A palladium-containing catalyst, a preparation method thereof and its application in the preparation of L-menthol

Abstract

The present invention relates to the field of fragrance synthesis, and discloses a palladium-containing catalyst, a preparation method thereof, and an application thereof in the preparation of L-menthol. The palladium-containing catalyst comprises a first active metal, a second active metal, and a chiral phosphate ligand; the first active metal is palladium; the second active metal is one, two or more of rhodium, iridium, platinum, zinc, iron, copper, nickel, and ruthenium; the chiral phosphate ligand comprises one of a chiral monophosphate ligand or a chiral diphosphate ligand. Under the action of the palladium-containing catalyst, D-menthol can be isomerized to L-menthol under mild reaction conditions, and the reaction has a high D-menthol conversion rate and L-menthol selectivity, reduces subsequent separation operations, simplifies the production process, and reduces production energy consumption.

Description

Technical Field

[0001] The invention relates to the field of fragrance synthesis, and in particular to a palladium-containing catalyst, a preparation method thereof and application thereof in the preparation of L-menthol. Background Art

[0002] L-Menthol, commonly known as menthol, is a natural chiral compound extracted from mint. L-Menthol is widely used in medicine and health, flavors and fragrances, cigarettes, food industry and daily fine chemicals. Since the synthesis of L-menthol has high economic value, there are many reports on L-menthol in the literature. At present, the main synthetic routes of L-menthol are:

[0003] An industrialized asymmetric synthesis route developed by Takasago Co., Ltd. of Japan (Tani, K. et al; Chem. Soc. 1984, 106, 5208.) uses myrcene as a raw material, reacts with lithium diethylamine to obtain N,N'-diethylgeranylamine, and then obtains citronellal enamine under the catalysis of a chiral catalyst (S)-BINAP-Rh, and obtains dextrorotatory citronellal under the action of acid ions. Under the catalytic action of zinc bromide, the ring is closed to obtain isopulegol, and finally hydrogenated to obtain L-menthol. The product produced by this route is of high quality; however, the preparation conditions of the catalyst for catalytic asymmetric isomerization reaction are relatively harsh and difficult to recycle.

[0004] The L-menthol developed by Symrise in Germany has the highest yield of L-menthol. It uses cheap meta-cresol as raw material, generates thymol through alkylation reaction, generates eight isomers of menthol through catalytic hydrogenation, separates D, L-menthol through distillation, and then esterifies to generate D, L-menthol benzoate. Add single-configuration menthyl benzoate as seed, and prepare L-menthol ester through repeated selective crystallization of L-menthol, and then obtains L-menthol with high optical purity through chemical hydrolysis. However, the chemical splitting effect of menthyl benzoate ester is relatively poor, and the efficiency of single splitting is not high, which requires repeated crystallization.

[0005] BASF of Germany has developed a synthetic route using isobutylene and formaldehyde as starting materials (Heydrich, Getal. US2010 / 0249467A1, 2010.), which has now been successfully industrialized. The synthetic route first reacts isobutylene and formaldehyde to generate 3-methyl-2-butenol, and then undergoes oxidation, addition, and isomerization to obtain cis- and trans-citral. Cis-citral is obtained by distillation, and then asymmetric hydrogenation is catalyzed by a rhodium catalyst to obtain dextrorotatory citronellal. Dextrorotatory citronellal is cyclized by Lewis acid to obtain dextrorotatory isopulegol, and then hydrogenated to generate L-menthol. The synthetic route has a simple process, and the boiling points of the cis- and trans-isomers of citral are close. The distillation method to obtain cis-configuration citral has high requirements for production equipment; at the same time, a large amount of racemic menthol is generated in the final product, which has a poor aroma and a low price.

[0006] At present, in the existing reports, a large amount of racemic menthol will eventually be generated during the synthesis of L-menthol due to the presence of s-citronellal, resulting in a low yield of L-menthol and increased production costs. The racemic menthol product obtained by separation has a low selling price and poor market acceptance due to poor cooling sensation, resulting in a waste of resources. Therefore, it is urgent to develop a method for splitting racemic menthol to obtain L-menthol, improve the reaction yield of L-menthol, and reduce the production cost of L-menthol. Summary of the invention

[0007] The purpose of the present invention is to provide a palladium-containing catalyst, a preparation method thereof and application thereof in the preparation of L-menthol. The method adopts a high-efficiency palladium-containing catalyst to catalyze the isomerization of D-menthol in menthol under mild reaction conditions with high conversion rate and high L-menthol selectivity to obtain L-menthol, thereby reducing subsequent separation operations, simplifying the production process and reducing production energy consumption.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0009] The present invention provides a palladium-containing catalyst for isomerization reaction, wherein the palladium-containing catalyst comprises a first active metal, a second active metal and a chiral phosphate ligand (CPA for short);

[0010] The first active metal is palladium;

[0011] The second active metal is one, two or more of rhodium, iridium, platinum, zinc, iron, copper, nickel and ruthenium;

[0012] The chiral phosphate ligand is one of a chiral monophosphate ligand or a chiral diphosphate ligand.

