A method for catalytic oxidation of d-limonene to synthesize l-carvone

Abstract

The application discloses a method for synthesizing L-carvone from catalytic oxidation of D-limonene, which comprises the following steps: S1, catalyst preparation: uniformly mixing citric acid, an organic solvent and a metal compound, and evaporating the mixture to dryness to obtain a powdery solid; mixing the powdery solid with silicon dioxide, and calcining the mixture at a high temperature to obtain a silicon dioxide-supported catalyst; S2, oxidation: adding D-limonene and the silicon dioxide-supported catalyst into a second organic solvent, heating to reflux, and dropwise adding t-butyl hydroperoxide to react, so as to obtain L-carvone product. The selectivity of L-carvone is up to 52.0%, the purity of L-carvone is greater than or equal to 97% (mass), the mass is 7.2 g, and the reaction yield is 46.5%.

Description

Technical Field

[0001] This invention relates to the field of L-carvone production technology, and more particularly to a method for synthesizing L-carvone by catalytic oxidation of D-limonene. Background Technology

[0002] L-Carvone, also known as caraway ketone, is systematically named 2-methyl-5-(1-methylvinyl)-2-cyclohexene-1-one. L-Carvone is the main component (50-60%) of spearmint oil, possessing a strong spearmint aroma that is cool, gentle, and penetrating.

[0003] After being recognized for safety by the Joint FAO / WHO Expert Committee on Food Additives in 2001, it has gradually been recognized by the International Organization of the Flavor Industry (IOFI), the Food Flavor and Extraction Manufacturers Association (FEMA), and the European Commission on Flavors and Flavours. In my country, GB2760-1996 stipulates that it is an edible flavoring that is permitted for use.

[0004] L-Carvone is a colorless to pale yellow oily liquid with FEMA: 2249, density: 0.959 g / mL at 25℃ (lit.), boiling point: 227-230℃ at 760 mmHg (lit.), refractive index: n20 / D 1.498, flash point: 88.9℃, and optical rotation: -62.0° to -57.0°. It is insoluble in water but soluble in organic solvents such as ethanol, ether, and chloroform.

[0005] L-Carvyl ester is commonly used as a flavoring agent and food additive in the formulation of mint-flavored edible flavorings. Its dosage is as follows: FEMA (mg / kg): 850 for soft drinks; 120 for cold drinks; 180 for candies; 110 for baked goods; and 130 for alcoholic beverages.

[0006] Currently, the methods for obtaining L-carvone can be mainly divided into two categories: chemical synthesis and natural extraction. While naturally extracted carvone has advantages such as high product purity and low environmental pollution, its yield is low, extraction costs are high, and it is easily affected by climate and environmental factors, making it unable to meet market demand. Therefore, chemical synthesis of L-carvone is essential.

[0007] Currently, there are two main industrial methods for synthesizing L-carvone. One method uses D-limonene as a raw material and proceeds through a three-step reaction involving nitrosochlorination, dehydrochlorination, and hydrolysis to obtain L-carvone. The other method also uses D-limonene as a raw material and proceeds through a three-step reaction involving epoxidation, rearrangement, and oxidation to obtain L-carvone. The reaction equations are as follows:

[0008]

[0009]

[0010] The above method exhibits poor reaction selectivity, generates numerous byproducts, and produces large quantities of wastewater containing inorganic acids, nitrosamines, acetone oxime, and inorganic salts. These wastes are highly toxic and difficult to treat. Furthermore, the reaction intermediate, nitrosyl chloride, is a highly toxic substance, posing a serious threat to the safety of the reaction operators.

[0011] In Method 2, peroxides and catalysts are used to react with D-limonene for epoxidation. This reaction step produces epoxidation of exocyclic double bonds. Since the two are similar in properties, they are difficult to separate effectively by conventional distillation, which increases the difficulty of separation. After obtaining epoxidized limonene, it still needs to go through two more steps: ring-opening isomerization and oxidation. The steps are relatively complicated, and the yield of each single step is about 70%, with an overall yield of about 35%, which does not have much advantage.

[0012] Therefore, a new method for synthesizing carvone needs to be developed to overcome the shortcomings of existing technologies. Summary of the Invention

[0013] To address the above problems, this invention provides a method for the catalytic oxidation of D-limonene to synthesize L-carvone, comprising the following steps:

[0014] 1. Catalyst preparation: Citric acid, organic solvent and the metal compound to be supported are mixed and dissolved evenly, and then heated to 80-150℃ and evaporated to dryness to obtain a powder solid; silica is mixed with the obtained powder and calcined at 600-800℃ for 4h to obtain a silica-supported catalyst.

