FR2818275A1 - Process for the direct hydrogenation of mono- and di-carboxylic acids to the corresponding alcohols in the presence of a heterogeneous catalyst by dispersion or dissolution of the acids in lower alcohols or low alkyl esters - Google Patents

Abstract

Process for the direct hydrogenation of mono- and di-carboxylic acids to the corresponding mono- and di-ols in which the acid is dispersed or dissolved in a lower alcohol and/or lower alkyl ester of a fatty acid. The reaction is carried out in the presence of a heterogeneous catalyst.

Description

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Field of the invention
The invention is in the field of oleochemical raw materials and relates to a process for direct hydrogenation of monocarboxylic acids to the corresponding mono-ols or dicarboxylic acids to the corresponding diols.

State of the art
Fatty alcohols represent important oleochemical intermediates which are usually produced by hydrogenation of fatty acid alkyl esters in the presence of heterogeneous copper, chromium, manganese or aluminum catalysts, so-called catalysts of Adkins. For economic reasons it would be preferable to use instead of fatty acid alkyl ester, raw materials less ennobled and therefore more favorable in terms of cost.

 Thus European patents EP 0 254 189 B1 and EP 0 334 118 B1 (Henkel) disclose processes for direct hydrogenation of triglycerides to fatty alcohols for which the conversion occurs in the presence of copper / chromium oxide catalysts. / barium at temperatures in the region of 160 to 2500C and at pressures of 20 to 300 bar. However, a drawback is the fact that in this reaction, the coupling product does not produce the precious glycerol but the 1,2-propanediol which is much less important, which makes the process economically unprofitable.

 Instead of triglycerides, it is therefore recommended to use in the hydrogenation the fatty acids which must be released by steam cleavage, which because of the lower stage of ennoblement would be even more economical than the use alkyl esters. In this respect reference should be made to European Patent EP 0 602 108 B1 (Henkel) which relates to the hydrogenation of non-deacidified fats and oils.

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From this publication it can certainly be removed that the known Adkins catalysts can be used not only for the hydrogenation of esters but also of acids, but the problem of the undesired formation of propanediol is not solved. This is solved in accordance with the teaching of the European patent EP 0 280 982 B1 (Henkel) by the implementation of copper-chromium oxide catalysts which are provisionally temporarily protected by the addition of silica gel against attack by acids, but which does not nevertheless have no industrial life expectancy.

 Accordingly, the problem of the present invention has been to provide a process for the direct hydrogenation of carboxylic acids to the corresponding alcohols, a process which desirably avoids the disadvantages described above and in particular provide for sufficient lifetimes, high yields.

Description of the invention
The object of the invention is a process for the direct hydrogenation of carboxylic acids into corresponding alcohols in the presence of heterogeneous catalysts which are distinguished by the use of carboxylic acids which are present in the dispersed or dissolved state. in lower alcohols and / or lower alkyl esters of fatty acids.

 Surprisingly, it has been found that the disadvantage of defective activity and defective corrosion resistance of conventional Adkins catalysts can be overcome by dispersing or dissolving this process. carboxylic acids in suitable organic solvents, in particular methanol and / or fatty acid methyl esters. In this way, in the hydrogenation yields above 90% of the theory are reached as well as lifetimes, which are not

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 not less than those obtained during the hydrogenation of the methyl esters.

Carboxylic acids
A first group of carboxylic acids which are in question for the reduction to the corresponding alcohols comprises monocarboxylic acids of the long chain fatty acid type which preferably correspond to the formula I, R 1 CO-OH (I) in which CO represents a linear or branched acyl, saturated or unsaturated, optionally functionalized with hydroxy, containing from 6 to 22, preferably 12 to 18 carbon atoms and 0 and / or 1 to 3 double bonds. Typical examples are caproic acid, caprylic acid, 2-ethylhexanoic acid, capric acid, lauric acid, isotridecanoic acid, myristic acid, palmitic acid, palmoleic acid , stearic acid, isostearic acid, oleic acid, elaidic acid, petroselinic acid, linoleic acid, linolenic acid, eléostearic acid, ricinoleic acid, eleostearic acid, ricinoleic acid, 12hydroxystearic acid, arachic acid, gadoleic acid, behenic acid, and erucic acid, as well as their industrial mixtures, which occur, for example, during the cutting of fats and natural oils, when reducing aldehydes from Roelen oxosynthesis or unsaturated fatty acid dimerization. Industrial (cut-off) fatty acids having from 12 to 18 carbon atoms are preferred, such as, for example, coconut, palm, palm kernel or tallow fatty acids as well as isostearic acid.

