Menthol optical isomerization catalyst and preparation method, menthol catalytic transposition method and method for preparing menthone by dehydrogenation

Abstract

The present invention provides a menthol optical isomerization catalyst and a preparation method, a menthol catalytic transposition method and a method for preparing menthone by dehydrogenation. The menthol optical isomerization catalyst includes a carrier and a transition metal loaded on the carrier, and the carrier is a nitrogen-doped porous carbon material. In terms of mass percentage, the nitrogen content in the nitrogen-doped porous carbon material is 0.01%-0.2%. The present invention uses a nitrogen-doped porous carbon material with a specific nitrogen content as a carrier, utilizes the chelation effect of the lone electron of the nitrogen atom to the transition metal, improves the dispersion and stability of the transition metal in the porous carbon material, and simultaneously utilizes the nitrogen-doped porous carbon material and the loaded transition metal to cooperate with each other, thereby improving the selectivity of the catalyst, and can significantly improve the menthol stereoisomerization transposition efficiency under mild reaction conditions.

Description

Technical Field

[0001] The invention relates to the technical field of menthol catalysts, and in particular to a menthol optical isomerization catalyst and a preparation method thereof, a menthol catalytic transposition method and a method for preparing menthone by dehydrogenation. Background Art

[0002] Menthol is a cyclic monoterpene compound and an important flavor. The main body of the menthol molecule is cyclohexane. When the three substituents of cyclohexane, methyl, hydroxyl and isopropyl, are in a relatively stable transverse bond, it is ortho-menthol (also known as menthol). The thermodynamic stability of ortho-menthol makes the content of ortho-menthol in the synthesis of menthol and the subsequent stereotransposition of isomers in a better state. Ortho-menthol is divided into left-handed menthol and right-handed menthol. Among them, left-handed menthol has a refreshing and cool smell and is widely used in cosmetics, toothpaste, medicine and other fields. It has great commercial value, while right-handed menthol has a lower commercial value.

[0003] At present, the world's menthol mainly comes from the extraction of natural menthol, but due to climate uncertainty, the stable production of natural menthol cannot be guaranteed, and the total production of natural menthol cannot meet people's daily needs for menthol. Therefore, seeking an efficient and stable chemical synthesis method to produce L-menthol to make up for the shortage of natural menthol has become a good solution. Menthol has three chiral centers and eight stereoisomers. Since only L-menthol can be used in daily life, choosing a suitable catalyst to stereoisomerize menthol of other configurations into L-menthol is an important step in chemical synthesis.

[0004] In view of this, the present invention is proposed. Summary of the invention

[0005] The main purpose of the present invention is to provide a menthol optical isomerization catalyst and a preparation method, a menthol catalytic transposition method and a method for preparing menthone by dehydrogenation, so as to increase the yield of L-menthol.

[0006] In order to achieve the above-mentioned purpose, according to one aspect of the present invention, a menthol optical isomerization catalyst is provided, which comprises a carrier and a transition metal supported on the carrier, wherein the carrier is a nitrogen-doped porous carbon material, and the nitrogen content in the nitrogen-doped porous carbon material is 0.05%-0.181% by mass.

[0007] Furthermore, the transition metal is selected from at least one of nickel, iron, cobalt, copper, manganese or titanium.

[0008] Furthermore, the above transition metals include nickel, iron and titanium.

[0009] Furthermore, in terms of mass percentage, the nickel content in the above catalyst is 3%-7.5%, preferably 4%-5.5%.

[0010] Furthermore, the iron content is 1%-5%, preferably 1.2%-3%.

[0011] Furthermore, the titanium content is 0.01%-1%, preferably 0.03%-0.3%.

[0012] Furthermore, the specific surface area of ​​the nitrogen-doped porous carbon material is 402-732 m 2 / g, preferably 517-728m 2 / g.

[0013] Furthermore, the nitrogen-doped porous carbon material is prepared by mixing chitosan and salt and then performing a first calcination in nitrogen or an inert gas.

[0014] Furthermore, the mass ratio of chitosan to salt is (15-25):10, preferably (18-22):10.

[0015] Furthermore, the above-mentioned salt includes at least one of sodium bicarbonate, sodium chloride, potassium chloride or sodium carbonate.

[0016] Furthermore, the first calcination comprises the following steps:

[0017] S1, heating the mixture of chitosan and salt to 250-350°C, keeping the temperature for 55-65 minutes, to obtain an initial calcined product, preferably at a heating rate of 4.5-5.5°C / min;

[0018] S2, heating the above-mentioned initial calcined product to 750-850°C, keeping the temperature for 1.5-2.5h to obtain a roasted product, preferably with a heating rate of 4.5-5.5°C / min;

[0019] S3, cooling and washing the calcined product to obtain a nitrogen-doped porous carbon material.

[0020] According to another aspect of the present invention, a method for preparing the above-mentioned menthol optical isomerization catalyst is provided, and the preparation method comprises the following steps:

[0021] A, mixing raw materials including a soluble transition metal salt, a nitrogen-doped porous carbon material, water, and a pH adjuster to form a mixed system with a pH of 8.0-9.0;

[0022] B, aging the mixed system for 18-30 hours and then separating the solid and the liquid to obtain a catalyst precursor, wherein the preferred aging time is 18-22 hours;

[0023] C, the catalyst precursor is subjected to a second calcination under a mixed gas condition formed by nitrogen and hydrogen to obtain a menthol optical isomerization catalyst, and the second calcination temperature is preferably 500-800° C. and the time is 1.5-2.5 h.

[0024] Furthermore, in the mixed gas, the volume ratio of nitrogen to hydrogen is (1.5-2.5):1, preferably 2:1;

[0025] Furthermore, the heating rate of the catalyst precursor to the second calcination is 4.5-5.5°C / min.

[0026] According to a third aspect of the present invention, a method for catalytic transposition of menthol is provided, comprising catalytic transposition of isomenthol to ortho-menthol, catalytic transposition of neomenthol to ortho-menthol, or catalytic transposition of dextro-menthol to levo-menthol.

[0027] Further, the temperature of the catalytic translocation is 50-180°C, preferably 110-150°C, and the time of the catalytic translocation is 5-7h, preferably 5.5-6.5h;

[0028] Furthermore, hydrogen is introduced during the catalytic transposition process, and the hydrogen pressure is 1-50 bar, preferably 1-10 bar.