[0015] 2. Oxidation: D-limonene and a supported catalyst are added to a second organic solvent, and the mixture is heated to reflux and tert-butyl hydrogen peroxide is added dropwise to react and oxidize to obtain L-carvone product.

[0016] Furthermore, the reaction principle is as follows:

[0017] Furthermore, in the preparation of the catalyst, the metal compound is selected from one or more of ferric nitrate, silver nitrate, cerium chloride, zirconium oxide, ferric oxide, ferrous oxide, cobalt nitrate, and nickel acetate.

[0018] Furthermore, in the preparation of the catalyst, the amount of citric acid used is 0.1-2 times the amount of the metal compound.

[0019] Furthermore, in the preparation of the catalyst, the amount of organic solvent used is 10-100 times the amount of the metal compound.

[0020] Furthermore, in the preparation of the catalyst, the organic solvent is selected from one or more of anhydrous ethanol, anhydrous methanol, tetrahydrofuran, dimethyl sulfoxide, and isopropanol.

[0021] Furthermore, in the preparation of the catalyst, the amount of silicon dioxide used is 5-20 times the amount of the metal compound.

[0022] Furthermore, in the oxidation step, the amount of the second organic solvent used is 2-10 times the amount of D-limonene.

[0023] Furthermore, in the oxidation step, the second organic solvent is selected from one or more of acetonitrile, benzene, toluene, tetrahydrofuran, dimethyl sulfoxide, and isopropanol.

[0024] Furthermore, in the oxidation step, the amount of the supported catalyst is 0.01-1 times the amount of D-limonene.

[0025] Furthermore, in the oxidation step, the amount of tert-butyl hydroperoxide used is 0.5-2 times the amount of D-limonene.

[0026] Compared with the prior art, the beneficial effects of the present invention are:

[0027] 1. In view of the problems that the existing synthesis method for L-carvone, which uses a three-step reaction of nitrosyl chloride, dehydrochlorination and hydrolysis, generates a large amount of waste, and the intermediate product nitrosyl chloride compound is highly toxic, difficult to handle and harmful to operators, this invention uses a silica-supported catalyst to carry out a one-step oxidation reaction to prepare L-carvone. The common organic peroxide tert-butyl hydroperoxide is used as the oxidant, which is stable, safe to use, easy to control, and the reaction steps are simple, generate less waste, and have no highly toxic intermediate products.

[0028] 2. Compared with the problem of difficult separation of reaction products in the three-step method of hydrogen peroxide epoxidation, rearrangement and oxidation to prepare L-carvone, the reaction products of this invention are fewer, have greater differences in properties, are easy to separate, and the catalyst used in the reaction can be reused.

[0029] 3. This reaction uses SiO2 as the catalyst support material because it has a high specific surface area, strong adsorption performance, high loading performance, high reusability, long service life, stable catalytic effect, and low price of the supported metal catalyst. Therefore, this catalyst has a great advantage in terms of reaction efficiency and price. At the same time, this catalyst has a high selectivity for carvone, reaching more than 50%. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a gas chromatogram of L-carvone synthesized in Example 1 of the present invention. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Reagent and instrument instructions:

[0034] Toluene: Chinese medicine, purity 98wt%;

[0035] tert-butyl hydroperoxide: Maclean's reagent;

[0036] Deuterated reagent: deuterated chloroform, purity 98 wt%;

[0037] D-Limonene: Jiucheng Industrial LDC, purity 94wt%;

[0038] Ethanol, methanol, acetonitrile, tetrahydrofuran: Exploration platform, purity 98wt%;

[0039] Silica, citric acid, ferric nitrate, cerium chloride, zirconium oxide, nickel acetate: Aladdin reagent, purity 98wt%;

[0040] Gas chromatograph: Shimadzu GC-2030;

[0041] Muffle furnace: Jinchuan, SX21013 general purpose muffle furnace;

[0042] Nuclear magnetic resonance analyzer: BRUKER, Ultrashield 400.

[0043] Example 1

[0044] A method for catalytic oxidation of D-limonene to synthesize L-carvone includes the following steps:

[0045] 1. Add 0.2 mol citric acid, 0.1 mol cerium chloride, 2 mol silicon dioxide and 10 mol tetrahydrofuran to a reaction vessel. Stir thoroughly at room temperature until citric acid and cerium chloride are completely dissolved. Then heat to 80°C and slowly evaporate the tetrahydrofuran to obtain a powdered solid product. Pour the product into a crucible and place it in a muffle furnace. Calcinate at 800°C for 4 hours to obtain a silicon dioxide supported catalyst.

