A double bond isomerization catalyst, a preparation method thereof, and a double bond isomerization method

Abstract

The present application discloses a double-bond isomerization catalyst, a preparation method thereof, and a double-bond isomerization method, which belong to the technical field of organic chemical industry. The cinchona alkaloid in the catalyst can promote the allylic deprotonation of coordinated olefins, thereby accelerating the reaction process. It can also act as a ligand to coordinate with metal atom vanadium to form a complex and act on the substrate, having both base-catalysis and metal-catalysis dual functions, making the catalyst exhibit high activity characteristics. Using magnetic Fe3O4 nanoparticles as the carrier is conducive to the dispersion of more active sites on the surface of the catalyst. Loading the cinchona alkaloid not only reduces the usage amount but also facilitates its recycling and the separation and purification of products. When the double-bond isomerization catalyst is used in the synthesis of double-bond isomerization, the reaction has high catalytic efficiency, short reaction time, high catalytic activity, good selectivity, and high yield. The reaction system is a solvent-free system, with simple post-treatment and reduced solvent recovery cost.

Description

Technical Field

[0001] The present application belongs to the technical field of organic chemical industry, and in particular relates to a double bond isomerization catalyst and a preparation method thereof and a double bond isomerization method. Background Art

[0002] Double bond isomerization reaction is a very important type of organic chemical reaction, which is mostly used in the research and development and production of fine chemical products such as synthetic fragrances, pesticide intermediates, and pharmaceutical intermediates, such as isoeugenol, vanillin, jasminoids, piperonyl butoxide, anethole, anisaldehyde, raspberry ketone, isopentenol, citral, privet aldehyde, methyl heptenone, linalool, myrcene, geraniol, lyral, citric aldehyde, ambergris ketone, pseudoionone, ionone, vitamin A, etc.

[0003] Isoeugenol is a light yellow liquid with a soft, sweet and spicy aroma, similar to carnation and lilac. It is mainly used in the preparation of flavors. Isoeugenol can be prepared by isomerization of eugenol. Vanillin is a white to slightly yellow crystalline powder with the aroma of vanilla beans and a strong milky aroma. It is widely used in the cosmetics, tobacco, cakes, candies, and baked food industries. Vanillin can be prepared by isomerization of eugenol to isoeugenol, which is then oxidized.

[0004] Heliotropin, a white or light yellow crystalline solid, has the aroma of heliotropin and is widely used in flavors, medicine, electroplating and pesticide industries. Heliotropin can be obtained by isomerization of safrole to isosafrole and then oxidation. Piperonyl butoxide, an amber liquid, is mainly used as a synergist for insecticides and can be used to improve the insecticidal activity of pyrethrins, rotenone and carbamate insecticides. Piperonyl butoxide can be obtained by isomerization of safrole to isosafrole and then hydrogenation, chloromethylation and etherification.

[0005] Anethole, a colorless to light yellow liquid, has a sweet anise aroma and is widely used in toothpaste flavors and spices, as well as in food, medicine and other fields. Anethole can be prepared by isomerization of estragole. Anisaldehyde, a colorless to light yellow liquid with a hawthorn-like odor, is widely used in daily chemical flavors and edible flavor formulations, and is also used in medicine, food and daily chemical industries. Anisaldehyde can be prepared by isomerization of estragole to anethole and then oxidation. Raspberry ketone, a white needle-shaped crystal or granular solid, has a raspberry aroma and a fruity sweet taste. It is used to prepare food flavors and has the effect of enhancing flavor and sweetness. It can also be used in cosmetics and soap flavors. Raspberry ketone can be prepared by isomerization of estragole to anethole, and then oxidation, condensation, hydrogenation and demethylation.

[0006] Isopentenol, a colorless, transparent liquid with a strong ester aroma, is mainly used to synthesize citral, pyrethroid insecticides, water reducers and other products. Isopentenol can be prepared by isomerization of 3-methyl-3-butene-1-ol. Citral, a colorless liquid with a strong lemon aroma, is mainly used as a flavoring agent to prepare lemon essence, and is also used as a raw material for synthesizing ionone and vitamin A. Citral can be prepared by isomerization of 3-methyl-3-butene-1-ol to isopentenol, and then by acetalization, cleavage and rearrangement.

