A preparation method of beta-carotene

Abstract

The present invention provides a preparation method of beta-carotene, the preparation method comprising the steps of: (1) mixing 2-methyl-4-(2,2,6-trimethyl-1-cyclohexenyl)-2-butenal, 2,7-dimethyl-2,4,6-octatriene dialdehyde, an alkaline electrolyte, a phase transfer catalyst, and a solvent to prepare an electrolyte; (2) adding the electrolyte prepared in step (1) to an electrolytic cell for electrolysis, and electrolytic reduction at the cathode of the electrolytic cell to obtain the beta-carotene. The preparation method provided in the present invention has the characteristics of simple preparation process, high conversion rate and selectivity, high atom economy, less three wastes, low energy consumption, low cost, and no organic phosphine salt residue in the product.

Description

Technical Field

[0001] The invention belongs to the technical field of beta-carotene preparation, and particularly relates to a method for preparing beta-carotene. Background Art

[0002] Carotene is one of the most effective antioxidants against free radicals, boosting immunity and reducing the risk of cancer, heart disease, cardiovascular disease, and other conditions. Carotene is an important source of vitamin A. Within the human body, one carotene molecule breaks down into two molecules of vitamin A. It is used in medicine, food, cosmetics, feed additives, and dyes. Carotene is internationally recognized as a safe and nutritious food additive, currently approved for use in 52 countries and regions worldwide, and holds great market potential. β-carotene is the most common and representative carotenoid, and also the first artificially synthesized carotenoid.

[0003] Beta-carotene comes from two sources: natural and chemically synthesized. Natural sources are primarily extracted from plants, microorganisms, and algae that contain beta-carotene. It wasn't until 1954 that a breakthrough in chemical synthesis of beta-carotene was achieved, leading to its commercialization and commercialization. Currently, the major international companies using chemical synthesis for beta-carotene are DSM and BASF.

[0004] Currently, there are many publicly available methods for synthesizing β-carotene. The main method uses vitamin A and its derivatives as starting materials. Retinol or its derivatives react with triarylphosphines to produce an organic phosphine salt, which is then condensed with vitamin A aldehyde via a Wittig reaction to produce β-carotene. This Wittig reaction requires harsh, anhydrous, and oxygen-free conditions. Furthermore, vitamin A aldehyde is chemically unstable, resulting in significant raw material losses. Current national standards for carotenoid products require a triphenylphosphine oxide content of less than 100 ppm. However, existing β-carotene synthesis methods often leave residual triphenylphosphine oxide in the product, making its removal costly.

[0005] CN107653459A discloses a method for synthesizing β-carotene, which comprises dissolving an organic phosphonium salt of vitamin A alcohol or a derivative thereof in a solvent, using a basic compound as a catalyst, and conducting an oxidative coupling reaction under the action of an electric current to obtain β-carotene. While the β-carotene synthesis method provided by this technical solution has advantages such as mild reaction conditions, high yield, and environmental friendliness, it still uses an organic phosphonium salt during the reaction, resulting in residual organic phosphonium salt in the product and high removal costs.

[0006] CN114534729A discloses a method for electrochemically preparing beta-carotene from vitamin A triphenylphosphine salt. The method uses an aqueous solution of vitamin A triphenylphosphine salt as an electrolyte, and in the presence of a catalyst and an alkali, performs an electrolytic reaction to produce beta-carotene. The catalyst is a graphene-supported metal ferrite and a metal oxide catalyst, wherein the metal ferrite loading is 4-10wt% and the metal oxide loading is 10-25wt% based on the mass of the graphene support. While the method for electrochemically preparing beta-carotene from vitamin A triphenylphosphine salt provided by this technical solution has a high product yield and avoids the use of oxidants in conventional processes, resulting in high safety and environmental friendliness, the method still uses an organic phosphine salt to react during the reaction, which results in residual organic phosphine salt in the product and a high removal cost.

[0007] In summary, the current methods for synthesizing β-carotene have disadvantages such as complex production process, long synthesis route, poor atom economy, residual organic phosphine salts in the product, and high removal cost.

[0008] Therefore, it is necessary to develop a preparation method for β-carotene with a simple preparation process, high atom economy, and no residual organic phosphine salt in the product. Summary of the Invention

[0009] In view of the deficiencies in the prior art, the present invention aims to provide a method for preparing beta-carotene. The method uses 2-methyl-4-(2,2,6-trimethyl-1-cyclohexenyl)-2-butenal and 2,7-dimethyl-2,4,6-octatriene dialdehyde as raw materials to prepare beta-carotene through an electrochemical reaction. The method has the characteristics of a wide range of raw material sources, a simple preparation process, high conversion rate and selectivity, high atom economy, less three wastes, low energy consumption, low cost, and no organic phosphine salt residue in the product.