 Instead of the monocarboxylic acids, the corresponding dicarboxylic acids can also be used.

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and they can be hydrogenated to the corresponding diols which preferably correspond to formula (II),
HOOC- (CH 2) n -COOH (II) wherein n represents numbers ranging from 1 to 18, preferably from 4 to 10. Typical examples are malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, as well as 1,9nonanedicarboxylic acid, 1,16-hexadecanedicarboxylic acid, 1,18-octadecannedicarboxylic acid, and 1,12-dodecane dicarboxylic acid, of which the latter is preferred. Finally, dicarboxylic acids also come into question as products, those in the form of dimer and trimer fatty acids in question, which have on average from 36 to 54 carbon atoms and which are industrially prepared by di- or trimerization of oleic acid.

Dispersant and solvent
In the sense of the process according to the invention, it is necessary to present the carboxylic acids in a suitable dispersing agent. For this purpose, for example, lower alcohols of formula (III) ROH (III) in which R 2 represents an alkyl radical having from 1 to 4 carbon atoms are suitable.

 Typical examples are ethanol as well as isomeric propanols and butanols, but especially methanol. In addition, it is also possible to use, as dispersing agent, carboxylic acid lower alkyl esters of formula (IV), R3CO-OR4 (IV).

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dans laquelle ECO représente un reste acyle linéaire ou ramifié ayant de 1 à 22, de préférence de 6 à 18 atomes de carbone et R représente un radical alkyle ayant de 1 à 4 atomes de carbone. Des exemples typiques sont les esters éthylique, propylique, butylique et en particulier l'ester méthylique de l'acide formique, de l'acide acétique, de l'acide propionique, des acides butyriques et de l'acide valérianique ainsi que des acides gras déjà mentionnés, de préférence ceux ayant de 12 à 18 atomes de carbone. Il est apparu comme particulièrement avantageux si les restes acyle des acides carboxyliques à hydrogéner et les esters fonctionnant comme agent dispersant sont mis en accord. Des mélanges de méthanol et d'ester méthylique d'acide gras sont utilisés. Un autre mode d'exécution avantageux consiste dans le fait de mettre en oeuvre comme agent dispersant des mélanges de méthanol et d'esters méthyliques d'acide gras, par exemple dans le rapport pondéral de 10 : 90 à 90 : 10, de préférence de 25 : 75 à 75 : 25 et en particulier de 40 : 60 à 60 : 40. Le rapport d'utilisation molaire des acides carboxyliques et de l'agent dispersant peut s'élever de 1 : 1 à 1 : 10, de préférence de 1 : 2 à 1 : 8 et en particulier de 1 : 3 à 1 : 5.

wherein ECO represents a linear or branched acyl residue having from 1 to 22, preferably from 6 to 18 carbon atoms and R represents an alkyl radical having 1 to 4 carbon atoms. Typical examples are the ethyl, propyl and butyl esters and in particular the methyl ester of formic acid, acetic acid, propionic acid, butyric acids and valerianic acid, and also fatty acids. already mentioned, preferably those having from 12 to 18 carbon atoms. It has been found particularly advantageous if the acyl radicals of the carboxylic acids to be hydrogenated and the esters functioning as dispersing agents are brought into agreement. Mixtures of methanol and fatty acid methyl ester are used. Another advantageous embodiment consists in using, as dispersing agent, mixtures of methanol and fatty acid methyl esters, for example in the weight ratio of from 10: 90 to 90: 10, preferably from 25: 75 to 75:25 and in particular 40:60 to 60:40. The molar utilization ratio of the carboxylic acids and the dispersing agent can be from 1: 1 to 1: 10, preferably from 1: 2 to 1: 8 and in particular 1: 3 to 1: 5.

hydrogenation
The hydrogenation can be carried out in a manner known per se, also at temperatures in the range of 150 to 3000 ° C. and at pressures in the region of 20 to 300 bar. Usually it operates in tubular reactors or tunnel reactors in which the catalysts are arranged in pieces, also for example pellets. In particular, the hydrogenation can be carried out in a fixed-bed reactor. Suitable catalysts are commercial catalysts, such as zinc-copper, aluminum-zinc, copper-aluminum or copper-chromium, which can be controlled, for example, from Engelhard or SüdChemie, the latter of which, because of their particular acid stability, are preferred. These catalysts by

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 contact can be doped with other metals such as barium, manganese, magnesium, cadmium or cerium. For reasons of protection against corrosion, it is furthermore recommended to build the hydrogenation plant made of special steel.

