Preparation method of ethyl p-aminobenzoate
By combining esterification and hydrogenation reactions, the problems of harsh reaction conditions and environmental pollution in the synthesis of ethyl p-aminobenzoate are solved, a low-cost and efficient production process is achieved, and safety risks and equipment requirements are reduced.
Patent Information
- Application Number
- CN202510966587.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-14
- Publication Date
- 2025-10-03
AI Technical Summary
The existing synthesis process of ethyl p-aminobenzoate has the problems of harsh reaction conditions, high equipment requirements, high production costs, high safety risks and serious environmental pollution.
A method combining esterification reaction and hydrogenation reaction is adopted, using concentrated sulfuric acid as a catalyst. After ethyl p-nitrobenzoate is generated by esterification, a hydrogenation reaction is performed to generate ethyl p-aminobenzoate. The reaction conditions and equipment requirements are reduced by optimizing the post-processing steps.
Mild reaction conditions are achieved, equipment investment and production costs are reduced, product yield is improved, the use of toxic and hazardous reagents and environmental pollution are reduced, and safety risks are reduced.
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Figure CN120736995A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of organic synthesis, in particular to a method for preparing ethyl p-aminobenzoate. Background Art
[0002] The existing synthesis routes of ethyl p-aminobenzoate mainly include esterification, acyl chloride method, transesterification method, enzyme catalysis method, etc. The reaction principles and disadvantages of each synthesis process are as follows:
[0003] 1)Esterification method
[0004] Reaction principle: Using p-aminobenzoic acid and ethanol as raw materials, an esterification reaction occurs under the action of concentrated sulfuric acid and other catalysts to produce ethyl p-aminobenzoate.
[0005] Disadvantages: Concentrated sulfuric acid is highly corrosive, has high requirements for equipment, and the post-reaction treatment is complicated, which will produce a large amount of acidic wastewater and cause serious environmental pollution.
[0006] 2) Acid chloride method
[0007] Reaction principle: First, p-aminobenzoic acid reacts with thionyl chloride to generate p-aminobenzoyl chloride, which then reacts with ethanol to obtain ethyl p-aminobenzoate.
[0008] Disadvantages: Reagents such as thionyl chloride are highly toxic, and a large amount of harmful gases are produced during the reaction, requiring strict tail gas treatment measures, and the production cost is relatively high.
[0009] 3) Transesterification
[0010] Reaction principle: methyl p-aminobenzoate and ethanol undergo ester exchange reaction under the action of a catalyst to produce ethyl p-aminobenzoate and methanol.
[0011] Disadvantages: The reaction usually needs to be carried out at higher temperature and pressure, which requires higher equipment and longer reaction time.
[0012] 4) Enzyme catalysis method
[0013] Reaction principle: Use lipase and other biological enzymes as catalysts to catalyze the esterification reaction of p-aminobenzoic acid and ethanol.
[0014] Disadvantages: The cost of enzymes is high, the stability is relatively poor, the dosage and activity of enzymes in the reaction system must be strictly controlled, and industrial scale-up is difficult. Summary of the Invention
[0015] The present invention aims to provide a method for preparing ethyl p-aminobenzoate, which solves the problems existing in the prior art such as harsh reaction conditions, high equipment requirements, high production costs, high safety risks, and serious environmental pollution.
[0016] To achieve the above object, the present invention provides a method for preparing ethyl p-aminobenzoate, comprising the following steps:
[0017] S1, adding p-nitrobenzoic acid and ethanol to a reactor, adding concentrated sulfuric acid dropwise and heating to carry out esterification reaction to prepare ethyl p-nitrobenzoate;
[0018] S2, post-treating the ethyl p-nitrobenzoate obtained in step S1;
[0019] S3, adding ethyl p-nitrobenzoate and ethanol obtained by the post-treatment of step S2 to a hydrogenation reactor, adding a catalyst, passing nitrogen and hydrogen in sequence, and finally heating the reaction in a hydrogen atmosphere to obtain ethyl p-aminobenzoate;
[0020] S4. Post-treating the ethyl p-aminobenzoate obtained in step S3 to obtain the final target product.
[0021] Preferably, in step S1, the amount of p-nitrobenzoic acid used is 150.75-184.25 kg, the amount of ethanol used is 450-550 L, and the amount of concentrated sulfuric acid used is 47.5-52.5 L.
[0022] Preferably, in step S1, the temperature of the esterification reaction is 65-75° C., and the reaction time is 3 h.
[0023] Preferably, in step S2, the specific operation of the post-treatment is: recovering part of the ethanol by atmospheric distillation to maintain the fluidity of the material, then washing with 450-550 L of water at a temperature of 45-55° C., cooling to 0° C. and then centrifuging to obtain a wet product of ethyl p-nitrobenzoate.
[0024] Preferably, in step S3, the amount of ethyl p-nitrobenzoate used is 355.5-434.5 kg, and the amount of ethanol used is 1035-1265 L.
[0025] Preferably, in step S3, the catalyst is a Pd / C catalyst diluted with ethanol, wherein the amount of ethanol used is 103.5-126.5 L, and the amount of Pd / C catalyst used is 2.85-3.15 kg.
