Composite catalyst and preparation method thereof, and preparation method of salicylate compound

Abstract

The application provides a composite catalyst and a preparation method thereof, and a preparation method of a salicylate compound. The preparation method of the composite catalyst comprises the following steps: mixing a carbon carrier with a hydrotalcite for mixing treatment to prepare a mixture; and performing calcination treatment on the mixture to prepare the composite catalyst. When the composite catalyst prepared by the preparation method is used in an ester exchange reaction, the catalyst has high catalytic activity and is not prone to reaction with water, and can be repeatedly used.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of organic synthesis, in particular to a composite catalyst and a preparation method and application thereof. BACKGROUND

[0002] Salicylate compounds containing long-chain alkyl groups are important chemical industrial products or medicines. For example, salicylic acid-2-ethylhexyl ester is a commonly used ultraviolet absorber, which can maintain its structure stable without decomposition while absorbing the ultraviolet part of sunlight and fluorescent light sources. When plastics and other polymer materials are exposed to sunlight or fluorescent light, they are easily oxidized due to the action of ultraviolet light, leading to degradation of the polymer and deterioration of the appearance and mechanical properties. The addition of ultraviolet absorbers such as salicylic acid-2-ethylhexyl ester can selectively absorb high-energy ultraviolet light in light, making it harmless energy and releasing or consuming it.

[0003] There are mainly two methods for preparing salicylate compounds: 1. Directly using acid and alcohol to undergo esterification reaction under the action of catalysts such as sulfuric acid; 2. Selecting methyl salicylate and alcohol containing long-chain alkyl groups as raw materials to prepare and synthesize by ester exchange method. Compared with the esterification method, the probability of side reactions in the ester exchange method is lower, but the yield and purity of the traditional ester exchange method still need to be improved. In addition, strong alkaline substances such as sodium methoxide are often used as catalysts, which can easily react with water, and the reaction environment is harsh, the equipment is severely corroded, and the process of removing the catalyst will produce a lot of wastewater, which is not conducive to industrial production.

[0004] Therefore, the traditional technology still needs to be improved. SUMMARY

[0005] Therefore, the present application provides a composite catalyst and a preparation method and application thereof, which has high catalytic activity and is not prone to react with water when used in ester exchange reaction, and can improve the yield and purity of the product.

[0006] The technical scheme of the present application is as follows.

[0007] In a first aspect, the present application provides a preparation method of a composite catalyst, comprising the following steps:

[0008] Mixing and treating the carbon carrier with hydrotalcite to prepare a mixture;

[0009] Calcining the mixture to prepare a composite catalyst.

[0010] In the preparation method of the composite catalyst, a specific carrier is mixed with hydrotalcite and calcined, and the hydrotalcite forms metal oxide loaded on the carbon carrier during the calcination process to form a composite catalyst. When used in ester exchange reaction, the catalyst has high catalytic activity and is not prone to react with water, and can be reused.

[0011] Further, the composite catalyst prepared by the above preparation method is difficult to dissolve in water and most organic substances, and can be directly filtered for recovery when used in ester exchange reaction, which is environment-friendly and more conducive to industrial production.

[0012] In some embodiments, before the mixing step, the method further comprises the following steps:

[0013] The carbon carrier is immersed in a strong acid solution for immersion treatment.

[0014] The carbon carrier is immersed in a strong acid solution for immersion treatment, which can remove impurities in the carbon carrier and improve the adsorption of the carbon carrier to hydrotalcite and its calcined product, thereby further improving the catalytic activity of the prepared composite carrier.

[0015] In some embodiments, the immersion treatment satisfies at least one of the following conditions (1)-(3):

[0016] (1) the immersion treatment is carried out under reflux conditions;

[0017] (2) the immersion treatment time is 4-6 hours;

[0018] (3) the strong acid solution comprises concentrated sulfuric acid and concentrated nitric acid, and the volume ratio of the concentrated sulfuric acid to the concentrated nitric acid is (2-4):1.

[0019] In some embodiments, the preparation method satisfies at least one of the following conditions (1)-(3):

[0020] (1) the mass ratio of the carbon carrier to the hydrotalcite is 1:(1-3);

[0021] Adjusting the mass ratio of the carbon carrier to the hydrotalcite can further improve the effective

[0022] component in the prepared composite catalyst.