[0007] Ligustrum lucidum is a colorless or very light yellow liquid with a strong fresh and grassy fragrance. It is suitable for the preparation of soaps, cosmetics, detergents and other flavors. Ligustrum lucidum can be prepared by isomerization of 4-methyl-1,3-pentadiene to 2-methyl-1,3-pentadiene and then by diene addition.

[0008] Methyl heptenone, a colorless or light yellow liquid, has the aroma of lemongrass and isobutyl acetate. It is an important intermediate for the synthesis of linalool, citral, etc. Methyl heptenone (6-methyl-5-heptene-2-one) can be prepared by isomerization of 6-methyl-6-heptene-2-one.

[0009] β-Myrcene is a colorless or light yellow liquid, mainly used in cologne and deodorants. It is also an important raw material for synthesizing spices such as geraniol, linalool, lyral, citric aldehyde, and ambergris. β-Myrcene can be prepared by isomerization of α-myrcene.

[0010] Ambergris ketone is a colorless to light yellow liquid with woody and ambergris aromas. It can be widely used in perfume, cosmetics, soaps, synthetic detergents and other fragrance formulas. Ambergris ketone can be isomerized from 1-(1,6-dimethyl-4-(4-methyl-4-pentenyl)-cyclohex-3-ene)-ethanone to isoprispermone (1-(1,6-dimethyl-4-(4-methyl-3-pentenyl)-cyclohex-3-ene)-ethanone) and then cyclized to obtain it.

[0011] Pseudoionone, a light yellow liquid with a light violet aroma, is widely used in flavors and fragrances, medicine, food additives and synthetic chemistry. Pseudoionone (6,10-dimethyl-3,5,9-undecantrien-2-one) can be prepared by isomerization of 6,10-dimethyl-3,5,10-undecantrien-2-one. Ionone, a colorless to slightly yellow liquid with a warm woody aroma and a strong violet aroma, is mainly used to prepare flavors and is also an important raw material for synthesizing vitamin A. Ionone can be prepared by isomerization of 6,10-dimethyl-3,5,10-undecantrien-2-one to pseudoionone, which is then cyclized.

[0012] Patent CN103408407A reported a method for obtaining isoeugenol. Under the catalysis of potassium hydroxide, using glycol solvents as reaction solvents, eugenol was isomerized at 160 - 170 °C for 6 - 8 h, followed by acidification, extraction, and distillation. The yield was 88%, but this method had a complex process, a long process flow, produced a large amount of waste salt, caused serious environmental pollution, and had the problems of long reaction time and low efficiency.

[0013] Patent CN103012080A used iron carbonyl as a catalyst and added antioxidant sodium sulfite to isomerize eugenol into isoeugenol at 80 - 85 °C for 2 - 4 h, and the yield could reach 96%. However, the catalyst iron carbonyl was expensive and could not be reused, and this method had a high cost.

[0014] Chemical Education, 2019, 40(2), 44 used RhCl3 as a catalyst, absolute ethanol as a solvent, and refluxed at 140 - 145 °C for 5 h. The yield of isoeugenol was 94%, but this method had the problem of long reaction time.

[0015] Applied Chemical Industry, 2018, 47(3), 474 used Pd(OAc)2 and Al(OTf)3 as catalysts and acetonitrile as a solvent for eugenol isomerization. The reaction was carried out at 50 °C for 6 h, and the yield was as high as 96.3%, but this method had a long reaction time.

[0016] Organic Letters, 2014, 16, 2818 used eugenol as a raw material, without solvent, and a supported imidazolyl phosphorus ruthenium catalyst for catalytic reaction. The reaction was carried out at room temperature (25 °C) for 2 h, and the yield was 81%. This method had the problem of low yield.

[0017] CN106040305A used an organic solution formed by dissolving ruthenium complex RuH2CO(PPh3)3 and a second metal salt in a solvent as a catalytic system to make eugenol react at 50 - 90 °C for 1 - 3 h. The yield of isoeugenol exceeded 90%, but this method used a solvent and had a high separation cost.

[0018] CN113893838A used self - made Zr - N / Meso - Al2O3(OH - ) as a catalyst, ethanol as a solvent, and eugenol reacted at 70 °C for 1 h. The conversion rate was 99.5%, and the selectivity of isoeugenol was 98.7%. This method also used a solvent, increasing the separation cost.

