Solid acid catalyst as well as preparation method and application thereof

Abstract

The invention discloses a solid acid catalyst as well as a preparation method and application thereof, and relates to the technical field of synthesis of morpholine derivatives. The preparation of the solid acid catalyst comprises the following steps: carbonizing the organic carrier, sulfonating the carbonized product, and post-treating the sulfonated product to obtain the solid acid catalyst. The raw materials for preparing the catalyst belong to biomass, are wide in source, and have the characteristics of cheap and easily available raw materials and green and environment-friendly preparation process; the prepared solid acid catalyst has very high catalytic activity and stability, is convenient to separate from a reaction system, and can be recycled. The solid acid catalyst can be used for preparing N-acetylmorpholine, and the prepared N-acetylmorpholine is relatively high in yield and purity.

Description

Technical Field

[0001] The invention relates to the technical field of synthesizing morpholine derivatives, and in particular to a solid acid catalyst and a preparation method and application thereof. Background Art

[0002] The commonly used synthesis methods of N-acetylmorpholine are acetic acid method and acetic anhydride method. The acetic acid method uses morpholine and acetic acid as raw materials, and the two are first pre-reacted to generate morpholine acetate, and then further heated and dehydrated to generate N-acetylmorpholine. There are obvious defects in the acetic acid method, the volatility of the raw material acetic acid is strong, and the moisture in the mixed product needs to be removed for a long time. In the acetic anhydride method, morpholine and acetic anhydride react to generate N-acetylmorpholine and acetic acid, and the by-product acetic acid is not conducive to the separation and purification of the product.

[0003] In the prior art, the commonly used catalysts for the synthesis reaction of N-acetylmorpholine include concentrated sulfuric acid, ionic liquids and the like. The concentrated sulfuric acid catalyst is highly corrosive, has very stringent requirements on equipment and process, and will also cause many environmental problems. The preparation process of the ionic liquid catalyst is complicated, and its catalytic activity and stability are difficult to control.

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

[0005] The purpose of the present invention is to provide a solid acid catalyst and a preparation method and application thereof to solve the above technical problems.

[0006] The present invention is achieved in that:

[0007] In a first aspect, an embodiment of the present invention provides a method for preparing a solid acid catalyst, the method comprising carbonizing an organic carrier, then sulfonating the carbonized product, and post-treating the sulfonated product to obtain a solid acid catalyst; the carbonization and sulfonation are both performed in an inert atmosphere;

[0008] The mass ratio of the carbonized product to the sulfonating agent for sulfonation treatment is 1:(20-25).

[0009] In a second aspect, an embodiment of the present invention provides a solid acid catalyst prepared by the aforementioned preparation method.

[0010] In a third aspect, an embodiment of the present invention provides a use of a solid acid catalyst prepared by the aforementioned preparation method in the preparation of N-acetylmorpholine.

[0011] The present invention has the following beneficial effects:

[0012] The solid acid catalyst provided by the embodiment of the present invention is a new catalyst with high catalytic activity. The raw material for preparing the catalyst belongs to biomass, has a wide range of sources, and has the characteristics of cheap and easy-to-obtain raw materials and green and environmentally friendly preparation process; in addition, the solid acid catalyst of the present invention is easy to separate from the reaction system and can be recycled. The above-mentioned solid acid catalyst is applied to the production of N-acetylmorpholine, and N-acetylmorpholine with higher yield and purity can be obtained. DETAILED DESCRIPTION

[0013] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0014] N-acetylmorpholine is one of the most important morpholine derivatives and has a good market application prospect. N-acetylmorpholine can be used as an absorption solvent for desulfurization and decarbonization of natural gas or synthetic oil, and can meet the deep purification of H2S and CO2 acidic gases. In addition, N-acetylmorpholine can also be used as a synthetic raw material for enoylmorpholine and flumorph, and is widely used in the field of pesticide synthesis.