[0013] The chiral monophosphate ligand structure is as follows:

[0014]

[0015] Wherein, R is one or two of -H, substituted or unsubstituted phenyl or condensed aromatic hydrocarbons, and the substituent on the phenyl is one or more of C1~C4 alkyl or C1~C4 alkoxy; preferably one or two of H, -Ph, 2,4,6-(i-Pr)3C6H2-, -SiPh3 (phenylsilyl), -9-phenanthryl (9-phenanthryl), -9-anthryl (9-anthryl), 4-CH3O-Ph-. For example, one, two or more of (R)-PA-H, (R)-PA-Ph, (R)-PA-2,4,6-iPrC6H2, (R)-PA-PhSi, (R)-PA-9-phenanthryl, (R)-PA-9-anthryl, (R)-PA-4-PhOCH3. The specific structure is as follows:

[0016]

[0017] The structure of the chiral bisphosphate ligand is shown in Formula 1 or Formula 2:

[0018] General formula 1:

[0019]

[0020] Wherein, R1 and R2 are one or two of substituted or unsubstituted phenyl groups, and the substituent on the phenyl group is one or more of C1~C6 alkyl or halogen; preferably one or two of -2,4,6-(iPr)3-C6H2, -2,4,6-(Pent)3-C6H2, -C6F5, -2,4,6-(Hex)3-C6H2. The specific structure is as follows:

[0021]

[0022]

[0023] General formula 2:

[0024]

[0025] Wherein, R1 and R2 are one or two of substituted or unsubstituted phenyl groups, and the substituent on the phenyl group is one or more of C1~C6 alkyl, C5~C6 cycloalkyl or tolyl; preferably one or two of -2,4,6-Cy3C6H2 and -3,5-(o-TOL)2C6H3. The specific structure is as follows:

[0026]

[0027] In a second aspect, the present invention provides a method for preparing the catalyst according to the first aspect, the preparation method comprising:

[0028] The first active metal source, the second active metal source, the chiral phosphate ligand and the first solvent are mixed according to a molar ratio and stirred to obtain the catalyst.

[0029] As a preferred technical solution of the present invention, the first active metal source includes a palladium salt and / or a palladium complex.

[0030] In the present invention, the first active metal source includes one, two or more of PdCl2, Pd(PPh3)2Cl2, Pd(PCy3)2Cl2, Pd(NO3)2·2H2O, PdSO4·2H2O, and Pd(acac)2.

[0031] The second active metal source includes any one of the second active metal nitrate, sulfate, chloride, acetate, hydroxide or hydrate thereof, or a combination of at least two thereof. Typical but non-limiting combinations include: a combination of nitrate and sulfate, a combination of chloride and acetate, a combination of hydroxide and hydrate, etc.

[0032] As a preferred technical solution of the present invention, the first solvent includes deionized water.

[0033] The molar ratio of the first active metal source to the second active metal source is 1:1-7, preferably 1:3-5.

[0034] The molar ratio of the second active metal source to the chiral phosphate ligand is 1:0.5-4.0, preferably 1:0.5-2.0.

[0035] In a third aspect, the present invention provides a method for preparing L-menthol, the method comprising:

[0036] The reaction substrate is mixed with the palladium-containing catalyst described in the first aspect, and then subjected to an asymmetric isomerization reaction to obtain L-menthol;

[0037] The reaction substrate is D-menthol, racemic menthol or partially racemic menthol.

[0038] The molar ratio of the reaction substrate to the palladium-containing catalyst is 1:0.01-0.1, preferably 1:0.03-0.07, and the molar amount of the palladium-containing catalyst is calculated based on the Pd therein.

[0039] The temperature of the isomerization reaction is 80-160°C, preferably 80-120°C.

[0040] The isomerization reaction time is 3.0 to 6.0 h, preferably 3.0 to 5.0 h.

[0041] In the present invention, the asymmetric isomerization reaction can be carried out in the presence of a second solvent or in the absence of a solvent.

[0042] The second solvent includes any one of methanol, ethanol, isopropanol or water, or a combination of at least two of them, wherein typical but non-limiting combinations include: a combination of methanol and ethanol, a combination of ethanol and n-propanol, a combination of isopropanol and water, and the like.

[0043] The mass ratio of the reaction substrate to the second solvent is 1:1.0-4.0, preferably 1:1.0-2.0.

[0044] In the present invention, the asymmetric isomerization reaction can be carried out intermittently or continuously; the equipment for the asymmetric isomerization reaction is equipment suitable for isomerization reaction at the pressure and temperature, which can be an autoclave, a tubular reactor or a loop reactor.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] (1) The catalyst provided by the present invention uses chiral phosphoric acid as an organic ligand. The P atom and the transition metal ion in the ligand form a structurally stable complex through coordination bonds, which reduces the loss of active components; the hydroxyl group connected to the P atom forms an intermolecular hydrogen bond with the H atom in the reaction substrate, thereby improving the selectivity of the reaction to L-menthol. The ligand contains a Bronsted acid site that can activate the substrate; at the same time, the size of the 3,3'-substituent in the organic ligand can effectively adjust the enantioselective L-menthol of the catalyst; the first active metal is firmly combined with the doped second active metal through a metal bond, which reduces the loss of active components, so that the catalyst has high activity and L-menthol selectivity while improving the stability of the catalyst, realizing the recycling of the catalyst and reducing the production cost.

