Oligomerization of light olefins

The polyaddition of light olefins (ethylene, n-opylene. butenes), gives rise to oligomeric olefins with a molecular weight that is a multiple of the starting olefin. The following can be distinguished 

This second conversion takes place between 200 and 300 C, at low er pressure (5.10 Pa). The triethylaluminum is recovered and recycled. 

Industrially, the process is usually conducted in two steps, growth followed by displacement, but it can be carried out in a single step around 200 at 25.10 Pa pressure in the presence of much smaller amounts of triethytalummum (0.5 per cent weight). In this case, it is unnecessary to recover the alkylaluminum, and it can be hydrolysed with the formation of alumina. Ethyl Corporation in the United States uses the two-step process, while Oulf Oil in the United States and Mitsubishi Chemiad in Japan use the one-step process. 

Variants of this ethyiece oligomerization techniqi have been developed by Esso and Mitsui PetrochemicaL which use titanium base catalysts, and Shell, which uses a complex of nickel with phosphin  

The metathesis or transaikyiideiiation reaction is cataU-zed by complexes of tungsten, moiybdennm or rhenium, in a heterogeneous or homogeneous phase, and consists in the scission of the double bond with the formation di two new olefins. 

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The oligomerization of light olefins such as ethylene for the production of synthetic fuels using zeolites as catalysts has been extensively studied.[25-28] In general, it has been found that the rate of oligomerization of ethylene over ZSM-5 zeolite is slower compared with other olefins and higher reaction temperatures are necessary. The catalytic performance of this reaction is related to the nature and number of acid sites of the zeolite. 

Inui, T. and Kim, J. B. High quality gasoline synthesis by selective oligomerization of light olefins and successive hydrogenation. Stud. Surf. Sci. Catal., 1996, 100, 489 498. 

HIGH QUALITY GASOLINE SYNTHESIS BY SELECTIVE OLIGOMERIZATION OF LIGHT OLEFINS AND SUCCESSIVE HYDROGENATION... 

Other Solid-add Catalysts - Chromium on an aluminophosphate support, which is supposed to be a polymerization catalyst, was used in the oligomerization of light olefins and ethylene. For ethylene oligomerization, the catalyst exhibited activity for dimerization, with around 60% conversion to C4 fractions. In another patent the support and the active phase were the same as in the previous patent, except that the support had been treated with a solution of triethylaluminium in toluene before being contacted with the chromium compound. The catalyst system showed selectivity towards trimerization. When... 

Fluidized bed, WHSV >0.1,0.14-1.5 MPa, 342-482 °C, sufficient for concurrent oligomerization of light olefins while cracking n-paraffins... 

Zeolites - The oligomerization of light olefins in the presence of zeolites has... 

Schmidt, R., Welch, M.B., and Randolph, B.B. (2008) Oligomerization of C5 olefins in light catalytic naphtha. Energy Fuels, 22, 1148-1155. 

Elucidating rates of p-scission on various zeolites will be key to determining what firacfion of light olefins, particularly propylene and butenes, are products of the aromatic- versus olefin-based carbon pool however, the prevalence of secondary reactions, such as olefin oligomerization and dehydrocyclization, may hinder the measurement of kinetic parameters of p-scissioa... 

Furthermore, the major problem of reducing aromatics is focused around gasoline production. Catalytic reforming could decrease in capacity and severity. Catalytic cracking will have to be oriented towards light olefins production. Etherification, alkylation and oligomerization units will undergo capacity increases. 

I> = (dc/df)//abs where dc/dr is the rate of disappearance of the olefinic double bonds per unit volume and /abs the rate at which the incident light is absorbed per unit volume of the KBr pellet containing the sample. The rates of disappearance of the olefinic double bonds during oligomerization and polymerization were monitored by infrared (IR) spectroscopy. 

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