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A Ziegler–Natta catalyst, named after Karl Ziegler and Giulio Natta, is a catalyst used in the synthesis of polymers of 1-alkenes (alpha-olefins). Two broad classes of Ziegler–Natta catalysts are employed, distinguished by their solubility: * Heterogeneous supported catalysts based on titanium compounds are used in polymerization reactions in combination with cocatalysts, organoaluminum compounds such as triethylaluminium, Al(C2H5)3. This class of catalyst dominates the industry. * Homogeneous catalysts usually based on complexes of Ti, Zr or Hf. They are usually used in combination with a different organoaluminum cocatalyst, methylaluminoxane (or methylalumoxane, MAO). These catalysts traditionally include metallocenes but also feature multidentate oxygen- and nitrogen-based ligands.〔"Handbook of Transition Metal Polymerization Catalysts" Ray Hoff, Robert T. Mathers, Eds. 2010 John Wiley & Sons. Online ISBN 9780470504437〕 Ziegler–Natta catalysts are used to polymerize terminal 1-alkenes (ethylene and alkenes with the vinyl double bond): :n CH2=CHR → −()n− ==History== German Karl Ziegler, for his discovery of first titanium-based catalysts, and Italian Giulio Natta, for using them to prepare stereo regular polymers from propylene, were awarded the Nobel Prize in Chemistry in 1963. Ziegler–Natta catalysts have been used in the commercial manufacture of various polyolefins since 1956. In 2010, the total volume of plastics, elastomers, and rubbers produced from alkenes with these and related (especially Phillips) catalysts worldwide exceeds 100 million metric tons. Together, these polymers represent the largest-volume commodity plastics as well as the largest-volume commodity chemicals in the world. In the early 1950s workers at Phillips Petroleum discovered that chromium catalysts are highly effective for the low temperature polymerization of ethylene, which launched major industrial technologies. A few years later, Ziegler discovered that a combination of TiCl4 and Al(C2H5)2Cl gave comparable activities for the production of polyethylene. Natta used crystalline α-TiCl3 in combination with Al(C2H5)3 to produce first isotactic polypropylene.〔G. Natta, F. Danusso, eds. ''Stereoregular Polymers and Stereospecific Polymerizations'', Pergamon Press, 1967.〕 Usually Ziegler catalysts refer to Ti-based systems for conversions of ethylene and Ziegler–Natta catalysts refer to systems for conversions of propylene. In the 1970s, magnesium chloride was discovered to greatly enhance the activity of the Ti-based catalysts. These catalysts were so active that the residual Ti was no longer removed from the product. They enabled to the commercialization of linear low-density polyethylene (LLDPE) resins and allowed the development of noncrystalline copolymers.〔T. E. Nowlin , R. I. Mink , Y. V. Kissin Supported Magnesium/Titanium - Based Ziegler Catalysts for Production of Polyethylene" in "Handbook of Transition Metal Polymerization Catalysts" Ray Hoff, Robert T. Mathers, Eds. 2010 John Wiley & Sons, Inc. Online ISBN 9780470504437.〕 Also, in the 1960s, BASF developed a gas phase, mechanically stirred polymerization process for making polypropylene. In that process, the particle bed in the reactor was either not fluidized or not fully fluidized. In 1968, the first gas phase fluidized-bed polymerization process, i.e., the UNIPOL process, was commercialized by Union Carbide to produce polyethylene. In the mid-1980s, the UNIPOL process was further extended to produce polypropylene. The features of the fluidized-bed process, including its simplicity and product quality, made it widely accepted all over the world. As of today, the fluidized-bed process is one of the two most widely used technologies for producing polypropylene.〔(【引用サイトリンク】title= Polypropylene Production via Gas Phase Process, Technology Economics Program )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Ziegler–Natta catalyst」の詳細全文を読む スポンサード リンク
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