Oligomerization of ethylene

Ethylene, propylene, 1. VOClj/AlRjCl 2. CpjZrClj/MAO Elastic polymer (elastomer) that 

Poly-4-methyl-1 - Zeigler-Natta Highly transparent and very 

Poly (1-decene) poly (1-dodecene) Zeigler-Natta type Very high-molecular-weight polymers used in parts per million levels to improve flow properties of oU in oil pipelines. 

Oligomerization of ethylene to give linear terminal alkenes or a-olefins is a very important industrial reaction. The linear a-olefins with about 10-18 carbon atoms are important feedstock for a variety of detergents. As mentioned earlier (see Section 5.2), for the detergent application, the linear a-olefins must he converted to linear a-alcohols. This is achieved by a cobalt- plus phosphine-based catalytic system where a-olefins are hydroformylated and hydrogenated to a-alcohols. 

In the following section, we discuss the industrial process for the manufacture of a-olefins utilizing nickel complexes as catalysts. This process is known as Shell higher olefin process or SHOP. The mechanism of oligomerization by the Ni-based catalyst is basically the same as that discussed in Section 6.3. However, in this case the ligand environment around the nickel is such that the chain length remains low, but not too low. 

The dimerization of alkenes is an important method for the production of higher olefins as well as oligomers that find extensive application as industrial intermediates. The stimulus in this direction was provided by the pioneering studies of Ziegler in the early 1950s. He explored the use of organoaluminum compounds in the selective dimerization of alkenes [1,2]. 

Three types of mechanisms are reported for the dimerization of olefins degenerated polymerization, concerted coupling, and reductive dimerization [1]. 

The three important steps involved in the first mechanism are (1) initiation reaction (formation) of an activated complex, (2) insertion of a monomer into the activated complex, and (3) transfer reaction (deactivation of the chain). 

Coordination of the olefin at the metal hydride center and subsequent insertion of the carbon-carbon double bond of the coordinated olefin into the metal-hydride bond can be related to the initial step of a classical polymerization. The metal-carbon bond formed in this way inserts a second monomer molecule previously coordinated into the same metal center (the propagation step). The dimer is formed by a p-hydride subtraction, a common cleavage reaction of transition metal-carbon bonds. The p-hydrogen of this alkyl group attached to the 

The ease of -hydrogen abstraction depends of the metal, its valency state, and the ligand environment. The metals of the extreme and of the transition series are prone to p-hydrogen abstraction easily from an attached alkyl group. The complexes based on these metals are good catalysts for the dimerization of olefins. 

Oligomerization of ethylene to give linear terminal alkenes or the so-called a-olefins is a very important industrial reaction. The linear a-olefins with 10 to 

18 carbon atoms are important feed stock for a variety of detergents. Oligomers with 4-10 carbon atoms find uses as co-monomers in the manufacture of polyethylene and also as starting materials for the manufacture of plasticizer alcohols by the hydroformylation reaction. 

The addition of one olefin molecule to a second and to a third, etc. to form a dimer, a trimer, etc. is termed oligomerization. The reaction is normally acid-catalyzed. When propene or butenes are used, the formed 

Oligomerization of ethylene using a Ziegler catalyst produces unbranched alpha olefins in the C12-C16 range by an insertion mechanism. A similar reaction using triethylaluminum produces linear alcohols for the production of biodegradable detergents. 

Dimerization of ethylene to butene-1 has been developed recently by using a selective titanium-based catalyst. Butene-1 is finding new markets as a comonomer with ethylene in the manufacture of linear low-density polyethylene (LLDPE). 

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Simplest examples are prepared by the cyclic oligomerization of ethylene oxide. They act as complexing agents which solubilize alkali metal ions in non-polar solvents, complex alkaline earth cations, transition metal cations and ammonium cations, e.g. 12—crown —4 is specific for the lithium cation. Used in phase-transfer chemistry. ... 

One of the mam uses of the linear a olefins prepared by oligomerization of ethylene is in the preparation of linear low density polyethylene Linear low density polyethylene is a copoly mer produced when ethylene is polymerized in the presence of a linear a olefin such as 1 decene [H2C=CH(CH2)7CH3] 1 Decene replaces ethylene at random points in the growing polymer chain Can you deduce how the structure of linear low density polyethylene differs from a linear chain of CH2 units ... 

Manufacture of Monomers. The monomers of the greatest interest are those produced by oligomerization of ethylene (qv) and propylene (qv). Some olefins are also available as by-products from refining of petroleum products or as the products of hydrocarbon (qv) thermal cracking. 