[0047] (2) The catalyst provided by the present invention can convert D-menthol in racemic menthol into L-menthol through isomerization reaction under relatively mild reaction conditions, with high product yield, high selectivity for L-menthol and low production cost, thus realizing resource utilization of by-products in the menthol production process and reducing the production cost of L-menthol. DETAILED DESCRIPTION

[0048] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0049] Menthol is produced by the company itself, with a purity of 99.70% and a ratio of L- and D- of 50:50.

[0050] D-Menthol is produced by the company itself with a purity of 99.5%.

[0051] BINOL ligand structure:

[0052]

[0053] Unless otherwise specified, the reagents used in the following examples and comparative examples are all commercially available.

[0054] Example 1

[0055] In a 500 mL autoclave, PdCl2 (1.773 g, 0.01 mol), FeCl3·6H2O (2.70 g, 0.01 mol), and L1 ligand (0.02 mol) were dispersed in 20 mL of deionized water and stirred at 60 °C for 2 hours. After uniform dispersion, 100 g of ethanol and 100 g of menthol were added, and the temperature was raised to 100 °C. The reaction was allowed to proceed for 4 hours. The reaction was monitored by gas chromatography. The conversion rate of D-menthol was 96.2%, and the selectivity of L-menthol was 97.3%.

[0056] Calculation method:

[0057] D-menthol conversion amount = mass of D-menthol in raw materials - mass of D-menthol in products;

[0058] Increased amount of L-menthol = mass of L-menthol in the product - mass of L-menthol in the raw material;

[0059] D-menthol conversion rate = D-menthol conversion amount / mass of D-menthol in raw materials;

[0060] L-menthol selectivity = L-menthol increase / D-menthol conversion*100%.

[0061] Example 2

[0062] In a 500 mL autoclave, PdCl2 (1.773 g, 0.01 mol), FeCl3·6H2O (5.41 g, 0.02 mol), and L1 ligand (0.04 mol) were dispersed in 20 mL of deionized water and stirred at 60 °C for 2 hours. After uniform dispersion, 100 g of ethanol and 100 g of menthol were added, and the temperature was raised to 100 °C. The reaction was allowed to proceed for 4 hours. The reaction was monitored by gas chromatography. The conversion rate of D-menthol was 97.1%, and the selectivity of L-menthol was 97.8%.

[0063] Example 3

[0064] In a 500 mL autoclave, PdCl2 (1.773 g, 0.01 mol), FeCl3·6H2O (8.11 g, 0.03 mol), and L1 ligand (0.06 mol) were dispersed in 20 mL of deionized water and stirred at 60 °C for 2 hours. After uniform dispersion, 100 g of ethanol and 100 g of menthol were added, and the temperature was raised to 100 °C. The reaction was allowed to proceed for 4 hours. The reaction was monitored by gas chromatography. The conversion rate of D-menthol was 98.2%, and the selectivity of L-menthol was 98.5%.

[0065] Example 4

[0066] In a 500 mL autoclave, PdCl2 (1.773 g, 0.01 mol), FeCl3·6H2O (10.81 g, 0.04 mol), and L1 ligand (0.08 mol) were dispersed in 40 mL of deionized water and stirred at 60 °C for 2 hours. After uniform dispersion, 100 g of ethanol and 100 g of menthol were added, and the temperature was raised to 100 °C. The reaction was allowed to proceed for 4 hours. The reaction was monitored by gas chromatography. The conversion rate of D-menthol was 98.6%, and the selectivity of L-menthol was 99.1%.

[0067] Example 5

[0068] In a 500 mL autoclave, PdCl2 (1.773 g, 0.01 mol), FeCl3·6H2O (13.52 g, 0.05 mol), and L1 ligand (0.1 mol) were dispersed in 40 mL of deionized water and stirred at 60 °C for 2 hours. After uniform dispersion, 100 g of ethanol and 100 g of menthol were added, and the temperature was raised to 100 °C. The reaction was allowed to proceed for 4 hours. The reaction was monitored by gas chromatography. The conversion rate of D-menthol was 99.2%, and the selectivity of L-menthol was 99.4%.

[0069] Example 6

[0070] In a 500 mL autoclave, PdCl2 (1.773 g, 0.01 mol), FeCl3·6H2O (16.22 g, 0.06 mol), and L1 ligand (0.12 mol) were dispersed in 40 mL of deionized water and stirred at 60 °C for 2 hours. After uniform dispersion, 100 g of ethanol and 100 g of menthol were added, and the temperature was raised to 100 °C. The reaction was allowed to proceed for 4 hours. The reaction was monitored by gas chromatography. The conversion rate of D-menthol was 99.5%, and the selectivity of L-menthol was 99.3%.

[0071] Example 7

[0072] In a 500 mL autoclave, PdCl2 (1.773 g, 0.01 mol), FeCl3·6H2O (18.92 g, 0.07 mol), and L1 ligand (0.14 mol) were dispersed in 40 mL of deionized water and stirred at 60 °C for 2 hours. After uniform dispersion, 100 g of ethanol and 100 g of menthol were added, and the temperature was raised to 100 °C. The reaction was allowed to react for 4 hours. The reaction was monitored by gas chromatography. The conversion rate of D-menthol was 99.7%, and the selectivity of L-menthol was 99.2%.

