MgCl2 Supported Titanium Catalysts Research Articles

Effect of novel amido ester internal donor on the performance of Ziegler-Natta catalyst for propylene polymerization

Various classes of molecules like diethers, succinates, diesters, amido esters are currently being used as internal donors on MgCl2 supported titanium catalysts for isotactic polypropylene as an alternative to phthalate donors owing to their potential health risk laid down by REACH legislation. In the present paper, design and synthesis of a few novel amido ester internal donors with single chiral center (7–11) by mimicking the model amido ester 3 having two chiral centers; and their catalyst preparation method were described. Further preliminary polymerization tests with newly synthesized donor molecules were investigated and results revealed that by structurally mimicking 3 with one chiral center and also with varied substitutional patterns in ester/amido moiety decline the polypropylene activity as well as isotacticity. These donor molecules are ineffective for appropriate coordination on MgCl2 sites on inducing steric hindrance for improved isotacticity; nevertheless also induces poisoning effect for the active Ti centers leading to catalyst fouling in many cases.

Sustainable rosin acid ester as internal electron donors in Ziegler-Natta catalysts for synthesis of isotactic polypropylene with high melt flow rate

In this contribution, novel bio-derived rosin acid ester compounds have been developed and used as internal electron donors to prepare MgCl2 supported titanium catalysts for propylene polymerization. The results of the polymerization showed that tri-n-amyl maleate, triiso-amyl maleate and tri-n-heptyl maleate as internal electron donors in Ziegler-Natta catalysts all have high polymerization activity and stereoregularity. In particular, the Ziegler-Natta catalyst with tri-n-amyl maleate as the internal electron donor has the highest activity (up to 33.4 kgPP·gCat−1·h−1) for propylene polymerization and the isotacticity of polypropylene is as high as 96.8% determined by 13C NMR. Simultaneously, the obtained polypropylene with a relatively broad molecular weight distribution of 9.0 and melt flow rate of 160.3 g/10 min, which is beneficial to processing and has practical industrial application value when used as the basic material of melt blown cloth for medical mask.

New penta-ether as the internal donor in the MgCl2-supported Ziegler-Natta catalysts for propylene polymerization

The penta-ether compound was synthesized by the reaction of di(trimethylolpropane) with sodium hydride as the strong base and methyl iodide as the alkyl halide. This compound was characterized by NMR, FTIR, and GC techniques. The MgCl2-supported titanium catalysts were incorporated with varying amounts of penta-ether compound as the internal donor and also the catalysts without the internal donor were synthesized. The synthesized catalysts and the conventional Ziegler- Natta catalyst were characterized. The titanium contents were determined by spectrophotometry, magnesium by complexometric titration and chloride by argentometric titration. The effects of the new internal donor on propylene polymerization with the prepared MgCl2-supported Ziegler-Natta catalysts were investigated and then these results were compared to the results obtained using the conventional diisobutyl phthalate-besed-Ziegler-Natta catalyst. The highest crystallinity degree, melting temperature, and isotacticity of polypropylene were obtained using the catalyst with a penta-ether/Mg molar ratio equal to 0.21.

Ziegler-Natta catalysts with novel internal electron donors for propylene polymerization

Four new diester compounds were prepared and used as internal donors (ID) to prepare MgCl2 supported titanium catalysts. Different diesters had notable influences on the porosity and the specific surface areas of the catalysts. The propylene polymerizations results showed that isopropyl groups(ID-2), cyclopentyl(ID-4) were more suitable substituents for diester compounds to replace phenyl(DIBP). The effects of different external donor (ED), Si/Ti ratio and hydrogen response on new ID precatalysts were evaluated by propylene polymerization.

Nature of Phthalates as Internal Donors in High Performance MgCl2 Supported Titanium Catalysts

High performance MgCl2 supported titanium catalyst having diisobutyl phthalate (DIBP) as internal donor has been synthesized. The organic components present in the catalyst have been studied through FTIR, 1D and 2D NMR spectroscopy. The results indicate presence of diethyl phthalate also in addition to DIBP. WAXD analysis has been done to study the features of MgCl2 crystallites. Impact of donor components on the catalyst preparation leading to reaction pathways and performance for propylene polymerization has been evaluated.

