Process for the Production of Branched Fatty Acids and Esters Thereof

This invention relates to a process for the production of branched fatty acids and esters thereof by reaction of unsaturated fatty acids and esters thereof with aliphatic, non-activated olefins in the presence of layer silicates and active carbon.

Branched fatty acids are distinguished from linear fatty acids by lower pour points, lower volatility, better oxidation stability, higher wetting power and easier compoundability. Accordingly, they are important raw materials for the production of surface-active agents, for example surfactants, lubricants, rolling and drawing oils, textile auxiliaries and cosmetics.

One method of producing branched fatty acids and esters thereof is based on the Guerbet reaction [Soap, Cosm. Chem. Spec., 52, (1987)] which, by dimerization of alcohols, gives beta-branched alcohols which in turn can be reacted by oxidation to form alpha-branched acids. However, this process involved considerable preparative effort.

A well-known process for the production of branched fatty acids is based on the thermal treatment of unsaturated fatty acids, more particularly tall oil fatty acid, with montmorillonite and water or homogeneous ruthenium catalysts [Fette, Seifen, Anstrichm., 72, 667 (1970), J. Am. Oil. Chem. Soc., 56, 782 (1979), Rev. Fr. Corps, Gras 33, 431 (1986)]. However, the reaction mixture obtained in this process essentially contains high molecular weight dimeric, trimeric and tetrameric fatty acids while the percentage content of branched monomeric fatty acids, for example isostearic acid, is comparatively low and can only be removed from the mixture at considerable cost. Accordingly, the dimerization of fatty acids is of only limited value for the economic production of branched fatty acids.

It is known from U.S. Pat. No. 2,361,018 (1944) that drying oils can be activated with activated olefins, for example cyclopentadiene, dicyclopentadiene or indene, to form branched fatty acids which are used in the paint industry. The Dieis-Alder and ene reactions of unsaturated fatty acids and other activated olefins, such as for example acrolein, acrylic acid, crotonaldehyde, crotonic acid, maleic anhydride, maleic acid or methyl vinyl ketone, are reported in Fette, Seifen, Anstrichm., 63, 633 (1961) and in Fat Sci. Techn. 90, 1 (1988). The reaction of butadiene with unsaturated fatty acids is described in J. Chem. Soc. Chem. Comm., 7, 251 (1974). According to the teaching of published Japanese patent application JP 53/34708, erucic acid ester can be reacted with ethylene in the presence of tungsten hexachloride and organoaluminium compounds. However, all the processes mentioned above can only be carried out with considerable outlay on equipment.

Finally, a simple process for the production of branched fatty acid esters thereof is known from Fette, Seifen, Anstrichm., 65, 105 (1963). In this process, unsaturated fatty acids are reacted with short-chain C.sub.2-4 olefins in a diene reaction. However, the process only gives satisfactory yields where ethylene and propylene are used. With increasing chain length both of the unsaturated fatty acids and of the olefin used, the yields obtained are so poor that the process is unsuitable for industrial application.

Accordingly, the problem addressed by the present invention was to provide a process for the production of branched fatty acids and esters thereof which would be free from the disadvantages mentioned above.

The present invention relates to a process for the production of branched fatty acids and esters thereof by reaction of unsaturated fatty acids or esters thereof with aliphatic non-activated olefins in the presence of layer silicates and active carbon.

It has surprisingly been found that the reaction of unsaturated fatty acids with aliphatic non-activated olefins takes place in a short time and gives comparatively high yields. The present invention also includes the observation that the reaction in the presence of layer silicates and active carbon leads to distinctly smaller percentage contents of oligomeric secondary products than might have been expected from the prior art.

In the context of the invention, unsaturated fatty acids are aliphatic linear carboxylic acids containing 16 to 24 carbon atoms and 1 to 5 double bonds. Typical examples are palmitoleic acid, elaidic acid, petroselic acid, linolenic acid, erucic acid, arachidonic acid or clupanodonic acid. By virtue of their ready accessibility, it is preferred to use unsaturated fatty acids containing 1, 2 or 3 double bonds, more particularly oleic acid, 9,12-linoleic acid and 9,11-linoleic acid ("conjuene acid").

As usual in oleochemistry, the unsaturated fatty acids may even be present in the form of technical mixtures of the type formed in the hydrogenation of natural fats and oils, such as for example coriander oil, soybean oil, cottonseed oil, peanut oil, linseed oil, fish oil or beef tallow. Saturated fatty acids may also be present in these mixtures providing they do not make up more than 50% by weight of the fatty acid composition. By virtue of their high content of oleic and linoleic acid, fatty acid mixtures based on rapeseed oil and sunflower oil are preferred.

The unsaturated fatty acids may also be present in the form of their alkyl or glycerol mono-, di- or triesters. Alkyl esters are understood to be esters of the unsaturated fatty acids with aliphatic alcohols containing 1 to 22 carbon atoms and 0, 1, 2 or 3 double bonds. Typical examples are ethyl, n-propyl, i-propyl, n-butyl, pentyl, hexyl, octyl, 2-ethylhexyl, decyl, lauryl, myristyl, cetyl, stearyl, oleyl, elaidyl, petroselinyl, linolyl, linolenyl, behenyl or erucyl esters. However, methyl esters are preferably used.

