Process for the selective hydrogenation of vegetable oils

Abstract

This invention relates to a process for the selective hydrogenation of vegetable oils. In particular the invention relates to a process for the hydrogenation of vegetable oils which is capable of selectively converting polyunsaturated fatty acids into mono-unsaturated fatty acids and products obtained therefrom. The vegetable oils obtained from the process according to the invention have in particular a high mono-unsaturated fatty acids content and are particularly suitable for use as raw materials for the synthesis of chemical intermediates.

Claims

1. Process for the catalytic hydrogenation of a vegetable oil wherein the oil is placed in contact with molecular hydrogen in the presence of a catalyst comprising supported metallic Palladium, wherein said process is performed in the presence of an amount of water in an amount between 5:1 and 100:1 with respect to the weight of metallic Palladium, and at a temperature from 0 C. to 130 C.

2. Process according to claim 1, wherein said process is performed in the presence of an amount of water from 7:1 to 50:1 with respect to the weight of metallic Palladium.

3. Process according to claim 1, wherein the hydrogenation is performed in the presence of 30 mg/kg-500 mg/kg of metallic Palladium with respect to the vegetable oil.

4. Process according to claim 1, wherein said catalyst comprises 0.1-1% by weight of metallic Palladium.

5. Process according to claim 1, wherein said metallic Palladium is supported on a support selected from the group consisting of alumina, carbon, CeO.sub.2, ZrO.sub.2, CrO.sub.2, TiO.sub.2, silica, inorganic-organic sol-gel matrix, polycrystalline oxide substrates, amorphous carbon, zeolites, aluminosilicates, alkaline earth carbonates such as magnesium carbonate, calcium carbonate or barium carbonate, barium sulphate, montmorillonites, polymeric matrices, multifunctional resins, ceramic supports.

6. Process according to claim 5, wherein the catalyst comprises metallic Palladium supported on alumina or on carbon.

7. Process according to claim 1, wherein said process is performed at a molecular hydrogen pressure from 1 to 15 bar.

8. Process according to claim 1, wherein said process is performed at a temperature from 70 to 130 C. and at hydrogen pressure from 1 to 6 bar.

9. Process according to claim 1, wherein said process is performed at temperatures from 0 to 50 C., at hydrogen pressures of from 1 to 2 bar, and in the presence of an organic solvent.

10. Process according to claim 9 wherein the organic solvent is selected from hydrocarbons, esters, ketones.

11. Process according to claim 1, wherein said vegetable oil is selected from the group consisting of soya oil, olive oil, castor oil, sunflower oil, peanut oil, maize oil, palm oil, jatropha oil, cardoon oil, cuphea oil, Brassicaceae oil, Lesquerella oil, waste frying oils, exhausted vegetable oils or mixtures thereof.

12. A process for the conversion of a polyunsaturated fatty acid into a monounsaturated fatty acid of a vegetable oil, which comprises hydrogenating the vegetable oil with at least a catalyst comprising metallic Palladium, said hydrogenating being performed in presence of an amount of water between 5:1 and 100:1 with respect to the weight of the metallic Palladium.

13. Process according to claim 12 wherein the vegetable oil is selected from the group consisting of sunflower oil, oil from Brassicaceae, cardoon oil or mixtures thereof.

14. An oxidative cleavage process wherein the staring material comprises a vegetable oil obtained from the process according to claim 1.

15. A vegetable oil which comprises: a di-unsaturated acid content of less than 10% by weight with respect to the total fatty acids content; a mono-unsaturated acid content of more than 70% by weight with respect to the total fatty acids content; a trans monounsaturated isomer content higher than 1.5% and lower than 12% by weight with respect to the total fatty acids content.

16. A vegetable oil according to claim 15 wherein the mono-unsaturated acids comprise more than 80% of 9-cis and 12-cis isomers.

17. An oxidative cleavage process wherein the staring material comprises the vegetable oil of claim 15.

18. Process according to claim 2, wherein the hydrogenation is performed in the presence of 30 mg/kg-500 mg/kg of metallic Palladium with respect to the vegetable oil.

19. Process according to claim 2, wherein said catalyst comprises 0.1-1% by weight of metallic Palladium.

Description

EXAMPLES

(1) The oil fatty acid composition in the following examples was determined after transesterification of 140 l of oil samples in 140 l of methanolic KOH (2N). Fatty acid methyl esters were extracted from the methanolic solutions into 3 ml hexane and then analyzed in a gas chromatograph equipped with a flame ionization detector (FID) and a SLB-IL111 100 m0.25 mm0.2 m capillary column (SUPELCO) at a constant pressure of 275 kPa. Oven temperature program: 100 C. (35 min)2.5 C./min-140 C. (30 min)5.0/min-260 C. (25 min) for a total run time of 130 min. Injector temperature: 250 C.; split ratio: 250:1; carrier gas: Helium.

(2) The conversion of di-unsaturated acids (C18:2) was determined as follows:

(3) $\begin{array}{cc}\frac{\left(.Math.\mathrm{starting}C18\text{:}2-.Math.\mathrm{final}C18\text{:}2\right)}{.Math.\mathrm{starting}C18\text{:}2},& \end{array}$
wherein starting C18:2 and final C18:2 corresponded to the sum of the weight % of the various isomers of C18 diunsaturated acids with respect to the total fatty acid composition respectively before and after the hydrogenation reaction.