[0010] To achieve this object, the present invention adopts the following technical solutions:

[0011] The present invention provides a method for preparing beta-carotene, which comprises the following steps:

[0012] (1) mixing 2-methyl-4-(2,2,6-trimethyl-1-cyclohexenyl)-2-butenal, 2,7-dimethyl-2,4,6-octatriene dialdehyde, an alkaline electrolyte, a phase transfer catalyst, and a solvent to prepare an electrolyte;

[0013] (2) adding the electrolyte prepared in step (1) into an electrolytic cell for electrolysis to obtain the β-carotene.

[0014] In the present invention, the preparation method uses 2-methyl-4-(2,2,6-trimethyl-1-cyclohexenyl)-2-butenal and 2,7-dimethyl-2,4,6-octatriene dialdehyde as raw materials, adds an alkaline electrolyte and a phase transfer catalyst, and undergoes electrolysis and electrolytic reduction at the cathode of an electrolytic cell to obtain the beta-carotene. The preparation method can ensure that the cathode region maintains a weak alkaline environment during the electrolysis process by adding an alkaline electrolyte and a phase transfer catalyst. The phase transfer catalyst increases the solubility of the raw materials, accelerates the mass transfer effect in the electrolyte system, and improves the product yield. In a weakly alkaline environment, 1-(2,6,6-trimethyl-1-cyclohexenyl)-2-butenal rearranges to produce 1-(2,6,6-trimethyl-1-cyclohexenyl)-3-methyl-2-butene-4-al. 1-(2,6,6-trimethyl-1-cyclohexenyl)-3-methyl-2-butene-4-al is then electrolytically reduced at the cathode to produce a 1-(2,6,6-trimethyl-1-cyclohexenyl)-3-methyl-2-butene free radical. The 1-(2,6,6-trimethyl-1-cyclohexenyl)-3-methyl-2-butene free radical is then coupled with 2,7-dimethyl-2,4,6-octatrienal to produce β-carotene. The preparation method does not involve the use of organic phosphine salts, and the resulting product contains no organic phosphine salt residues. The preparation method also has the characteristics of a wide range of raw material sources, a simple preparation process, high conversion rate and selectivity, high atom economy, low waste, low energy consumption, and low cost.

[0015] Preferably, the electrolytic cell is a diaphragmless electrolytic cell.

[0016] Preferably, the molar ratio of the 2,7-dimethyl-2,4,6-octatriene dialdehyde to 2-methyl-4-(2,2,6-trimethyl-1-cyclohexenyl)-2-butenal is (1-1.5):1, for example, 1.05:1, 1.1:1, 1.15:1, 1.2:1, 1.25:1, 1.3:1, 1.35:1, 1.4:1 or 1.45:1, and more preferably (1.1-1.2):1.

[0017] Preferably, the alkaline electrolyte includes any one of potassium hydroxide, sodium hydroxide, potassium carbonate or sodium carbonate, or a combination of at least two thereof, and more preferably potassium hydroxide and / or sodium hydroxide.

[0018] Preferably, the molar ratio of the alkaline electrolyte to 2-methyl-4-(2,2,6-trimethyl-1-cyclohexenyl)-2-butenal is (0.05-0.2):1, for example, 0.07:1, 0.09:1, 0.11:1, 0.13:1, 0.15:1, 0.17:1 or 0.19:1, etc., and further preferably (0.1-0.15):1.

[0019] Preferably, the phase transfer catalyst comprises any one of tetrabutylammonium perchlorate, tetrapropylammonium hydroxide, tetrapropylammonium chloride, tetrabutylammonium hydroxide or tetrabutylammonium chloride, or a combination of at least two thereof, and more preferably tetrabutylammonium hydroxide and / or tetrabutylammonium chloride.

[0020] Preferably, based on the total mass of the electrolyte as 100%, the mass of the phase transfer catalyst is 0.3%-1% (eg 0.4%, 0.5%, 0.6%, 0.7%, 0.8% or 0.9%, etc.), more preferably 0.5%-0.8%.

[0021] Preferably, the solvent includes any one of a benzene solvent, a nitrile solvent or an alcohol solvent, or a combination of at least two of them.