Effect of an external donor upon chain-transfer reactions in propylene polymerization with a MgCl 2-supported titanium catalyst system

The chain-end groups of the polypropylene (PP) polymerized without addition of molecular hydrogen over a MgCl 2·TiCl 4·dioctylphthalate/Et 3Al catalyst system consisted of n-butyl, n-propyl, vinylidene and vinyl groups in addition to ethyl and i-butyl groups which were detected in the PP prepared under the same polymerization conditions except for the addition of diphenyldimethoxysilane (DPDMS) as an external donor. The newly detected chain-end groups indicate that the additional chain-transfer reactions were brought about by Et 3Al at 2,1-inserted sites and by β-hydrogen elimination at both 1,2- and 2,1-inserted sites. These chain-transfer reactions could account for the observed drops of the activity and the molecular weight in the absence of DPDMS. In addition, the detected chain ends in the PP polymerized with addition of molecular hydrogen over this catalyst system having no DPDMS suggest that the molecular hydrogen addition leads not only to the conversion of the dormant 2,1-inserted sites into the active sites, but also to a decrease in the frequency of 2,1-insertion.

Two-step polymerization of propylene over MgCl2-supported titanium catalyst

Two-step polymerization of propylene over MgCl2-supported titanium catalyst

Two-step polymerization of propylene over MgCl2-supported titanium catalyst

The prepolymerization effect on propylene polymerization in the presence of a MgCl2-supported titanium catalyst was studied. The catalyst was pre-activated by polymerizing a small amount of propylene in the presence of Et3Al and cyclohexylmethyldimethoxysilane under mild conditions, and then it was used in a second step of propylene polymerization. Comparative studies of the polymerization process involving the investigated catalyst and its unmodified counterpart showed the rate-enhancement effect of prepolymerization and the same molecular weights, MWD's and isotacticities of the polymers obtained. Concentrations of active sites and propagation rate as well as transfer rate constants were found from detailed kinetic studies. The findings revealed that the activating effect of catalyst prepolymerization resulted from the increased concentration of active sites. This in turn is the result of the slow and uniform fragmentation of initial catalyst agglomerates with the prepolymer created under mild conditions. The prepolymerization process causes no change in the reactivity of active sites since the chain propagation and chain transfer rates are the same for single-step and two-step polymerization reactions; similarly, the properties of the polymers produced are unchanged.

Two-step polymerization of propylene over MgCl2-supported titanium catalyst

Two-step polymerization of propylene over MgCl2-supported titanium catalyst

A study of chain-end structures of polypropylene prepared with MgCl2-supported titanium catalyst

The chain ends of polypropylene (PP) polymerized at 100°C without molecular hydrogen addition over an MgCl2· TiCl4· dioctylphthalate/Et3Al/diphenyldimethoxysilane catalyst system consisted of ethyl and isobutyl groups. This indicates that the chain-transfer reaction in the production of this PP occurred mainly by Et3Al at 1,2-inserted sites. On the other hand, the terminal groups of PP obtained at 100°C with molecular hydrogen addition over this catalyst system were ethyl, isobutyl, n-propyl and n-butyl groups. The newly detected terminal groups were formed by chain-transfer reactions by hydrogen at 2,1-inserted sites. The observed activity enhancement in this catalyst system would be due to the conversion of dormant 2,1-inserted sites into the active sites by hydrogen addition.

Effect of external donor in polymerization of propylene by a MgCl2 supported titanium catalyst

Polypropylene (PP) prepared with a MgCl2/TiCl4-Et3Al/Ph2Si(OMe)2 catalyst system was fractionated by temperature rising elution fractionation method in order to investigate the effect of Ph2Si(OMe)2 as an external donor (ED). This PP had a broad and continuous distribution of tacticity. In comparison to the system without donor, however, ED brought a decrease of lower isotactic portions and an increase of higher isotactic ones simultaneously to the resulting polymer. The latter portions were eluted at higher temperature than the corresponding component obtained without donor, showing that the higher isotactic PP was newly produced by ED.