[0015] In view of the fact that in the prior art, the catalyst for preparing N-acetylmorpholine has strict requirements on equipment and process, and at the same time, it will cause environmental problems or the problem that the catalytic activity and stability are difficult to control, the present invention is now proposed, a new solid acid catalyst with biomass raw materials as carriers, which has the characteristics of green and environmentally friendly preparation process, cheap and easy to obtain raw materials, and the prepared solid acid catalyst is easy to separate from the reaction system and can be recycled. The solid acid catalyst is applied to the production of N-acetylmorpholine to obtain N-acetylmorpholine with a higher yield. The details are as follows:

[0016] In a first aspect, an embodiment of the present invention provides a method for preparing a solid acid catalyst, the method comprising carbonizing an organic carrier, then sulfonating the carbonized product, and post-treating the sulfonated product to obtain a solid acid catalyst; the carbonization and sulfonation are both performed in an inert atmosphere;

[0017] The mass ratio of the carbonized product to the sulfonating agent for sulfonation treatment is 1:(20-25).

[0018] It should be noted that the solid acid catalyst of the present invention uses an organic carrier as a raw material, which belongs to biomass, has a wide source, is cheap and easy to obtain; carbonization treatment can increase the pores between molecules to obtain a material with a porous structure, which is convenient for subsequent sulfonation treatment.

[0019] In an optional embodiment of the present invention, the organic carrier is selected from at least one of starch, sucrose and lignin; further, the starch is selected from any one of corn starch, potato starch, sweet potato starch and pea starch.

[0020] In a preferred embodiment of the present invention, the organic carrier is a starch-based substance.

[0021] It should be noted that starch materials are selected because the solid acid catalyst prepared by using starch materials as carrier raw materials has excellent catalytic performance.

[0022] In an optional embodiment of the present invention, the temperature of the carbonization treatment is 300°C-500°C, and the time is 30min-60min; the temperature of the sulfonation treatment is 70°C-90°C, and the time is 8h-12h.

[0023] It should be noted that the processes of carbonization and sulfonation are both carried out in an inert atmosphere. The presence of an inert gas can ensure the stability of the reaction environment, reduce the oxygen content in the reaction system, avoid the formation of carbon oxides, affect the specific surface area of ​​the product, and further affect the preparation of the carrier. The present invention does not particularly limit the type of inert gas, and an inert gas such as nitrogen, argon or helium can be selected according to actual conditions. In an embodiment of the present invention, the specific temperature and time of the carbonization and sulfonation can be reasonably adjusted according to the actual amount of raw materials processed.

[0024] Carbonization is the process of heating and decomposing organic matter in an air-tight environment, which is beneficial to changing the structure of organic matter and forming countless tiny pores on its surface, thereby obtaining active porous carbon materials. Their high specific surface area and excellent adsorption properties facilitate the efficient subsequent sulfonation treatment.

[0025] Specifically, the carbonization process in the embodiment of the present invention is as follows: a certain amount of starch is weighed, and carbonized at a constant temperature for a period of time in a nitrogen atmosphere to obtain a black solid product after carbonization treatment, which is then ground into a uniform fine powder after cooling to obtain a carbonized product.

[0026] Sulfonation treatment is achieved by introducing sulfonic acid groups into organic matter. The product of carbonization treatment is subjected to sulfonation treatment in order to make it have catalytic active sites.

[0027] In an optional embodiment of the present invention, the sulfonating agent is selected from at least one of trifluoromethanesulfonic acid and p-toluenesulfonic acid; further, the sulfonating agent includes trifluoromethanesulfonic acid.

[0028] In an optional embodiment of the present invention, post-processing the sulfonated product includes filtering and washing the sulfonated product until the washed filtrate is neutral, and then drying the washed sulfonated product; wherein the washing solution is water, and the water temperature is 90°C-100°C.

[0029] It should be noted that the purpose of post-treatment is to remove unreacted raw materials and by-products produced during the reaction process; washing the sulfonated product until the filtrate is neutral is to avoid the influence of acidic substances on the subsequent conversion rate of morpholine or the yield of N-acetylmorpholine. The water used can be deionized water, purified water or ultrapure water according to actual needs.