[0019] CN103360215B reported that a water-soluble complex formed by a Group VIII water-soluble metal salt and a water-soluble ligand was used as a catalyst. Under an inert atmosphere (nitrogen or argon) and at 30 - 120 °C, the reaction was stirred for 0.2 - 2 h to carry out the catalytic isomerization reaction of 3-methyl-3-buten-1-ol in a water-organic two-phase system to synthesize isoprenol. The conversion rate of the raw material reached 68.23%, and the selectivity of isoprenol reached 99.65%. However, this technical solution has problems such as relatively harsh operating conditions and difficulty in separating the products.

[0020] In summary, in the existing technology of double bond isomerization reaction, there are various problems, such as low yield, long reaction time, and high production cost. Summary of the Invention

[0021] The purpose of the implementation of this application is to provide a double bond isomerization catalyst, its preparation method and a double bond isomerization method to solve the technical problems of low yield, long reaction time, and high catalyst usage cost existing in the double bond isomerization reaction in the existing technology.

[0022] To achieve the above purpose, the technical solution adopted in this application is: to provide a double bond isomerization catalyst, which includes a magnetic nanomaterial and a cinchona alkaloid.

[0023] In one embodiment,

[0024] The magnetic nanomaterial is magnetic iron oxide (Fe3O4) nanoparticles coated with vanadium pentoxide (V2O5).

[0025] In one embodiment,

[0026] The cinchona alkaloid is one of quinine, quinidine, cinchonine or cinchonidine.

[0027] In one embodiment,

[0028] The mass ratio of vanadium pentoxide to magnetic iron oxide nanoparticles is 0.01 - 0.05 : 1; the mass ratio of cinchona alkaloid to magnetic iron oxide nanoparticles is 0.005 - 0.1 : 1.

[0029] This application also provides a preparation method of a double bond isomerization catalyst, which specifically includes the following steps:

[0030] (1). Disperse magnetic iron oxide nanoparticles and vanadyl acetylacetonate in an ethanol / water mixture solvent, ultrasonically mix, and stir at a constant temperature to deposit the vanadium species after hydrolysis of vanadyl acetylacetonate on the surface of the magnetic iron oxide nanoparticles, thereby forming a vanadium pentoxide coating; wait for the solution to cool to room temperature, filter, wash, dry, and calcine to obtain magnetic iron oxide nanoparticles coated with vanadium pentoxide Fe3O4@V2O5;

[0031] (2) Disperse vanadium pentoxide-coated magnetic iron oxide nanoparticles and cinchona alkaloid in an ethanol / water mixture solvent, ultrasonically mix, stir at a constant temperature, wait for the solution to cool to room temperature, filter, wash, and dry to obtain a double bond isomerization catalyst: cinchona alkaloid / Fe3O4@V2O5.

[0032] In one embodiment,

[0033] In step (1), the time for ultrasonic treatment is 10 - 30 min, the temperature for stirring at a constant temperature is 100 - 120 °C, the time is 10 - 12 h, the temperature for calcination is 400 - 600 °C, and the time is 2 - 4 h.

[0034] In one embodiment,

[0035] In step (2), the time for ultrasonic treatment is 10 - 30 min, the temperature for stirring at a constant temperature is 100 - 120 °C, the time is 10 - 12 h, and the drying temperature is 60 - 120 °C.

[0036] This application also provides a double bond isomerization method. Under a nitrogen atmosphere, the double bond isomerization catalyst obtained by the preparation method of any of the above embodiments and a compound containing a terminal olefin are introduced into a tubular reactor through a suspension particle metering pump, and a compound containing an internal olefin is obtained by reaction;

[0037] Furthermore, the structural formula of the compound containing a terminal olefin is formula (I); the structural formula of the compound containing an internal olefin is formula (II);

[0038]

[0039] (I)(II)

[0040] Among them, R is a hydrocarbon group, an alkoxy group, a hydroxyalkyl group, or an aryl group;

[0041] The compounds containing a terminal olefin include but are not limited to eugenol, safrole, estragole, 3 - methyl - 3 - buten - 1 - ol, 4 - methyl - 1,3 - pentadiene, 6 - methyl - 6 - hepten - 2 - one, α - myrcene, 1 - (1,6 - dimethyl - 4 - (4 - methyl - 4 - pentenyl) - cyclohex - 3 - enyl) - ethanone, 6,10 - dimethyl - 3,5,10 - undecatriene - 2 - one, and their structural formulas are respectively:

