Triethylaluminum, addition ethylene

Addition of ethylene to triethylaluminum is first-order in monomeric triethylaluminum and ethylene (7) Since triethyl-aluminum is largely dimeric in the liquid phase, kinetics of the growth reaction take the following form ... 

In the case of cobalt, modified Ziegler systems have limited activity toward ethylene dimerization and oligomerization [141]. Cobalt(II) or cobalt(IIl) and a reducing organometallic compound system have been specially proposed for this reaction. Tris(acetylacetonato)Co(llI) and triethylaluminum convert ethylene at 30°C into n-butenes with a selectivity of 99.5% [142]. The product consists of a mixture of 95% 2-butenes and 5% 1-butenes. The molar ratio of AIR3/C0 must be between 2 and 5 beyond that, the activity decreases. On the other hand, the addition of triphenylphosphine decreases the rate of the reaction. 

Thermal stability of aluminum alkyls is highly dependent upon the ligands bonded to aluminum. For example, triethylaluminum is stable up to about 120 °C (37) and its initial mode of decomposition is by )S-hydride elimination to generate diethyl-aluminum hydride and ethylene (eq 4.20). Diethylaluminum hydride may decompose further to aluminum, hydrogen and two additional equivalents of ethylene (eq 4.21). The overall equation for decomposition is shown in eq 4.22. 

In the second reaction, ethylene is reacted with the alkylaluminums to form n-a-olefins and to regenerate triethylaluminum (Figure 2). Although the reaction can be conducted without a catalyst by operating at high temperatures (3, 6), the reaction is normally carried out at lower temperatures in the presence of a nickel, cobalt, or platinum catalyst. Reaction conditions are moderate, 2500 p.s.i. and 200° F. when less than 0.01% of nickel catalyst is used. The catalyst is formed in situ by the addition of a nickel salt. A small amount of alkylaluminum will react with the nickel salt, reducing it to colloidal nickel. 

The net, over-all reaction of the Ziegler a-olefin process is the addition of ethylene to alkylaluminums to form n-a-olefins and to regenerate triethylaluminum. 

The fourth process used to produce phthalate alcohols is the Ziegler process and the Ziegler displacement process. In the Ziegler process straight chain even-numbered carbon alcohols are produced from ethylene. Triethylaluminum is produced from aluminum, hydrogen, and ethylene. With the addition of more... 

Each type of support was evaluated in a 2.2-liter stainless steel autoclave fitted with a temperature control jacket and a marine stirrer. Each supported, finished catalyst was prepared in situ by sequentially adding to the polymerization reactor 10-100 mg of finished support, 2.0 ml of a toluene solution containing 0.5 wt% (n-butyCpj ZrCl, 0.6 liter of isobutane, 1.0 mmol triethylaluminum and a second addition of 0.6 liter of isobutane. The contents of the reactor were stirred at 400 rpm while the reactor was heated to 90°C, after which ethylene was added to the reactor system to maintain total pressure at 550 psig. After the polymerization experiment, the ethylene flow to the reactor was stopped, the reactor was cooled to ambient temperature and solvents were removed by evaporation, and the reactor was opened and the polymer was collected. Note that no reactor fouling was detected and the granular polyethylene had acceptable morphology important for a commercial process. 

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