[0022] Preferably, the mass ratio of the 2,7-dimethyl-2,4,6-octatriene dialdehyde to the solvent is (0.1-0.5):1 (for example, 0.15:1, 0.2:1, 0.25:1, 0.3:1, 0.35:1, 0.4:1 or 0.45:1, etc.), and more preferably (0.2-0.4):1.

[0023] Preferably, the solvent includes any one of benzene, acetonitrile, methanol, ethanol or propanol, or a combination of at least two thereof.

[0024] Preferably, the temperature of the electrolysis in step (2) is 20-60°C (e.g., 25°C, 30°C, 35°C, 40°C, 45°C, 50°C or 55°C, etc.), more preferably 30-40°C.

[0025] Preferably, the electrolysis time in step (2) is 10-40 h (e.g., 13 h, 16 h, 19 h, 22 h, 25 h, 28 h, 31 h, 34 h or 37 h, etc.), more preferably 20-30 h.

[0026] Preferably, the voltage of the electrolytic cell is 4-8V (eg, 4.5V, 5.0V, 5.5V, 6.0V, 6.5V, 7.0V or 7.5V, etc.), more preferably 5-6V.

[0027] Preferably, the current density of the electrolysis is 500-2000A / m 2 (e.g. 700A / m 2 , 900A / m 2 、1100A / m 2 、1300A / m 2 、1500A / m 2 、1700A / m 2 or 1900A / m 2 etc.), more preferably 500-1000A / m2 .

[0028] Preferably, the electrolysis further includes filtering and washing steps.

[0029] Preferably, the washing comprises washing with hot water at 60-75°C (eg 62°C, 64°C, 66°C, 68°C, 70°C, 72°C or 74°C, etc.).

[0030] Preferably, the anode of the electrolytic cell is any one of a platinum electrode, a platinum-titanium electrode, a graphite electrode or a titanium-based metal oxide coating anode (DSA electrode).

[0031] Preferably, the metal oxide in the titanium-based metal oxide coating anode includes any one of lead dioxide (PbO2), iridium dioxide (IrO2), ruthenium dioxide (RuO2) or tin antimony oxide.

[0032] Preferably, the cathode is any one of a lead electrode, a cadmium electrode or a graphite electrode.

[0033] Preferably, the electrolytic cell is made of any one of polypropylene (PP), polytetrafluoroethylene (PTFE) or titanium, more preferably titanium.

[0034] Preferably, the preparation method specifically comprises the following steps:

[0035] (1) 2-methyl-4-(2,2,6-trimethyl-1-cyclohexenyl)-2-butenal, 2,7-dimethyl-2,4,6-octatriene dialdehyde, an alkaline electrolyte, a phase transfer catalyst, and a solvent are mixed to prepare an electrolyte.

[0036] (2) adding the electrolyte prepared in step (1) to an electrolytic cell for electrolysis, and electrolytically reducing the β-carotene at the cathode of the electrolytic cell; the molar ratio of the 2,7-dimethyl-2,4,6-octatriene dialdehyde to the 2-methyl-4-(2,2,6-trimethyl-1-cyclohexenyl)-2-butenal is (1-1.5):1, for example, 1.05:1, 1.1:1, 1.15:1, 1.2:1, 1.25:1, 1.3:1, 1.35:1, 1.4:1 or 1.45:1, etc.

[0037] The molar ratio of the alkaline electrolyte to 2-methyl-4-(2,2,6-trimethyl-1-cyclohexenyl)-2-butenal is (0.05-0.2):1, for example, 0.07:1, 0.09:1, 0.11:1, 0.13:1, 0.15:1, 0.17:1 or 0.19:1.

[0038] Based on the total mass of the electrolyte as 100%, the mass of the phase transfer catalyst is 0.3%-1%, for example, 0.4%, 0.5%, 0.6%, 0.7%, 0.8% or 0.9%.

[0039] The mass ratio of the 2,7-dimethyl-2,4,6-octatriene dialdehyde to the solvent is (0.1-0.5):1, for example, 0.15:1, 0.2:1, 0.25:1, 0.3:1, 0.35:1, 0.4:1 or 0.45:1, etc.

[0040] The electrolysis temperature in step (2) is 20-60°C, for example, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C or 55°C, and the electrolysis time is 10-40h, for example, 13h, 16h, 19h, 22h, 25h, 28h, 31h, 34h or 37h, etc.

[0041] The voltage of the electrolytic cell is 4-8V, such as 4.5V, 5.0V, 5.5V, 6.0V, 6.5V, 7.0V or 7.5V.