[0030] Specifically, the process of sulfonation treatment and post-treatment in the embodiment of the present invention is as follows:

[0031] The carbonized product is added to a sulfonating agent, and sulfonation treatment is carried out at a certain temperature in a nitrogen atmosphere. After cooling, the sulfonated product is added to deionized water, stirred, allowed to stand, and filtered. The filter cake is repeatedly washed with hot deionized water until the filtrate is neutral. The washed sulfonated product is dried to obtain a solid acid catalyst.

[0032] It should be noted that during the washing process, in an optional embodiment of the present invention, the mass ratio of the sulfonated product to water is 1: (40-60), and hot water is used for washing at the same time, which can quickly and efficiently clean the unreacted substances or residual impurities on the surface of the sulfonated product. After washing until the filtrate is neutral, the washed sulfonated product is dried.

[0033] The drying process is vacuum drying, which includes: temperature of 100°C-120°C, pressure of -0.09MPa to -0.10MPa, and time of 18h-24h;

[0034] It should be noted that the drying method in the present invention is vacuum drying, which is helpful for preparing a catalyst with a large specific surface area.

[0035] In a second aspect, an embodiment of the present invention provides a solid acid catalyst prepared by the aforementioned preparation method.

[0036] In a third aspect, an embodiment of the present invention provides a use of a solid acid catalyst prepared by the aforementioned preparation method in the preparation of N-acetylmorpholine.

[0037] In an optional embodiment of the present invention, the preparation of N-acetylmorpholine comprises the following steps:

[0038] The N-acetylmorpholine is prepared by mixing morpholine, isopropyl acetate and a solid acid catalyst for reaction;

[0039] The molar ratio of morpholine to isopropyl acetate is 1:(1.2-1.4); and the amount of the solid acid catalyst used is 0.4wt%-0.8wt% of the total mass of morpholine and isopropyl acetate.

[0040] The temperature of the mixed reaction is 120°C-140°C, and the time is 5h-8h.

[0041] After the mixed reaction is completed, the reaction product is subjected to impurity removal and rectification, and the fractions are collected to obtain N-acetylmorpholine.

[0042] It should be noted that the preparation principle of N-acetylmorpholine is as follows:

[0043]

[0044] Specifically, the preparation process of N-acetylmorpholine is as follows:

[0045] Morpholine and isopropyl acetate are reacted under the action of the solid acid catalyst at 120° C.-140° C. for 5 h-8 h.

[0046] If the reaction temperature of the reaction raw materials under the action of solid acid catalyst is lower than 120°C or the reaction time is less than 5h, the product yield is low; if the reaction temperature is higher than 140°C or the reaction time is longer than 8h, the by-products increase.

[0047] The molar ratio of morpholine to isopropyl acetate is 1:(1.2-1.4). Within the above molar ratio range, a higher yield of N-acetylmorpholine can be obtained.

[0048] The amount of the solid acid catalyst used is 0.4wt%-0.8wt% of the total mass of the reaction raw materials.

[0049] If the amount of the solid acid catalyst exceeds 0.8wt%, more by-products are likely to be produced; if the amount of the solid acid catalyst is less than 0.4wt%, the reaction is incomplete. However, within the range defined in the embodiment of the present invention, the yield of the reaction product can be guaranteed.

[0050] After the reaction is completed, the solid acid catalyst is removed by filtration, and then the unreacted morpholine and isopropyl acetate in the crude product, as well as the by-product isopropyl alcohol produced during the reaction are removed by distillation, and then atmospheric distillation is performed to collect the fraction at 240° C.-243° C., which is the N-acetylmorpholine product.

[0051] It should be noted that isopropanol, a byproduct produced during the preparation of N-acetylmorpholine, is an excellent solvent and dehydrating agent and has a high utilization value.

[0052] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0053] Example 1

[0054] This embodiment provides a solid acid catalyst and N-acetylmorpholine.

[0055] (1) The preparation of the solid acid catalyst comprises the following steps:

[0056] The corn starch was carbonized at 350°C for 60 minutes in a nitrogen atmosphere to obtain a black solid product, which was ground into a uniform fine powder after cooling to obtain a carbonized product. 1g of the carbonized product was added to 20g of trifluoromethanesulfonic acid and sulfonated at 80°C for 12 hours in a nitrogen atmosphere. After cooling, the sulfonated product was added to deionized water, stirred, allowed to stand, and filtered. The filter cake was repeatedly washed with hot deionized water at 90°C until the filtrate was neutral. The filter cake was placed in a vacuum drying oven at 110°C and -0.095MPa and dried for 18 hours to obtain a solid acid catalyst.

