Process for the selective hydrogenation of vegetable oils using egg-shell type catalysts

Abstract

The invention relates to a process for the hydrogenation of vegetable oils that selectively converts polyunsaturated fatty acids into mono-unsaturated fatty acids, and to the products obtained therefrom. Vegetable oils obtained by the process according to the invention have a particularly high content of monounsaturated fatty acids and are suitable for use as raw materials for the synthesis of chemical intermediates.

Claims

1. A process for the catalytic hydrogenation of a vegetable oil comprising a mixture of triglycerides of fatty acids comprising polyunsaturated fatty acids in which the oil is placed in contact with molecular hydrogen in the presence of a supported metal catalyst, wherein the said catalyst is of the egg-shell type and the process is carried out at a molecular hydrogen pressure of between 1 and 15 bar at a temperature from 0 C. to 30 C., wherein said polyunsaturated fatty acids are selectively converted into monounsaturated fatty acids.

2. The process according to claim 1 in which the said metal catalyst is selected from the group comprising nickel, platinum, palladium, copper, iron, rhodium, ruthenium, molybdenum, osmium, iridium, tungsten and mixtures thereof.

3. The process according to claim 2, in which the metal catalyst comprises metallic palladium.

4. The process according to claim 3, in which the hydrogenation is carried out in the presence of 20 mg/kg-500 mg/kg of metallic palladium with respect to the quantity of vegetable oil.

5. The process according to claim 3, in which the metal catalyst comprises 0.1-10% by weight of palladium metal.

6. The process according to claim 1, in which the support for the metal catalyst is selected from the group comprising alumina, carbon, CeO.sub.2, ZrO.sub.2, CrO.sub.2, TiO.sub.2, MgO, silica, inorganic-organic sol-gel matrices, polycrystalline oxide substrates, amorphous carbon, zeolites, aluminosilicates, alkaline earth carbonates such as magnesium carbonate, calcium carbonate or barium carbonate, barium sulphate, montmorillonites, polymer matrices, multifunctional resins, ion exchange resins, ceramic supports or mixtures of two or more of these.

7. The process according to claim 6, in which the catalyst comprises metallic palladium supported on alumina or carbon.

8. The process according to claim 1, in which the temperature is comprised between 0 C. and 25 C.

9. The process according to claim 1 carried out in the presence of an organic solvent selected from the group comprising hydrocarbons, esters, ketones, C3-C6 alcohols, and ethers.

10. The process according to claim 9 in which the organic solvent is in a ratio of between 0.25:1 and 3:1 by weight with respect to the vegetable oil.

11. The process according to claim 1 carried out in the presence of a quantity of water of 400:1 or less with respect to the weight of metal catalyst.

12. The process according to claim 1 wherein the vegetable oil is selected from the group comprising sunflower oil, Brassicaceae oils or thistle oils.

13. The process according to claim 4, in which the metal catalyst comprises 0.1-10% by weight of palladium metal.

14. The process according to claim 2, in which the support for the metal catalyst is selected from the group comprising alumina, carbon, CeO.sub.2, ZrO.sub.2, CrO.sub.2, TiO.sub.2, MgO, silica, inorganic-organic sol-gel matrices, polycrystalline oxide substrates, amorphous carbon, zeolites, aluminosilicates, alkaline earth carbonates such as magnesium carbonate, calcium carbonate or barium carbonate, barium sulphate, montmorillonites, polymer matrices, multifunctional resins, ion exchange resins, ceramic supports or mixtures of two or more of these.

15. The process according to claim 3, in which the support for the metal catalyst is selected from the group comprising alumina, carbon, CeO.sub.2, ZrO.sub.2, CrO.sub.2, TiO.sub.2, MgO, silica, inorganic-organic sol-gel matrices, polycrystalline oxide substrates, amorphous carbon, zeolites, aluminosilicates, alkaline earth carbonates such as magnesium carbonate, calcium carbonate or barium carbonate, barium sulphate, montmorillonites, polymer matrices, multifunctional resins, ion exchange resins, ceramic supports or mixtures of two or more of these.

16. The process according to claim 4, in which the support for the metal catalyst is selected from the group comprising alumina, carbon, CeO.sub.2, ZrO.sub.2, CrO.sub.2, TiO.sub.2, MgO, silica, inorganic-organic sol-gel matrices, polycrystalline oxide substrates, amorphous carbon, zeolites, aluminosilicates, alkaline earth carbonates such as magnesium carbonate, calcium carbonate or barium carbonate, barium sulphate, montmorillonites, polymer matrices, multifunctional resins, ion exchange resins, ceramic supports or mixtures of two or more of these.

17. The process according to claim 5, in which the support for the metal catalyst is selected from the group comprising alumina, carbon, CeO.sub.2, ZrO.sub.2, CrO.sub.2, TiO.sub.2, MgO, silica, inorganic-organic sol-gel matrices, polycrystalline oxide substrates, amorphous carbon, zeolites, aluminosilicates, alkaline earth carbonates such as magnesium carbonate, calcium carbonate or barium carbonate, barium sulphate, montmorillonites, polymer matrices, multifunctional resins, ion exchange resins, ceramic supports or mixtures of two or more of these.

18. The process according to claim 2 carried out in the presence of an organic solvent selected from the group comprising hydrocarbons, esters, ketones, C3-C6 alcohols, and ethers.

19. The process according to claim 3 carried out in the presence of an organic solvent selected from the group comprising hydrocarbons, esters, ketones, C3-C6 alcohols, and ethers.