[0042]

[0043] EugenolSafroleEstragole

[0044]

[0045] 3-Methyl-3-buten-1-ol, 4-methyl-1,3-pentadiene, 6-methyl-6-hepten-2-one

[0046]

[0047] α-Myrcene

[0048]

[0049] 1-(1,6-Dimethyl-4-(4-methyl-4-pentenyl)-cyclohex-3-enyl)-ethanone

[0050]

[0051] 6,10-Dimethyl-3,5,10-undecatriene-2-one

[0052] The corresponding compounds containing internal olefins obtained are: isoeugenol, isosafrole, anethole, isoprenol, 2-methyl-1,3-pentadiene, methylheptenone, β-myrcene, isopulegone, pseudoionone, and their structural formulas are respectively:

[0053]

[0054] Isoeugenol, Isosafrole, Anethole

[0055]

[0056] Isoprenol, 2-Methyl-1,3-pentadiene, Methylheptenone

[0057]

[0058] β-Myrcene, Isopulegone, Pseudoionone

[0059] In one embodiment,

[0060] The mass ratio of the double bond isomerization catalyst to the compound containing terminal olefins is 0.005 - 0.03:1.

[0061] In one embodiment,

[0062] The pressure of the reaction is atmospheric pressure, the temperature is 20 - 60 °C, and the time is 10 - 30 min.

[0063] The present application provides a double bond isomerization catalyst, a preparation method thereof and a double bond isomerization method. In the catalyst, cinchona alkaloid has alkalinity, which can promote the allylic deprotonation of coordinated olefins to accelerate the reaction process. At the same time, cinchona alkaloid can also act as a ligand to coordinate with metal atom vanadium to form a complex and act on the substrate, having both the functions of base catalysis and metal catalysis, making the catalyst exhibit high activity characteristics. In addition, magnetic Fe3O4 nanoparticles are used as the carrier. Due to their small size, they have a large specific surface area, which is beneficial to the dispersion of more active sites on the catalyst surface. V2O5 is used to coat the surface of magnetic Fe3O4 nanoparticles, and the coating layer increases its chemical stability. The cinchona alkaloid is loaded, which not only reduces the usage amount but also facilitates its recycling and the separation and purification of products. Moreover, due to the magnetic property of the catalyst itself, the catalyst can be easily separated by applying an external magnetic field, and the recycling is simple and convenient. When the above double bond isomerization catalyst is used in the synthesis of double bond isomerization, the reaction has high catalytic efficiency, short reaction time, high catalytic activity, good selectivity and high yield. The reaction system is a solvent-free system, and the post-treatment is simple and the solvent recovery cost is reduced. Brief Description of the Drawings

[0064] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0065] Figure 1 It is the electron microscope photograph of the double bond isomerization catalyst in Example 1. Detailed Description of the Embodiments

[0066] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clear and understandable, the present application will be further described in detail. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0067] Example 1

[0068] A preparation method of a double bond isomerization catalyst includes the following steps:

[0069] (1) Disperse 50 g of magnetic iron oxide nanoparticles and 5.74 g of vanadyl acetylacetonate in 200 ml of an ethanol / water mixture solvent, sonicate for 20 min, mix evenly, place in a hydrothermal reaction kettle, and stir at a constant temperature of 120 °C for 10 h to deposit the vanadium species after the hydrolysis of vanadyl acetylacetonate on the surface of the magnetic iron oxide nanoparticles, thereby forming a V2O5 coating layer; wait for the solution to cool to room temperature, filter and wash, and then dry and calcine at 500 °C for 3 h to obtain magnetic iron oxide nanoparticles coated with vanadium pentoxide, Fe3O4@3%V2O5;

[0070] (2) Disperse the Fe3O4@3%V2O5 obtained in step (1) and 2.5 g of quinine in 200 ml of an ethanol / water mixture solvent, sonicate for 20 min, mix evenly, place in a hydrothermal reaction kettle, and stir at a constant temperature of 120 °C for 10 h. Wait for the solution to cool to room temperature, filter and wash, and then dry at 100 °C to prepare a double bond isomerization catalyst, 5% quinine / Fe3O4@3%V2O5, denoted as catalyst A, and store it for later use. The electron microscope structure is as Figure 1 shown.