[0029] According to a fourth aspect of the present invention, there is provided a method for preparing menthone by catalytic dehydrogenation of menthol, wherein the catalyst used in the method is any one of the above-mentioned menthol optical isomerization catalysts.

[0030] Furthermore, the temperature for dehydrogenating menthol to prepare menthone is 150-210° C., preferably 160-200° C.;

[0031] Furthermore, inert gas or nitrogen is introduced as protective gas during the process of dehydrogenating menthol to prepare menthone.

[0032] By applying the technical solution of the present invention, a nitrogen-doped porous carbon material with a specific nitrogen content is used as a carrier, and the chelation effect of the lone electron of the nitrogen atom on the transition metal is utilized to improve the dispersion and stability of the transition metal in the porous carbon material. At the same time, the nitrogen-doped porous carbon material and the loaded transition metal cooperate with each other to improve the selectivity of the catalyst, and the stereoisomerization efficiency of menthol can be significantly improved under mild reaction conditions. DETAILED DESCRIPTION

[0033] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below in conjunction with the embodiments.

[0034] As analyzed in the background technology of this application, the existing chemically synthesized menthol has three chiral centers and eight stereoisomers, and it is necessary to select a suitable catalyst to stereoisomerize menthol of other configurations into L-menthol. In order to solve this problem, this application provides a menthol optical isomerization catalyst and preparation method, menthol catalytic transposition method and dehydrogenation method for preparing menthone.

[0035] In a typical embodiment of the present application, a menthol optical isomerization catalyst is provided, which includes a carrier and a transition metal supported on the carrier, the carrier is a nitrogen-doped porous carbon material, and the nitrogen content in the nitrogen-doped porous carbon material is 0.05%-0.181% by mass.

[0036] The transition metal includes any transition metal element, or an alloy or composite formed by at least two different transition metals, which can be loaded on the carrier in any form, including but not limited to forming a continuously distributed transition metal layer, forming a discontinuously distributed flake or dot transition metal, and forming granular transition metal particles.

[0037] Nitrogen-doped porous carbon materials are new materials produced by connecting or combining nitrogen atoms into the skeleton of carbon materials through chemical bonds. Since the sizes of nitrogen and carbon atoms are similar, the degree of destruction of the skeleton structure of the carbon material is small during the process of nitrogen atoms replacing carbon atoms, and the stability of the porous carbon material can be maintained. In addition, on the one hand, the introduction of nitrogen components can effectively regulate the overall acid-base properties and wettability, and improve its ability to activate reactant or product molecules. On the other hand, the presence of five available valence electrons in nitrogen is conducive to the interaction between nitrogen and transition metals, improving the dispersion and stability of transition metals in porous carbon materials and improving catalytic performance.

[0038] In addition, the nitrogen content will affect the performance of the catalyst. If the nitrogen content is too high, the overall skeleton structure of the porous carbon material will collapse, the number of defects will increase, and the stability of the catalyst will be affected. If the nitrogen content is too low, the wettability and activation ability of the reactants will be reduced, affecting the catalytic performance.

[0039] The present application adopts a nitrogen-doped porous carbon material with a specific nitrogen content as a carrier, and utilizes the chelation effect of the lone electron of the nitrogen atom on the transition metal to improve the dispersion and stability of the transition metal in the porous carbon material. At the same time, the nitrogen-doped porous carbon material and the loaded transition metal cooperate with each other to improve the selectivity of the catalyst, and can significantly improve the stereoisomerization efficiency of menthol under mild reaction conditions.

[0040] Typically but not limiting, in terms of mass percentage, the nitrogen content in the nitrogen-doped porous carbon material is 0.05%, 0.08%, 0.1%, 0.12%, 0.15%, 0.18% or 0.181%.

[0041] In some embodiments of the present application, the transition metal is selected from a single substance or an alloy or a complex formed by several single substances of any one of nickel, iron, cobalt, copper or titanium. In particular, when the transition metal includes nickel, iron and titanium, the porous carbon material doped with nickel, iron, titanium and nitrogen cooperates with each other, and the catalyst has higher selectivity, which is more conducive to improving the stereoisomerization efficiency of menthol under mild reaction conditions.

[0042] In addition, the catalytic performance of the catalyst is affected by the nickel content, iron content and titanium content. The catalytic activity of the catalyst is different when the nickel content, iron content and titanium content are different. In terms of mass percentage, in the catalyst, when the nickel content is 3%-7.5%, the iron content is 1%-5%, and the titanium content is 0.01-1%, the synergistic effect of the transition metal and the nitrogen-doped porous carbon material is obvious, and the catalytic property of the catalyst is excellent, especially when the nickel content is 1.4%-6%, the iron content is 1.1%-5%, and the titanium content is 0.03-0.4%, the synergistic effect of the transition metal and the nitrogen-doped porous carbon material is obviously more prominent, the catalyst has higher activity, and can further improve the efficiency of menthol stereoisomerization transposition.

[0043] Typically, but not limiting, in terms of mass percentage, the nickel content in the catalyst is 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7% or 7.5%, the iron content is 1%, 1.1%, 1.5%, 2%, 3%, 4% or 5%, and the titanium content is 0.01%, 0.03%, 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.4%, 0.5%, 0.8% or 1%.

[0044] The catalyst provided in the present application uses nitrogen-doped porous carbon material as a carrier of transition metals. The carrier has a loose and porous structure. Carriers with different specific surface areas have different loading capacities for transition metals. When the specific surface area is large, the transition metal can be well loaded evenly on the carrier surface. The specific surface area of ​​the carrier is preferably 402-732 m 2 / g, which is beneficial to improve the dispersion and stability of transition metal loading on the carrier surface, especially when the specific area of ​​the carrier is 517-728m 2 / g, the dispersion and stability of the transition metal loaded on the carrier surface are better, which is more conducive to improving the catalytic activity and stability of the catalyst.

[0045] In some embodiments of the present application, the nitrogen-doped porous carbon material is prepared by mixing chitosan and salt and then calcining in nitrogen or inert gas. Chitosan is selected as the raw material, and the chitosan molecule contains nitrogen and carbon elements. After the first calcination, the nitrogen-doped porous carbon material with nitrogen uniformly distributed in the porous carbon material can be obtained. Compared with introducing nitrogen atoms into the porous carbon material by adding organic compounds with high nitrogen content such as urea and melamine, the process is simpler and more conducive to the uniform distribution of nitrogen in the porous carbon material.