[0023] (2) the carbon carrier comprises at least one of carbon nanotubes, carbon paper, activated carbon, fullerene and graphene;

[0024] (3) the hydrotalcite comprises at least one of magnesium-aluminum hydrotalcite, iron-cobalt hydrotalcite and magnesium-aluminum-zinc hydrotalcite.

[0025] The second aspect of the present application also provides a composite catalyst prepared by the preparation method of the composite catalyst of the first aspect.

[0026] In a third aspect of the present application, a composite catalyst is provided, which comprises a carbon carrier and an effective component supported on the carbon carrier, wherein the effective component comprises a metal oxide formed after calcination of hydrotalcite.

[0027] The composite catalyst has high catalytic activity and is not prone to react with water when used in transesterification, and can be reused.

[0028] In a fourth aspect of the present application, a preparation method of a salicylate compound is provided, which comprises the following steps:

[0029] The compound (1) and the compound (2) are subjected to transesterification under the action of a catalyst to prepare a salicylate compound represented by formula (3); the catalyst comprises the composite catalyst according to claim 8 or 9.

[0030] The compound (1), the compound (2) and the salicylate compound represented by formula (3) have the following structures:

[0031]

[0032] R1 is an alkyl group with 2-10 carbon atoms.

[0033] In some embodiments, the compound (1) is methyl salicylate, the compound (2) is isooctanol, and the salicylate compound represented by formula (3) is salicylic acid-2-ethylhexyl ester.

[0034] In some embodiments, at least one of the following conditions (1)-(3) is met:

[0035] (1) the temperature of the transesterification is 100-130℃;

[0036] (2) the molar ratio of the compound (1) to the compound (2) is 1:(1-3);

[0037] (3) the mass of the effective component in the composite catalyst is 0.1%-3% of the mass of the compound (1); the effective component comprises a metal oxide formed after calcination of hydrotalcite. DETAILED DESCRIPTION

[0038] In order to facilitate the understanding of the present application, the present application will be described more fully below, and preferred embodiments of the present application will be given. However, the present application can be realized in many different forms, and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0040] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is two or more, unless otherwise explicitly specified.

[0041] The "range" disclosed in the present application can be limited in the form of lower limit and upper limit, and the given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit limit the boundary of the specific range. The range limited in this way can be inclusive or exclusive of the end values, either end value can be independently included or excluded, and can be arbitrarily combined, i.e. any lower limit can be combined with any upper limit to form a range. For example, if the ranges of 60~120 and 80~110 are listed for a particular parameter, it is understood that the ranges of 60~110 and 80~120 are also anticipated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4 and 5 are also listed, the following ranges can all be anticipated: 1~3, 1~4, 1~5, 2~3, 2~4 and 2~5. In the present application, unless otherwise specified, the numerical range "a~b" represents a shorthand representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0~5" means that all real numbers between "0~5" have been listed herein, and "0~5" is only a shorthand representation of these numerical combinations. In addition, when it is stated that a parameter is an integer ≥2, it is equivalent to listing the parameter as, for example, integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For example, when it is stated that a parameter is an integer selected from "2~10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9 and 10.

[0042] In the present application, "optionally", "optional" and "optional" mean optional, i.e. selected from either of the two parallel schemes "with" or "without". If there are multiple "options" in a technical solution, each "option" is independent unless otherwise specified, and there is no contradiction or mutual restriction.

[0043] Reference to an "embodiment" herein means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive of one another. As will be apparent to those of ordinary skill in the art, embodiments described herein can be combined with other embodiments.

[0044] In the present application, the steps of the present application are carried out at "room temperature" unless otherwise specified. "Room temperature" generally refers to 4-30°C, preferably 20±5°C.

[0045] In the present application, when the connection site in the group is not specified, it means that any optional connection site in the group is taken as the connection site.

[0046] In the present application, the term "alkyl" refers to a group formed by removing one hydrogen from an alkane, for example, removing one hydrogen from methane to form a methyl group.