Improvement of Stereospecificity of an MgCl2-Supported Titanium Catalyst upon Treatment with Al(C2H5)3

Magnesium dichloride supported titanium catalysts were prepared by solubilizing anhydrous magnesium dichloride in 2-ethyl-1-hexanol followed by treatment with titanium tetrachloride. 2,2-Dimethoxypropane was used as an internal Lewis base. Solid products were characterized by compositional analysis, and specific surface area. Titanium magnesium catalysts (Ti-Mg) in conjunction with triethylaluminium showed high activity (5110 g PP/g Ti) and high stereospecificity (I.I = 92) for propylene polymerization. The variation in the amount of 2,2-dimethoxypropane during catalyst synthesis governs the productivity of the catalyst. Furthermore, the increase in the chain length of the alkyl group from ethyl to hexyl of trialkylaluminum cocatalyst retards the activity of the catalyst system, with minor variation in the isotactic index of polypropylene. The addition of diphenyldimethoxysilane into triethylaluminum further improves the stereospecificity of the catalyst system.

Tacticity distribution of polypropylene prepared by MgCl 2-supported titanium catalyst

Polypropylenes (PP) prepared with MgCl 2 TiCl 4 Et 3 Al and MgCl 2/TiCl 4/bis(2-ethylhexyl)phthalate-Et 3Al/Ph 2Si(OMe) 2 catalyst systems were fractionated by the temperature-rising elution fractionation method in the wide temperature range of −65 to 140°C. The fractionations were proved to take place mainly on the basis of isotacticity from the analyses of key fractions by 13C nuclear magnetic resonance, gel permeation chromatography, differential scanning calorimetry and X-ray diffraction. PP was shown to have a broad and continuous distribution of tacticity, ranging from nearly atactic to highly isotactic structures in the case of no electron donor system. The addition of electron donor, however, drastically reduced the amount of atactic and low isotactic PP, resulting in a very sharp tacticity distribution.

A new mechanism for the transition metal catalyzed copolymerization of conjugated dienes with olefins: The double coordination mechanism

AbstractWe have focused our interest on the ethylene‐ butadiene copolymerizations catalyzed with Ziegler‐Natta type catalysts. The catalysts used are MgCl2 supported titanium catalysts. The main features of these copolymerizations (stereospecificity of the butadiene enchainments, multiblock structure, gel formation) cannot be rationalized on the basis of the Cossee mechanism. We propose a new model: The double coordination mechanism. It explains all the phenomena observed. Experimental confirmations will be presented in this paper.

Metallocene‐methylaluminoxane catalysts for olefin polymerization. V. Comparison of Cp2ZrCl2 and CpZrCl3

AbstractThe ethylene polymerization by Cp2ZrCl2/MAO (Cp = η5: cyclopentadienyl; MAO = methyl aluminoxane) and CpZrCl3/MAO have been studied. The MW and PD (= Mw/Mw) of polymers obtained after 2.5‐60 min are the same, which indicate short chain lifetime. The values of rate constants for Cp2ZrCl2 at 70°C are: kp = 168−1670 (M s)−1 and ktrA1 = 0.012‐0.81 s−1 depending upon [Zr] and [MAO,] ktrβ = 0.28 s−1, and ktrH = 0.2 M−1 torr−1/2 s−1. These chain transfer rate constant values are two to three orders of magnitude greater than the corresponding values found for MgCl2 supported titanium catalysts. One significant difference between the heterogeneous and homogeneous catalysts is that the former decays according to an apparent second order kinetics, whereas the latter decay is simple first order at 0°C and biphasic first order at higher temperatures. The productivity of the catalysts depends weekly on temperature while the MW decreases strongly with increase of temperature above 30°C. All the active species were formed upon mixing Cp2ZrCl2 with MAO while it took up to 20 min for the CpZnCl3/MAO system. The productivity of the former increase more strongly with the decrease of [Zr] than the latter. Otherwise, the two catalyst systems have all their kinetic parameters differing less than a factor of two.

MgCl2 supported titanium catalyst prepared by mechanical pulverization

MgCl2 supported titanium catalysts were prepared by mechanical pulverization or MgCl2 with titanium compounds using two types of machines, rotatory mill and vibratory mill. Both methods gave substantially the same results, although vibratory mill much saved the milling time. The nature of the fixed titanium compounds was not homogeneous, and the titanium compounds fixed at an earlier stage of milling, which could be located at exposed “active” edge positions of MgCl2 particles, showed higher activity in ethylene polymerization. On the other hand, those fixed at the later stage showed lower activity and caused reaggregation of the particles. Furthermore, chlorine-free titanate compounds, Ti(OBu)4 and Ti(OEt)4, also could be fixed on MgCl2 which showed high activity in ethylene polymerization.