contains phthalic anhydride (PA) as ID, and Cat- 3 contains anisole as ID. The influences of two kinds of ID on comonomer effect, the role of hydrogen, polymerization kinetics in ethylene/1-hexene copolymerization were investigated. The addition of ID improves the catalysts activities in ethylene polymerization. In comparison with ethylene homopolymerization, these ethylene/1-hexene copolymerization systems all showed strong comonomer effects. However, internal donor, especially anisole, weakens the extent of comonomer activity enhancement. When the concentration of 1-hexene is 0.6 mol/L, catalysts activities increase remarkably with adding a small amount of hydrogen. But, the addition of ID reduces the sensitivity of catalyst activity to hydrogen. The introduction of anisole increases the homo-polymerization rate rapidly at the initial stage, but makes it decay earlier. In ethylene/1-hexene copolymerization with hydrogen, the addition of phthalic anhydride as ID can stabilize the polymerization rate, but anisole accelerates the decaying trends. The results are discussed based on a kinetic mechanistic model of the ID effect on ethylene copolymerization.

Feasibility of Focused‐Pulsed Treated Waste Activated Sludge as a Supplemental Electron Donor for Denitrification

We evaluated the feasibility of using waste activated sludge (WAS) from a wastewater treatment plant as an internal electron donor to fuel denitrification, by increasing its bioavailability with Focused-Pulsed (FP) technology. The focused-pulsed treatment of WAS (producing FP-WAS) increased the semi-soluble chemical oxygen demand (SSCOD) by 26 times compared with the control WAS. The maximum denitrification rate of FP-WAS (0.25 g nitrate-nitrogen [NO3- -N]/g volatile suspended solids [VSS] x d) was greater than for untreated WAS (0.05 g NO3- -N/g VSS x d) and methanol (0.15 NO3- -N/g VSS x d). Centrifuging out the larger suspended solids created FP-centrate, which had a rate (0.14 g NO3- -N/g VSS x d) comparable with that of methanol. Thus, FP treatment of WAS created SSCOD, which was an internal electron donor that was able to drive denitrification at a rate similar to or greater than methanol. One trade-off of using FP-WAS for denitrification is an increase in total Kjeldahl nitrogen (TKN) loading. While FP-WAS achieved the lowest total nitrogen and NO3- -N concentrations in the batch denitrification test, its final ammonia-nitrogen (NH3-N) concentration was the highest, as a result of the release of organic nitrogen from the FP-treated biomass; FP-centrate had less release of total soluble nitrogen. While the return of total nitrogen (TN) is small compared with the SSCOD, the effects of the added nitrogen loading need to be considered.

Effect of electron donors on polymerization of propylene in the presence of titanium-magnesium catalysts

The effect of internal and external electron donors on the polymerization of propylene in a liquid monomer or a hydrocarbon diluent (hexane) in the presence of a titanium-magnesium nanocatalyst activated with an organoaluminum compound (triethylaluminum, triisobutylaluminum) and the properties of the resulting PP are studied. The polymerization of propylene in the absence of internal and external donors yields atactic PP, whereas, in the presence of a catalyst containing an aryl internal donor, isotactic PP is formed. The activity and stereospecificity of the catalytic system substantially depends on the method of electron-donor introduction. The thermal treatment of the catalyst with an electron donor affects its activity and stereospecificity.

Magnesium chloride supported Ziegler‐Natta catalysts containing succinate internal electron donors for the polymerization of propylene

AbstractFour of 9,10‐dihydroanthracene‐9,10‐α,β‐alkyl succinates have been synthesized and used as internal electron donors in MgCl2‐supported Ziegler‐Natta catalysts. The performances of the catalysts on the propylene polymerization have been investigated. The obtained polymers possess high‐isotacticity and the polymerization activity is comparable with the catalysts using 9,9‐bis(methoxymethyl)fluorene and diisobutyl phthalate as internal donor. With dimethoxydiphenylsilane as external donor, the catalysts for the polymerization of propylene exhibit satisfactory activities and are sensitive toward hydrogen. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Structure of Donor Molecule 9,9-Bis(Methoxymethyl)-Fluorene in Ziegler-Natta Catalyst by Infrared Spectroscopy and Quantum Chemical Calculation

Infrared vibrational spectroscopy has been used to reveal the conformations of the Ziegler−Natta catalysts internal electron donor 9,9-bis(methoxymethyl)-fluorene and its selectively deuterated derivative (9,9-bis(1,1-dideutero-methoxymethyl)-fluorene), in the solid state, complexed with TiCl4 and MgCl2 and in the catalyst precursor. The experimental spectra have been interpreted by means of spectroscopic correlations and theoretical results from quantum chemical calculations on selected molecular models. From experimental and theoretical data two chelating geometries of the donors with both oxygen directly interacting with Ti or Mg atoms turn out to be favorable. They can be identified by the four dihedral angles along the CH3−(O−CH2−R−CH2−O)−CH3 residue that take on conformations of approximately trans (T), gauche+ (G), or gauche− (G′), namely, TGGT and TGG′T. We propose the TGGT conformations for the crystal phase of the donor, the TGG′T when it is complexed with TiCl4, and both TGGT and TGG′T when complexed with MgCl2 along the [110] lateral cut. In the precatalysts, donors molecules are complexed along the [110] MgCl2 lateral cut and likewise the MgCl2 complex. A model for the catalytic sites consisting of TiCl4 species and donor molecules complexed along the [110] lateral cut is proposed.