[0057] (2) The preparation of N-acetylmorpholine comprises the following steps:

[0058] 1 mol of morpholine and 1.2 mol of isopropyl acetate are reacted at 120°C for 8 hours, and the amount of solid acid catalyst used is 0.8wt% of the total mass of the reaction raw materials. After the reaction is completed, the catalyst is removed by filtration to obtain a crude N-acetylmorpholine product. Morpholine, isopropyl acetate and isopropanol in the crude product are first removed by distillation, and then atmospheric distillation is performed to collect the fraction at 240°C-243°C, which is the N-acetylmorpholine product.

[0059] Example 2

[0060] This embodiment provides a solid acid catalyst and N-acetylmorpholine.

[0061] (1) The preparation of the solid acid catalyst comprises the following steps:

[0062] The corn starch was carbonized at 500°C for 30 minutes in a nitrogen atmosphere, and a black solid product was obtained by carbonization treatment. After cooling, it was ground into uniform fine powder to obtain a carbonized product. 1g of the carbonized product was added to 25g of trifluoromethanesulfonic acid, and sulfonated at 90°C for 8h in a nitrogen atmosphere. After cooling, the sulfonated product was added to deionized water, stirred, allowed to stand, and filtered. The filter cake was repeatedly washed with hot deionized water at 100°C until the filtrate was neutral. The filter cake was placed in a vacuum drying oven at 100°C and -0.1MPa and dried for 24h to obtain a solid acid catalyst.

[0063] (2) The preparation of N-acetylmorpholine comprises the following steps:

[0064] 1 mol of morpholine and 1.4 mol of isopropyl acetate are reacted at 140°C for 5 hours, and the amount of solid acid catalyst used is 0.6wt% of the total mass of the reaction raw materials. After the reaction is completed, the catalyst is removed by filtration to obtain a crude N-acetylmorpholine product. Morpholine, isopropyl acetate and isopropanol in the crude product are first removed by distillation, and then atmospheric distillation is performed to collect the fraction at 240°C-243°C, which is the N-acetylmorpholine product.

[0065] Example 3

[0066] This embodiment provides a solid acid catalyst and N-acetylmorpholine.

[0067] (1) The preparation of the solid acid catalyst comprises the following steps:

[0068] The corn starch was carbonized at 400°C for 40 minutes in a nitrogen atmosphere, and a black solid product was obtained by carbonization treatment. After cooling, it was ground into uniform fine powder to obtain a carbonized product. 1g of the carbonized product was added to 25g of trifluoromethanesulfonic acid, and sulfonated at 70°C for 12 hours in a nitrogen atmosphere. After cooling, the sulfonated product was added to deionized water, stirred, allowed to stand, and filtered. The filter cake was repeatedly washed with hot deionized water at 90°C until the filtrate was neutral. The filter cake was placed in a vacuum drying oven at 120°C and -0.1MPa and dried for 24 hours to obtain a solid acid catalyst.

[0069] (2) The preparation of N-acetylmorpholine comprises the following steps:

[0070] 1 mol of morpholine and 1.3 mol of isopropyl acetate are reacted at 140°C for 6 hours, and the amount of solid acid catalyst used is 0.5wt% of the total mass of the reaction raw materials. After the reaction is completed, the catalyst is removed by filtration to obtain a crude N-acetylmorpholine product. Morpholine, isopropyl acetate and isopropanol in the crude product are first removed by distillation, and then atmospheric distillation is performed to collect the fraction at 240°C-243°C, which is the N-acetylmorpholine product.

[0071] Example 4

[0072] This embodiment provides a solid acid catalyst and N-acetylmorpholine.