[0046] The porosity in the porous carbon material can be regulated by controlling the mass ratio of chitosan and salt. Preferably, when the mass ratio of chitosan and salt is (15-25):10, the porosity of the nitrogen-doped porous material obtained by the first calcination is moderate, which is beneficial to improving the catalytic activity of the catalyst. Especially when the mass ratio of chitosan and salt is (18-24):10, the porosity of the nitrogen-doped porous material obtained by the first calcination is more moderate and the catalytic activity of the catalyst is also higher.

[0047] Typically, but not limiting, the mass ratio of chitosan to salt is, for example, 15:10, 18:10, 20:10, 22:10 or 25:10.

[0048] The above salt is not particularly limited as long as it is a soluble salt. For example, the salt includes but is not limited to any one or a mixture of sodium bicarbonate, sodium chloride, potassium chloride or sodium carbonate.

[0049] In some embodiments of the present application, the first calcination comprises the following steps:

[0050] S1, heating the mixture of chitosan and salt to 250-350°C and keeping the temperature for 55-65 minutes to obtain an initial calcined product;

[0051] S2, heating the initial calcined product to 750-850°C and keeping the temperature for 1.5-2.5 hours to obtain a calcined product;

[0052] S3, cooling and washing the calcined product to obtain a nitrogen-doped porous carbon material. The calcined product is washed to remove the salt from the calcined product to form a nitrogen-doped porous carbon material with a porous structure.

[0053] In the above steps S1 and S2, the mixture of chitosan and salt is first calcined at low temperature to produce a dehydration reaction so that the carrier structure can be quickly fixed; then it is calcined at high temperature to further crack and remove oxygen atoms in the material, thereby increasing the carbon content of the carrier, which is more conducive to the generation of nitrogen-doped porous carbon materials with stable properties.

[0054] Preferably, the heating rate is controlled to be 4.5-5.5° C. / min in both steps S1 and S2 to ensure the stability of the heating process, facilitate the interaction between chitosan and salt, and subsequently generate nitrogen-doped porous carbon materials with stable performance.

[0055] In the above step S3, the cooling method is not limited, as long as the calcined product can be cooled, such as natural cooling, air cooling or water cooling, preferably natural cooling, which is beneficial to improving the stability of the nitrogen-doped porous carbon material. If the calcined product needs to be washed repeatedly for many times to remove the salt, the calcined product can be ground and then washed to reduce the number of washing times.

[0056] Typically but not limitatively, in the above step S1, the calcination temperature is 250°C, 280°C, 300°C, 320°C or 350°C, and the insulation time is 55min, 58min, 60min, 62min or 65min; in the above step S2, the calcination temperature is 750°C, 780°C, 800°C, 820°C or 850°C, and the calcination time is 1.5h, 1.8h, 2h, 2.2h or 2.5h; the heating rates of the above steps S1 and S2 are independently 4.5°C / min, 4.8°C / min, 5°C / min, 5.2°C / min or 5.5°C / min.

[0057] In another typical embodiment of the present application, a method for preparing the above-mentioned menthol optical isomerization catalyst is provided, and the preparation method comprises the following steps:

[0058] A, mixing raw materials including a soluble transition metal salt, a nitrogen-doped porous carbon material, water, and a pH adjuster to form a mixed system with a pH of 8.0-9.0;

[0059] B. After aging the mixed system for 18-30 hours, solid-liquid separation is performed to obtain a catalyst precursor, so as to facilitate sufficient loading of the transition metal salt on the nitrogen-doped porous carbon material, especially when the aging time is 18-22 hours, the transition metal salt is more fully loaded on the nitrogen-doped porous carbon material;

[0060] C. The catalyst precursor is subjected to a second calcination under a mixed gas condition formed by nitrogen and hydrogen to obtain a menthol optical isomerization catalyst.

[0061] The pH value that the above-mentioned steps A controls the mixed system is 8.0-9.0, and under weakly alkaline conditions, the above-mentioned soluble transition metal salt is gradually precipitated on the nitrogen-doped porous carbon material in the form of hydroxide through aging, and the transition metal salt is fully utilized. The second calcination is carried out under the mixed gas formed by nitrogen and hydrogen, and on the one hand, the transition metal salt in the catalyst can be reduced to a transition metal element, and on the other hand, it is also possible to avoid introducing impurities into the catalyst, affecting the catalytic performance of the catalyst. In the mixed gas, the volume ratio of preferably nitrogen and hydrogen is (1.5-2.5): 1, which is beneficial to ensure that the transition metal salt is reduced fully in the second calcination process, especially when the volume ratio of nitrogen and hydrogen is 2: 1, it is more beneficial to the reduction reaction in the second calcination process to be carried out more fully.

[0062] In the above step C, the second calcination temperature is preferably 500-800°C and the time is 1.5-2.5h, so as to facilitate more complete calcination and avoid damage to the nitrogen-doped porous carbon structure that has been formed. The heating rate of the catalyst precursor to the second calcination is preferably 4.5-5.5°C / min, so as to improve the stability of the generated catalyst.

[0063] In the above step A, the transition metal salt comes from various transition metal-containing compounds, for example, the nickel salt comes from nickel compounds, such as nickel chloride or nickel acetate; the iron salt comes from iron compounds, such as ferric chloride, ferric nitrate or ferric sulfate; the pH adjuster comes from various compounds capable of adjusting pH, including but not limited to ammonia water or sodium hydroxide.

[0064] Typically but not limiting, in the above step A, the pH of the mixed system is 8.0, 8.2, 8.5, 8.8 or 9.0; in the above step B, the aging time of the mixed system is 18h, 19h, 20h, 21h, 22h, 25h, 28h or 30h; in the above step C, the second calcination temperature is 500℃, 550℃, 600℃, 650℃, 700℃, 750℃ or 800℃, and the time is 1.5h, 1.8h, 2h, 2.2h or 2.5h; the heating rate of the catalyst precursor to the second calcination is 4.5℃ / min, 4.8℃ / min, 5℃ / min, 5.2℃ / min or 5.5℃ / min.

[0065] In a third typical embodiment of the present application, a menthol catalytic transposition method is provided, and the catalyst used in the menthol catalytic transposition method is the menthol optical isomerization catalyst provided in the first typical embodiment of the present application.

[0066] The menthol optical isomerization catalyst provided by the present application is used to carry out the catalytic transposition of menthol. The catalyst has high selectivity and can significantly improve the efficiency of the stereoisomerization transposition of menthol under mild reaction conditions.