[0071] Example 2

[0072] The difference between this example and Example 1 is that in step (1), the sonication time is 10 min, the constant temperature stirring temperature is 100 °C, and the time is 12 h; the calcination temperature is 400 °C, and the time is 4 h; in step (2), quinine is replaced with quinidine, the sonication time is 10 min, and the rest of the operations are the same to prepare a double bond isomerization catalyst, 5% quinidine / Fe3O4@3%V2O5, denoted as catalyst B.

[0073] Example 3

[0074] The difference between this example and Example 1 is that in step (1), the sonication time is 30 min, the constant temperature stirring temperature is 110 °C, and the time is 11 h; the calcination temperature is 600 °C, and the time is 2 h; in step (2), quinine is replaced with cinchonine, and the constant temperature stirring time is 12 h, and the rest of the operations are the same to prepare a double bond isomerization catalyst, 5% cinchonine / Fe3O4@3%V2O5, denoted as catalyst C.

[0075] Example 4

[0076] The difference between this example and Example 1 is that in step (2), quinine is replaced with cinchonidine, the sonication time is 30 min, the constant temperature stirring temperature is 100 °C, and the rest of the operations are the same to prepare a double bond isomerization catalyst, 5% cinchonidine / Fe3O4@3%V2O5, denoted as catalyst D.

[0077] Example 5

[0078] The difference between this example and Example 1 is that in step (i), the amount of vanadyl acetylacetonate used is 1.91 g, and Fe3O4@1%V2O5 is obtained; the remaining operations are the same, and the double bond isomerization catalyst 5% quinine / Fe3O4@1%V2O5 is prepared, denoted as catalyst E.

[0079] Example 6

[0080] The difference between this example and Example 1 is that in step (i), the amount of vanadyl acetylacetonate used is 9.57 g, and Fe3O4@5%V2O5 is obtained; the remaining operations are the same, and the double bond isomerization catalyst 5% quinine / Fe3O4@5%V2O5 is prepared, denoted as catalyst F.

[0081] Example 7

[0082] The difference between this example and Example 1 is that in step (ii), the amount of quinine used is 0.25 g, and the drying temperature is 60 °C; the remaining operations are the same, and the double bond isomerization catalyst 0.5% quinine / Fe3O4@3%V2O5 is prepared, denoted as catalyst G.

[0083] Example 8

[0084] The difference between this example and Example 1 is that in step (ii), the amount of quinine used is 5 g, and the drying temperature is 120 °C; the remaining operations are the same, and the double bond isomerization catalyst 10% quinine / Fe3O4@3%V2O5 is prepared, denoted as catalyst H.

[0085] Example 9

[0086] A method for synthesizing isoeugenol. Under a nitrogen atmosphere, catalyst A and eugenol are fed into a tubular reactor through a suspension particle metering pump, and the mass ratio of catalyst A to eugenol is 0.015:1; the reaction is carried out for 20 min under the action of catalyst A, during which the reaction pressure is controlled at atmospheric pressure and the temperature is 50 °C; the reaction solution flowing out of the tubular reactor is condensed and then enters a collection tank, and a sample is taken for gas chromatography detection and analysis, and the conversion rate of the raw material eugenol is obtained as 99.9%, and the selectivity of the product isoeugenol is 99.8%.

[0087] The difference between Examples 10 - 16 and Example 9 is that the types of catalysts are different, and the other steps are the same. The reaction solution is obtained, and a sample is taken for gas chromatography detection and analysis, and the conversion rate of the raw material eugenol and the selectivity of the product isoeugenol are obtained. The results are shown in Table 1.

[0088] Table 1 Summary of experimental data and results of Examples 9 - 16

[0089]

[0090] Comparing Comparative Examples 9-16, it can be seen that the double bond isomerization catalysts prepared in Examples 1-8 of the present application all have excellent catalytic activity and can catalyze the isomerization of raw material eugenol into isoeugenol to achieve the efficient synthesis of isoeugenol. Among them, Catalyst A has the best catalytic effect, with the conversion rate of raw material eugenol as high as 99.9% and the selectivity of product isoeugenol as high as 99.8%.

[0091] Examples 17-22 are different from Example 9 in that the reaction parameters are different while other steps are the same. The reaction solution is obtained, sampled and analyzed by gas chromatography to obtain the conversion rate of raw material eugenol and the selectivity of product isoeugenol. The results are shown in Table 2.