[0047] The term "alkyl" refers to a group formed by removing one hydrogen from an alkane, for example, removing one hydrogen from methane to form a methyl group.

[0048] In an embodiment of the present application, a preparation method of a composite catalyst is provided, comprising the following steps S10-S20.

[0049] Step S10, mixing and treating the carbon carrier with hydrotalcite to prepare a mixture.

[0050] Step S20, calcining the mixture to prepare a composite catalyst.

[0051] It is found that the material of the carrier has a great influence on the adsorption of hydrotalcite and its calcined product, therefore, in the above preparation method of the composite catalyst, a specific carrier is mixed with hydrotalcite for calcination. Hydrotalcite forms metal oxide loaded on the carbon carrier during calcination to form a composite catalyst. When used for ester exchange reaction, the catalyst has high catalytic activity and is not easy to react with water, and can be reused.

[0052] Further, the composite catalyst prepared by the above preparation method is difficult to dissolve in water and most organic substances. When used for ester exchange reaction, it can be recovered directly by filtration, which is environmentally friendly and more conducive to industrial production.

[0053] In some embodiments, before the mixing and treating, the method further comprises the following step S11.

[0054] Step S11: immersing the carbon carrier in a strong acid solution for immersion treatment.

[0055] The carbon carrier is immersed in a strong acid solution, which can remove impurities in the carbon carrier, and can improve the adsorption of the carbon carrier to the hydrotalcite and the calcined product thereof, and can further improve the catalytic activity of the prepared composite carrier.

[0056] In some embodiments, the immersion treatment is performed under reflux conditions.

[0057] In some embodiments, the immersion treatment is performed for 4-6 hours.

[0058] In the above "4-6 hours", the values include the minimum and maximum values of the range, and every value between the minimum and maximum values, and specific examples include but are not limited to the point values in the embodiments and the following point values: 4h, 4.5h, 5h, 5.5h, 6h; or a range composed of any two numerical values.

[0059] In some embodiments, the strong acid solution includes concentrated sulfuric acid and concentrated nitric acid, and the volume ratio of the concentrated sulfuric acid to the concentrated nitric acid is (2-4):1.

[0060] In the above "(2-4):1", the values include the minimum and maximum values of the range, and every value between the minimum and maximum values, and specific examples include but are not limited to the point values in the embodiments and the following point values: 4:1, 3.5:1, 3:1, 2:1; or a range composed of any two numerical values.

[0061] In some embodiments, the mass-to-volume ratio of the carbon carrier to the strong acid solution is (0.08-0.13)g:1mL.

[0062] In some embodiments, the process further includes filtering the product after the immersion treatment to obtain a solid product.

[0063] Further, the solid product is washed and dried.

[0064] In some embodiments, the washing is performed with water until the water is neutral.

[0065] In some embodiments, the mass ratio of the carbon carrier to the hydrotalcite is 1:(1-3).

[0066] Adjusting the mass ratio of the carbon carrier to the hydrotalcite can further improve the effective component in the prepared composite catalyst.

[0067] In some embodiments, the mass ratio of the carbon carrier to the hydrotalcite is 1:(1-3).

[0068] In the above-mentioned “1:(1~3)”, the values include the minimum value and the maximum value of the range, and each value between the minimum value and the maximum value, and specific examples include but are not limited to the following point values in the embodiments: 1:1, 1:12, 1:3; or a range composed of any two numerical values.

[0069] In some embodiments, the carbon carrier includes at least one of carbon nanotubes, carbon paper, activated carbon, fullerene, and graphene.

[0070] In some embodiments, the hydrotalcite includes at least one of magnesium-aluminum hydrotalcite, iron-cobalt hydrotalcite, and magnesium-aluminum-zinc hydrotalcite.

[0071] In some embodiments, the step S10 mixing treatment includes the following steps:

[0072] The carbon carrier and the hydrotalcite are dispersed in water, and then sequentially subjected to a standing treatment, a solid-liquid separation treatment, and a drying treatment.

[0073] In some embodiments, the total mass of the carbon carrier and the hydrotalcite to the volume of water is (40~80) g:100 mL.

[0074] In some embodiments, the dispersion step is performed under stirring to fully mix the two as soon as possible.