[0067] The above-mentioned catalytic transposition method includes but is not limited to the catalytic transposition of isomenthol into ortho-menthol, the catalytic transposition of neomenthol into ortho-menthol, or the catalytic transposition of dextro-menthol into levo-menthol.

[0068] The above catalytic translocation can be carried out under relatively mild reaction conditions, such as a catalytic translocation temperature of 50-180° C. and a time of 5-7 hours, which is conducive to overcoming the limitations of high temperature and high pressure conditions and promoting the development of the menthol chemical synthesis industry. In particular, when the catalytic translocation temperature is 110-150° C. and the time is 5.5-6.5 hours, it is more conducive to improving the catalytic translocation efficiency of menthol by controlling the process conditions of the catalytic translocation of menthol.

[0069] Typically, but not limiting, the catalytic translocation temperature is 50°C, 80°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C or 180°C, and the time is 5h, 5.5h, 6h, 6.5h or 7h.

[0070] In some embodiments of the present application, hydrogen is introduced during the catalytic transposition process. When the hydrogen pressure is 1-50 bar, it is beneficial to promote the catalytic transposition reaction. Preferably, the catalytic transposition is carried out at a hydrogen pressure of 1-10 bar, which is more conducive to the control of reaction conditions.

[0071] Typically, but not limiting, during the catalytic metathesis process, the hydrogen pressure is 1 bar, 2 bar, 5 bar, 8 bar, 10 bar, 20 bar, 30 bar, 40 bar or 50 bar.

[0072] In a fourth typical embodiment of the present application, a method for preparing menthone by catalytic dehydrogenation of menthol is provided, wherein the catalyst used in the method is the menthol optical isomerization catalyst provided in the first typical embodiment of the present application.

[0073] The menthol optical isomerization catalyst provided in the present application can catalyze the dehydrogenation of menthol to prepare menthone under mild reaction conditions, which is beneficial to improving the conversion efficiency of menthone.

[0074] In some embodiments of the present application, when the temperature of menthol dehydrogenation to prepare menthone is 150-210° C., menthol can be catalytically dehydrogenated to form menthone. In particular, when the temperature is 160-200° C., it is more conducive to improving the catalytic efficiency of menthol dehydrogenation to form menthone.

[0075] Typically, but not limiting, the temperature for dehydrogenation of menthol to produce menthone is 150°C, 160°C, 170°C, 180°C, 190°C, 200°C or 210°C.

[0076] In some embodiments of the present application, an inert gas or nitrogen is introduced as a protective gas during the dehydrogenation of menthol to prepare menthone to prevent impurity gases from affecting the catalytic effect of the catalyst. Preferably, the protective gas is nitrogen, which is beneficial to reduce costs while protecting the catalytic reaction.

[0077] The beneficial effects of the present application will be further illustrated below in combination with embodiments and comparative examples.

[0078] It should be noted that “%” in the following examples and comparative examples is an abbreviation of “wt %”.

[0079] Example 1

[0080] This embodiment provides a menthol optical isomerization catalyst, which includes a nitrogen-doped porous carbon material and nickel supported on the nitrogen-doped porous carbon material. The catalyst is prepared according to the following steps:

[0081] (1) Weigh 20 g of chitosan and 10 g of sodium bicarbonate and mix them thoroughly to form a mixture, then place the mixture in a tube furnace, heat the mixture to 300° C. at a heating rate of 5° C. / min under nitrogen protection, and keep the temperature for 1 hour, then heat the mixture to 800° C. at a heating rate of 5° C. / min and keep the temperature for 2 hours, and then naturally cool the mixture to room temperature to obtain a black solid, grind the black solid, and wash the ground black solid with water to remove unreacted salt therein, to obtain a nitrogen-doped porous carbon material, wherein the nitrogen content of the nitrogen-doped porous carbon material is 0.103%, and the specific surface area is 694 m 2 / g;

[0082] (2) Weigh 10 g of nitrogen-doped porous carbon material, 2 g of nickel nitrate, and 1.2 g of ferric nitrate nonahydrate in a round-bottom flask, add 10 mL of deionized water, stir the two salts at room temperature, add 10% ammonia water dropwise to adjust the pH to 8.0-9.0, and then add 0.1 g of titanium tetrachloride dropwise while continuing to stir to obtain a mixed system, let the mixed system stand for 20 hours, and filter to obtain a catalyst precursor;

[0083] (3) The catalyst precursor was transferred to a tube furnace under a mixed gas condition of nitrogen and hydrogen (volume ratio 1:1), and the temperature was raised to 600°C at a rate of 5°C / min and kept at that temperature for 2 hours for a second calcination, and then naturally cooled to room temperature to obtain a menthol optical isomerization catalyst. According to ICP detection, the nickel content of the catalyst was 4.91%, the iron content was 1.54%, and the titanium content was 0.12%.

[0084] Example 2

[0085] This embodiment provides a menthol optical isomerization catalyst, the structure of the catalyst is the same as that of embodiment 1, and the difference between the preparation method and embodiment 1 is that in step (2), the amount of titanium tetrachloride used is 0.4 g, and the remaining raw materials and preparation methods are the same as those of embodiment 1, which are not described here. According to ICP detection, the nickel content of the catalyst is 5.03%, the iron content is 1.52%, and the titanium content is 0.40%.

[0086] Example 3

[0087] This embodiment provides a menthol optical isomerization catalyst, the structure of the catalyst is the same as that of embodiment 1, and the difference between the preparation method and embodiment 1 is that in step (2), the amount of titanium tetrachloride used is 0.1g, and 0.05g of manganese acetate is added dropwise at the same time, and the remaining raw materials and preparation methods are the same as those of embodiment 1, which are not described here. According to ICP detection, the nickel content of the catalyst is 4.91%, the iron content is 1.53%, the titanium content is 0.13%, and the manganese content is 0.09%.

[0088] Example 4

[0089] This embodiment provides a menthol optical isomerization catalyst, the structure of the catalyst is the same as that of embodiment 1, and the difference between the preparation method and embodiment 1 is that in step (2), the amount of nickel nitrate is 3.1g, the amount of ferric nitrate nonahydrate is 0.8g, titanium tetrachloride is not added, and the remaining raw materials and preparation methods are the same as those of embodiment 1, which will not be described in detail. According to ICP detection, the nickel content of the catalyst is 7.64% and the iron content is 0.89%.