[0092] Table 2 Summary of experimental data and results of Examples 9, 17-22

[0093]

[0094] Comparing Examples 9, 17-22, it can be seen that the three factors of reaction temperature, catalyst dosage, and reaction time all have a certain influence on the reaction conversion rate and product selectivity.

[0095] Examples 23-38 are different from Example 9 in that the types of compounds containing terminal olefins in the substrate are different and the reaction parameters are different while other steps are the same. The reaction solution is obtained, sampled and analyzed by gas chromatography to obtain the conversion rate of raw material terminal olefin and the selectivity of product internal olefin. The results are shown in Table 3.

[0096] Table 3 Summary of experimental data and results of Examples 9, 23-38

[0097]

[0098] Comparing Examples 9, 23-38, it can be seen that the catalysts prepared in the examples of the present application all have excellent catalytic activity, can catalyze the isomerization of different substrate terminal olefins into corresponding internal olefins to achieve the efficient synthesis of internal olefins, and have high universality. At the same time, it can also be seen that the suitable optimal reaction conditions for different substrates are somewhat different.

[0099] Example 39

[0100] The Catalyst A used in Example 1 was recycled 50 times under the corresponding reaction conditions. The fluctuation of eugenol conversion rate was measured to be ±0.2%, and the fluctuation of isoeugenol selectivity was ±0.2%. This shows that the catalyst prepared by the present invention has excellent stability.

[0101] Comparative Example 1

[0102] A method for synthesizing isoeugenol. Under a nitrogen atmosphere, eugenol and the catalyst Fe3O4@3%V2O5 are introduced into a tubular reactor through a suspension particle metering pump (the mass ratio of the catalyst to eugenol is 0.015:1), and the reaction is carried out under the action of the catalyst. During this period, the reaction temperature is controlled at 50 °C and the reaction time is 20 min. The reaction solution flowing out of the tubular reactor is condensed and then enters a collection tank. A sample is taken for gas chromatography detection and analysis, and it is found that the conversion rate of the raw material eugenol is 5.4%, and the selectivity of the product isoeugenol is 10.3%.

[0103] Comparative Example 2

[0104] A method for synthesizing isoeugenol. Under a nitrogen atmosphere, eugenol and the catalyst quinine are introduced into a tubular reactor through a suspension particle metering pump (the mass ratio of the catalyst to eugenol is 0.015:1), and the reaction is carried out under the action of the catalyst. During this period, the reaction temperature is controlled at 50 °C and the reaction time is 20 min. The reaction solution flowing out of the tubular reactor is condensed and then enters a collection tank. A sample is taken for gas chromatography detection and analysis, and it is found that the conversion rate of the raw material eugenol is 52.7%, and the selectivity of the product isoeugenol is 55.8%.

[0105] Comparative Example 3

[0106] A method for synthesizing isoeugenol. Under a nitrogen atmosphere, quinine and Fe3O4@3%V2O5 are physically mixed to prepare a catalyst; the catalyst and eugenol are introduced into a tubular reactor through a suspension particle metering pump (the mass ratio of the catalyst to eugenol is 0.015:1), and the reaction is carried out under the action of the catalyst. During this period, the reaction temperature is controlled at 50 °C and the reaction time is 20 min. The reaction solution flowing out of the tubular reactor is condensed and then enters a collection tank. A sample is taken for gas chromatography detection and analysis, and it is found that the conversion rate of the raw material eugenol is 60.2%, and the selectivity of the product isoeugenol is 58.6%.

[0107] Comparing Example 9 with Comparative Examples 1-3, it can be seen that the reaction conversion rate and product selectivity of Comparative Examples 1-3 are much lower than those of Example 9, indicating that using only cinchona alkaloids or magnetic iron oxide nanoparticles coated with vanadium pentoxide or simple physical mixing as catalysts cannot achieve the reaction activity of the catalyst prepared in this application; thus, it can be known that there is a synergistic effect between the magnetic iron oxide nanoparticles coated with vanadium pentoxide and the cinchona alkaloid component. This synergistic effect greatly improves the catalytic activity of the catalyst, realizes the rapid and efficient progress of the double bond isomerization reaction, and significantly improves the reaction conversion rate and product selectivity.

