Triethylaluminium Ziegler catalyst

Ziegler catalysts studied for the oligomerisation of a-olefins tend to be based on modified first-generation catalysts, i.e. triethylaluminium/titanium tetrachloride. The aluminium/fitanium ratio has a marked effect on product properties, at less than 0.8 1, liquids were produced, whereas at ratios above 1 1, waxy products were obtained [6, 7]. This effect is believed to relate to changes in the catalysis mechanism, from cationic to anionic with higher proportions of aluminium. 

Ziegler catalyst derivative of a transition metal (such as titanium) md organoaluminium compound (such as triethylaluminium) supported on inorganic and organic support (such as silica, magnesium dichloride etc.)... 

A typical Ziegler-Natta catalyst is the complex prepared from titanium tetrachloride and triethylaluminium. It is fed into the reaction vessel first, after which ethylene is added. Reaction is carried out at low pressures and low temperatures, typically no more than 70 °C, with rigorous exclusion of air and moisture, which would destroy the catalyst. The poly(ethylenes) produced by such processes are of intermediate density, giving values of about 0.945 g cm. A range of relative molar masses may be obtained for such... 

As early as 1954, Karl Ziegler [301,302] has assumed that colloidal nickel in triethylaluminium is the crucial co-catalyst which effects the controlled polymerization... 

In reporting a Ziegler-Natta catalyst, the kind of transition metal compound should not be omitted. Group 4-8 transition metal compounds, such as halides, oxyhalides, alkoxides, acetylacetonates, etc., have been used as catalyst precursors with activators such as alkyl derivatives or hydrides of group 1-4 metals. Titanium chlorides and triethylaluminium are most commonly applied for the preparation of heterogeneous catalysts in an aliphatic hydrocarbon medium. Also, vanadium oxychloride or acetylacetonate and dialkyaluminium chloride are often used for the preparation of homogeneous catalysts in an aliphatic hydrocarbon or an aromatic hydrocarbon medium. 

The formation of linear isotactic or syndiotactic polymers can be achieved by metal-catalysed polymerisation. This employs Ziegler-Natta catalysts, made from triethylaluminium (Et3Al) and titanium tetrachloride (TiCl4), which react with alkenes by a complex mechanism. The polymerisation of ethylene (CH2=CH2) leads to the formation of (linear) high-density polyethylene, which is of greater strength than the (branched) low-density polyethylene produced on radical polymerisation. 

A typical Ziegler-Natta catalyst is the complex prepared from titanium tetrachloride and triethylaluminium. It is fed into the reaction vessel first, after which ethylene is added. Reaction is carried out at low pressures and low temperatures, typically no... 

In addition Ziegler-Natta polymerization reactions have also shown some success when carried out in ionic liquids. The most common production methods for this form of polymerization involve the use of triethylaluminium catalysts at ca. 100°C and 100 atmospheres pressure. Advances have been developed through the use of organometallic transition metal catalysts, typically nickel or titanium. Given the solvent characteristics of ionic liquids it should be possible to effectively immobilize such catalysts in an ionic liquid solvent. Indeed, Carlin and Wilkes have reported the Ziegler-Natta polymerization of ethene in an ionic liquid solvent. In these reactions an acidic [Cj-mimJCl-AlClj ionic liquid solvent was used to support dichlorobis(Ti -cyclopentadienyl)titanium(IV) with an alkyl-chloroaluminium(III) co-catalyst. 

By treatment of these materials with titanium tetrachloride valuable supported catalysts for the propene Ziegler-Natta type polymerization were obtained. These catalysts were tested by slurry polymerization using triethylaluminium as cocatalyst and showed an interesting activity compared with that exhibited by a commercial catalysts. The polymer products were also characterized by measuring the molecular weight distribution by gel permeation chromatography technique. 

Primary alcohols are the second most important class of detergent feedstocks after alkylbenzenes. They are produced either by the catalytic hydrogenation of methyl esters or fatty acids derived from oils and fats e.g. coconut oil or tallow, or from synthetic sources. Alcohols manufactured from Ziegler type processes produce even-numbered chain length primary alcohols. The basic process steps are synthesis of the triethylaluminium catalyst, chain growA from an ethylene precursor, oxidation and finally hydrolysis. 

Acrylonitrile-butadiene copolymers may also be prepared by the use of Ziegler-Natta catalysts. Catalysts such as a triethylaluminium, aluminium chloride and vanadium chloride combination give copolymers with a high degree of alternation. Such copolymers appear to have improved mechanical properties but have not attracted much commercial interest. 

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