[0042] The current density of the electrolysis is 500-2000A / m 2 , for example 700A / m 2 , 900A / m 2 、1100A / m 2 、1300A / m 2 、1500A / m 2 、1700A / m 2 or 1900A / m 2 wait.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] The preparation method of the present invention uses 2-methyl-4-(2,2,6-trimethyl-1-cyclohexenyl)-2-butenal and 2,7-dimethyl-2,4,6-octatriene dialdehyde as raw materials, adds an alkaline electrolyte and a phase transfer catalyst, and prepares β-carotene through electrolysis. The preparation method improves the product yield by adding the alkaline electrolyte and phase transfer catalyst. The preparation method does not involve the use of organic phosphine salts, and the prepared product does not contain any organic phosphine salt residue. The preparation method also has the characteristics of a wide range of raw material sources, a simple preparation process, high conversion rate and selectivity, high atom economy, less waste, low energy consumption, and low cost. DETAILED DESCRIPTION

[0045] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0046] The sources of the reagents and raw materials used in the examples of the present invention are as follows. Unless otherwise specified, the other reagents and raw materials are common commercial products.

[0047] 2-Methyl-4-(2,2,6-trimethyl-1-cyclohexenyl)-2-butenal: Chengdu Pusi Biotechnology Co., Ltd., purity 95 wt%;

[0048] 2,7-Dimethyl-2,4,6-octatriene dialdehyde: Beijing Yinuokai Technology Co., Ltd., purity 98%;

[0049] Potassium hydroxide: Beijing Yinuokai Technology Co., Ltd., purity 85%;

[0050] Sodium hydroxide: Beijing Yinuokai Technology Co., Ltd., purity 96%;

[0051] Tetrabutylammonium perchlorate: Aladdin reagent, purity 98%;

[0052] Tetrapropylammonium hydroxide: Beijing Yinuokai Technology Co., Ltd., purity: 25% by mass, solvent: water;

[0053] Tetrabutylammonium chloride: Beijing Yinuokai Technology Co., Ltd., purity 98%;

[0054] Methanol: Aladdin reagent, purity AR, 99%;

[0055] Acetonitrile: Xilong Chemical Reagent, purity AR, 98%;

[0056] Diaphragmless electrolyzer: The manufacturer is Jiangsu Ankaite Technology Co., Ltd.

[0057] Example 1

[0058] This embodiment provides a method for preparing β-carotene, which comprises the following steps:

[0059] (1) 2-methyl-4-(2,2,6-trimethyl-1-cyclohexenyl)-2-butenal, 2,7-dimethyl-2,4,6-octatriene dialdehyde, an alkaline electrolyte (potassium hydroxide), a phase transfer catalyst (tetrabutylammonium perchlorate), and a solvent (methanol) are mixed to prepare an electrolyte;

[0060] The molar ratio of 2,7-dimethyl-2,4,6-octatriene dialdehyde to 2-methyl-4-(2,2,6-trimethyl-1-cyclohexenyl)-2-butenal in the above electrolyte is 1:1;

[0061] The molar ratio of alkaline electrolyte to 2-methyl-4-(2,2,6-trimethyl-1-cyclohexenyl)-2-butenal is 0.05:1;

[0062] Based on the total mass of the electrolyte being 100%, the mass of the phase transfer catalyst is 0.3%;

[0063] The mass ratio of 2,7-dimethyl-2,4,6-octatriene dialdehyde to the solvent is 0.1:1.

[0064] (2) The electrolyte prepared in step (1) is added to a non-diaphragm electrolytic cell, the electrolytic cell is made of PP, the cathode electrode is a lead electrode, and the anode electrode is a graphite electrode. After the electrolytic cell is heated to 20°C, current is passed through to carry out electrolytic reaction. The voltage of the electrolytic cell is 4.0V and the current density is 1500A / m 2 The electrolytic reaction was stopped after 20 hours, and the β-carotene crystals generated by cathode electrolysis reduction of the electrolytic cell were precipitated. The reaction solution was filtered to obtain crude β-carotene, which was then washed with hot water at 70°C to obtain β-carotene.

[0065] Example 2

[0066] This embodiment provides a method for preparing β-carotene, which differs from Example 1 only in that tetrabutylammonium perchlorate is replaced with tetrapropylammonium hydroxide of the same mass, and other conditions are the same as those in Example 1.

[0067] Example 3

[0068] This embodiment provides a method for preparing β-carotene, which differs from Example 1 only in that tetrabutylammonium perchlorate is replaced with tetrabutylammonium hydroxide of the same mass, and other conditions are the same as those in Example 1.