Aliphatic non-activated olefins are understood to be linear, cyclic or branched C.sub.5-20 alkenes with a double bond in the alpha position or an internal double bond. Typical examples of such alkenes are pent-1-ene, hex-1-ene, cyclohexene, hept-1-ene, oct-1-ene, cyclooctene, non-1-ene, dec-1-ene, undec-1-ene, dodec-1-ene, cyclodecene, tetradec-1-ene, hexadec-1-ene, octadec-1-ene, eicos-1-ene and their double bond and skeletal isomers. Linear alpha-olefins containing 6 to 18 and, more particularly, 8 to 10 carbon atoms show particularly high reactivity. Accordingly, they are preferably used.

In the context of the invention, layer silicates are understood to be the elements of main groups 1 to 3 of the periodic system which have a crystal lattice with SiO.sub.4 tetrahedrons linked in one plane ("layer lattice") [Ullmanns Enzyclopaedie der technischen Chemie, 4th Edition, Vol. 21, 365 (1984)]. Typical examples are tallow Mg.sub.3 [(OH).sub.2 .vertline.[Si.sub.4 O.sub.10 ] and kaolinite Al.sub.4 [(OH).sub.8 .vertline.Si.sub.4 O.sub.10 ]. Montmorillonite Al.sub.2 [(OH).sub.2 .vertline.Si.sub.4 O.sub.10 ] has proved to be a particularly effective catalyst and, accordingly, is preferably used.

The molar ratio of saturated fatty acid or ester to olefin is 1:0.5 to 1:5 and preferably 1:1 to 1:3.5. An optimal reaction rate and a low percentage of secondary products are observed where molar ratios of 1:2 to 1:2.75 are used.

The reaction of the unsaturated fatty acids or esters thereof with the olefins is carried out in the presence of 1 to 30% by weight and preferably 3 to 15% by weight layer silicate, based on the starting materials fatty acid or fatty acid ester plus olefin. Particular selectivity for the formation of monomeric branched fatty acids is observed where 5 to 10% by weight layer silicate is used.

The reaction of the unsaturated fatty acids or esters thereof with olefins is carried out in the simultaneous presence of 0.01 to 3% by weight active carbon, based on the starting materials. Particular selectivity for the formation of monomeric branched fatty acids is observed where 0.1 to 1% by weight active carbon is used.

The reaction of the unsaturated fatty acids or esters thereof with olefins in the presence of layer silicates and active carbon is carried out at temperatures of 200.degree. to 280.degree. C. To obtain an optimal reaction rate, it is of advantage to carry out the reaction at 220.degree. to 260.degree. C. It is advisable, particularly where low-boiling olefins are used, to carry out the reaction under autogenous pressure in an autoclave.

The reaction of the unsaturated fatty acids or esters thereof with olefins in the presence of layer silicates and active carbon is carried out over a period of 0.1 to 5 h. The branched fatty acids and esters are obtained in high yields after only 0.25 to 1.5 h, particularly where oct-1-ene and dec-1-ene are used.

On completion of the reaction, the branched fatty acids can be recovered by distillation.

The branched fatty acids are suitable for the production of surface-active agents, for example surfactants, lubricants, rolling and drawing oils, textile auxiliaries and cosmetics.

The following Examples are intended to illustrate the invention.

A1. Technical sunflower oil fatty acid, Edenor.RTM. SB05, a product of Henkel KGaA

A2. Technical oleic acid, Edebor.RTM. TiO.sub.5, a product of Henkel KGaA

A3. Technical sunflower oil

B1. Oct-1-ene (97% by weight), a product of Janssen Chimica

Average molecular weight : 112

B2. Dec-1-ene (96% by weight), a product of Janssen Chimica

Average molecular weight : 140

C. Montmorillonite K 10, a product of Sudchemie

D. Active carbon, powdered, highly pure, a product of Merck

1 Mol fatty acid A1 or A2 and 2 to 2.75 mol olefin B1 or B2 were introduced into a 1 liter stirred autoclave, after which 5 to 10% by weight montmorillonite and 0.1% by weight active carbon, based in each case on the starting materials, were added. The reaction mixture was heated to T=240.degree.-260.degree. C. and stirred for t=0.25-1.5 h. On completion of the reaction, the reaction mixture was cooled to 20.degree. C. and the solids were removed through a nutsch filter.

The filtrate was then distilled in a high vacuum of 40 Pa and at a temperature of 20.degree. to 240.degree. C. First runnings essentially containing excess olefin and oligomerization and isomerization products thereof and small quantities of fatty acid initially distilled over at a vapor temperature of 20.degree. to 195.degree. C. and were discarded. The branched fatty acids were obtained in the form of a light yellow liquid at a vapor temperature of 195.degree. to 240.degree. C. and were separated off. Oligomerized fatty acids remained behind in the sump in the form of a dark brown viscous liquid.

The reaction parameters and the yields obtained after distillation are shown in Table 1.

Examples 1 to 3 were repeated using 886 g (1 mol) sunflower (A3), 924 g (8.25 mol) oct-1-ene, 10% by weight montmorillonite and 0.1% by weight active carbon, based in each case on the starting materials. The reaction was carried out over t=1.5 h at T=260.degree. C.

Distillation was carried out after pressure hydrogenation of the triglycerides in the same way as in Examples 1 to 3.