Compound , alkylaluminium

The reaction takes place at low temperature (40-60 °C), without any solvent, in two (or more, up to four) well-mixed reactors in series. The pressure is sufficient to maintain the reactants in the liquid phase (no gas phase). Mixing and heat removal are ensured by an external circulation loop. The two components of the catalytic system are injected separately into this reaction loop with precise flow control. The residence time could be between 5 and 10 hours. At the output of the reaction section, the effluent containing the catalyst is chemically neutralized and the catalyst residue is separated from the products by aqueous washing. The catalyst components are not recycled. Unconverted olefin and inert hydrocarbons are separated from the octenes by distillation columns. The catalytic system is sensitive to impurities that can coordinate strongly to the nickel metal center or can react with the alkylaluminium derivative (polyunsaturated hydrocarbons and polar compounds such as water). 

The particle size depends on the chain length of the aluminium-alkyl group and the concentration of the tri-alkylaluminium compound applied. If mixtures of, e.g., Fe- and Co-carbonyl compounds are used, Fe/Co alloy particles are formed. When the magnetic particles... 

Fires involving alkylaluminium compounds are difficult to control and must be treated appropriately to particular circumstances [1,5,6], usually with dry-powder extinguishers. Halocarbon fire extinguishants (carbon tetrachloride, chloro-bromomethane, etc.), water or water-based foam must not be applied to alkylaluminium fires. Carbon dioxide is ineffective unless dilute solutions are involved [5,6], Suitable handling and disposal procedures have been detailed for both laboratory [1,2,5,6,7] and manufacturing [5,6] scales of operation. 

Three main structural sub-groups can be recognised alkylaluminium dihalides, dialkylaluminium halides, and trialkyldialuminium trihalides (equimolar complexes of a trialkylaluminium and an aluminium trihalide). While this is generally a very reactive group of compounds, similar in reactivity to trialkylaluminium compounds, increase in size of the alkyl groups present and in the degree of halogen substitution tends to reduce pyrophoricity. 

ALKYLALUMINIUM DERIVATIVES, ALKYLBORANES, ALKYLHALOBORANES ALKYLHALOPHOSPHINES, ALKYLHALOSILANES, ALKYLMETALS ALKYLNON-METAL HYDRIDES, ALKYLPHOSPHINES, ALKYLSILANES ARYLMETALS, BORANES, CARBONYLMETALS, COMPLEX ACETYLIDES COMPLEX HYDRIDES, HALOACETYLENE DERIVATIVES HEXAMETHYLNITRATODIALUMINATE SALTS, METAL HYDRIDES NON-METAL HYDRIDES, ORGANOMETALLICS, PYROPHORIC ALLOYS PYROPHORIC CATALYSTS, PYROPHORIC IRON-SULFUR COMPOUNDS PYROPHORIC METALS... 

The catalyst and the concomitant technology have undergone drastic changes over the years. The titanium catalysts can be prepared by the interaction of TiCl4 and alkylaluminium compounds in a hydrocarbon solvent. 

This compound, which exists as the dimer, explodes on contact with water. See ALKYLALUMINIUM DERIVATIVES See related ALKYLSILANES... 

It is worth noting that, to obtain efficient supported Ziegler-Natta catalysts of the third and fourth generation, it is TiCU rather than preformed TiCL that is supported. When TiCl3 was supported on MgCl2 (e.g. by deposition from the solution of a TiCl3.3Py complex) and then activated with an alkylaluminium compound, the obtained catalyst appeared to be aspecific for propylene polymerisation [69], However, it could be converted into an isospecific catalyst by adding a Lewis base such as ethyl benzoate [70],... 

It may be interesting, in connection with the ethylene/propylene copolymers mentioned above, to present here some homogeneous Ziegler-Natta catalysts formed by soluble complexes of titanium and magnesium chlorides with alkyl phosphates as catalyst precursors and alkylaluminium compounds as activators (TiCl4)x.(MgCl2)r [0=P(0Bu)3]3-A1(/-Bu)3 and Cl3TiOMgCl-[0 = P(0Bu)3]3- A1(z -Bu)3 (Al/Ti molar ratio of ca 10 1). These catalysts have been used for random ethylene/propylene copolymerisation [73],... 

In connection with the above characteristic features of metallocene methy-laluminoxane catalysts, it must be emphasised that alternative, potentially cheaper alkylaluminoxanes, such as ethyl or z-butyl derivatives, which are more soluble in aliphatic hydrocarbons than methylaluminoxane, or other alkylaluminium compounds used as activators for metallocene procatalysts, show inferior activity. 

Allene has been polymerised to high molecular weight linear polymers by various Ziegler-Natta catalysts based on compounds of such transition metals as Ti, V, Cr, Mn, Fe, Co and Ni as precursors and alkylaluminium compounds as activators [439-441], Crystalline and amorphous polymers have been produced, in various proportions, with each of the catalysts used. The crystalline polymers consist predominantly of 1,2-linked (head-to-tail) monomeric units formed by insertion polymerisation as in scheme (68), but some regioirregular-ities resulting from the 2,1-insertion, leading to head-to-head and tail-to-tail arrangements, may be present in the polymer chain ... 

Cycloolefins having rings with more than four carbon atoms do not homo-polymerise in the presence of Ziegler-Natta catalysts based on titanium or vanadium compounds as precursors and alkylaluminium activators. However, these cycloolefins may copolymerise with ethylene via the double bonds while preserving the cycloolefin ring ethylene is able to compensate the steric hindrance at the Ca atom of the growing chain after and before the 1,2-insertion of the cycloolefin [2],... 

The isospecific polymerisation of styrene was first reported by Natta et al. [1,2], They obtained isotactic polystyrene, employing for the polymerisation a heterogeneous catalyst derived from titanium tetrachloride and an alkylaluminium compound. 

Styrene polymerisation with heterogeneous Ziegler Natta catalysts activated by alkylaluminium compounds generally produces a mixture of isotactic and non-stereoregular polymer. For example, polystyrene produced with the... 

Alkylaluminium compounds were transformed by xenon difluoride mainly to fluorides, while Al-carbon bond cleavage is accompanied with bright chemiluminescence141-144. 

The Lewis acidity of organoaluminium compounds is the reason of their association. The association of alkylaluminium molecules and aluminium hydrides proceeds by way of electron-deficient bonds [143a], The associates of dimethylberyllium, dimethyl- and diethylmagnesium, methyl- and ethyl-lithium are of the same type each alkyl group is simultaneously bound to two or three metal atoms [143b],... 

The polymerization of conjugated dienes to products with a controlled structure usually occurs in the presence of alkylaluminium compounds. The choice not only the transition metal but also of its ligands is of importance. Some systems produce a certain kind of stereochemical structure irrespective of external conditions. So, for example, vanadium compounds yield predominantly the trans-1,4 structure whereas cobalt salts yield the c -1,4 structure. Other catalysts are very sensitive, and a small external effect completely changes their stereochemical activity [267b] [e. g. Cr(acetylacetona-te)3-R3Al]. Examples of several catalytic systems are summarized in Table 7. 

The growing alkyl migrates between the neighbouring Ti atoms at the crystal surface. Rodriguez and Van Looy consider the complexed alkylaluminium compound as an integral part of the active centre even though growth only takes place at the transition metal—carbon bond [302],... 

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