[0075] In some embodiments, the standing treatment is performed for 60 min~120 min.

[0076] The solid-liquid separation treatment can use a method commonly used in the art, including but not limited to: filtration, suction filtration, etc.

[0077] In some embodiments, after the step of solid-liquid separation treatment and before the step of drying treatment, a step of washing the solid product of the solid-liquid separation treatment is further included. Further, the washing can be performed using water and ethanol.

[0078] In some embodiments, the temperature of the step S20 calcination treatment is 400℃~550℃.

[0079] The temperature of the calcination treatment is controlled to fully calcine the hydrotalcite to form metal oxides.

[0080] In the above-mentioned "400℃~550℃", the values include the minimum value and the maximum value of the range, and every value between the minimum value and the maximum value, and the specific examples include but are not limited to the point values in the embodiments and the following point values: 400℃, 410℃, 420℃, 430℃, 440℃, 450℃, 460℃, 470℃, 480℃, 490℃, 500℃, 510℃, 520℃, 530℃, 340℃, 550℃; or a range composed of any two numerical values.

[0081] In some embodiments, the calcination treatment time is 4h~6h.

[0082] An embodiment of the present application further provides a composite catalyst prepared by the preparation method of the composite catalyst.

[0083] An embodiment of the present application further provides a composite catalyst, which comprises a carbon carrier and an effective component supported on the carbon carrier, and the effective component comprises a metal oxide formed after calcination of a hydrotalcite.

[0084] The composite catalyst has high catalytic activity and is not prone to react with water when used in an ester exchange reaction, and can be repeatedly used.

[0085] It can be understood that the effective component supported on the carbon carrier means that the effective component can be supported on the surface of the carbon carrier, or doped or inlaid in the interior of the carbon carrier.

[0086] In some embodiments, the metal in the metal oxide formed after calcination of the hydrotalcite comprises at least one of magnesium, aluminum, iron, cobalt and zinc.

[0087] In some embodiments, the mass fraction of the effective component in the composite catalyst is 40%~80%; and optionally 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75% or 80%.

[0088] An embodiment of the present application provides a preparation method of a salicylate compound, which comprises the following steps:

[0089] The compound (1) and the compound (2) are subjected to an ester exchange reaction under the action of a catalyst to prepare a salicylate compound shown in formula (3); and the catalyst comprises the composite catalyst.

[0090] In the formula, the structures of the compound (1), the compound (2) and the salicylate compound shown in formula (3) are as follows:

[0091]

[0092] In the formula, R1 is selected from an alkyl group with 2~10 carbon atoms.

[0093] The composite catalyst has high catalytic activity and is not prone to reaction with water, thereby reducing the probability of side reactions and improving the yield and purity of the salicylate compound.

[0094] In some embodiments, R1 is selected from branched alkyl groups having 3 to 10 carbon atoms.

[0095] In some embodiments, R1 is selected from branched alkyl groups having 3 to 10 carbon atoms.

[0096] In some embodiments, R1 is selected from branched alkyl groups having 3 to 8 carbon atoms.

[0097] In some embodiments, R1 is selected from branched alkyl groups having 5 to 7 carbon atoms.

[0098] In some embodiments, R1 has the following structure:

[0099]

[0100] * represents a connection site.

[0101] In some embodiments, the compound (1) is methyl salicylate, which has the following structure:

[0102]

[0103] In some embodiments, the compound (2) is isooctanol.

[0104] In some embodiments, the salicylate compound represented by formula (3) is salicylic acid-2-ethylhexyl ester.

[0105] In some embodiments, the temperature of the transesterification reaction is 100°C to 130°C.

[0106] In the above "100°C to 130°C", the values include the minimum and maximum values of the range, as well as every value between such minimum and maximum values, and specific examples include but are not limited to the following point values in the embodiments: 100°C, 110°C, 120°C, 130°C; or a range composed of any two numerical values.

[0107] In some embodiments, the molar ratio of the compound (1) to the compound (2) is 1:(1-3).

[0108] In the above "1:(1-3)", the values include the minimum and maximum values of the range, as well as every value between such minimum and maximum values, and specific examples include but are not limited to the following point values in the embodiments: 1:1, 1:2, 1:3; or a range composed of any two numerical values.