[0046] 2. Add 0.1 mol D-limonene, 0.1 mol silica-supported catalyst and 1 mol toluene to a reaction vessel, heat to 120℃ under stirring and keep under reflux, slowly add 0.2 mol tert-butyl hydroperoxide dropwise to the reaction vessel over 30 min, and continue the reaction for 2 h after the addition is complete, and the reaction is completed to obtain L-carvone reaction solution.

[0047] 3. Gas chromatography was performed on the L-carvone reaction solution. The gas chromatograph injection temperature was set to 300℃, the column to be DB-5 (30m×0.25mm×0.25μm), and the split ratio to be 40:1. The temperature program was as follows: 60℃ for 2 min, then increased to 150℃ at 10℃ / min and held for 1 min, followed by increasing to 300℃ at 15℃ / min and holding for 10 min. The FID detector temperature was set to 300℃.

[0048] 4. The prepared L-carvone reaction solution was placed in a distillation reactor, the Roots vacuum pump was turned on, and the reaction solution was heated to 60°C to remove the organic solvent. The solution was then purified by column chromatography to obtain the L-carvone product. The results are as follows: Figure 1 As shown, the first peak is the solvent peak, the second peak is the raw material peak, the third peak is the by-product peak (bimodal structure), and the fourth peak is the product peak.

[0049] Example 2

[0050] The difference between this embodiment and Example 1 is that, in the preparation of the catalyst, the added metal compound is 0.1 mol cobalt nitrate, the added citric acid is 0.2 mol, the added organic solvent is 10 mol ethanol, the evaporation temperature is 100°C, and the calcination temperature is 800°C.

[0051] In the oxidation step: the added organic solvent is 1 mol acetonitrile, the added tert-butyl hydroperoxide is 0.2 mol, and the reflux temperature is 120℃.

[0052] The rest is exactly the same as in Example 1.

[0053] Example 3

[0054] The difference between this embodiment and Example 1 is that, in the preparation of the catalyst, the added metal compound is 0.1 mol iron oxide, the added citric acid is 0.2 mol, the added organic solvent is 10 mol methanol, the evaporation temperature is 100℃, and the calcination temperature is 800℃.

[0055] In the oxidation step: the added organic solvent is 1 mol of benzene, the added tert-butyl hydroperoxide is 0.2 mol, and the reflux temperature is 120℃.

[0056] The rest is exactly the same as in Example 1.

[0057] Example 4

[0058] The difference between this embodiment and Example 1 is that, in the preparation of the catalyst, the added metal compound is 0.1 mol silver nitrate, the added citric acid is 0.1 mol, the added organic solvent is 5 mol dimethyl sulfoxide, the evaporation temperature is 90°C, and the calcination temperature is 700°C.

[0059] In the oxidation step: the added organic solvent is 0.5 mol tetrahydrofuran, the added tert-butyl hydroperoxide is 0.1 mol, and the reflux temperature is 120℃.

[0060] The rest is exactly the same as in Example 1.

[0061] Example 5

[0062] The difference between this embodiment and Example 1 is that, in the preparation of the catalyst, the added metal compound is 0.1 mol zirconium oxide, the added citric acid is 0.1 mol, the added organic solvent is 5 mol isopropanol, the evaporation temperature is 90°C, and the calcination temperature is 700°C.

[0063] In the oxidation step: the added organic solvent is 0.5 mol dimethyl sulfoxide, the added tert-butyl hydroperoxide is 0.1 mol, and the reflux temperature is 120°C.

[0064] The rest is exactly the same as in Example 1.

[0065] Example 6

[0066] The difference between this embodiment and Example 1 is that, in the preparation of the catalyst, the added metal compound is 0.1 mol ferrous oxide, the added citric acid is 0.1 mol, the added organic solvent is 5 mol ethanol, the evaporation temperature is 90°C, and the calcination temperature is 700°C.

[0067] In the oxidation step: the added organic solvent is 0.5 mol acetonitrile, the added tert-butyl hydroperoxide is 0.1 mol, and the reflux temperature is 120℃.

[0068] The rest is exactly the same as in Example 1.

[0069] Example 7

[0070] The difference between this embodiment and Example 1 is that, in the preparation of the catalyst, the added metal compound is 0.1 mol cobalt nitrate, the added citric acid is 0.01 mol, the added organic solvent is 1 mol isopropanol, the evaporation temperature is 80°C, and the calcination temperature is 600°C.

[0071] In the oxidation step: the added organic solvent is 0.2 mol acetonitrile, the added tert-butyl hydroperoxide is 0.05 mol, and the reflux temperature is 120℃.

[0072] The rest is exactly the same as in Example 1.

