Butene Ziegler—Natta polymerization

Ziegler-Natta polymerization is used extensively for the polymerization of simple olefins (such as ethylene, propene, and 1-butene) and is the focus of much academic attention, as even small improvements to a commercial process operated on... 

The application of Ziegler-Natta catalysts to monomer isomerization polymerization, in which an olefin such as 2-butene is first isomerized to 1-butene and then polymerized, has been described in an extensive series of papers by Endo and Otsu.431 The non-participation of 2-butene in Ziegler-Natta polymerization (taking precautions to exclude the possibility of carbocationic polymerization)432 also allowed the selective polymerization of 1-butene from mixtures of butene isomers.433 It was proposed that isomerization and polymerization took place on Ti(ll) and Ti(lll) species, respectively.434 The relative rates of isomerization and polymerization were dependent on the catalyst system, polymerization being more rapid with TiCl3/AlEt3 than with Ti(OBu)4/AlEt3. 

Ziegler-Natta polymerization is used extensively for the polymerization of simple olefins (e.g. ethene, propene and 1-butene) and is the focus of much academic attention, as even small improvements to a commercial process operated on this scale can be important. Ziegler-Natta catalyst systems, which in general are early transition metal compounds used in conjunction vyith alkylaluminum compounds, lend themselves to study in the chloroaluminate(iii) ionic liquids, especially those with an acidic composition. 

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. 

Polyd-butene) Produced commercially in isotactic for by Ziegler-Natta polymerization of butene-1. 

Polybutene (polybutylene) (PB) is manufactured by stereospecific Ziegler-Natta polymerization of 1-butene ... 

UNIPOL [Union Carbide Polymerization] A process for polymerizing ethylene to polyethylene, and propylene to polypropylene. It is a low-pressure, gas-phase, fluidized-bed process, in contrast to the Ziegler-Natta process, which is conducted in the liquid phase. The catalyst powder is continuously added to the bed and the granular product is continuously withdrawn. A co-monomer such as 1-butene is normally used. The polyethylene process was developed by F. J. Karol and his colleagues at Union Carbide Corporation the polypropylene process was developed jointly with the Shell Chemical Company. The development of the ethylene process started in the mid 1960s, the propylene process was first commercialized in 1983. It is currently used under license by 75 producers in 26 countries, in a total of 96 reactors with a combined capacity of over 12 million tonnes/y. It is now available through Univation, the joint licensing subsidiary of Union Carbide and Exxon Chemical. A supported metallocene catalyst is used today. 

Traditional Ziegler-Natta and metallocene initiators polymerize a variety of monomers, including ethylene and a-olefins such as propene, 1-butene, 4-methyl-1-pentene, vinylcyclo-hexane, and styrene. 1,1-Disubstituted alkenes such as isobutylene are polymerized by some metallocene initiators, but the reaction proceeds by a cationic polymerization [Baird, 2000]. Polymerizations of styrene, 1,2-disubstituted alkenes, and alkynes are discussed in this section polymerization of 1,3-dienes is discussed in Sec. 8-10. The polymerization of polar monomers is discussed in Sec. 8-12. 

H. Schnecko, K. A. Jung, and W. Kern, The Number of Active Sites for the Polymerization of Ethylene, Propylene, and Butene-1 by Ziegler-Natta Catalysts, in Ref. 9, p. 73. 

The Unipol process employs a fluidized bed reactor (see Section 3.1.2) for the preparation of polyethylene and polypropylene. A gas-liquid fluid solid reactor, where both liquid and gas fluidize the solids, is used for Ziegler-Natta catalyzed ethylene polymerization. Hoechst, Mitsui, Montedison, Solvay et Cie, and a number of other producers use a Ziegler-type catalyst for the manufacture of LLDPE by slurry polymerization in hexane solvent (Fig. 6.11). The system consists of a series of continuous stirred tank reactors to achieve the desired residence time. 1-Butene is used a comonomer, and hydrogen is used for controlling molecular weight. The polymer beads are separated from the liquid by centrifugation followed by steam stripping. 

Acyclic internal olefins such as cis- and /raar-2-butene can be polymerized using Brookhart-type Ni(ll) and Pd(ll) complexes430 but in the absence of isomerization do not homopolymerize using Ziegler-Natta catalysts, although examples of co-polymerizations of ethylene with an internal olefin are known.313... 

TiCl3 catalysts for 1-butene polymerization have relatively low activity.883 The old Shell process made use of a first-generation Ziegler-Natta catalyst, and required de-ashing of the final polymer. The new Basell process makes use of a much improved high yield MgCl2-supported Ti-based ZN catalyst and a two-reactor setup. Improved... 

Metallocenes are far more versatile in controlling polymer stereochemistry compared to Ziegler-Natta catalysts, as extensively demonstrated in the case of PP. Also in 1-butene polymerization, all kinds of chain microstructures can be obtained with different metallocenes. The 13C NMR pentad analysis of polybutene is somewhat less immediate than that of PP, and has been reported for both ZN 886,887 and metallocenes.180 The 13C NMR spectrum of atactic polybutene, with pentad assignments of the C(3) methylene region, is shown in Figure 37. 

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