[0109] In some embodiments, the mass of the effective component in the composite catalyst is 0.1% to 3% of the mass of compound (1); the effective component includes metal oxides formed after calcination of the hydrotalcite.

[0110] The use amount of the effective component in the composite catalyst is regulated to improve the transesterification reaction efficiency.

[0111] In some embodiments, the mass of the effective component in the composite catalyst is 1% to 1.5% of the mass of compound (1).

[0112] In some embodiments, the above-mentioned "0.1% to 3%" includes the minimum value and the maximum value of the range, and every value between the minimum value and the maximum value, specific examples include but are not limited to the following point values: 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%; or a range composed of any two numerical values.

[0113] The present application will be described in detail below with reference to specific embodiments, but the present application is not limited to the following embodiments, it should be understood that the appended claims generalize the scope of the present application, and those skilled in the art should realize that certain changes to the embodiments of the present application will be covered by the spirit and scope of the claims of the present application.

[0114] The following are specific embodiments.

[0115] Embodiment 1

[0116] (1) Preparation of composite catalyst A

[0117] 20g carbon nanotubes were placed in a mixed solution of 200mL concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 3:1, stirred at 80°C for 120min, cooled, filtered, washed with deionized water until neutral, and dried to obtain acid-impregnated carbon nanotubes.

[0118] The above-mentioned 20g acid-impregnated carbon nanotubes and 20g magnesium-aluminum hydrotalcite were placed in 100mL deionized water, stirred uniformly, and allowed to stand for 60min, then filtered, washed with deionized water and anhydrous ethanol, and dried and placed in a muffle furnace, calcined at 400°C for 5h to obtain composite catalyst A.

[0119] The mass percentage of the effective component in the composite catalyst A was calculated to be 50.2% according to the following formula.

[0120] The mass percentage of the effective component = (the mass of the composite catalyst A - the mass of the acid-impregnated carbon nanotubes) / the mass of the composite catalyst A x 100%.

[0121] (2) Preparation of salicylic acid-2-ethylhexyl ester

[0122] Put 103 g of methyl salicylate, 133 g of isooctanol, and 2.6 g of composite catalyst A into a reactor, replace the atmosphere with nitrogen for protection, reduce the pressure to less than -0.1 MPa (the absolute pressure is about 4.39 KPa) on the pressure gauge, and heat to 115°C for 4 h of reaction. After filtering and separating the catalyst, the filtrate is treated to remove the raw material, and then distilled at 160°C under reduced pressure to obtain salicylic acid-2-ethylhexyl ester. The synthesis route is as follows:

[0123]

[0124] The purity of salicylic acid-2-ethylhexyl ester is tested by gas chromatography.

[0125] The yield of salicylic acid-2-ethylhexyl ester is calculated according to the following formula:

[0126] Yield = (molar mass of salicylic acid-2-ethylhexyl ester) / (molar mass of methyl salicylate) x 100%

[0127] The molar mass of salicylic acid-2-ethylhexyl ester = (mass of salicylic acid-2-ethylhexyl ester product) x (purity) / (relative molecular mass).

[0128] The blackness of salicylic acid-2-ethylhexyl ester is measured by a CM 5 spectrophotometer of KONICA MINOLTA. The lower the blackness, the fewer the side reactions.

[0129] The specific results are shown in Table 1.

[0130] Example 2

[0131] Example 2 is basically the same as Example 1, except that composite catalyst A is replaced by composite catalyst B. The preparation steps of composite catalyst B are as follows:

[0132] Put 20 g of carbon nanotubes into a mixed solution of 200 mL of concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 2:1, stir and reflux at 80°C for 120 min, cool, filter, and wash with deionized water until neutral, and dry to obtain acid-impregnated carbon nanotubes.

[0133] Put the above 20 g of acid-impregnated carbon nanotubes and 20 g of magnesium-aluminum-zinc hydrotalcite into 100 mL of deionized water, stir evenly, stand for 60 min, filter, and wash with deionized water and anhydrous ethanol, and then dry and place in a muffle furnace, and calcine at 400°C for 5 h to obtain composite catalyst B.