[0069] Example 4

[0070] This embodiment provides a method for preparing β-carotene, which differs from Example 1 only in that tetrabutylammonium perchlorate is replaced with tetrabutylammonium chloride of the same mass, and other conditions are the same as those in Example 1.

[0071] Example 5

[0072] This embodiment provides a method for preparing β-carotene. The only difference between this embodiment and Example 1 is that the mass of the phase transfer catalyst (tetrabutylammonium perchlorate) is adjusted to 0.96% based on the total mass of the electrolyte as 100%. Other conditions are the same as those in Example 1.

[0073] Example 6

[0074] This embodiment provides a method for preparing β-carotene. The only difference between this embodiment and Example 1 is that the mass of the phase transfer catalyst (tetrabutylammonium perchlorate) is adjusted to 0.38% based on the total mass of the electrolyte as 100%. Other conditions are the same as those in Example 1.

[0075] Example 7

[0076] This embodiment provides a method for preparing β-carotene, which differs from Example 1 only in that the temperature of the electrolytic cell is raised to 30° C. in step (2), and other conditions are the same as those in Example 1.

[0077] Example 8

[0078] This embodiment provides a method for preparing β-carotene, which differs from Example 1 only in that the temperature of the electrolytic cell is raised to 60° C. in step (2), and other conditions are the same as those in Example 1.

[0079] Example 9

[0080] This embodiment provides a method for preparing β-carotene, which differs from Example 1 only in that potassium hydroxide is replaced with sodium carbonate in an equal molar amount, and other conditions are the same as those in Example 1.

[0081] Example 10

[0082] This embodiment provides a method for preparing β-carotene, which comprises the following steps:

[0083] (1) 2-methyl-4-(2,2,6-trimethyl-1-cyclohexenyl)-2-butenal, 2,7-dimethyl-2,4,6-octatriene dialdehyde, an alkaline electrolyte (potassium hydroxide), a phase transfer catalyst (tetrabutylammonium perchlorate), and a solvent (methanol) are mixed to prepare an electrolyte;

[0084] The molar ratio of 2,7-dimethyl-2,4,6-octatriene dialdehyde to 2-methyl-4-(2,2,6-trimethyl-1-cyclohexenyl)-2-butenal in the above electrolyte is changed to 1.5:1;

[0085] The molar ratio of alkaline electrolyte to 2-methyl-4-(2,2,6-trimethyl-1-cyclohexenyl)-2-butenal is 0.2:1;

[0086] Based on the total mass of the electrolyte being 100%, the mass of the phase transfer catalyst becomes 1%;

[0087] The mass ratio of 2,7-dimethyl-2,4,6-octatriene dialdehyde to the solvent was changed to 0.5:1.

[0088] (2) The electrolyte prepared in step (1) is added to a non-diaphragm electrolytic cell, the electrolytic cell is made of PP, the cathode electrode is a lead electrode, and the anode electrode is a graphite electrode. After the electrolytic cell is heated to 20°C, current is passed through to carry out electrolytic reaction. The voltage of the electrolytic cell is 4.0V and the current density is 1500A / m 2The electrolytic reaction was stopped after 20 hours, and the β-carotene crystals generated by cathode electrolysis reduction of the electrolytic cell were precipitated. The reaction solution was filtered to obtain crude β-carotene, which was then washed with hot water at 70°C to obtain β-carotene.

[0089] Example 11

[0090] This embodiment provides a method for preparing β-carotene, which comprises the following steps:

[0091] (1) 2-methyl-4-(2,2,6-trimethyl-1-cyclohexenyl)-2-butenal, 2,7-dimethyl-2,4,6-octatriene dialdehyde, an alkaline electrolyte (potassium hydroxide), a phase transfer catalyst (tetrabutylammonium hydroxide) and a solvent (methanol) are mixed to prepare an electrolyte;

[0092] The molar ratio of 2,7-dimethyl-2,4,6-octatriene dialdehyde to 2-methyl-4-(2,2,6-trimethyl-1-cyclohexenyl)-2-butenal in the above electrolyte is 1.1:1;

[0093] The molar ratio of alkaline electrolyte to 2-methyl-4-(2,2,6-trimethyl-1-cyclohexenyl)-2-butenal is 0.1:1;

[0094] Based on the total mass of the electrolyte being 100%, the mass of the phase transfer catalyst is 0.8%;

[0095] The mass ratio of 2,7-dimethyl-2,4,6-octatriene dialdehyde to the solvent is 0.4:1.