[0073] Example 8

[0074] In a 500 mL autoclave, PdCl2 (1.773 g, 0.01 mol), FeCl3·6H2O (13.52 g, 0.05 mol), and L1 ligand (0.1 mol) were dispersed in 40 mL of deionized water and stirred at 60 °C for 2 hours. After uniform dispersion, 100 g of ethanol and 100 g of menthol were added, and the temperature was raised to 80 °C. The reaction was allowed to proceed for 4 hours. The reaction was monitored by gas chromatography. The conversion rate of D-menthol was 98.7%, and the selectivity of L-menthol was 99.2%.

[0075] Example 9

[0076] In a 500 mL autoclave, PdCl2 (1.773 g, 0.01 mol), FeCl3·6H2O (13.52 g, 0.05 mol), and L1 ligand (0.1 mol) were dispersed in 40 mL of deionized water and stirred at 60 °C for 2 hours. After uniform dispersion, 100 g of ethanol and 100 g of menthol were added, and the temperature was raised to 120 °C. The reaction was allowed to proceed for 4 hours. The reaction was monitored by gas chromatography. The conversion rate of D-menthol was 99.5%, and the selectivity of L-menthol was 99.3%.

[0077] Example 10

[0078] In a 500 mL autoclave, PdCl2 (1.773 g, 0.01 mol), FeCl3·6H2O (13.52 g, 0.05 mol), and L1 ligand (0.1 mol) were dispersed in 40 mL of deionized water and stirred at 60 °C for 2 hours. After uniform dispersion, 100 g of ethanol and 100 g of menthol were added, and the temperature was raised to 140 °C. The reaction was allowed to proceed for 4 hours. The reaction was monitored by gas chromatography. The conversion rate of D-menthol was 99.4%, and the selectivity of L-menthol was 99.1%.

[0079] Embodiment 11

[0080] In a 500 mL autoclave, PdCl2 (1.773 g, 0.01 mol), FeCl3·6H2O (13.52 g, 0.05 mol), and L1 ligand (0.1 mol) were dispersed in 40 mL of deionized water and stirred at 60 °C for 2 hours. After uniform dispersion, 100 g of ethanol and 100 g of menthol were added, and the temperature was raised to 160 °C. The reaction was allowed to proceed for 4 hours. The reaction was monitored by gas chromatography. The conversion rate of D-menthol was 99.6%, and the selectivity of L-menthol was 99.2%.

[0081] Example 12

[0082] In a 500 mL autoclave, PdCl2 (1.773 g, 0.01 mol), FeCl3·6H2O (13.52 g, 0.05 mol), and L1 ligand (0.1 mol) were dispersed in 40 mL of deionized water and stirred at 60 °C for 2 hours. After uniform dispersion, 100 g of ethanol and 100 g of menthol were added, and the temperature was raised to 100 °C. The reaction was allowed to react for 2 hours. The reaction was monitored by gas chromatography. The conversion rate of D-menthol was 96.4%, and the selectivity of L-menthol was 99.3%.

[0083] Embodiment 13

[0084] In a 500 mL autoclave, PdCl2 (1.773 g, 0.01 mol), FeCl3·6H2O (13.52 g, 0.05 mol), and L1 ligand (0.1 mol) were dispersed in 40 mL of deionized water and stirred at 60 °C for 2 hours. After uniform dispersion, 100 g of ethanol and 100 g of menthol were added, and the temperature was raised to 100 °C. The reaction was allowed to proceed for 3 hours. The reaction was monitored by gas chromatography. The conversion rate of D-menthol was 97.8%, and the selectivity of L-menthol was 99.2%.

[0085] Embodiment 14

[0086] In a 500 mL autoclave, PdCl2 (1.773 g, 0.01 mol), FeCl3·6H2O (13.52 g, 0.05 mol), and L1 ligand (0.1 mol) were dispersed in 40 mL of deionized water and stirred at 60 °C for 2 hours. After uniform dispersion, 100 g of ethanol and 100 g of menthol were added, and the temperature was raised to 100 °C. The reaction was allowed to proceed for 5 hours. The reaction was monitored by gas chromatography. The conversion rate of D-menthol was 99.5%, and the selectivity of L-menthol was 99.2%.

[0087] Embodiment 15

[0088] In a 500 mL autoclave, PdCl2 (1.773 g, 0.01 mol), FeCl3·6H2O (13.52 g, 0.05 mol), and L1 ligand (0.1 mol) were dispersed in 40 mL of deionized water and stirred at 60 °C for 2 hours. After uniform dispersion, 100 g of ethanol and 100 g of menthol were added, and the temperature was raised to 100 °C. The reaction was allowed to react for 6 hours. The reaction was monitored by gas chromatography. The conversion rate of D-menthol was 99.7%, and the selectivity of L-menthol was 98.7%.

[0089] Example 16

[0090] In a 500 mL autoclave, PdCl2 (1.773 g, 0.01 mol), FeCl3·6H2O (13.52 g, 0.05 mol), and L1 ligand (0.1 mol) were dispersed in 40 mL of deionized water and stirred at 60 °C for 2 hours. After uniform dispersion, 100 g of methanol and 100 g of menthol were added, and the temperature was raised to 100 °C. The reaction was allowed to proceed for 4 hours. The reaction was monitored by gas chromatography. The conversion rate of D-menthol was 99.4%, and the selectivity of L-menthol was 99.3%.