EXAMPLES Examples 1 to 4, Comparative Examples VI and V2
A test tunnel reactor having a diameter of 30 mm and a length of 1.5 was charged to me with a copper-chromium catalyst of the Engelhard Cu 1986T 1/8 "type. As the feedstock for the hydrogenation, one industrial palm kernel fatty acid (Edenor () pu, Cognis Deutschland GmbH, PKFS) and one azelaic acid (<K AS) were used. which have been converted from 220 to 2600C at a hydrogen pressure of 250 to 300 bar, and at a rate of 1 l / h of palm kernel alcohol or 1,9-nonanediol.

 In the examples according to the invention 1 to 4, the fatty acids are introduced into a dispersing agent (methanol = MeOH, palm kernel fatty acid methyl ester = PKFSME), in the comparison examples V1 and V2 the reaction is omitted. dispersing agent. The results are collated in Table 1. The yields are indicated as a function of the catalyst life.

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Table 1 Hydrogenation of carboxylic acids

<Tb>
<tb> 1 <SEP> 2 <SEP> V1 <SEP> 3 <SEP> 4 <SEP> V2
<tb> Acid <SEP> AS
<tb> Agent <SEP> MeOH / <SEP> - <SEP> MeOH <SEP> MeOH <SEP> PKFSME <SEP> 1: 1
<tb><SEP> carboxylic acid <SEP> 1 <SEP>: <SEP> 10 <SEP> 1 <SEP>: <SEP> 8 <SEP> - <SEP> 1 <SEP>: <SEP> 2 <SEP> 1 <SEP>: <SEP> 2 <SEP> than <SEP>:
<tb> agent <SEP> dispersant
<tb> Temperature <SEP> [C] <SEP> 220 <SEP> 220 <SEP> 220 <SEP> 260 <SEP> 260 <SEP> 260
<tb> Pressure <SEP> 300 <SEP> 300 <SEP> 300
<tb> Yield <SEP> Mono- <SEP> or <SEP> Diol <SEP> [% <SEP> of <SEP> the <SEP> Theory]
<tb> immediately <SEP> 93 <SEP> 93 <SEP> 89 <SEP> 96 <SEP> 95 <SEP> 84
<tb> after <SEP> 92 <SEP> 92 <SEP> 56 <SEP> 96 <SEP> 95 <SEP> 49
<tb> after <SEP> 92 <SEP> 92 <SEP> 14 <SEP> 96 <SEP> 94 <SEP> 11
<tb> after <SEP> weeks <SEP> 91 <SEP> 91 <SEP> - <SEP> 95 <SEP> 94 <SEP> -
<Tb>

Claims (1)

 10) Process for the direct hydrogenation of carboxylic acids into corresponding alcohols in the presence of heterogeneous catalysts, characterized in that carboxylic acids are used which are in the dispersed or dissolved state in lower alcohols and / or in lower fatty acid alkyl esters.  20) Process according to Claim 1, characterized in that monocarboxylic acids of formula

 (I), RCO-OH (I) wherein ECO represents a linear or branched, saturated or unsaturated acyl residue having 6 to 22 carbon atoms and 0 and / or 1 to 3 double bonds.  30) Process according to claim 1, characterized in that dicarboxylic acids of formula (II) HOOC- (CH2) n -COOH (II) are used in which n represents numbers ranging from 1 to 18.  40. Process according to at least one of Claims 1 to 3, characterized in that lower alcohols of formula (III) are used as the dispersing agent.

 ROH <Desc / Clms Page number 9>  wherein R2 represents an alkyl radical having 1 to 4 carbon atoms.  50) Process according to Claim 4, characterized in that methanol is used as the dispersing agent.  60) Process according to at least one of Claims 1 to 5, characterized in that a fatty acid lower alkyl ester of formula (IV), R3CO-OR4 (IV), is used as the dispersing agent. wherein CO represents a linear or branched acyl residue having from 1 to 22 carbon atoms and R4 represents an alkyl radical having 1 to 4 carbon atoms.  70. Process according to claim 6, characterized in that a fatty acid methyl ester is used as dispersing agent.  80) Process according to at least one of Claims 1 to 7, characterized in that mixtures of methanol and fatty acid methyl ester are used.  90) Process according to at least one of Claims 1 to 8, characterized in that the carboxylic acids and the dispersing agent are used in a molar ratio of 1: 1 to 1: 10. <Desc / Clms Page number 10>  100) Process according to at least one of Claims 1 to 9, characterized in that the hydrogenation is carried out in a fixed-bed reactor.