[0073] Example 8

[0074] The difference between this embodiment and Example 1 is that, in the preparation of the catalyst, the added metal compound is 0.1 mol nickel acetate, the added citric acid is 0.01 mol, the added organic solvent is 1 mol tetrahydrofuran, the evaporation temperature is 80°C, and the calcination temperature is 600°C.

[0075] In the oxidation step: the added organic solvent is 0.2 mol benzene, the added tert-butyl hydroperoxide is 0.05 mol, and the reflux temperature is 120℃.

[0076] The rest is exactly the same as in Example 1.

[0077] Example 9

[0078] The difference between this embodiment and Example 1 is that, in the preparation of the catalyst, the added metal compound is 0.1 mol nickel acetate, the added organic solvent is 5 mol ethanol, the evaporation temperature is 100°C, and the calcination temperature is 600°C.

[0079] In the oxidation step, the added organic solvent is 0.5 mol acetonitrile solution, and the reflux temperature is 120°C.

[0080] The rest is exactly the same as in Example 1.

[0081] Example 10

[0082] The difference between this embodiment and Example 1 is that, in the preparation of the catalyst, the added metal compound is 0.1 mol zirconium oxide and 0.1 mol cerium chloride, the added organic solvent is 10 mol acetonitrile, the evaporation temperature is 85°C, and the calcination temperature is 600°C.

[0083] The rest is exactly the same as in Example 1.

[0084] Detection and Results

[0085] The gas phase analysis results of the L-carvone reaction liquid and the quality test results of the L-carvone finished product are shown in Table 1:

[0086] Table 1

[0087]

[0088] As shown in Table 1, the method for synthesizing L-carvone by catalytic oxidation of D-limonene provided in this embodiment has a selectivity of L-carvone greater than or equal to 52.0% and a reaction yield of ≥44.6%; among them, the selectivity of L-carvone is the highest at 52.0%, the mass (g) of L-carvone with a purity ≥97% is 7.2g, and the reaction yield is 46.5%.

[0089] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for catalytic oxidation of D-limonene to synthesize L-carvone, characterized in that, Includes the following steps: S1. Catalyst preparation: Citric acid, organic solvent and metal compound are mixed evenly and evaporated to dryness to obtain a powder solid; silica is mixed with the obtained powder and then calcined at high temperature to obtain a silica-supported catalyst; S2. Oxidation: D-limonene and silica-supported catalyst were added to the second organic solvent, the mixture was heated to reflux and tert-butyl hydrogen peroxide was added dropwise to react and give L-carvone product; In the preparation of the catalyst, the metal compound is selected from one or more of ferric nitrate, silver nitrate, cerium chloride, zirconium oxide, ferric oxide, ferrous oxide, cobalt nitrate, and nickel acetate.

2. The method for synthesizing L-carvone by catalytic oxidation of D-limonene as described in claim 1, characterized in that, In the preparation of the catalyst, the amount of citric acid used is 0.1-2 times the amount of the metal compound.

3. The method for synthesizing L-carvone by catalytic oxidation of D-limonene as described in claim 1, characterized in that, In the preparation of the catalyst, the amount of organic solvent used is 10-100 times the amount of the metal compound.

4. The method for synthesizing L-carvone by catalytic oxidation of D-limonene as described in claim 1, characterized in that, In the preparation of the catalyst, the organic solvent is selected from one or more of anhydrous ethanol, anhydrous methanol, tetrahydrofuran, dimethyl sulfoxide, and isopropanol.

5. The method for synthesizing L-carvone by catalytic oxidation of D-limonene as described in claim 1, characterized in that, In the preparation of the catalyst, the amount of silicon dioxide used is 5-20 times the amount of the metal compound.

6. The method for synthesizing L-carvone by catalytic oxidation of D-limonene as described in claim 1, characterized in that, In the oxidation step, the amount of the second organic solvent used is 2-10 times the amount of D-limonene.

7. The method for synthesizing L-carvone by catalytic oxidation of D-limonene as described in claim 1, characterized in that, In the oxidation step, the second organic solvent is selected from one or more of acetonitrile, benzene, toluene, tetrahydrofuran, dimethyl sulfoxide, and isopropanol.

8. The method for synthesizing L-carvone by catalytic oxidation of D-limonene as described in claim 1, characterized in that, In the oxidation step, the amount of supported catalyst used is 0.01-1 times the amount of D-limonene.

9. The method for synthesizing L-carvone by catalytic oxidation of D-limonene as described in claim 1, characterized in that, In the oxidation step, the amount of tert-butyl hydroperoxide used is 0.5-2 times the amount of D-limonene.

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