[0091] Embodiment 17

[0092] In a 500 mL autoclave, PdCl2 (1.773 g, 0.01 mol), FeCl3·6H2O (13.52 g, 0.05 mol), and L1 ligand (0.1 mol) were dispersed in 40 mL of deionized water and stirred at 60 °C for 2 h. After uniform dispersion, 100 g of isopropanol and 100 g of menthol were added, and the temperature was raised to 100 °C. The reaction was allowed to proceed for 4 h. The reaction was monitored by gas chromatography. The conversion rate of D-menthol was 99.2%, and the selectivity of L-menthol was 99.4%.

[0093] Embodiment 18

[0094] In a 500 mL autoclave, PdCl2 (1.773 g, 0.01 mol), FeCl3·6H2O (13.52 g, 0.05 mol), and L1 ligand (0.1 mol) were dispersed in 40 mL of deionized water and stirred at 60 °C for 2 h. After uniform dispersion, 100 g of water and 100 g of menthol were added, and the temperature was raised to 100 °C. The reaction was allowed to proceed for 4 h. The reaction was monitored by gas chromatography. The conversion of D-menthol was 98.5%, and the selectivity of L-menthol was 98.6%.

[0095] Actual Example 19

[0096] In a 500 mL autoclave, PdCl2 (1.773 g, 0.01 mol), FeCl3·6H2O (13.52 g, 0.05 mol), and L1 ligand (0.1 mol) were dispersed in 40 mL of deionized water and stirred at 60 °C for 2 hours. After uniform dispersion, 100 g of menthol was added, the temperature was raised to 100 °C, and the reaction was carried out for 4 hours. The reaction was monitored by gas chromatography. The conversion rate of D-menthol was 99.2%, and the selectivity of L-menthol was 97.5%.

[0097] Embodiment 20

[0098] In a 500 mL autoclave, PdCl2 (1.773 g, 0.01 mol), FeCl3·6H2O (13.52 g, 0.05 mol), and L1 ligand (0.1 mol) were dispersed in 40 mL of deionized water and stirred at 60 °C for 2 hours. After uniform dispersion, 200 g of ethanol and 100 g of menthol were added, and the temperature was raised to 100 °C. The reaction was allowed to proceed for 4 hours. The reaction was monitored by gas chromatography. The conversion rate of D-menthol was 99.4%, and the selectivity of L-menthol was 99.1%.

[0099] Embodiment 21

[0100] In a 500 mL autoclave, PdCl2 (1.773 g, 0.01 mol), FeCl3·6H2O (13.52 g, 0.05 mol), and L1 ligand (0.1 mol) were dispersed in 40 mL of deionized water and stirred at 60 °C for 2 hours. After uniform dispersion, 300 g of ethanol and 100 g of menthol were added, and the temperature was raised to 100 °C. The reaction was allowed to proceed for 4 hours. The reaction was monitored by gas chromatography. The conversion rate of D-menthol was 98.9%, and the selectivity of L-menthol was 99.3%.

[0101] Embodiment 22

[0102] In a 500 mL autoclave, PdCl2 (1.773 g, 0.01 mol), FeCl3·6H2O (13.52 g, 0.05 mol), and L1 ligand (0.1 mol) were dispersed in 40 mL of deionized water and stirred at 60 °C for 2 hours. After uniform dispersion, 400 g of ethanol and 100 g of menthol were added, and the temperature was raised to 100 °C. The reaction was allowed to proceed for 4 hours. The reaction was monitored by gas chromatography. The conversion rate of D-menthol was 98.5%, and the selectivity of L-menthol was 99.4%.

[0103] Embodiment 23

[0104] In a 500 mL autoclave, PdCl2 (1.773 g, 0.01 mol), FeCl3·6H2O (13.52 g, 0.05 mol), and L1 ligand (0.025 mol) were dispersed in 40 mL of deionized water and stirred at 60 °C for 2 hours. After uniform dispersion, 100 g of ethanol and 100 g of menthol were added, and the temperature was raised to 100 °C. The reaction was allowed to react for 4 hours. The reaction was monitored by gas chromatography. The conversion rate of D-menthol was 96.3%, and the selectivity of L-menthol was 97.2%.

[0105] Embodiment 24

[0106] In a 500 mL autoclave, PdCl2 (1.773 g, 0.01 mol), FeCl3·6H2O (13.52 g, 0.05 mol), and L1 ligand (0.05 mol) were dispersed in 40 mL of deionized water and stirred at 60 °C for 2 hours. After uniform dispersion, 100 g of ethanol and 100 g of menthol were added, and the temperature was raised to 100 °C. The reaction was allowed to proceed for 4 hours. The reaction was monitored by gas chromatography. The conversion rate of D-menthol was 97.1%, and the selectivity of L-menthol was 97.8%.

[0107] Embodiment 25

[0108] In a 500 mL autoclave, PdCl2 (1.773 g, 0.01 mol), FeCl3·6H2O (13.52 g, 0.05 mol), and L1 ligand (0.15 mol) were dispersed in 40 mL of deionized water and stirred at 60 °C for 2 hours. After uniform dispersion, 100 g of ethanol and 100 g of menthol were added, and the temperature was raised to 100 °C. The reaction was allowed to proceed for 4 hours. The reaction was monitored by gas chromatography. The conversion rate of D-menthol was 99.5%, and the selectivity of L-menthol was 99.6%.

