Oligomerization of ethene

Ni(sacsac)P(nBu3)Cl (sacsac = pentane-2,4-dithionate) was activated by AlEt2Cl to form a catalytically active species for the oligomerization of ethene and propene. This study is noteworthy in that it uses in situ UV-VIS spectroscopy to monitor the course of the polymerization. In this reaction, the aluminum reagent serves both to activate the transition metal and to scavenge any moisture present. 

Heveling, J., Van der Beek, A. and De Pender, M. Oligomerization of ethene over nickel-exchanged zeolite Y into a diesel-range product, Appl. Catal., 1988, 42, 325-336. 

Davydov, A. A., Kantcheva, M. and Chepotko, M. L. FTIR spectroscopic study on nickel(II)-exchanged sulfated alumina nature of the active sites in the catalytic oligomerization of ethene. Catal. Lett., 2002, 83, 97-108. 

Espinoza, R. L., Snel, R., Korf, C. J. and Nicolaides, C. P. Catalytic oligomerization of ethene over nickel-exchanged amorphous silica-aluminas effect of the acid strength of the support. Appl. Catal., 1987, 29, 295-303. 

Heydenrych, M. D., Nicolaides, C. P. and Scurrell, M. S. Oligomerization of ethene in a slurry reactor using a nickel(II)-exchanged silica-alumina catalyst. J. Catal., 2001, 197, 49-57. 

Sakaguchi, T., Mita, S., Matsui, E., Takahashi, M., Okazaki, N. and Tada, A. Oligomerization of ethene over several catalyst beds consisting of both Ni/Si02.A1203 and BP04, Phosphorus Res. Bull., 2002, 14, 129-134. 

Example 10.4. Ethene oligomerization in the Shell Higher Olefin Process. The Shell Higher Olefin Process, abbreviated SHOP, produces predominantly internal straight-chain olefins in the C10 to C16 carbon-number range from ethene [107,109,119,120], Oligomerization of ethene to straight-chain 1-olefins of even carbon numbers is only... 

Triggered by the developments in late transition metal catalyzed polymerization, new catalyst systems were described very recently for the oligomerization of ethene. Nickel and palladium complexes based on a-diimine ligands 13 and imi-nophosphines 14 were reported to be very active and selective oligomerization catalysts [57, 58], Activation of the Ni(II) diimine halides with a large excess of MAO (210 equiv.) leads to oligomerization catalysts with activities of between... 

Pd,122-124,1 8 133 134 pt 123,124,128 an(j q,127 Metal complexes of iminophosphines have been used in various catalytic reactions, such as the coupling of organostannanes with aryl halides,135 oligomerization of ethene,122 Heck reactions,136 and allylic alkylation reactions.123... 

Propose a reasonable catalytic cycle for the Ni-catalyzed oligomerization of ethene that occurs during the first stage of SHOP. Assume that the active catalyst is L(X)Ni-H. 

Neutral nickel(II) complexes with a chelating pyridine-carboxylate ligand were shown to be active in both, the oligomerization of ethene and the copolymeriza-... 

The easiest technique to combine catalysis in a polar medium with product separation is shown in Figure 1. Both operations are done in the same unit at the same time. The nonpolar product phase is deposited from the polar catalyst phase and can be separated at the top of the reaction column. The SHOP oligomerization of ethene works in this way. The catalytic phase, consisting of 1,4-butanediol and nickel catalyst, always remains in the reaction unit. In the technical plant the reaction takes place not in only one reactor but in a series of tanks. This is so that the heat of reaction may be removed by water-cooled heat exchangers which are placed between the different reactor tanks. The flow scheme of the SHOP process is shown in Section 7.1. 

In coordination polymerization, monomer forms an adduct with a transition-metal complex, and further monomer is then successively inserted between metal and carbon. Termination occurs when the metal complex splits off from the polymer or the chain is broken intentionally by hydrogenolysis. Since the initiator is restored to its original form, the process is catalytic. The most important industrial processes are Ziegler-Natta polymerizations of a-olefins and employ solid catalysts. Most catalysts for coordination polymerization are hydride complexes of transition metals. An important example is the Shell Higher Olefin Process (SHOP) for homogeneous oligomerization of ethene with a complex nickel catalyst. The molecular-weight distribution is a Schulz-Flory distribution. The rate is first order in the catalyst metal. 

Fig. 26.9 Simplified catalytic cycle illustrating the oligomerization of ethene using a nickel-based catalyst L = phosphine, X = electronegative group.

The AlEts catalyzed oligomerization of ethene followed by an stoichiometric autoxidation with molecular oxygen leads - via Al(OR)3 -to even-numbered primary alcohols used in production of PVC plasticizers and biodegradable detergents. 

A common intermediate step was suggested, confirmed by the similarity, C4-C7, of the final products from the oligomerization of ethene, propene, a mixture of internal pentene isomers, hex-l-ene, and dec-l-ene over a zeolitic catalyst. ... 

In a different approach based on membrane technology, oligomerization of ethene has also been examined using a poly(ethersulfone)-supported ionic liquid membrane containing [EMIMjCl-AlCh ionic liquids with or without the presence of [NiCl2 P(cyclohexyl)3]2 dimerization catalyst and dichloroethylaluminate as an acid scavenging co-catalyst [107]. 

Completely different liquid/liquid two-phase applications for oligomerization of ethene have been reported. Chauvin used ionic liquids as solvents for oligomerization catalysts [73] (cf. Chapter 5). Another approach is the use of perfluorinated solvents together with catalysts bearing perfluorinated ligands (Chapter 4) [74,75]. 

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