[0090] Example 5

[0091] This embodiment provides a menthol optical isomerization catalyst, the structure of the catalyst is the same as that of embodiment 1, and the difference between the preparation method and embodiment 1 is that in step (2), the amount of nickel nitrate is 1g, the amount of ferric nitrate nonahydrate is 3g, titanium tetrachloride is not added, and the remaining raw materials and preparation methods are the same as those of embodiment 1, which will not be described in detail. According to ICP detection, the nickel content of the catalyst is 2.45%, and the iron content is 3.84%.

[0092] Example 6

[0093] This embodiment provides a menthol optical isomerization catalyst, the structure of the catalyst is the same as that of embodiment 1, and the difference between the preparation method and embodiment 1 is that in step (2), sodium hydroxide is used to replace 10% ammonia water as a pH regulator to adjust the pH of the mixed system, and the remaining raw materials and preparation methods are the same as those of embodiment 1, which are not described here. According to ICP detection, the nickel content of the catalyst is 4.94%, the iron content is 1.54%, and the titanium content is 0.12%.

[0094] Example 7

[0095] This embodiment provides a menthol optical isomerization catalyst, the structure of the catalyst is the same as that of embodiment 1, and the difference between the preparation method and embodiment 1 is that in step (2), sodium carbonate is used to replace 10% ammonia water as a pH regulator to adjust the pH of the mixed system, and the remaining raw materials and preparation methods are the same as those of embodiment 1, which are not described here. According to ICP detection, the nickel content of the catalyst is 4.93%, the iron content is 1.55%, and the titanium content is 0.11%.

[0096] Example 8

[0097] This embodiment provides a menthol optical isomerization catalyst, the structure of the catalyst is the same as that of embodiment 1, and the difference between the preparation method and embodiment 1 is that in step (3), the temperature of the second calcination is 700°C, and the other raw materials and preparation methods are the same as those of embodiment 1, which are not described here. According to ICP detection, the nickel content of the catalyst is 4.94%, the iron content is 1.54%, and the titanium content is 0.12%.

[0098] Example 9

[0099] This embodiment provides a menthol optical isomerization catalyst, the structure of the catalyst is the same as that of embodiment 1, and the difference between the preparation method and embodiment 1 is that in step (3), the temperature of the second calcination is 800°C, and the other raw materials and preparation methods are the same as those of embodiment 1, which are not described here. According to ICP detection, the nickel content of the catalyst is 4.91%, the iron content is 1.54%, and the titanium content is 0.12%.

[0100] Example 10

[0101] This embodiment provides a menthol optical isomerization catalyst, the structure of the catalyst is the same as that of embodiment 3, and the difference between the preparation method and embodiment 3 is that in step (3), the temperature of the second calcination is 700°C, and the other raw materials and preparation methods are the same as those of embodiment 1, which are not described here. According to ICP detection, the nickel content of the catalyst is 4.91%, the iron content is 1.54%, the titanium content is 0.13%, and the manganese content is 0.09%.

[0102] Embodiment 11

[0103] This embodiment provides a menthol optical isomerization catalyst, the structure of the catalyst is the same as that of embodiment 3, and the difference between the preparation method and embodiment 3 is that in step (2), the amount of titanium tetrachloride used is 0.2g, and the other raw materials and preparation methods are the same as those of embodiment 3, and the other raw materials and preparation methods are the same as those of embodiment 1, which are not repeated here. According to ICP detection, the nickel content of the catalyst is 4.92%, the iron content is 1.53%, the titanium content is 0.22%, and the manganese content is 0.09%.

[0104] Example 12

[0105] This embodiment provides a menthol optical isomerization catalyst, the structure of the catalyst is the same as that of embodiment 10, and the difference between the preparation method and embodiment 10 is that in step (2), the amount of titanium tetrachloride used is 0.1g, and 0.05g of copper nitrate is added dropwise at the same time, and the remaining raw materials and preparation methods are the same as those of embodiment 1, which are not repeated here. According to ICP detection, the nickel content of the catalyst is 4.9%, the iron content is 1.53%, the titanium content is 0.13%, and the copper content is 0.07%.

[0106] Embodiment 13

[0107] This embodiment provides a menthol optical isomerization catalyst, the structure of the catalyst is the same as that of embodiment 10, and the difference between the preparation method and embodiment 10 is that in step (2), 0.05 g of copper nitrate is added dropwise, and the remaining raw materials and preparation methods are the same as those of embodiment 1, which are not repeated here. According to ICP detection, the nickel content of the catalyst is 4.96%, the iron content is 1.53%, the titanium content is 0.13%, the manganese content is 0.09%, and the copper content is 0.07%.

[0108] Embodiment 14

[0109] This embodiment provides a menthol optical isomerization catalyst, the structure of the catalyst is the same as that of Example 13, and the difference between the preparation method and that of Example 13 is that in step (2), only 2 g of nickel nitrate is added, and the remaining raw materials and preparation method are the same as those of Example 13, which are not described in detail here. According to ICP detection, the nickel content in the catalyst is 4.97%.

[0110] Embodiment 15

[0111] This embodiment provides a menthol optical isomerization catalyst, the structure of the catalyst is the same as that of Example 13, and the difference between the preparation method and that of Example 13 is that in step (2), only 2 g of nickel nitrate and 1.2 g of ferric nitrate nonahydrate are added, and the remaining raw materials and preparation method are the same as those of Example 13, which are not described in detail here. According to ICP detection, the nickel content of the catalyst is 4.98% and the iron content is 1.53%.

[0112] Example 16

[0113] This embodiment provides a menthol optical isomerization catalyst, the structure of the catalyst is the same as that of Example 13, and the difference between the preparation method and that of Example 13 is that in step (2), only 2 g of nickel nitrate and 0.05 g of manganese nitrate are added, and the remaining raw materials and preparation method are the same as those of Example 13, which are not described here. According to ICP detection, the nickel content of the catalyst is 4.98%, and the manganese content is 0.09%.

[0114] Embodiment 17

[0115] This embodiment provides a menthol optical isomerization catalyst, the structure of the catalyst is the same as that of Example 13, and the difference between the preparation method and that of Example 13 is that in step (2), titanium tetrachloride is not added, and the remaining raw materials and preparation method are the same as those of Example 13, which are not described here. According to ICP detection, the nickel content of the catalyst is 4.96%, the iron content is 1.53%, the manganese content is 0.09%, and the copper content is 0.07%.