Other Higher Oleiins. Linear a-olefins, such as 1-hexene and 1-octene, are produced by catalytic oligomerization of ethylene with triethyl aluminum (6) or with nickel-based catalysts (7—9) (see Olefins, higher). Olefins with branched alkyl groups are usually produced by catalytic dehydration of corresponding alcohols. For example, 3-methyl-1-butene is produced from isoamyl alcohol using base-treated alumina (15). 

Oligomerization of Ethylene. 1-Butene is a small by-product in the production of linear alpha-olefins by oligomerisation of ethylene. Linear alpha-olefins have one double bond at the terminal position and comprise the homologous series of compounds with carbon atoms between 4 and 19. The primary use of alpha-olefins is in the detergent industry. About 245,000 t/yr of 1-butene was produced for chemical use in the Gulf Coast of the United States in 1988 (72). 

In the eaiTy 1950s, Kail Ziegler, then at the Max Planck Institute for Coal Reseaich in Gennany, was studying the use of aluminum compounds as catalysts for the oligomerization of ethylene. 

Biphasic catalysis is not a new concept for oligomerization chemistry. On the contrary, the oligomerization of ethylene was the first commercialized example of a biphasic, catalytic reaction. The process is known under the name Shell Higher Olefins Process (SHOP) , and the first patents originate from as early as the late 1%0 s. 

Figure 5.2-7 The cationic Ni-complex [(mall)Ni(dppmo)][SbFg] as used for the diphasic oligomerization of ethylene to a-olefins in, for example, [BMIM][PFg].

Figure 7.4-1 Nickel catalysts used for the polymerization and oligomerization of ethylene in...

A related study used the air- and moisture-stable ionic liquids [RMIM][PFg] (R = butyl-decyl) as solvents for the oligomerization of ethylene to higher a-olefins [49]. The reaction used the cationic nickel complex 2 (Figure 7.4-1) under biphasic conditions to give oligomers of up to nine repeat units, with better selectivity and reactivity than obtained in conventional solvents. Recycling of the catalyst/ionic liquid solution was possible with little change in selectivity, and only a small drop in activity was observed. 

Linear alcohols used for the production of ethoxylates are produced by the oligomerization of ethylene using Ziegler catalysts or by the Oxo reaction using alpha olefins. 

Linear alcohols (C12-C26) are important chemicals for producing various compounds such as plasticizers, detergents, and solvents. The production of linear alcohols by the hydroformylation (Oxo reaction) of alpha olefins followed by hydrogenation is discussed in Chapter 5. They are also produced by the oligomerization of ethylene using aluminum alkyls (Ziegler catalysts). 

Henrici-Olive, G. and Olive, S. Oligomerization of Ethylene with Soluble Transition-Metal Catalysts, pp. 496—577. 

Coordination-catalyzed ethylene oligomerization into n-a-olefins. The synthesis of homologous, even-numbered, linear a-olefins can also be performed by oligomerization of ethylene with the aid of homogeneous transition metal complex catalysts [26]. Such a soluble complex catalyst is formed by reaction of, say, a zero-valent nickel compound with a tertiary phosphine ligand. A typical Ni catalyst for the ethylene oligomerization is manufactured from cyclo-octadienyl nickel(O) and diphenylphosphinoacetic ester ... 

FIG. 7 Oligomerization of ethylene (reaction part). C, compressor R, reactor S, separator V, vessel. 

The corresponding iron-catalyzed oligomerization of ethylene was developed by Gibson and coworkers [125]. A combination of an iron precatalyst with MAO (methyl aluminoxane) yields a catalyst that affords ethylene oligomers (>99% linear ot-olefin mixtures). The activity of ketimine iron complexes (R = Me) is higher than that of the aldimine analogs (R = H) and also the a-value of the oligomer is better (Scheme 41). 

Contents G. Henrici-Olive, S. Olive Oligomerization of Ethylene with Soluble Transition-Metal Catalysts. A. Zambelli, C. Tosi Stereochemistry of Propylene Polymerization. C.-D.S. Lee, W.H. Daly Mercaptan-Containing Polymers. Yu. V. Kissin Structures of CopolymerS of High Olefins. 

Upon reaction with ethylene, neither supposed [(=SiO)2Ti(=CHCMe3)j nor [(=SiO)2Zr(=CHCMe3)] species produced neohexene, the expected metathetical exchange product Instead, oligomerization of ethylene was observed, in agreement with results reported for neopentylidenes of group 5 [50]. 

Linear hydrocarbons with a double bond at the end of the chain are made by oligomerization of ethylene. Compounds with 6-18 carbons are the most popular. Ziegler catalysts are used in this process. Note that certain olefins... 

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