Alkyldicarboxylic acids are important compounds for the preparation of plastics such as polyesters and polyamides. Particular mention may be made of high-performance plastics based on polyamides, as are used, for example, for the production of fuel lines. One of these dicarboxylic acids is 1,12-dodecanedicarboxylic acid (DDA). As industrial processors for preparing DDA, particular mention may be made of:
These processes are energy-intensive and produce large quantities of waste which is expensive to dispose of. In addition, the selectivity is often not high. Thus, for example, in the oxidative cleavage of cyclododecanol by means of nitric acid, the formation of short-chain “breakup acids” by oxidative degradation is a problem.
A new approach to the preparation of dicarboxylic acids is metathesis. A combination of ring-opening metatheses (ROM) with cross metathesis (CM) makes it possible to prepare aliphatic α,β-unsaturated dicarboxylic acids in one step from cycloalkenes and acrylic acid using suitable precatalysts. If cyclooctene (1) as starting material is reacted with acrylic acid (2), dodecane-2,10-diene-1,12-dicarboxylic acid (3) is obtained (scheme 1). The combination of the two reaction steps is also referred to as ROCM (ring-opening cross metathesis) or ROX metathesis.
The α,β-unsaturated dicarboxylic acid obtained can be hydrogenated in a second step to give the desired 1,12-dodecanedicarboxylic acid (4) (scheme 2).
Moreover, it is also conceivable to use the unsaturated dicarboxylic acid as monomer for the preparation of unsaturated polyamides or polyesters. The polymers obtained in this way can subsequently be crosslinked, which is of interest for many applications.
Metathesis reactions are equilibrium reactions giving a corresponding product distribution. The above-described reaction can take various reaction paths. Thus, the cycloalkene can react in a ring-opening metathesis polymerization to form a polyolefin. Furthermore, formation of various telechelic oligomers can occur. These secondary reactions have an adverse effect on the yield of desired product and also make work-up of the reaction mixture difficult. The formation of ethylene, which can be taken off as gas from the liquid phase, results in a shift of the equilibrium in the direction of the product. However, this effect is not sufficient to suppress secondary reactions such as polymerization completely.
In the prior art to date,
It has now surprisingly been found that a process according to the claims makes it possible to shift the equilibrium completely in the direction of the desired product without working at a high dilution. In addition, the process described makes effective recycling of the catalyst possible. This is achieved by, in contrast to previous practice, working at high substrate concentrations up to reactions in bulk. During the course of the reaction, the α,β-unsaturated dicarboxylic acid precipitates when the solubility product is exceeded and is thus removed from the equilibrium (in the homogeneous phase). This adds a second positive effect to the shifting of the equilibrium in the direction of the desired product by formation of gaseous ethylene.
A further challenge is separating off and, if appropriate, recycling the catalyst. The catalyst often has to be separated off by column chromatography in a complicated operation, which makes industrial implementation uneconomical.
As a result of the product being obtained as a solid in the process described here, this can easily be filtered off, purified and the catalyst dissolved in the filtrate can be recycled.
The reaction described is carried out at temperatures of from 10 to 100° C., preferably from 20 to 80° C. and particularly preferably from 20 to 60° C.
The reaction described can be carried out in bulk or using a solvent. Suitable solvents are acyclic and also cyclic hydrocarbons. Aromatic halogenated hydrocarbons are particularly suitable and aromatics having alkyl groups are very particularly suitable.
When the reaction is carried out in solution, cyclooctene concentrations of >1 M are preferred. Particular preference is given to cyclooctene concentrations of from 1 to 2 M and very particular preference is given to cyclooctene concentrations of from 2 to 4 M, based on the solvent.
In the process described, the catalyst is used in amounts of from 5 to 0.0001 mol %, based on the amount of cyclooctene. Preference is given to amounts of from 2 to 0.001 mol % and particular preference is given to amounts of from 1 to 0.5 mol % of catalyst, based on the molar amount of cyclooctene used.
To obtain the α,β-unsaturated dicarboxylic acid in polymer grade quality, purification by crystallization, distillation or a combination of the two is possible.
Suitable catalysts are ruthenium-carbene complexes which, as one of the characteristic features, bear an N-heterocyclic carbene ligand. Examples of preferred catalysts are shown in FIG. 1. Particular preference is given to catalysts of the type 7, with an electron-withdrawing group R′ on the benzylidene ligand.
Number | Date | Country | Kind |
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10 2008 002 092 | May 2008 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP2009/054519 | 4/16/2009 | WO | 00 | 9/15/2010 |
Publishing Document | Publishing Date | Country | Kind |
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WO2009/144089 | 12/3/2009 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
6828449 | Herwig et al. | Dec 2004 | B2 |
6861540 | Herwig et al. | Mar 2005 | B2 |
6927308 | Leininger et al. | Aug 2005 | B2 |
7084300 | Herwig et al. | Aug 2006 | B2 |
7253329 | Herwig et al. | Aug 2007 | B2 |
7495129 | Balduf et al. | Feb 2009 | B2 |
7608738 | Herwig et al. | Oct 2009 | B2 |
20070004903 | Hoff et al. | Jan 2007 | A1 |
20070265184 | Herwig et al. | Nov 2007 | A1 |
20090306367 | Roos et al. | Dec 2009 | A1 |
Entry |
---|
Saito, Isao et al., “Synthesis of Synthetic alpha, omega-Dicarboxylic Acids and Unsaturated Carboxylic Acids from Silyl Enol Ethers”, Tetrahedron Letters, vol. 24, No. 41, pp. 4439-4442, XP002529873, (1983). |
Randl, Stefan et al., “Ring opening-cross metathesis of unstrained cycloalkenes”, Chemical Communications, Chemcomm Communication, Journal the Royal Society of Chemistry, pp. 1796-1797, XP002334391, ISSN: 1359-7345, (Nov. 4, 2001). |
U.S. Appl. No. 12/865,018, filed Jul. 28, 2010, Hannen et al. |
U.S. Appl. No. 13/424,548, filed Mar. 20, 2012, Hannen et al. |
U.S. Appl. No. 13/142,505, filed Jun. 28, 2011, Meier et al. |
U.S. Appl. No. 13/634,111, filed Sep. 11, 2012, Petrat et al. |
Number | Date | Country | |
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20110015434 A1 | Jan 2011 | US |