Magnesium chloride support

The 1970s saw the introduction of higher activity catalysts based on magnesium chloride-supported titanium that improved the control of the physical properties of the polyethylene—molecular weights, stereospecificity, and the degree of copolymerization. 

Supported precursors for Ziegler-Natta catalysts may be obtained, depending on the kind of support, in two ways by treatment of the support containing surface hydroxyl groups with a transition metal compound with chemical covalent bond formation, and by the treatment of a magnesium alkoxide or magnesium chloride support with a Lewis base and transition metal compound with coordination bond formation. 

Chien, J. C. W., Most Advanced Magnesium Chloride Supported Ziegler-Natta Catalyst , in Catalysis in Polymer Synthesis, ACS Symp. Ser. 496, Washington, DC, 1992, pp. 25-55. 

Sacchi, M.C. Tritto, L Shan, C. Mendichi, R. Zannoni, G. Noristi, L. Role of the pair of internal and external donors in magnesium chloride-supported Ziegler-Natta catalysts. Macromolecules 1991, 24, 6823-1626. 

Albizzati, E. Galimberti, M. Giannini, U. Morini, G. The chemistry of magnesium chloride supported catalysts for polypropylene. Makromol. Chem., Macromol. Symp. 1991, 48/49, 223-238. 

There are also examples for which there is no need to separate a catalyst, because it can be left in the product without adverse effects. Magnesium chloride-supported catalysts for the polymerization of propylene attain such high mileage that they can be left in the polymer. Earlier less-efficient catalysts had to be removed by an acidic extraction process that produced titanium- and aluminum-containing wastes. The earlier processes also produced heptane-soluble polymer that had to be removed, and, sometimes, ended up as waste. The newer processes produce so little that it can be left in the product. Thus, improved catalysts have eliminated waste. 

PREPARATIVE TECHNIQUES Ziegler-Natta polymerization with titanium halide/ aluminum cdkyl catalyst and, optionally, ether, ester, or silane activator. Catalyst may be deposited on a magnesium chloride support. Slurry and gas phase processes are used. Catcdyst systems based on metallocenes are under development. Typical comonomers are ethylene and 1-butene. 

The principal kinetics of propylene polymerization with a magnesium chloride supported Ziegler-Natta catalyst was also developed. The polymerization rate is described by a Langmuir-Hinshelwood equation showing the dependence of die rate on the concentration of the aluminum alkyl ... 

Chien, J. C. W. Kno, C. 1. Magnesium chloride supported high-mileage catalyst for olefin polymerization. IX. Molecnlar weight and distribution and chain transfer processes. J. Polym. Sci., Part A Polym. Chem. 1986, 24, 1779-1818. 

Chadwick J, Severn J (2006) Single-site catalyst inunobilization using magnesium chloride supports. Kinet Catal 47 186-191... 

Studies on the Polymerization of Propylene Using Highly Active Magnesium Chloride Supported Ziegler-Natta Catalysts Effects of Alkyl Concentration on the Polymerization Rate and on the Active Centre Concentration... 

The most commonly and effectively used metal alkyls for propylene polymerization employing magnesium chloride - supported catalysts are invaricibly trlalkylaluminium confounds, dialkylaluminium halide conpounds giving much lower activities. In general the polymerization kinetics shown by catalysts of this type are strongly affected both by the trlalkylaluminium to titanium ratio and by the type of alkylaluminlum compounds which is used. 

One Inportant feature of ball-milled magnesium chloride-supported catalysts employing ethyl benzoate (EB) as an internal donor is that they often exhibit very... 

It Is evident from Figure 2 that the decrease in the rate of polymerization Is dependent on the trlethylalumlnlum concentration at constant catalyst concentration. These rate-time plots are in some ways similar to those obtained using spherical type magnesium chloride supports, although the latter class of catalysts shows a greater time stability. 

The magnesium supports used for polyethylene catalysts could be modified for use in polypropylene production, and magnesium chloride proved to be the most suitable when used with a Lewis base election donor. Milled magnesium chloride was known to have the same layer stracmre as a- and y-titanium trichloride with the quadrivalent titanium ion (0.068 nm diameter), being about the same size as the divalent magnesium ion (0.066 nm diameter). In 1968, Montedison and Mitsui Petrochemical Industries both disclosed the production of a highly active, very steieospecific catalyst that contained about 3% titanium on a magnesium chloride support, promoted with a Lewis base, such as ethyl benzoate. The polymer produced contained less than 1 ppm titanium with an isotactic index of more than 90%, which was improvement on the product made with previous catalysts. 

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