[0073] (1) The preparation of the solid acid catalyst comprises the following steps:

[0074] The corn starch was carbonized at 300°C for 50 minutes in a nitrogen atmosphere, and a black solid product was obtained by carbonization treatment. After cooling, it was ground into uniform fine powder to obtain a carbonized product. 1g of the carbonized product was added to 23g of trifluoromethanesulfonic acid, and sulfonated at 90°C for 10 hours in a nitrogen atmosphere. After cooling, the sulfonated product was added to deionized water, stirred, allowed to stand, and filtered. The filter cake was repeatedly washed with hot deionized water at 90°C until the filtrate was neutral. The filter cake was placed in a vacuum drying oven at 110°C and -0.09MPa and dried for 24 hours to obtain a solid acid catalyst.

[0075] (2) The preparation of N-acetylmorpholine comprises the following steps:

[0076] 1 mol of morpholine and 1.3 mol of isopropyl acetate are reacted at 120°C for 8 hours, and the amount of solid acid catalyst used is 0.8wt% of the total mass of the reaction raw materials. After the reaction is completed, the catalyst is removed by filtration to obtain a crude N-acetylmorpholine product. Morpholine, isopropyl acetate and isopropanol in the crude product are first removed by distillation, and then atmospheric distillation is performed to collect the fraction at 240°C-243°C, which is the N-acetylmorpholine product.

[0077] Example 5

[0078] This embodiment provides a solid acid catalyst and N-acetylmorpholine.

[0079] (1) Preparation of solid acid catalyst: same as in Example 1.

[0080] (2) The preparation of N-acetylmorpholine comprises the following steps:

[0081] 1 mol of morpholine and 1.4 mol of isopropyl acetate are reacted at 140°C for 7 hours, and the amount of solid acid catalyst used is 0.4wt% of the total mass of the reaction raw materials. After the reaction is completed, the catalyst is removed by filtration to obtain a crude N-acetylmorpholine product. Morpholine, isopropyl acetate and isopropanol in the crude product are first removed by distillation, and then atmospheric distillation is performed to collect the fraction at 240°C-243°C, which is the N-acetylmorpholine product.

[0082] Example 6

[0083] This embodiment provides a solid acid catalyst and N-acetylmorpholine.

[0084] (1) The preparation of the solid acid catalyst comprises the following steps:

[0085] The corn starch was carbonized at 350°C for 50 minutes in a nitrogen atmosphere to obtain a black solid product, which was ground into a uniform fine powder after cooling to obtain a carbonized product. 1g of the carbonized product was added to 23g of trifluoromethanesulfonic acid and sulfonated at 80°C for 10 hours in a nitrogen atmosphere. After cooling, the sulfonated product was added to deionized water, stirred, allowed to stand, and filtered. The filter cake was repeatedly washed with hot deionized water at 95°C until the filtrate was neutral. The filter cake was placed in a vacuum drying oven at 110°C and -0.1MPa and dried for 24 hours to obtain a solid acid catalyst.

[0086] (2) Preparation of N-acetylmorpholine: Same as Example 1.

[0087] Comparative Example 1

[0088] This comparative example provides a solid acid catalyst and N-acetylmorpholine, which differs from Example 1 in that the mass ratio of the carbonized product to trifluoromethanesulfonic acid in the preparation of the solid acid catalyst is not within the range, specifically including:

[0089] The preparation of the solid acid catalyst comprises the following steps: carbonizing corn starch at 350° C. for 60 min in a nitrogen atmosphere, obtaining a black solid product through carbonization treatment, grinding it into uniform fine powder after cooling, and obtaining a carbonized product. 1 g of the carbonized product is added to 10 g of trifluoromethanesulfonic acid, and sulfonated at 80° C. for 12 h in a nitrogen atmosphere, and after cooling, the sulfonated product is added to deionized water, stirred, allowed to stand, filtered, and the filter cake is repeatedly washed with hot deionized water at 90° C. until the filtrate is neutral, and the filter cake is placed in a vacuum drying oven at 110° C. and -0.095 MPa and dried for 18 h to obtain a solid acid catalyst.