[0116] Embodiment 18

[0117] This embodiment provides a menthol optical isomerization catalyst, the structure of the catalyst is the same as that of Example 13, and the difference between the preparation method and that of Example 13 is that in step (2), the amount of nickel nitrate is 2 g, the amount of ferric nitrate nonahydrate is 1.2 g, the amount of titanium tetrachloride is 1.0 g, and the amount of manganese acetate is 0.6 g. The remaining raw materials and preparation methods are the same as those of Example 13, which will not be described in detail here. According to ICP detection, the nickel content of the catalyst is 4.96%, the iron content is 1.53%, the manganese content is 1.08%, and the titanium content is 1.21%.

[0118] Embodiment 19

[0119] This embodiment provides a menthol optical isomerization catalyst, the structure of the catalyst is the same as that of Example 13, and the difference between the preparation method and that of Example 13 is that in step (2), the amount of nickel nitrate is 0.4 g, the amount of ferric nitrate nonahydrate is 1.2 g, and the amount of titanium tetrachloride is 1.0 g, and the remaining raw materials and preparation methods are the same as those of Example 13, which will not be described in detail here. According to ICP detection, the nickel content of the catalyst is 0.88%, the iron content is 1.53%, the manganese content is 0.09%, and the titanium content is 1.21%.

[0120] Embodiment 20

[0121] This embodiment provides a menthol optical isomerization catalyst. The structure of the catalyst is the same as that of embodiment 13. The difference between the catalyst and embodiment 13 is that chitosan is replaced by chitin in step (1), and the nitrogen content of the obtained nitrogen-doped porous carbon material is 0.05%, and the specific surface area is 420m 2 / g, and the remaining steps and raw materials are the same as those in Example 13 and will not be repeated here.

[0122] Embodiment 21

[0123] This embodiment provides a menthol optical isomerization catalyst, the structure of which is the same as that of embodiment 13, and the difference between the embodiment 13 and embodiment 13 is that in step (1), a mixture of chitosan and urea is used to replace chitosan, in which the chitosan is 20 g and the urea is 5 g, and the nitrogen content of the obtained nitrogen-doped porous carbon material is 0.181%, and the specific surface area is 402 m 2 / g, and the remaining steps and raw materials are the same as those in Example 13 and will not be repeated here.

[0124] Embodiment 22

[0125] This embodiment provides a menthol optical isomerization catalyst. The structure of the catalyst is the same as that of embodiment 13. The difference between the catalyst and embodiment 13 is that in step (1), 15 g of chitosan is used, and the specific surface area of ​​the obtained nitrogen-doped porous carbon material is 728 m 2 / g, and the remaining steps and raw materials are the same as those in Example 13 and will not be repeated here.

[0126] Embodiment 23

[0127] This embodiment provides a menthol optical isomerization catalyst. The structure of the catalyst is the same as that of embodiment 13. The difference between the catalyst and embodiment 13 is that in step (1), 25 g of chitosan is used, and the specific surface area of ​​the obtained nitrogen-doped porous carbon material is 646 m 2 / g, and the remaining steps and raw materials are the same as those in Example 13 and will not be repeated here.

[0128] Embodiment 24

[0129] This embodiment provides a menthol optical isomerization catalyst. The structure of the catalyst is the same as that of embodiment 13. The difference between the catalyst and embodiment 13 is that in step (1), 10 g of chitosan is used, and the specific surface area of ​​the obtained nitrogen-doped porous carbon material is 732 m 2 / g, and the remaining steps and raw materials are the same as those in Example 13 and will not be repeated here.

[0130] Embodiment 25

[0131] This embodiment provides a menthol optical isomerization catalyst. The structure of the catalyst is the same as that of embodiment 13. The difference between the catalyst and embodiment 13 is that in step (1), 40 g of chitosan is used, and the specific surface area of ​​the obtained nitrogen-doped porous carbon material is 517 m 2 / g, and the remaining steps and raw materials are the same as those in Example 13 and will not be repeated here.

[0132] Embodiment 26

[0133] The present embodiment provides a menthol optical isomerization catalyst, which is different from the embodiment 1 in that the calcination of the nitrogen-doped porous carbon material is different: 20 g of chitosan and 10 g of sodium bicarbonate are weighed and mixed thoroughly to form a mixture, and then the mixture is placed in a tube furnace, and the mixture is heated to 250° C. at a heating rate of 5° C. / min under nitrogen protection and kept warm for 65 min, and then heated to 850° C. at a heating rate of 5° C. / min and kept warm for 2.5 h, and then naturally cooled to room temperature to obtain a black solid, grind the black solid, and wash the ground black solid with water to remove unreacted salt therein, to obtain a nitrogen-doped porous carbon material, the nitrogen content of the nitrogen-doped porous carbon material is 0.09%, and the specific surface area is 619 m 2 / g.

[0134] Embodiment 27

[0135] The present embodiment provides a menthol optical isomerization catalyst, which is different from the embodiment 1 in that the calcination of the nitrogen-doped porous carbon material is different: 20 g of chitosan and 10 g of sodium bicarbonate are weighed and mixed thoroughly to form a mixture, and then the mixture is placed in a tube furnace, and the mixture is heated to 350° C. at a heating rate of 5° C. / min under nitrogen protection and kept warm for 55 min, and then heated to 750° C. at a heating rate of 5° C. / min and kept warm for 1.5 h, and then naturally cooled to room temperature to obtain a black solid, grind the black solid, and wash the ground black solid with water to remove unreacted salt therein, to obtain a nitrogen-doped porous carbon material, the nitrogen content of the nitrogen-doped porous carbon material is 0.106%, and the specific surface area is 637 m 2 / g.

[0136] Embodiment 28

[0137] This embodiment provides a menthol optical isomerization catalyst, the structure and preparation method of the catalyst are the same as those of Example 13, and the difference between the catalyst and Example 13 is that by adjusting the added amounts of nickel nitrate, ferric nitrate nonahydrate and titanium tetrachloride, the obtained menthol optical isomerization catalyst has a nickel content of 7.5%, an iron content of 1% and a titanium content of 0.01% as determined by ICP.

[0138] Embodiment 29

[0139] This embodiment provides a menthol optical isomerization catalyst, the structure and preparation method of the catalyst are the same as those of Example 13, and the difference between the catalyst and Example 13 is that by adjusting the added amounts of nickel nitrate, ferric nitrate nonahydrate and titanium tetrachloride, the obtained menthol optical isomerization catalyst has a nickel content of 3%, an iron content of 5% and a titanium content of 1% as determined by ICP.