20. The process according to claim 4 carried out in the presence of an organic solvent selected from the group comprising hydrocarbons, esters, ketones, C3-C6 alcohols, and ethers.

Description

EXAMPLES

(1) In the following examples the carboxylic acid composition of the oil was determined after transesterification of an oil sample (140 l) in 140 l of methanolic KOH (2N). The methyl esters of the carboxylic acids were extracted from the methanolic solutions in 3 ml of hexane and then analyzed in a gas chromatograph equipped with flame ionization detector (FID) and a capillary column SLB-IL111 100 m0.25 mm0.2 micron (SUPELCO) at a constant pressure of 275 kPa.

(2) Temperature programme of the oven: 100 C. (35 min)-2.5 C./min-140 C. (30 min)-5.0 C./min-260 C. (25 min) for a total time of 130 min.

(3) Temperature of the injector: 250 C.; split ratio=250:1; carrier gas:helium.

(4) The conversion of diunsaturated acids (C18:2) was determined as follows:

(5) $\frac{\left(.Math.\mathrm{starting}C18\text{:}2-.Math.\mathrm{final}C18\text{:}2\right)}{.Math.\mathrm{starting}C18\text{:}2}$
where starting C18: and final C18:2 correspond to the sum of the % weight of the various isomers of the diunsaturated C18 acids relative to the total carboxylic acid composition, before and after the hydrogenation reaction, respectively.

(6) The selectivity with respect to the monounsaturated acids (C18:1) was determined as follows:

(7) $\frac{\left(.Math.\mathrm{final}C18\text{:}1-.Math.\mathrm{starting}C18\text{:}1\right)}{\left(.Math.\mathrm{starting}C18\text{:}2-.Math.\mathrm{final}C18\text{:}2\right)}$
where final C18:1 and starting C18:1 correspond to the sum of the % weight of the various isomers of monounsaturated C18 acids relative to the total carboxylic acid composition, after and before the hydrogenation reaction, respectively, and starting C18:2 and final C18:2 correspond to the sum of the % weight of the various isomers of the diunsaturated C18 acids relative to the total carboxylic acid composition, before and after the hydrogenation reaction, respectively.

Example 1

(8) The hydrogenation reaction was performed in a 500 ml cylindrical reactor fitted with an electromagnetic stirrer and a thermometer and connected to a hydrogen cylinder through a mass flowmeter.

(9) The reactor was charged with 50 g of sunflower oil, approximately 110 ml of hexane and 0.05 g of powder catalyst comprising 5% Pd/C of the egg-shell type (Alfa & Aesar; dry).

(10) The reactor was connected to a pump to remove air and then fed with a flow of H.sub.2.

(11) The reactor was vigorously stirred for 144 minutes at 700 rpm, holding the temperature at 15 C. in a cryostat. The quantity of hydrogen absorbed, equal to 2.1 L, was measured by means of a counter at the outlet from the reactor.

(12) The catalyst was filtered and the organic solvent was evaporated off to obtain the hydrogenated sunflower oil. The percentage composition by weight of the C18 carboxylic acids in the hydrogenated oil in comparison with the total composition of carboxylic acids as measured by means of GC analysis after a reaction time of 144 minutes, in comparison with the composition of the starting oil, is shown in Table 1.

(13) The conversion of linoleic acid was 80.5% and the selectivity for oleic acid was 93.3%.

(14) TABLE-US-00001 TABLE 1 Carboxylic acid Sunflower Example 2 composition oil Example 1 (comparative) Example 3 Hydrogenation time 144 min 129 min 214 min C 18:0 3.3 6.7 11.6 6.3 C 18:1 cis 29.8 64.1 57.6 58.3 C 18:1 trans 10.6 9.3 22.3 C 18:2 59.7 11.6 14.4 6.2 C 18:3 0.2 C18:2 conversion 80.5% 75.8% 89.7% C18:1 selectivity 93.3% 82.1% 94.7%

Example 2 (Comparative)

(15) The hydrogenation reaction was performed as in Example 1, but using 0.05 g of powder catalyst comprising 5% non-egg-shell Pd/C (Aldrich; dry support).

(16) The reactor was stopped after 129 minutes; the quantity of hydrogen absorbed was 2.1 L.

(17) The catalyst was filtered off and the organic solvent was evaporated off in order to obtain the hydrogenated sunflower oil.

(18) As shown in Table 1, conversion to linoleic acid was only 75.8% while selectivity for oleic acid was 82.2%, i.e. more than 10% less than that obtained under the same conditions using the egg-shell type catalyst in Example 1.

Example 3

(19) The hydrogenation reaction was carried out in the same reactor as Example 1, charged with 85 g of sunflower oil, approximately 100 ml of isobutanol, 300 mg of water and 90 mg of catalyst comprising 5% Pd/C of the egg-shell type (Johnson & Matthey; 50% humidity).

(20) The reactor was vigorously stirred for 214 minutes at 700 rpm, maintaining a temperature of 16-17 C. The quantity of hydrogen absorbed was 2.15 L.

(21) The catalyst was filtered off and the organic solvent was evaporated off in order to obtain the hydrogenated sunflower oil. The percentage composition by weight of C18 carboxylic acids in the hydrogenated oil after a reaction time of 214 minutes is shown in Table 1.

(22) The conversion of linoleic acid was more than 89% and selectivity for oleic acid was 94.7%.