Ziegler-Natta catalysis supported catalysts

The low temperature limitation of homogeneous catalysis has been overcome with heterogeneous catalysts such as modified Ziegler-Natta solid-supported protonic adds and metal oxides. 

The discovery of active magnesium chloride as the ideal support for the fixation of titanium tetrachloride and its derivatives opened a new era in the field of Ziegler-Natta catalysis, both from the industrial and the scientific viewpoint. During the last 15 years MgCl2-supported catalysts brought about revolutionary industrial developments, as compared to those of the traditional Ziegler-Natta catalysts. 

The copolymerization theory presented in Chapter is of limited applicability to processes involving heterogeneous Ziegler-Natta catalysis. The simple copolymer model assumes the existence of only one active site for propagation, whereas the supported catalysts described above have reaction sites that vary in activity and stereoregulating ability. In addition, the catalytic properties of the active sites may vary with polymerization time. The simple copolymer model can be used with caution, however, by employing average or overall reactivity ratios to compare different catalysts and monomers. 

Broadly, the polymerization of ethylene and a-olefins by organometallic catalysts is one of the most important catalytic processes in the chemical industry and the Ziegler-Natta catalysis an impressive example of polymerization on and with molecular catalysts per se or on a support. The detailed understanding of this fundamental catalysis on all relevant chemical and physical scales, the molecular level of the catalyst structure, the microkinetic mechanistic reaction paths, and the macrokinetic reaction engineering level of the total polymerization process, reflects a story of innovations in science and technology that is still today undergoing further development. 

Kinetic Parameters in Some MgCl Supported Catalysts Ziegler-Natta Catalysis 57... 

The low temperature limitation of homogeneous catalysis has been overcome with heterogeneous catalysts such as modified Ziegler-Natta (28) sohd-supported protonic acids (29,30) and metal oxides (31). Temperatures as high as 80°C in toluene can be employed to yield, for example, crystalline... 

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. 

Applications of HT-type catalysts, prepared by the above methods, have been reported in recent years for basic catalysis (polymerization of alkene oxides, aldol condensation), steam reforming of methane or naphtha, CO hydrogenation as in methanol and higher-alcohol synthesis, conversion of syngas to alkanes and alkenes, hydrogenation of nitrobenzene, oxidation reactions, and as a support for Ziegler-Natta catalysts (Table 2). 

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