[0140] Embodiment 30

[0141] This embodiment provides a menthol optical isomerization catalyst, the structure and preparation method of the catalyst are the same as those of Example 13, and the difference between the catalyst and Example 13 is that by adjusting the added amounts of nickel nitrate, ferric nitrate nonahydrate and titanium tetrachloride, the obtained menthol optical isomerization catalyst has a nickel content of 4%, an iron content of 3% and a titanium content of 0.03% as determined by ICP.

[0142] Embodiment 31

[0143] This embodiment provides a menthol optical isomerization catalyst, the structure and preparation method of the catalyst are the same as those of Example 13, and the difference between the catalyst and Example 13 is that by adjusting the added amounts of nickel nitrate, ferric nitrate nonahydrate and titanium tetrachloride, the obtained menthol optical isomerization catalyst has a nickel content of 5.5%, an iron content of 1.2% and a titanium content of 0.12% as determined by ICP.

[0144] Embodiment 32

[0145] This embodiment provides a menthol optical isomerization catalyst, the structure and preparation method of the catalyst are the same as those of Example 13, and the difference between the catalyst and Example 13 is that by adjusting the added amounts of nickel nitrate, ferric nitrate nonahydrate and titanium tetrachloride, the obtained menthol optical isomerization catalyst has a nickel content of 2.45%, an iron content of 1.53% and a titanium content of 0.12% as determined by ICP.

[0146] Embodiment 33

[0147] This embodiment provides a menthol optical isomerization catalyst, the structure and preparation method of the catalyst are the same as those of Example 13, and the difference between the catalyst and Example 13 is that by adjusting the added amounts of nickel nitrate, ferric nitrate nonahydrate and titanium tetrachloride, the obtained menthol optical isomerization catalyst has a nickel content of 8.2%, an iron content of 1.53% and a titanium content of 0.12% as determined by ICP.

[0148] Embodiment 34

[0149] This embodiment provides a menthol optical isomerization catalyst, the structure and preparation method of the catalyst are the same as those of Example 13, and the difference between the catalyst and Example 13 is that no ferric nitrate nonahydrate is added, and by adjusting the addition amounts of nickel nitrate and titanium tetrachloride, the obtained menthol optical isomerization catalyst is tested by ICP, and the nickel content is 4.96%, the iron content is 0%, and the titanium content is 0.12%.

[0150] Embodiment 35

[0151] This embodiment provides a menthol optical isomerization catalyst, the structure and preparation method of the catalyst are the same as those of Example 13, and the difference between the catalyst and Example 13 is that by adjusting the added amounts of nickel nitrate, ferric nitrate nonahydrate and titanium tetrachloride, the obtained menthol optical isomerization catalyst has a nickel content of 4.96%, an iron content of 5.8% and a titanium content of 0.12% as determined by ICP.

[0152] Comparative Example 1

[0153] This comparative example provides a menthol optical isomerization catalyst, the structure of which is the same as that of Example 13. The difference between the catalyst and Example 13 is that in step (1), cellulose is used to replace chitosan, and the obtained porous carbon material is not doped with nitrogen and has a specific surface area of ​​529 m 2 / g, and the remaining steps and raw materials are the same as those in Example 13 and will not be repeated here.

[0154] Comparative Example 2

[0155] This comparative example provides a menthol optical isomerization catalyst, the structure of which is the same as that of Example 13. The difference between the catalyst and Example 13 is that in step (1), melamine is used to replace chitosan, and the obtained nitrogen-doped porous carbon material has a nitrogen content of 0.235% and a specific surface area of ​​583 m 2 / g, and the remaining steps and raw materials are the same as those in Example 13 and will not be repeated here.

[0156] Test Example 1

[0157] 2 g of the catalyst provided in the embodiment and the comparative example were weighed respectively, and mixed with 150 g of different isomers to obtain menthol (wherein the content of neomenthol was 80.54%, the content of isomenthol was 0.31%, and the content of normal menthol was 14.06%). The mixture was transferred to a 250 mL high pressure reactor for catalytic reaction. The reaction conditions were: temperature 130° C., hydrogen pressure 1 bar, reaction time 6 h, and the data measured by gas chromatography are shown in Table 1 below.

[0158] Table 1 Menthol catalytic translocation data table

[0159]

[0160]

[0161]

[0162] In the above table, "others" represent light hydrocarbon compounds produced during the reaction.

[0163] Test Example 2

[0164] 2 g of the catalyst provided in Example 13 and 180 g of D menthol were transferred to a 250 mL high pressure reactor for catalytic transposition. The reaction conditions were: temperature 130° C., hydrogen pressure 1 bar. The results of chiral gas chromatography at different reaction times are shown in Table 2 below.

[0165] Table 2D Menthol catalytic translocation data table (Example 13)

[0166]

[0167] In the above table, "others" represent light hydrocarbon compounds produced during the reaction.

[0168] It can be seen from the above table that when the reaction time is 6 hours, the translocation of D-menthol reaches a dynamic equilibrium, so it is more appropriate to determine the reaction time as 6 hours.

[0169] 2 g of the catalyst provided in the embodiment and the comparative example were respectively transferred to a 250 mL high pressure reactor with 180 g of D menthol for catalytic transposition. The reaction conditions were: temperature 130° C., hydrogen pressure 1 bar, reaction time 6 h. The results of chiral gas chromatography detection are shown in Table 3 below.

[0170] Table 3D Menthol catalytic translocation data table (Examples and Comparative Examples)

[0171]

[0172]

[0173]

[0174] In the above table, "others" represent light hydrocarbon compounds produced during the reaction.

[0175] Test Example 3

[0176] 2 g of the catalyst provided in Example 13 and 180 g of isomenthol were transferred to a 250 mL high pressure reactor for catalytic transposition. The reaction conditions were: temperature 130° C., hydrogen pressure 1 bar. The results of chiral gas chromatography at different reaction times are shown in Table 4 below.

[0177] Table 4 Isomenthol catalytic translocation data table (Example 13)

[0178]

[0179] In the above table, "others" represent light hydrocarbon compounds produced during the reaction.

[0180] It can be seen from the above table that when the reaction time is 4 hours, the translocation of isomenthol reaches a dynamic equilibrium, so it is more appropriate to determine the reaction time as 4 hours.