[0096] (2) The electrolyte prepared in step (1) is added to a non-diaphragm electrolytic cell, the electrolytic cell is made of PP, the cathode electrode is a lead electrode, and the anode electrode is a graphite electrode. After the electrolytic cell is heated to 30°C, current is passed through to carry out electrolytic reaction. The voltage of the electrolytic cell is 6V and the current density is 1000A / m 2 The reaction was stopped after 20 hours, and the β-carotene crystals generated by cathode electrolysis reduction of the electrolytic cell were precipitated. The reaction solution was filtered to obtain crude β-carotene, which was then washed with hot water at 75°C to obtain β-carotene.

[0097] Example 12

[0098] This embodiment provides a method for preparing β-carotene, which comprises the following steps:

[0099] (1) 2-methyl-4-(2,2,6-trimethyl-1-cyclohexenyl)-2-butenal, 2,7-dimethyl-2,4,6-octatriene dialdehyde, an alkaline electrolyte (sodium hydroxide), a phase transfer catalyst (tetrabutylammonium chloride) and a solvent (methanol) are mixed to prepare an electrolyte;

[0100] The molar ratio of the above-mentioned 2,7-dimethyl-2,4,6-octatriene dialdehyde to 2-methyl-4-(2,2,6-trimethyl-1-cyclohexenyl)-2-butenal is 1.2:1;

[0101] The molar ratio of alkaline electrolyte to 2-methyl-4-(2,2,6-trimethyl-1-cyclohexenyl)-2-butenal is 0.15:1;

[0102] Based on the total mass of the electrolyte being 100%, the mass of the phase transfer catalyst is 0.5%; the mass ratio of 2,7-dimethyl-2,4,6-octatriene dialdehyde to the solvent is 0.2:1.

[0103] (2) The electrolyte prepared in step (1) is added to a non-diaphragm electrolytic cell, the electrolytic cell is made of PP, the cathode electrode is a lead electrode, and the anode electrode is a graphite electrode. After the electrolytic cell is heated to 40°C, current is passed through to carry out electrolytic reaction. The voltage of the electrolytic cell is 5V and the current density is 500A / m 2 The reaction was stopped after 30 hours, and the β-carotene crystals generated by cathode electrolysis reduction of the electrolytic cell were precipitated. The reaction solution was filtered to obtain crude β-carotene, which was then washed with hot water at 60°C to obtain β-carotene.

[0104] The above examples were tested as follows.

[0105] The H-NMR structure was characterized using a Brucker ARX-400 nuclear magnetic resonance spectrometer. The H-NMR analysis data of β-carotene provided in Example 1 are as follows:

[0106] 1H NMR (300MHz, CDCl3): δ0.94(s,12H), δ1.53(m,4H), δ1.61(m,4H), δ1.76-1.77(m,18H), δ1.96(t,4H), δ6.23(s,4H), δ6.51(s,10H).

[0107] The β-carotene provided in the above embodiment was analyzed and tested using the liquid chromatography area correction normalization method. The instrument model was Agilent 1260; the chromatographic column was Suplex pKb-100 Alkylamide column (4.6 mm×25 cm, 5 μm).

[0108] Detection method: Acetonitrile and water (acetonitrile:water = 9:1, phase A) and ethyl acetate (phase B) were used as the liquid phase detection mobile phase at a flow rate of 1.0 mL / min and a column temperature of 30 ± 1°C. The UV detection wavelength was set at 455 nm.

[0109] β-carotene selectivity = [molar yield of β-carotene / molar consumption of 2-methyl-4-(2,2,6-trimethyl-1-cyclohexenyl)-2-butenal] × 100%;

[0110] Current efficiency = (molar yield of β-carotene × 2 × 96500) / (electrolysis current × electrolysis time) × 100%.

[0111] The test results are shown in Table 1 below:

[0112] Table 1

[0113]

[0114] As shown in Table 1, the conversion rate of 2-methyl-4-(2,2,6-trimethyl-1-cyclohexenyl)-2-butenal in the preparation method of β-carotene provided in Examples 1-12 is 92.7% to 97.2%, the selectivity of β-carotene is 84.8% to 92.3%, and the current efficiency is 83.7% to 89.6%.