[0134] The mass percentage of the effective components in composite catalyst B is calculated to be 50.1%.

[0135] Other steps and conditions are the same as in Example 1, and the specific results are shown in Table 1.

[0136] Example 3

[0137] Example 3 is basically the same as Example 1, except that the composite catalyst A is replaced by composite catalyst C, and the preparation steps of composite catalyst C are as follows:

[0138] 20 g of carbon nanotubes were placed in a mixed solution of 200 mL of concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 4:1, stirred at 80°C for 120 min, cooled, filtered, washed with deionized water until neutral, and dried to obtain acid-impregnated carbon nanotubes.

[0139] The above 20 g of acid-impregnated carbon nanotubes and 20 g of iron-cobalt hydrotalcite were placed in 100 mL of deionized water, stirred uniformly, and allowed to stand for 60 min. After filtration, deionized water and anhydrous ethanol were used for washing, and then dried and placed in a muffle furnace for calcination at 400°C for 5 h to obtain composite catalyst C.

[0140] The mass percentage of the effective component in composite catalyst C was calculated to be 49.8%.

[0141] Other steps and conditions are the same as in Example 1, and the specific results are shown in Table 1.

[0142] Example 4

[0143] Example 4 is basically the same as Example 1, except that the composite catalyst A is replaced by composite catalyst D, and the preparation steps of composite catalyst D are as follows:

[0144] The above 20 g of carbon nanotubes and 20 g of magnesium-aluminum-zinc hydrotalcite were placed in 100 mL of deionized water, stirred uniformly, and allowed to stand for 60 min. After filtration, deionized water and anhydrous ethanol were used for washing, and then dried and placed in a muffle furnace for calcination at 400°C for 5 h to obtain composite catalyst D.

[0145] Other steps and conditions are the same as in Example 1, and the specific results are shown in Table 1.

[0146] Example 5

[0147] Example 5 is basically the same as Example 2, except that the preparation of salicylic acid-2-ethylhexyl ester is as follows:

[0148] (1) 103 g of methyl salicylate, 133 g of isooctanol, and 2.6 g of composite catalyst B were placed in a reactor, and nitrogen was used for replacement control protection. After being heated to 115°C under reduced pressure for 4 h, the composite catalyst B was separated by filtration, and the filtrate was treated by removing the raw materials. Subsequently, salicylic acid-2-ethylhexyl ester was obtained by distillation at 160°C under reduced pressure.

[0149] (2) Using the composite catalyst B separated and recovered in step (1), step (1) was repeated 10 times, the yield of salicylic acid-2-ethylhexyl ester obtained in the last time was calculated, and the purity and the black color degree of the product were tested.

[0150] Other steps and conditions were the same as those in Example 2. The specific results are shown in Table 1.

[0151] Comparative Example 1

[0152] 103 g of methyl salicylate, 133 g of isooctanol, and 6.75 g of a 20 wt% sodium methoxide solution in methanol were added to a reactor, which was protected by nitrogen replacement control, and then the temperature was increased to 115°C under reduced pressure for 5 h of reaction. The reaction liquid was washed with acid and then washed with water until neutral. After dehydration under reduced pressure, the reaction liquid was treated by removing the raw materials, and then salicylic acid-2-ethylhexyl ester was obtained by distillation under reduced pressure at 160°C.

[0153] The yield, purity, and black color degree of salicylic acid-2-ethylhexyl ester were tested and calculated. The specific method was the same as that in Example 1. The specific results are shown in Table 1.

[0154] Comparative Example 2

[0155] Comparative Example 2 was basically the same as Example 1, except that the composite catalyst A was replaced by catalyst E, and the preparation steps were as follows:

[0156] The 20 g of magnesium-aluminum hydrotalcite was calcined at 400°C for 5 h to obtain catalyst E.

[0157] Other steps and conditions were the same as those in Example 1. The specific results are shown in Table 1.

[0158] Comparative Example 3

[0159] Comparative Example 3 was basically the same as Example 1, except that the composite catalyst A was replaced by composite catalyst F, and the preparation steps were as follows:

[0160] The above 20 g of alumina carrier particles and 20 g of magnesium-aluminum hydrotalcite were placed in 100 mL of deionized water, stirred uniformly, and then allowed to stand for 60 min. After filtration, the product was washed with deionized water and anhydrous ethanol, and then dried and placed in a muffle furnace for calcination at 400°C for 5 h to obtain composite catalyst F.