[0090] Comparative Example 2

[0091] This comparative example provides a solid acid catalyst and N-acetylmorpholine, which differs from Example 1 in that the sulfonation treatment temperature in the preparation of the solid acid catalyst is not within the range, specifically including:

[0092] The preparation of the solid acid catalyst includes the following steps: carbonizing corn starch at 350°C for 60 minutes in a nitrogen atmosphere, obtaining a black solid product through carbonization treatment, grinding it into uniform fine powder after cooling, and obtaining a carbonized product. 1g of the carbonized product is added to 20g of trifluoromethanesulfonic acid, and sulfonated at 50°C for 12 hours in a nitrogen atmosphere, and after cooling, the sulfonated product is added to deionized water, stirred, allowed to stand, and filtered, and the filter cake is repeatedly washed with hot deionized water at 90°C until the filtrate is neutral, and the filter cake is placed in a vacuum drying oven at 110°C and -0.095MPa and dried for 18 hours to obtain a solid acid catalyst.

[0093] Comparative Example 3

[0094] This comparative example provides a solid acid catalyst and N-acetylmorpholine, which differs from Example 1 in that the amount of the solid acid catalyst is not within the range, and specifically includes:

[0095] The preparation of N-acetylmorpholine comprises the following steps: reacting 1 mol of morpholine and 1.2 mol of isopropyl acetate at 120°C for 8 hours, using a solid acid catalyst in an amount of 0.2wt% of the total mass of the reaction raw materials, and removing the catalyst by filtration after the reaction to obtain a crude N-acetylmorpholine product. First, morpholine, isopropyl acetate and isopropanol in the crude product are removed by distillation, and then atmospheric distillation is performed to collect a fraction at 240°C-243°C, which is the N-acetylmorpholine product.

[0096] Comparative Example 4

[0097] This comparative example provides a solid acid catalyst and N-acetylmorpholine, which differs from Example 1 in that the reaction temperature for preparing N-acetylmorpholine is not within the range, specifically including:

[0098] The preparation of N-acetylmorpholine comprises the following steps: reacting 1 mol of morpholine and 1.2 mol of isopropyl acetate at 70°C for 8 hours, using a solid acid catalyst in an amount of 0.8wt% of the total mass of the reaction raw materials, and removing the catalyst by filtration after the reaction to obtain a crude N-acetylmorpholine product. First, morpholine, isopropyl acetate and isopropanol in the crude product are removed by distillation, and then atmospheric distillation is performed to collect a fraction at 240°C-243°C, which is the N-acetylmorpholine product.

[0099] Comparative Example 5

[0100] This comparative example provides a solid acid catalyst and N-acetylmorpholine, which differs from Example 1 in that the sulfonating agent in the preparation of the solid acid catalyst is changed from trifluoromethanesulfonic acid to concentrated sulfuric acid, specifically comprising:

[0101] The preparation of the solid acid catalyst includes the following steps: carbonizing corn starch at 350°C for 60 minutes in a nitrogen atmosphere, obtaining a black solid product through carbonization treatment, grinding it into uniform fine powder after cooling, and obtaining a carbonized product. 1g of the carbonized product is added to 20g of concentrated sulfuric acid, and sulfonated at 80°C for 12 hours in a nitrogen atmosphere. After cooling, the sulfonated product is added to deionized water, stirred, allowed to stand, and filtered. The filter cake is repeatedly washed with hot deionized water at 90°C until the filtrate is neutral, and the filter cake is placed in a vacuum drying oven at 110°C and -0.095MPa and dried for 18 hours to obtain a solid acid catalyst.

[0102] Test Example 1

[0103] In this test example, an Agilent 7820A gas chromatograph was used to test the conversion rate of morpholine, the yield and purity of N-acetylmorpholine product in Examples 1-6 and Comparative Examples 1-5. The relevant data are shown in Table 1.