[0109] Embodiment 26

[0110] In a 500 mL autoclave, PdCl2 (1.773 g, 0.01 mol), FeCl3·6H2O (13.52 g, 0.05 mol), and L1 ligand (0.175 mol) were dispersed in 40 mL of deionized water and stirred at 60 °C for 2 hours. After uniform dispersion, 100 g of ethanol and 100 g of menthol were added, and the temperature was raised to 100 °C. The reaction was allowed to proceed for 4 hours. The reaction was monitored by gas chromatography. The conversion rate of D-menthol was 99.5%, and the selectivity of L-menthol was 99.6%.

[0111] Embodiment 27

[0112] In a 500 mL autoclave, PdCl2 (1.773 g, 0.01 mol), FeCl3·6H2O (13.52 g, 0.05 mol), and L1 ligand (0.2 mol) were dispersed in 40 mL of deionized water and stirred at 60 °C for 2 hours. After uniform dispersion, 100 g of ethanol and 100 g of menthol were added, and the temperature was raised to 100 °C. The reaction was allowed to react for 4 hours. The reaction was monitored by gas chromatography. The conversion rate of D-menthol was 99.6%, and the selectivity of L-menthol was 99.2%.

[0113] Embodiment 28

[0114] In a 500 mL autoclave, PdCl2 (1.773 g, 0.01 mol), FeCl3·6H2O (13.52 g, 0.05 mol), and L2 ligand (0.1 mol) were dispersed in 40 mL of deionized water and stirred at 60 °C for 2 hours. After uniform dispersion, 100 g of ethanol and 100 g of menthol were added, and the temperature was raised to 100 °C. The reaction was allowed to proceed for 4 hours. The reaction was monitored by gas chromatography. The conversion rate of D-menthol was 99.3%, and the selectivity of L-menthol was 99.2%.

[0115] Embodiment 29

[0116] In a 500 mL autoclave, PdCl2 (1.773 g, 0.01 mol), FeCl3·6H2O (13.52 g, 0.05 mol), and L3 ligand (0.1 mol) were dispersed in 40 mL of deionized water and stirred at 60 °C for 2 hours. After uniform dispersion, 100 g of ethanol and 100 g of menthol were added, and the temperature was raised to 100 °C. The reaction was allowed to proceed for 4 hours. The reaction was monitored by gas chromatography. The conversion rate of D-menthol was 99.2%, and the selectivity of L-menthol was 99.4%.

[0117] Embodiment 30

[0118] In a 500 mL autoclave, PdCl2 (1.773 g, 0.01 mol), FeCl3·6H2O (13.52 g, 0.05 mol), and L4 ligand (0.1 mol) were dispersed in 40 mL of deionized water and stirred at 60 °C for 2 hours. After uniform dispersion, 100 g of ethanol and 100 g of menthol were added, and the temperature was raised to 100 °C. The reaction was allowed to proceed for 4 hours. The reaction was monitored by gas chromatography. The conversion rate of D-menthol was 99.3%, and the selectivity of L-menthol was 99.3%.

[0119] Embodiment 31

[0120] In a 500 mL autoclave, PdCl2 (1.773 g, 0.01 mol), FeCl3·6H2O (13.52 g, 0.05 mol), and L5 ligand (0.1 mol) were dispersed in 40 mL of deionized water and stirred at 60 °C for 2 hours. After uniform dispersion, 100 g of ethanol and 100 g of menthol were added, and the temperature was raised to 100 °C. The reaction was allowed to proceed for 4 hours. The reaction was monitored by gas chromatography. The conversion rate of D-menthol was 99.1%, and the selectivity of L-menthol was 99.2%.

[0121] Embodiment 32

[0122] In a 500 mL autoclave, PdCl2 (1.773 g, 0.01 mol), FeCl3·6H2O (13.52 g, 0.05 mol), and L6 ligand (0.1 mol) were dispersed in 40 mL of deionized water and stirred at 60 °C for 2 hours. After uniform dispersion, 100 g of ethanol and 100 g of menthol were added, and the temperature was raised to 100 °C. The reaction was allowed to proceed for 4 hours. The reaction was monitored by gas chromatography. The conversion rate of D-menthol was 99.3%, and the selectivity of L-menthol was 99.4%.

[0123] Embodiment 33

[0124] In a 500 mL autoclave, PdCl2 (1.773 g, 0.01 mol), FeCl3·6H2O (13.52 g, 0.05 mol), and L7 ligand (0.1 mol) were dispersed in 40 mL of deionized water and stirred at 60 °C for 2 hours. After uniform dispersion, 100 g of ethanol and 100 g of menthol were added, and the temperature was raised to 100 °C. The reaction was allowed to react for 4 hours. The reaction was monitored by gas chromatography. The conversion rate of D-menthol was 99.0%, and the selectivity of L-menthol was 99.2%.

[0125] Embodiment 34

[0126] In a 500 mL autoclave, PdCl2 (1.773 g, 0.01 mol), RhCl3·3H2O (13.17 g, 0.05 mol), and L8 ligand (0.1 mol) were dispersed in 40 mL of deionized water and stirred at 60 °C for 2 hours. After uniform dispersion, 100 g of ethanol and 100 g of menthol were added, and the temperature was raised to 100 °C. The reaction was allowed to proceed for 4 hours. The reaction was monitored by gas chromatography. The conversion rate of D-menthol was 99.5%, and the selectivity of L-menthol was 99.6%.