[0115] Compared with Examples 1-4, when tetrabutylammonium hydroxide (Example 3) or tetrabutylammonium chloride (Example 4) was used as the phase transfer catalyst, the conversion rate of 2-methyl-4-(2,2,6-trimethyl-1-cyclohexenyl)-2-butenal increased, the selectivity for β-carotene increased, and the current efficiency increased. Therefore, it can be seen that using tetrabutylammonium hydroxide and / or tetrabutylammonium chloride as the phase transfer catalyst is more effective.

[0116] Compared with Example 1, if the mass percentage of the phase transfer catalyst in the electrolyte is too high (Example 5), the conversion rate of 2-methyl-4-(2,2,6-trimethyl-1-cyclohexenyl)-2-butenal decreases, the selectivity for β-carotene decreases, and the current efficiency decreases. If the mass percentage of the phase transfer catalyst in the electrolyte is too low (Example 6), the conversion rate of 2-methyl-4-(2,2,6-trimethyl-1-cyclohexenyl)-2-butenal decreases, the selectivity for β-carotene decreases, and the current efficiency decreases. Therefore, it can be seen that the effect is better when the mass percentage of the phase transfer catalyst is 0.5%-0.8% based on the total mass of the electrolyte as 100%.

[0117] Compared with Example 7, if the electrolysis temperature is low (Example 1), the conversion rate of 2-methyl-4-(2,2,6-trimethyl-1-cyclohexenyl)-2-butenal is reduced, the selectivity of β-carotene is reduced, and the current efficiency is reduced. If the electrolysis temperature is high (Example 8), the conversion rate of 2-methyl-4-(2,2,6-trimethyl-1-cyclohexenyl)-2-butenal is reduced, the selectivity of β-carotene is reduced, and the current efficiency is reduced. It can be seen that the electrolysis temperature of 30-40°C is better.

[0118] Compared with Example 1, if potassium hydroxide is replaced with the same molar amount of sodium carbonate (Example 9), the conversion rate of 2-methyl-4-(2,2,6-trimethyl-1-cyclohexenyl)-2-butenal is reduced, the selectivity of β-carotene is reduced, and the current efficiency is reduced. It can be seen that the alkaline electrolyte is preferably potassium hydroxide and / or sodium hydroxide, which is more effective.

[0119] The applicant states that while the present invention uses the above-described embodiments to illustrate the present invention's method for preparing β-carotene, the present invention is not limited to these embodiments, nor does it necessarily rely on these embodiments for implementation. Those skilled in the art will appreciate that any improvements to the present invention, equivalent substitutions for raw materials in the present invention's products, addition of auxiliary ingredients, and selection of specific methods, etc., fall within the scope of protection and disclosure of the present invention.

Claims

1. A method for preparing β-carotene, characterized in that: The preparation method comprises the following steps: (1) mixing 2-methyl-4-(2,2,6-trimethyl-1-cyclohexenyl)-2-butenal, 2,7-dimethyl-2,4,6-octatriene dialdehyde, an alkaline electrolyte, a phase transfer catalyst, and a solvent to prepare an electrolyte; (2) adding the electrolyte prepared in step (1) into an electrolytic cell for electrolysis to obtain the β-carotene; The phase transfer catalyst includes any one of tetrabutylammonium perchlorate, tetrapropylammonium hydroxide, tetrapropylammonium chloride, tetrabutylammonium hydroxide or tetrabutylammonium chloride, or a combination of at least two thereof.

2. The preparation method according to claim 1, characterized in that The electrolytic cell is a diaphragmless electrolytic cell.

3. The preparation method according to claim 1, characterized in that The molar ratio of the 2,7-dimethyl-2,4,6-octatriene dialdehyde to the 2-methyl-4-(2,2,6-trimethyl-1-cyclohexenyl)-2-butenal is (1-1.5):

1.

4. The preparation method according to claim 1, characterized in that The molar ratio of the 2,7-dimethyl-2,4,6-octatriene dialdehyde to the 2-methyl-4-(2,2,6-trimethyl-1-cyclohexenyl)-2-butenal is (1.1-1.2):

1.

5. The preparation method according to claim 1, characterized in that The alkaline electrolyte includes any one of potassium hydroxide, sodium hydroxide, potassium carbonate or sodium carbonate, or a combination of at least two thereof.

6. The preparation method according to claim 1, characterized in that The alkaline electrolyte includes potassium hydroxide and / or sodium hydroxide.

7. The preparation method according to claim 1, characterized in that The molar ratio of the alkaline electrolyte to 2-methyl-4-(2,2,6-trimethyl-1-cyclohexenyl)-2-butenal is (0.05-0.2):

1.