A stacked neural network approach for yield prediction of propylene polymerization

AbstractPrediction of reaction yield as the most important characteristic process of a slurry polymerization industrial process of propylene has been carried out. Stacked neural network as an effective method for modeling of inherently complex and nonlinear systems–especially a system with a limited number of experimental data points–was chosen for yield prediction. Also, effect of operational parameters on propylene polymerization yield was modeled by the use of this method. The catalyst system was Mg(OEt)2/DIBP/TiCl4/PTES/AlEt3, where Mg(OEt)2, DIBP (diisobutyl phthalate), TiCl4, PTES (phenyl triethoxy silane), and triethyl aluminum (AlEt3) (TEAl) were employed as support, internal electron donor (ID), catalyst precursor, external electron donor (ED), and co‐catalyst, respectively. The experimental results confirmed the validity of the proposed model. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Preparation of MgCl 2-supported Ziegler–Natta catalyst systems with new electron donors

In the present work, the effect of new internal and external electron donors for Ziegler–Natta systems of the type MgCl 2/DI/TiCl 4/DE/AlR 3 was compared with the conventional use of n-butyl phthalate and dimethoxy-diphenylsilane as electron donors. Catalyst systems employing various internal and external donors were evaluated in propylene polymerization. The polymers were characterized by infrared absorption spectroscopy, differential scanning calorimetry and heptane extraction. The prepared catalysts with the new internal donors produced polypropylene with isotactic index up to 98% under the polymerization conditions employed.

Supported Ziegler–Natta catalysts for propylene polymerization. Study of surface species formed at interaction of electron donors and TiCl 4 with activated MgCl 2

Adsorption of various internal electron donors (IDs) and coadsorption of these IDs with TiCl 4 on activated MgCl 2 have been studied by DRIFT and analytical techniques. As a result, the structures of the ID species on the (1 0 4) and (1 1 0) MgCl 2 surfaces were proposed. Based on the ν(C O) band resolution data for the adsorbed ID, it was estimated that the activated MgCl 2 surface contains ca. 90% of the five-coordinated Mg cations residing on the (1 0 4) surface and ca. 10% of the four-coordinated Mg cations residing on the (1 1 0) surface. The size of ID molecule was found to influence its adsorption more significantly on the (1 0 4) MgCl 2 surface than on the (1 1 0) MgCl 2 surface. Coadsorption of the various ID and TiCl 4 demonstrated that TiCl 4 formed greatly weaker surface complexes than the ID; obviously, upon coadsorption TiCl 4 occupies mainly the adsorption sites that are inaccessible for the ID because of steric reasons.

Effect of internal electron donor on copolymerization of ethylene and 1-hexene catalyzed by supported Ziegler- Natta catalysts

AbstractThe four kinds of TiCl4/MgCl2 type supported Ziegler-Natta catalysts, Cat-1, Cat-2, Cat-3 and Cat-4, were prepared by reaction of MgCl2-ethanol adduct with TiCl4. Cat-1 contains no internal electron donor (ID), Cat-2 contains diethyl phthalate (DEP) as ID, Cat-3 contains anisole as ID, and Cat-4 contains both DEP and anisole as ID. Ethylene copolymerizations with 1-hexene by these catalysts were compared. Influences of the internal electron donor on catalyst activity, copolymer composition, composition distribution, molecular weight and molecular weight distribution were investigated. Cat-3 showed the largest ability of incorporating 1-hexene into copolymer chains among the four catalysts. Each copolymer sample was fractionated into two fractions: fraction soluble in boiling nheptane (HS) and fraction insoluble in boiling n-heptane (HI). 1-Hexene content of the HS fraction is 6~10 times of that in the HI fractions. Amount of the HS fraction of copolymer by Cat-2 and Cat-4 was much lower than that of Cat-1 and Cat-3. Introduction of internal donor to the catalysts, especially diethyl phthalate (DEP), increased the blockiness of HI fractions. The molecular weight of both fractions increased when there is ID in the catalyst. Addition of anisole reduced the difference in molecular weight between HS fraction and HI fraction, but addition of PA enlarged the difference. The results are discussed based on a mechanistic model of MgCl2-supported Ziegler-Natta catalysts.

Experimental and Computational Approaches on the Isospecific Role of Monoester‐Type Internal Electron Donor for TiCl4/MgCl2 Ziegler‐Natta Catalysts

AbstractIn this work, a combination of experimental and computational approaches on the isospecific role of monoester‐type internal electron donors (ED) such as phenylpropionate (PhP), ethylheptanoate (EH), methylbenzoate (MB), ethylbenzoate (EB) for TiCl4/ED/MgCl2 Ziegler‐Natta catalysts had been performed. The propylene polymerization results revealed that the isospecificity of catalysts increases in the following order: PhP < EH < MB < EB. The subsequent molecular modeling on the electronic properties of the donors and two kinds of cluster model catalysts: TiCl4/ED/MgCl2 and TiCl4/ED/(MgCl2)4 based on density functional theory (DFT) method was carried out. Two kinds of ED coordination on MgCl2 clusters through either O or O within the monoester‐type ED had been disclosed. A perfect correlation between the dipole moment of ED, the coordination bond length of O … Mg, the competitive coordination from O with Mg ion and the isospecificity of the catalysts had been established.