[0127] Embodiment 35

[0128] In a 500 mL autoclave, Pd(PPh3)2Cl2 (7.019 g, 0.01 mol), IrCl3·3H2O (17.63 g, 0.05 mol), and L9 ligand (0.1 mol) were dispersed in 40 mL of deionized water and stirred at 60 °C for 2 hours. After uniform dispersion, 100 g of ethanol and 100 g of menthol were added, the temperature was raised to 100 °C, and the reaction was carried out for 4 hours. The reaction was monitored by gas chromatography. The conversion rate of D-menthol was 99.6%, and the selectivity of L-menthol was 99.4%.

[0129] Embodiment 36

[0130] In a 500 mL autoclave, Pd(PCy3)2Cl2 (7.382 g, 0.01 mol), K2PtCl6 (24.30 g, 0.05 mol), and L10 ligand (0.1 mol) were dispersed in 40 mL of deionized water and stirred at 60 °C for 2 hours. After uniform dispersion, 100 g of ethanol and 100 g of menthol were added, the temperature was raised to 100 °C, and the reaction was carried out for 4 hours. The reaction was monitored by gas chromatography. The conversion rate of D-menthol was 99.3%, and the selectivity of L-menthol was 99.5%.

[0131] Embodiment 37

[0132] In a 500 mL autoclave, Pd(NO3)2·2H2O (2.665 g, 0.01 mol), FeCl3·6H2O (13.52 g, 0.05 mol), and L11 ligand (0.1 mol) were dispersed in 40 mL of deionized water and stirred at 60 °C for 2 hours. After uniform dispersion, 100 g of ethanol and 100 g of menthol were added, the temperature was raised to 100 °C, and the reaction was carried out for 4 hours. The reaction was monitored by gas chromatography. The conversion rate of D-menthol was 99.4%, and the selectivity of L-menthol was 99.6%.

[0133] Embodiment 38

[0134] In a 500 mL autoclave, PdSO4·2H2O (2.385 g, 0.01 mol), Zn(NO3)2·6H2O (14.87 g, 0.05 mol), and L12 ligand (0.1 mol) were dispersed in 40 mL of deionized water and stirred at 60 °C for 2 hours. After uniform dispersion, 100 g of ethanol and 100 g of menthol were added, the temperature was raised to 100 °C, and the reaction was carried out for 4 hours. The reaction was monitored by gas chromatography. The conversion rate of D-menthol was 99.2%, and the selectivity of L-menthol was 99.6%.

[0135] Embodiment 39

[0136] In a 500 mL autoclave, Pd(acac)2 (3.046 g, 0.01 mol), CuSO4·5H2O (12.48 g, 0.05 mol), and L13 ligand (0.1 mol) were dispersed in 40 mL of deionized water and stirred at 60 °C for 2 hours. After uniform dispersion, 100 g of ethanol and 100 g of menthol were added, and the temperature was raised to 100 °C. The reaction was allowed to proceed for 4 hours. The reaction was monitored by gas chromatography. The conversion rate of D-menthol was 99.4%, and the selectivity of L-menthol was 99.5%.

[0137] Embodiment 40

[0138] In a 500 mL autoclave, PdCl2(N4H8)2 (2.975 g, 0.01 mol), NiSO4·6H2O (13.14 g, 0.05 mol), and L14 ligand (0.1 mol) were dispersed in 40 mL of deionized water and stirred at 60 °C for 2 hours. After uniform dispersion, 100 g of ethanol and 100 g of menthol were added, and the temperature was raised to 100 °C. The reaction was allowed to proceed for 4 hours. The reaction was monitored by gas chromatography. The conversion rate of D-menthol was 99.2%, and the selectivity of L-menthol was 99.1%.

[0139] Embodiment 41

[0140] In a 500 mL autoclave, PdCl2 (1.773 g, 0.01 mol), FeCl3·6H2O (13.52 g, 0.05 mol), and L1 ligand (0.1 mol) were dispersed in 40 mL of deionized water and stirred at 60 °C for 2 hours. After uniform dispersion, 100 g of ethanol and 100 g of D-menthol were added, and the temperature was raised to 100 °C. The reaction was allowed to proceed for 5 hours. The reaction was monitored by gas chromatography. The conversion rate of D-menthol was 99.5%, and the selectivity of L-menthol was 99.6%.

[0141] Catalyst Application

[0142] After the reaction in Example 5 was completed, the reaction liquid was pressed out, the catalyst was separated by reduced pressure distillation, and it was dispersed in the recovered ethanol, and then put back into the high-pressure reactor, and 100g of menthol was added. The other operations were the same as in Example 5. The experimental results are shown in Table 1.

[0143] Table 1

[0144]

[0145] It can be seen that when the sixth batch was applied, the conversion rate of D-menthol decreased by 1.6%, and the selectivity of L-menthol decreased by 0.8%. It is speculated that this may be due to the trace loss of the ligand.