8. The preparation method according to claim 1, characterized in that The molar ratio of the alkaline electrolyte to 2-methyl-4-(2,2,6-trimethyl-1-cyclohexenyl)-2-butenal is (0.1-0.15):

1.

9. The preparation method according to claim 1, characterized in that The phase transfer catalyst includes tetrabutylammonium hydroxide and / or tetrabutylammonium chloride.

10. The preparation method according to claim 1, characterized in that Based on the total mass of the electrolyte being 100%, the mass of the phase transfer catalyst is 0.3%-1%.

11. The preparation method according to claim 1, characterized in that Based on the total mass of the electrolyte being 100%, the mass of the phase transfer catalyst is 0.5%-0.8%.

12. The preparation method according to claim 1, characterized in that The solvent includes any one of a benzene solvent, a nitrile solvent or an alcohol solvent, or a combination of at least two of them.

13. The preparation method according to claim 1, characterized in that The mass ratio of the 2,7-dimethyl-2,4,6-octatriene dialdehyde to the solvent is (0.1-0.5):

1.

14. The preparation method according to claim 1, characterized in that The mass ratio of the 2,7-dimethyl-2,4,6-octatriene dialdehyde to the solvent is (0.2-0.4):

1.

15. The preparation method according to claim 1, characterized in that The solvent includes any one of benzene, acetonitrile, methanol, ethanol or propanol, or a combination of at least two of them.

16. The preparation method according to claim 1, characterized in that The temperature of the electrolysis in step (2) is 20-60°C.

17. The preparation method according to claim 1, characterized in that The temperature of the electrolysis in step (2) is 30-40°C.

18. The preparation method according to claim 1, characterized in that The electrolysis time in step (2) is 10-40h.

19. The preparation method according to claim 1, characterized in that The electrolysis time in step (2) is 20-30h.

20. The preparation method according to claim 1, characterized in that The voltage of the electrolytic cell is 4-8V.

21. The preparation method according to claim 1, characterized in that The voltage of the electrolytic cell is 5-6V.

22. The preparation method according to claim 1, characterized in that The current density of the electrolysis is 500-2000A / m 2 .

23. The preparation method according to claim 1, characterized in that The current density of the electrolysis is 500-1000A / m 2 .

24. The preparation method according to claim 1, characterized in that The method further comprises filtering and washing steps after the electrolysis.

25. The preparation method according to claim 24, characterized in that The washing includes washing with hot water at 60-75°C.

26. The preparation method according to claim 1, characterized in that The anode of the electrolytic cell is any one of a platinum electrode, a platinum-titanium electrode, a graphite electrode or a titanium-based metal oxide coating anode, and the cathode is any one of a lead electrode, a cadmium electrode or a graphite electrode.

27. The preparation method according to claim 26, characterized in that The metal oxide in the titanium-based metal oxide coating anode includes any one of lead dioxide, iridium dioxide, ruthenium dioxide or tin antimony oxide.

28. The preparation method according to claim 1, characterized in that The electrolytic cell is made of any one of polypropylene, polytetrafluoroethylene or titanium.

29. The preparation method according to claim 1, characterized in that The electrolytic cell is made of titanium.

30. The preparation method according to any one of claims 1 to 29, characterized in that: The preparation method specifically comprises the following steps: (1) mixing 2-methyl-4-(2,2,6-trimethyl-1-cyclohexenyl)-2-butenal, 2,7-dimethyl-2,4,6-octatriene dialdehyde, an alkaline electrolyte, a phase transfer catalyst, and a solvent to prepare an electrolyte; (2) adding the electrolyte prepared in step (1) into an electrolytic cell for electrolysis, and electrolytically reducing the β-carotene at the cathode of the electrolytic cell; The molar ratio of the 2,7-dimethyl-2,4,6-octatriene dialdehyde to the 2-methyl-4-(2,2,6-trimethyl-1-cyclohexenyl)-2-butenal is (1-1.5):1; The molar ratio of the alkaline electrolyte to 2-methyl-4-(2,2,6-trimethyl-1-cyclohexenyl)-2-butenal is (0.05-0.2):1; Based on the total mass of the electrolyte being 100%, the mass of the phase transfer catalyst is 0.3%-1%; The mass ratio of the 2,7-dimethyl-2,4,6-octatriene dialdehyde to the solvent (0.1-0.5): 1; The electrolysis temperature in step (2) is 20-60° C., and the electrolysis time is 10-40 h; The voltage of the electrolytic cell is 4-8V; The current density of the electrolysis is 500-2000A / m 2 .

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