[0104] Table 1 Gas chromatography test data results

[0105] Morpholine conversion rate / % N-acetylmorpholine yield / % N-acetylmorpholine purity / % Example 1 98.9 95.2 98.3 Example 2 98.6 95.3 98.3 Example 3 98.7 94.6 97.9 Example 4 98.5 94.1 98.2 Example 5 97.7 93.2 97.6 Example 6 97.4 93.4 98.1 Comparative Example 1 89.2 84.2 97.0 Comparative Example 2 85.3 80.1 96.9 Comparative Example 3 81.0 75.6 96.4 Comparative Example 4 72.8 67.4 95.9 Comparative Example 5 87.7 81.9 97.2

[0106] As can be seen from Table 1, in the embodiments 1-6 provided in the embodiments of the present invention, when the solid acid catalyst and the preparation method of N-acetylmorpholine are within the scope provided in the embodiments of the present invention, the yield and purity of the prepared N-acetylmorpholine are higher, and the conversion rate of the morpholine raw material is high. In Comparative Examples 1-2, the mass ratio of the carbonized product and trifluoromethanesulfonic acid during the preparation of the solid acid catalyst in Example 1 is increased, and the sulfonation treatment temperature is reduced, and the results show that the yield of the prepared N-acetylmorpholine decreases. In Comparative Example 3, the amount of solid acid catalyst in Example 1 is reduced, and the results show that the yield of the prepared N-acetylmorpholine decreases. In Comparative Example 4, the reaction temperature of the preparation of N-acetylmorpholine in Example 1 is reduced, and the results show that the yield of the prepared N-acetylmorpholine decreases. In Comparative Example 5, the sulfonating agent is changed from trifluoromethanesulfonic acid to concentrated sulfuric acid, and the results show that the yield of the prepared N-acetylmorpholine decreases.

[0107] In summary, the catalytic activity of the solid acid catalyst provided by the embodiment of the present invention is high, and the preparation process is green and environmentally friendly, and no waste is produced. The above-mentioned solid acid catalyst is applied to the production of N-acetylmorpholine, a higher N-acetylmorpholine yield can be obtained, and the utilization rate of raw material morpholine is high. In addition, the by-product isopropyl alcohol produced by the preparation process has very high added value.

[0108] 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. A method for preparing a solid acid catalyst, characterized in that: The preparation method comprises: carbonizing an organic carrier, then sulfonating the carbonized product, and post-treating the sulfonated product to obtain the solid acid catalyst; the carbonization and sulfonation are both performed in an inert atmosphere; The mass ratio of the carbonized product to the sulfonating agent for sulfonation treatment is 1:(20-25).

2. The preparation method according to claim 1, characterized in that: The organic carrier is selected from at least one of starch, sucrose and lignin; Preferably, the starch material is selected from any one of corn starch, potato starch, sweet potato starch and pea starch.

3. The preparation method according to claim 1, characterized in that: The carbonization treatment temperature is 300°C-500°C, and the time is 30min-60min; The temperature of the sulfonation treatment is 70° C.-90° C., and the time is 8 h-12 h.

4. The preparation method according to claim 1, characterized in that: The sulfonating agent is selected from at least one of trifluoromethanesulfonic acid and p-toluenesulfonic acid; Preferably, the sulfonating agent comprises trifluoromethanesulfonic acid.

5. The preparation method according to claim 1, characterized in that: The post-processing includes: The sulfonated product is filtered and washed until the washed filtrate is neutral, and then the washed sulfonated product is dried.

6. The preparation method according to claim 5, characterized in that: The drying treatment is vacuum drying; the temperature of the vacuum drying is 100°C-120°C, the pressure is -0.09MPa to -0.10MPa, and the time is 18h-24h.

7. A solid acid catalyst obtained by the preparation method according to any one of claims 1 to 6.

8. Use of a solid acid catalyst obtained by the preparation method according to any one of claims 1 to 6 in the preparation of N-acetylmorpholine.

9. The use according to claim 8, characterized in that: The preparation of the N-acetylmorpholine comprises the following steps: Mixing morpholine, isopropyl acetate and the solid acid catalyst to produce the N-acetylmorpholine; The molar ratio of the morpholine to the isopropyl acetate is 1:(1.2-1.4); The solid acid catalyst is used in an amount of 0.4 wt % to 0.8 wt % of the total mass of the morpholine and the isopropyl acetate.

10. The use according to claim 9, characterized in that: The temperature of the mixed reaction is 120°C-140°C, and the time is 5h-8h; Preferably, the preparation of N-acetylmorpholine further comprises: After the mixed reaction is completed, the reaction product is subjected to impurity removal and rectification, and the fractions are collected to obtain N-acetylmorpholine.

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