[0161] Other steps and conditions were the same as those in Example 1. The specific results are shown in Table 1.

[0162] The catalyst types and test results of each example and comparative example are shown in Table 1.

[0163] Table 1

[0164]

[0165] According to the data in Table 1, the test results of Comparative Examples 1-4 and Comparative Examples 1-3 show that the catalyst prepared by using the composite catalyst or the preparation method of the composite catalyst of the present application has high catalytic activity when catalyzing the transesterification reaction, and can reduce the probability of side reactions, thereby improving the yield and purity of salicylate compounds.

[0166] Further, according to Example 5, the composite catalyst of the present application can be directly filtered and recovered, is environmentally friendly, and can be reused. Even if it is reused for 10 times, it can still maintain high catalytic activity, which is more conducive to industrial production.

[0167] The technical features of the above-described embodiments can be combined arbitrarily. In order to make the description simple, all possible combinations of the technical features in the above-described embodiments are not described, but as long as the combinations of the technical features do not exist contradictory, they should be considered as the scope of the present disclosure.

[0168] The above examples only express several embodiments of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent application. It should be pointed out that for ordinary skilled persons in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the scope of the present application. Therefore, the protection scope of the present patent should be subject to the appended claims.

Claims

1. A method for producing a salicylate compound, characterized by, The method comprises the following steps: The ester exchange reaction of methyl salicylate and isooctanol is carried out under the action of a composite catalyst to prepare a salicylate compound, the salicylate compound is 2-ethylhexyl salicylate, the composite catalyst comprises a carbon carrier and an effective component supported on the carbon carrier, the effective component comprises a metal oxide formed after calcination of a hydrotalcite, the carbon carrier comprises at least one of carbon nanotubes, carbon paper, activated carbon, fullerene and graphene, and the hydrotalcite comprises at least one of magnesium-aluminum hydrotalcite, iron-cobalt hydrotalcite and magnesium-aluminum-zinc hydrotalcite.

2. The method for preparing a salicylate compound according to claim 1, wherein At least one of the following (1)-(3) is satisfied: (1) the temperature of the ester exchange reaction is 100-130 DEG C; (2) the molar ratio of the methyl salicylate to the isooctanol is 1:(1-3); (3) the mass of the effective component in the composite catalyst is 0.1-3% of the mass of the methyl salicylate.

3. The method for preparing salicylate compounds as described in claim 1, characterized in that, The mass ratio of the carbon carrier to the hydrotalcite is 1:(1-3).

4. The method for producing a salicylate compound according to any one of claims 1 to 3, wherein The preparation of the composite catalyst comprises the following steps: The carbon carrier and the hydrotalcite are mixed to prepare a mixture; The mixture is calcined to prepare the composite catalyst.

5. The method for preparing a salicylate compound according to claim 4, wherein the compound of formula (2) is prepared by the reaction of the compound of formula (3) with the compound of formula (4) in the presence of a base. Before the mixing step, the following step is further included: The carbon carrier is immersed in a strong acid solution.

6. The method for preparing a salicylate compound according to claim 5, wherein the compound of formula (2) is prepared by the reaction of the compound of formula (3) with the compound of formula (4) in the presence of a base. The immersion satisfies at least one of the following (1)-(3): (1) the immersion is carried out under reflux conditions; (2) the immersion time is 4-6 hours; (3) the strong acid solution comprises concentrated sulfuric acid and concentrated nitric acid, and the volume ratio of the concentrated sulfuric acid to the concentrated nitric acid is (2-4):

1.

7. The method for preparing salicylate compounds according to claim 4, characterized in that, The calcination temperature is 400-550 DEG C, and the calcination time is 4-6 hours.

8. The method of producing a salicylate compound according to any one of claims 5 to 7, wherein The mixing comprises the following steps: The carbon carrier and the hydrotalcite are dispersed in water, and then static treatment, solid-liquid separation and drying are carried out in sequence.

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