Chemistry of hydrocarbon compounds – Unsaturated compound synthesis – By addition of entire unsaturated molecules – e.g.,...
Patent
1996-05-16
1998-12-15
Lewis, Michael L.
Chemistry of hydrocarbon compounds
Unsaturated compound synthesis
By addition of entire unsaturated molecules, e.g.,...
585533, 502 74, 502337, C07C 202, B01J 2300
Patent
active
058499725
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for the oligomerization of olefins of 2 to 6 carbon atoms, and precipitation catalysts for this purpose.
Olefins of 2 to 6 carbon atoms and mixtures thereof, in particular olefins of 4 carbon atoms, are available in large amounts both from FCC plants and from steam crackers. The particular C.sub.4 cut, ie. the mixture of butenes and butanes, is very suitable for the preparation of oligomers, in particular octenes and dodecenes, after separation of the isobutene. After hydroformylation and subsequent hydrogenation to the corresponding alcohols, both the octenes and dodecenes can be used, for example, for the preparation of plasticizers.
With regard to the use as a plasticizer alcohol, the degree of branching plays a decisive role with respect to the properties of the plasticizer. The degree of branching is described by the ISO index, which specifies the average number of methyl branches in the particular fraction.
For example, n-octenes with 0, methylheptenes with 1 and dimethylhexenes with 2 contribute to the ISO index of a C.sub.8 fraction. The lower the ISO index, the more linear are the molecules in the particular fraction. The higher the linearity, ie. the lower the ISO index, the higher are the yields in the hydroformylation and the better are the properties of the plasticizer prepared therewith. A lower ISO index, for example in the case of phthalate plasticizers, has an advantageous effect in terms of low volatility and better brittleness temperature of the flexible PVC produced using the plasticizer. Slightly branched oligomers of lower olefins are obtainable from reactions of both homogeneous and heterogeneous catalysts which contain predominantly nickel as the active component. However, other catalytically active metals, such as ruthenium (G. Braca, La Chimica e l'Industria, 56 (1974), 110-116), palladium, according to U.S. Pat. No. 4,436,946, and copper, cobalt, iron, chromium and titanium, according to GB 824 002, have also been described. Only the nickel-containing catalysts have become industrially important.
DE 28 55 423 discloses, as a homogeneous catalyst, a system which consists of the nickel(II) salt of octanoic acid, ethylaluminum dichloride and a free fatty acid. A catalyst system of this type is also used in the only homogeneously catalyzed process of industrial importance for olefin oligomerization (Y. Chuvin, Chemistry and Industry, 1974, 375-378).
Homogeneously catalyzed processes for the oligomerization of olefins present problems on the one hand owing to the removal of the catalyst and on the other hand owing to the substantially higher catalyst costs per ton of product in comparison with a procedure catalyzed by heterogeneous catalyst. In the removal and destruction of the catalyst, which is fed through the plant in a straight pass with the stream of starting materials, wastewater containing heavy metals and ammonium is also formed and has to be appropriately worked up and disposed of.
In addition to the homogeneous catalysts, a large number of heterogeneous catalyst systems based on nickel and silicon, which often additionally contain aluminum and are prepared by a wide range of methods, have also been described.
U.S. Pat. No. 5,169,824 discloses, for example, the preparation of a nickel precipitation catalyst on Al.sub.2 O.sub.3 /SiO.sub.2. The NiO content is adjusted so that the Al.sub.2 O.sub.3 /SiO.sub.2 carrier is covered with one layer, ie. from 0.07 to 0.12% by weight of NiO per 1 m.sup.2 of carrier surface.
Under conditions which are supercritical for the starting olefin trans-2-butene and with the addition of decane as a subcritical solvent, this catalyst gives a conversion in the autoclave of 86%, a C.sub.8 selectivity of 53% and an ISO index of 1.3 in the C.sub.8 fraction.
According to DD 273 055, nickel and aluminum are precipitated onto SiO.sub.2. With a hydrogen-saturated butene/butane mixture, a conversion of 57% to oligomers is achieved with 91% C.sub.8 selectivity and an ISO index of 1.2.
According to DE 20 51 402, a c
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Polanek Peter
Vicari Maximilian
BASF - Aktiengesellschaft
Ghyka Alexander G.
Lewis Michael L.
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