[0146] Comparative Example 1

[0147] In a 500 mL autoclave, PdCl2 (1.773 g, 0.01 mol) and L1 ligand (0.02 mol) were dispersed in 40 mL of deionized water and stirred at 60 °C for 2 hours. After uniform dispersion, 100 g of ethanol and 100 g of menthol were added, the temperature was raised to 100 °C, and the reaction was carried out for 4 hours. The reaction was monitored by gas chromatography. The conversion rate of D-menthol was 74.6%, and the selectivity of L-menthol was 80.1%.

[0148] Comparative Example 2

[0149] In a 500 mL autoclave, FeCl3·6H2O (13.52 g, 0.05 mol) and L1 ligand (0.1 mol) were dispersed in 40 mL of deionized water and stirred at 60 °C for 2 h. After uniform dispersion, 100 g of ethanol and 100 g of menthol were added, and the temperature was raised to 100 °C. The reaction was allowed to proceed for 4 h. The reaction was monitored by gas chromatography. The conversion of D-menthol was 58.3%, and the selectivity of L-menthol was 72.5%.

[0150] Comparative Example 3

[0151] In a 500 mL autoclave, PdCl2 (1.773 g, 0.01 mol), FeCl3·6H2O (13.52 g, 0.05 mol), and (R)-BINOL ligand (0.1 mol) were dispersed in 40 mL of deionized water and stirred at 60 °C for 2 h. After uniform dispersion, 100 g of ethanol and 100 g of menthol were added, and the temperature was raised to 100 °C. The reaction was allowed to react for 4 h. The reaction was monitored by gas chromatography. The conversion rate of D-menthol was 85.6%, and the selectivity of L-menthol was 76.2%.

[0152] The applicant declares that the present invention illustrates the detailed structural features of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned detailed structural features, that is, it does not mean that the present invention must rely on the above-mentioned detailed structural features to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the components selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0153] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0154] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0155] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A palladium-containing catalyst for isomerization of D-menthol to obtain L-menthol, characterized in that: comprising a first active metal, a second active metal and a chiral phosphate ligand; The first active metal is palladium; The second active metal is one, two or more of rhodium, iridium, platinum, zinc, iron, copper, nickel and ruthenium; The chiral phosphate ligand is one of a chiral monophosphate ligand or a chiral diphosphate ligand; The chiral monophosphate ligand structure is as follows: ； Wherein, R is one or two of H, substituted or unsubstituted phenyl or condensed aromatic hydrocarbons, and the substituent on the phenyl is one or more of C1~C4 alkyl or C1~C4 alkoxy; The structure of the chiral bisphosphate ligand is shown in Formula 1 or Formula 2: General formula 1: ； In general formula 1, R1 and R2 are one or two of substituted or unsubstituted phenyl groups, and the substituent on the phenyl group is one or more of C1-C6 alkyl or halogen; General formula 2: ； In general formula 2, R1 and R2 are one or two of substituted or unsubstituted phenyl groups, and the substituent on the phenyl group is one or more of C1~C6 alkyl, C5~C6 cycloalkyl or tolyl.

2. The palladium-containing catalyst for isomerization of D-menthol to obtain L-menthol according to claim 1, characterized in that: The chiral phosphate ligand is one of L1 to L14, and the structural formula is as follows: ； ； ； 。 3. A method for preparing a palladium-containing catalyst as claimed in claim 1 or 2, characterized in that: The following steps are involved: Mixing a first active metal source, a second active metal source, a chiral phosphate ligand and a first solvent, and stirring to obtain the palladium-containing catalyst; The first active metal source includes a palladium salt and / or a palladium complex; The second active metal source includes any one of a nitrate, a sulfate, a chloride, an acetate, a hydroxide or a hydrate thereof of the second active metal, or a combination of at least two thereof.

4. The preparation method of the palladium-containing catalyst according to claim 3, wherein The first active metal source includes one, two or more of PdCl2, Pd(PPh3)2Cl2, Pd(PCy3)2Cl2, Pd(NO3)2·2H2O, PdSO4·2H2O, and Pd(acac)2.

5. The preparation method of the palladium-containing catalyst according to claim 3, characterized in that The first solvent is water.

6. The method for preparing a palladium-containing catalyst according to claim 3, wherein The molar ratio of the first active metal source to the second active metal source is 1:1-7; The molar ratio of the second active metal source to the chiral phosphate ligand is 1:0.5-4.

0.

7. A method for preparing L-menthol, characterized in that: include: Mixing the reaction substrate with the palladium-containing catalyst according to claim 1 or 2 or the palladium-containing catalyst obtained by the preparation method according to any one of claims 3 to 6, and then performing an asymmetric isomerization reaction to obtain L-menthol; The reaction substrate is D-menthol.

8. The method for preparing L-menthol according to claim 7, characterized in that: The molar ratio of the reaction substrate to the palladium-containing catalyst is 1:0.01-0.

1.

9. The method for preparing L-menthol according to claim 7, characterized in that: The temperature of the asymmetric isomerization reaction is 80-160° C., and the time of the asymmetric isomerization reaction is 3.0-6.0 h.

10. The method for preparing L-menthol according to claim 7, characterized in that: The asymmetric isomerization reaction is carried out in a second solvent or in the absence of a solvent; The second solvent includes any one of methanol, ethanol, isopropanol or water, or a combination of at least two thereof; The mass ratio of the reaction substrate to the second solvent is 1:1.0-4.0.

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