[0181] 2 g of the catalyst provided in the embodiment and the comparative example were respectively transferred to a 250 mL high pressure reactor with 180 g of isomenthol for catalytic transposition. The reaction conditions were: temperature 130° C., pressure 1 bar, reaction time 4 h. The results of chiral gas chromatography detection are shown in Table 5 below.

[0182] Table 5 Isomenthol catalytic translocation data table (Examples and Comparative Examples)

[0183]

[0184]

[0185]

[0186] In the above table, "others" represent light hydrocarbon compounds produced during the reaction.

[0187] Test Example 4

[0188] 20 g of the catalyst provided in the embodiment and the comparative example were respectively transferred to a fixed bed for dehydrogenation to prepare menthone. The reaction conditions were: temperature 180° C., feed rate: 5 mL / min, menthol ratio: isomenthol 60%, neomenthol 35%, neoisomenthol 5%, and the results of gas chromatography detection are shown in Table 6 below.

[0189] Table 6 Data table of preparation of menthone from menthol by dehydrogenation

[0190]

[0191]

[0192] In the above table, "others" represent light hydrocarbon compounds produced during the reaction.

[0193] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects: a nitrogen-doped porous carbon material with a specific nitrogen content is used as a carrier, and the chelation effect of the lone electron of the nitrogen atom on the transition metal is utilized to improve the dispersion and stability of the transition metal in the porous carbon material. At the same time, the nitrogen-doped porous carbon material and the loaded transition metal cooperate with each other to improve the selectivity of the catalyst, and the stereoisomerization efficiency of menthol can be significantly improved under mild reaction conditions.

[0194] In addition, the menthol optical isomerization catalyst provided in the present application is used to carry out the catalytic transposition of menthol. The catalyst has high selectivity and can significantly improve the efficiency of the stereoisomerization transposition of menthol under mild reaction conditions.

[0195] In addition, the menthol optical isomerization catalyst provided in the present application can also catalyze the dehydrogenation of menthol to prepare menthone under mild reaction conditions, thereby improving the conversion efficiency of menthone.

[0196] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. Use of a menthol optical isomerization catalyst in menthol catalytic transposition, characterized in that: The catalyst used for the menthol catalytic transposition is a menthol optical isomerization catalyst; The menthol catalytic transposition includes catalytic transposition of isomenthol to ortho-menthol, catalytic transposition of neo-menthol to ortho-menthol, or catalytic transposition of dextro-menthol to levo-menthol; The menthol optical isomerization catalyst comprises a carrier and a transition metal supported on the carrier, wherein the carrier is a nitrogen-doped porous carbon material, and the nitrogen content of the nitrogen-doped porous carbon material is 0.05%-0.181% by mass percentage; The transition metals include nickel, iron and titanium; In terms of mass percentage, in the catalyst, the nickel content is 3%-7.5%, the iron content is 1%-5%, and the titanium content is 0.01%-1%.

2. The use according to claim 1, characterized in that: The temperature of the catalytic translocation is 50-180° C., and the time of the catalytic translocation is 5-7 hours.

3. The use according to claim 2, characterized in that: The temperature of the catalytic transposition is 110-150°C.

4. The use according to claim 2, characterized in that: The time of the catalytic translocation is 5.5-6.5h.

5. The use according to claim 1, characterized in that: Hydrogen is introduced during the catalytic transposition process, and the hydrogen pressure is 1-50 bar.

6. The use according to claim 5, characterized in that: Hydrogen is introduced during the catalytic transposition process, and the hydrogen pressure is 1-10 bar.

7. The use according to claim 1, characterized in that: In terms of mass percentage, the nickel content in the catalyst is 4%-5.5%.

8. The use according to claim 1, characterized in that: In terms of mass percentage, the iron content in the catalyst is 1.2%-3%.

9. The use according to claim 1, characterized in that: In terms of mass percentage, the titanium content in the catalyst is 0.03%-0.4%.

10. The use according to claim 1, characterized in that: The specific surface area of ​​the nitrogen-doped porous carbon material is 402-732 m 2 / g.

11. The use according to claim 10, characterized in that: The specific surface area of ​​the nitrogen-doped porous carbon material is 517-728 m 2 / g.

12. The use according to claim 1, characterized in that: The nitrogen-doped porous carbon material is prepared by mixing chitosan and salt and then performing a first calcination in an inert gas.

13. The use according to claim 1, characterized in that: The nitrogen-doped porous carbon material is prepared by mixing chitosan and salt and then performing a first calcination in nitrogen.

14. The use according to claim 12 or 13, characterized in that: The mass ratio of the chitosan to the salt is (15-25):

10.

15. The use according to claim 14, characterized in that: The mass ratio of the chitosan to the salt is (18-22):

10.

16. The use according to claim 12 or 13, characterized in that: The salt includes at least one of sodium bicarbonate, sodium chloride, potassium chloride or sodium carbonate.

17. The use according to claim 12 or 13, characterized in that: The first calcination comprises the following steps: S1, heating the mixture of the chitosan and the salt to 250-350° C., keeping the temperature for 55-65 min, to obtain an initial calcined product, the heating rate being 4.5-5.5° C. / min; S2, heating the initial calcined product to 750-850°C, keeping the temperature for 1.5-2.5h to obtain a roasted product, with a heating rate of 4.5-5.5°C / min; S3, cooling and washing the calcined product to obtain a nitrogen-doped porous carbon material.

18. The use according to claim 1, characterized in that: Preparation method of the menthol optical isomerization catalyst The following steps are involved: A, mixing raw materials including a soluble transition metal salt, the nitrogen-doped porous carbon material, water, and a pH adjuster to form a mixed system with a pH of 8.0-9.0; B, aging the mixed system for 18-30 hours and then separating the solid and the liquid to obtain a catalyst precursor; C. The catalyst precursor is subjected to a second calcination under a mixed gas condition formed by nitrogen and hydrogen to obtain a menthol optical isomerization catalyst.

19. The use according to claim 18, characterized in that The aging time is 18-22 hours.

20. The use according to claim 18, characterized in that The second calcination temperature is 500-800° C. and the time is 1.5-2.5 hours.

21. The use according to claim 18, characterized in that In the mixed gas, the volume ratio of nitrogen to hydrogen is (1.5-2.5):

1.

22. The use according to claim 21, characterized in that In the mixed gas, the volume ratio of nitrogen to hydrogen is 2:

1.

23. The use according to claim 18, characterized in that The heating rate of the catalyst precursor to the second calcination is 4.5-5.5°C / min.

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