(4) The selectivity towards monounsaturated acids (C18:1) was determined as follows:

(5) $\frac{\left(.Math.\mathrm{final}C18\text{:}1-.Math.\mathrm{starting}C18\text{:}1\right)}{\left(.Math.\mathrm{starting}C18\text{:}2-.Math.\mathrm{final}C18\text{:}2\right)}$
wherein final C18:1 and starting C18:1 corresponded to the sum of the weight % of the various isomers of C18 monounsaturated acids with respect to the total fatty acid composition respectively after and before the hydrogenation reaction, and starting C18:2 and final C18:2 corresponded to the sum of the weight % of the various isomers of C18 diunsaturated acids with respect to the total fatty acid composition respectively before and after the hydrogenation reaction.

Example 1 (Comparative)

(6) 500 g of sunflower oil containing 56% by weight of linoleic acid with respect to the total fatty acids content were hydrogenated in an autoclave fitted with a stirrer in the presence of 15.5 g of catalyst based on palladium supported on -alumina (0.2% by weight of Pd-G68G produced by Sud Chemie) at a temperature of 118 C., maintaining a hydrogen pressure between 2 and 5 bar. The reaction was interrupted after 80 minutes. The conversion of linoleic acid, determined by gas chromatographic analysis, was 34.5%, with selectivity for mono-unsaturated acids of 28.9%.

Example 2

(7) The hydrogenation reaction was performed under the same conditions as in Example 1 (comparative) with the addition of 0.37 g of water to the reaction mixture. After 80 minutes the conversion of linoleic acid was 63.4% and the selectivity for mono-unsaturated acids was 33.3%.

Example 3

(8) The hydrogenation reaction was performed under the same conditions as in Example 1 (comparative) with the addition of 0.74 g of water to the reaction mixture. After 80 minutes the conversion of linoleic acid was 68.3% and the selectivity for mono-unsaturated acids was 35.6%.

Example 4

(9) The hydrogenation reaction was performed under the same conditions as in Example 1 (comparative) with the addition of 1.23 g of water to the reaction mixture. After 80 minutes the conversion of linoleic acid was 37.8% and the selectivity for mono-unsaturated acids was 33.1%.

Example 5

(10) The hydrogenation reaction was performed in a 500 ml glass flask, equipped with an electromagnetic stirrer and connected through a tube to a graduated funnel with a water head for the dosage of H.sub.2.

(11) The flask was filled with 50 g of cardoon oil, 150 ml of petroleum ether and 0.85 g of 0.3% Pd/Al.sub.2O.sub.3 catalyst in powder form (Johnson Matthey; water content 4.2% by weight).

(12) The flask was connected to a pump to remove the air and then filled with 2.7 l of molecular hydrogen, which was bubbled through the water head in the graduated funnel and was saturated with water (at a temperature of 20-25 C.). The quantity of water fed together with the hydrogen was of 52 mg. The resulting water:metallic Pd weight ratio was of about 35:1.

(13) The flask was vigorously stirred for 140 minutes at 700 rpm while maintaining a temperature of 5-6 C. through a cooling water bath. The catalyst was filtered off and the organic solvent was evaporated to obtain hydrogenated cardoon oil.

(14) The weight percentage composition of the C18 fatty acids of the hydrogenated oil with respect to the total fatty acid composition as measured by GC analysis after 100 minutes and after 140 minutes of reaction, compared to the composition of the starting cardoon oil is reported in table 1.

(15) The conversion of linoleic acid was of 85% after 100 minutes, and continued to rise up to the notable value of 94% after 140 minutes of reaction. At the end of the reaction the selectivity towards C18 monounsaturated acid was of 93.1%, the C18 monounsaturated trans isomers content was below 10%, and the sum of 9-cis and 12-cis isomers corresponded to 86.3% of the monounsaturated acids.

Example 6

(16) The hydrogenation reaction was performed under the same conditions as in Example 5 but in the presence of 75 ml petroleum ether instead of 150 ml.

(17) After 140 minutes the conversion of linoleic acid was 92.6%, the selectivity towards C18 monounsaturated acid was of 92.4%, and the sum of 9-cis and 12-cis isomers corresponded to 85.1% of the monounsaturated acids. The composition of the hydrogenated oil as measured by GC analysis is reported in table 1.

(18) TABLE-US-00001 TABLE 1 Cardoon Fatty acid composition oil Example 5 Example 6 Hydrogenation time 100 min 140 min 140 min C 18:0 3.2 6.6 7.5 7.7 C 18:1 cis 25.6 65.6 67.8 65.5 C 18:1 trans 7.5 9.8 9.9 C 18:2 59.4 8.9 3.6 4.4 C 18:3 0.2 Conversion C18:2 85.0% 94.0% 92.6% Selectivity C18:1 94.1% 93.1% 92.4% 9-cis C18:1/ C18:1 96.7% 62.5% 60.6% 60.8% 12-cis C18:1/ C18:1 26.3% 25.7% 24.3%

Example 7

(19) The hydrogenation reaction was performed in the same apparatus of Examples 5-6.

(20) The flask was filled with 50 g of sunflower oil, 150 ml of petroleum ether and 0.85 g of 0.3% Pd/Al.sub.2O.sub.3 catalyst in powder form (Johnson Matthey; water content 4.2% by weight).

(21) The flask was connected to a pump to remove the air and then filled with 2.5 l of molecular hydrogen, which was bubbled through the water head in the graduated burette and is saturated with water (at a temperature of 20-25 C.). The quantity of water fed together with the hydrogen was of 48.8 mg, corresponding to a water:metallic Pd weight ratio of about 33.5:1.

(22) The flask was vigorously stirred at 700 rpm while maintaining a temperature of 30 C. through a cooling water bath.

(23) The catalyst was filtered off and the organic solvent was evaporated to obtain hydrogenated cardoon oil.

(24) After 50 minutes the conversion of linoleic acid was 90.1% and the selectivity towards C18 monounsaturated acid was of 88.3%.