[0108] The present application provides a double bond isomerization catalyst, a preparation method thereof and a double bond isomerization method. The double bond isomerization catalyst is a cinchona alkaloid type catalyst supported on magnetic nanomaterials. Cinchona alkaloid has alkalinity, which can promote the allylic deprotonation of coordinated olefins to accelerate the reaction process. At the same time, cinchona alkaloid can also act as a ligand to coordinate with metal atom vanadium to form a complex and act on the substrate, having both the functions of base catalysis and metal catalysis, making the catalyst exhibit high activity characteristics. In addition, magnetic Fe3O4 nanoparticles are used as the carrier. Due to their small size, they have a large specific surface area, which is beneficial to the dispersion of more active sites on the catalyst surface. V2O5 is used to coat the surface of the magnetic Fe3O4 nanoparticles, and the coating layer increases its chemical stability. The cinchona alkaloid is loaded, which not only reduces the usage amount but also facilitates its recycling and the separation and purification of products. Moreover, due to the magnetic property of the catalyst itself, the catalyst can be easily separated by applying an external magnetic field, and the recycling is simple and convenient. When the above double bond isomerization catalyst is used in the synthesis of double bond isomerization, the reaction has high catalytic efficiency, short reaction time, high catalytic activity, good selectivity and high yield. The reaction system is a solvent-free system, and the post-treatment is simple and the solvent recovery cost is reduced.

[0109] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present application, "a plurality of" means two or more unless otherwise specifically defined.

[0110] The above are only the preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A preparation method of a double bond isomerization catalyst, characterized in that, Specifically, it includes the following steps: (1) Disperse magnetic iron oxide nanoparticles and vanadium acetylacetonate in an ethanol / water mixture solvent, ultrasonically mix them, place them in a hydrothermal reactor and stir at a constant temperature, so that the vanadium species after hydrolysis of vanadium acetylacetonate are deposited on the surface of the magnetic iron oxide nanoparticles, thereby forming a vanadium pentoxide coating layer; wait for the solution to cool to room temperature, filter, wash, dry, and calcine to obtain magnetic iron oxide nanoparticles coated with vanadium pentoxide; (2) Disperse the magnetic iron oxide nanoparticles coated with vanadium pentoxide and cinchona alkaloid in an ethanol / water mixture solvent, ultrasonically mix them, place them in a hydrothermal reactor and stir at a constant temperature. Wait for the solution to cool to room temperature, filter, wash, and dry to prepare a double bond isomerization catalyst.

2. The preparation method of a double bond isomerization catalyst according to claim 1, characterized in that The cinchona alkaloid is one of quinine, quinidine, cinchonine or cinchonidine.

3. The preparation method of a double bond isomerization catalyst according to claim 1, characterized in that, The mass ratio of vanadium pentoxide to magnetic iron oxide nanoparticles is 0.01 - 0.05:1; the mass ratio of cinchona alkaloid to magnetic iron oxide nanoparticles is 0.005 - 0.1:

1.

4. The preparation method of a double bond isomerization catalyst according to claim 1, characterized in that, In step (1), the ultrasonic time is 10 - 30 min, the temperature of constant temperature stirring is 100 - 120 °C, the time is 10 - 12 h, and the calcination temperature is 400 - 600 °C, the time is 2 - 4 h.

5. The preparation method of a double bond isomerization catalyst according to claim 1, characterized in that, In step (2), the ultrasonic time is 10 - 30 min, the temperature of constant temperature stirring is 100 - 120 °C, the time is 10 - 12 h, and the drying temperature is 60 - 120 °C.

6. A double bond isomerization catalyst, characterized in that, Obtained by the preparation method according to any one of claims 1 - 5.

7. A double bond isomerization method, characterized in that Under a nitrogen atmosphere, the double bond isomerization catalyst according to claim 6 and a compound containing terminal olefin are introduced into a tubular reactor through a suspension particle metering pump, and the reaction is carried out to obtain a compound containing internal olefin.

8. A double bond isomerization method according to claim 7, characterized in that, The mass ratio of the double bond isomerization catalyst to the compound containing terminal olefin is 0.005 - 0.03:

1.

9. A double bond isomerization method according to claim 7, characterized in that, The pressure of the reaction is normal pressure, the temperature is 20 - 60 °C, and the time is 10 - 30 min.

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