[0026] Preferably, in step S3, nitrogen is introduced to 0.2 MPa to purge the reactor three times, vented, and then hydrogen is introduced to 0.3-0.7 MPa to purge nitrogen in the reactor three times.
[0027] Preferably, in step S3, the reaction temperature is 55-65° C. and the reaction time is 3 h.
[0028] Preferably, in step S4, the specific operation of the post-treatment is: filtering to recover the catalyst, then performing reduced pressure distillation on the filtrate to recover part of the ethanol to maintain the fluidity of the material, finally cooling to 0°C and then centrifuging, and finally vacuum drying to obtain the target product.
[0029] Preferably, the temperature of the reduced pressure distillation is 75-85°C, and the temperature of the vacuum drying is 55-65°C.
[0030] Therefore, the preparation method of ethyl p-aminobenzoate provided by the present invention has the following beneficial effects:
[0031] (1) The reaction conditions are mild and easy to operate, without the need for harsh conditions such as high temperature and high pressure;
[0032] (2) The equipment used is common equipment, which requires less investment and reduces production costs;
[0033] (3) The product yield is high, which improves production efficiency and economic benefits;
[0034] (4) The safety risk is low, which reduces the use of toxic and harmful reagents and the generation of harmful gases, and reduces safety hazards and environmental pollution in the production process.
[0035] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS
[0036] Figure 1 This is an infrared spectrum of ethyl p-nitrobenzoate prepared in an embodiment of the present invention;
[0037] Figure 2 This is the infrared spectrum of ethyl p-aminobenzoate prepared in an embodiment of the present invention. DETAILED DESCRIPTION
[0038] The technical solution of the present invention is further described below by means of the accompanying drawings and examples. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. Any other changes, modifications, substitutions, combinations, and simplifications made without violating the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the protection scope of the present invention. In addition, it should be understood that after reading the contents of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application and belong to the scope of protection of the present invention.
[0039] References to "embodiments" herein mean that the specific features, structures, or characteristics described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the word "embodiment" in various places in the specification does not necessarily refer to the same embodiment, nor does it particularly limit its independence or relevance to other embodiments. In principle, in this application, as long as there are no technical contradictions or conflicts, the various technical features mentioned in the embodiments can be combined in any manner to form a corresponding implementable technical solution.
[0040] Unless otherwise defined, the technical terms used herein have the same meanings as those generally understood by those skilled in the art to which this application belongs; the use of relevant terms herein is only for describing specific embodiments and is not intended to limit this application.
[0041] Unless otherwise specified in the present invention, the reagents, instruments, equipment and performance testing methods used are those commonly used by those skilled in the art.
[0042] Example
[0043] This embodiment provides a method for preparing ethyl p-aminobenzoate, and the specific steps are as follows:
[0044] S1. Add 167.5 kg of p-nitrobenzoic acid and 500 L of ethanol to an esterification reactor, stir to dissolve, then slowly add 50 L of concentrated sulfuric acid dropwise, heat to 70° C. and react for 3 h to obtain ethyl nitrobenzoate.
[0045] S2. Recover part of the ethanol by atmospheric distillation to maintain the fluidity of the material, then wash it with 500L of hot water at 50°C, and finally cool it to 0°C and centrifuge it. The filter cake obtained is ethyl p-nitrobenzoate, and the filtrate is transferred to the waste liquid treatment center.
[0046] S3, get 395kg of ethyl p-nitrobenzoate after the aftertreatment, add it to the hydrogenation reactor, then add 1150L of ethanol, stir and dissolve; then add 3kg of 5% Pd / C wet catalyst diluted with 115L of ethanol, then pass into nitrogen to 0.2MPa, purge the reactor three times, and vent; then pass into hydrogen to 0.5MPa to purge nitrogen in the reactor three times, under this hydrogen atmosphere, warm up to 60 ℃ of reaction 3h to obtain ethyl p-aminobenzoate, after the reaction is completed, stop passing hydrogen, and purge with 1MPa nitrogen 3 times after venting.
[0047] S4. Filter the reaction liquid to recover the catalyst, then transfer the filtrate to a distillation kettle, distill part of the ethanol under reduced pressure at 80°C to maintain the fluidity of the material, and finally cool the remaining material to 0°C and transfer it to a centrifuge for filtration to obtain wet material ethyl para-aminobenzoate. The wet material is vacuum dried at 60°C to obtain the target product, and the filtrate is transferred to waste liquid treatment.
[0048] The infrared spectra of the intermediate product ethyl p-nitrobenzoate and the target product ethyl p-aminobenzoate prepared in this example are as follows: Figure 1 and Figure 2 As shown. Figure 1 and Figure 2 It can be seen that the structure of the product obtained in this example is consistent with that of the product obtained by the existing method.
[0049] Four parallel experiments were performed to prepare the intermediate product ethyl p-nitrobenzoate and the target product ethyl p-aminobenzoate. The yield, purity and yield of ethyl p-nitrobenzoate and ethyl p-aminobenzoate prepared in each experiment are shown in Tables 1 and 2 below, respectively.
[0050] Table 1
[0051]
[0052] Table 2
[0053]
[0054]
[0055] It can be seen from the data in Table 1 and Table 2 that the yield and purity of the product obtained by the preparation method of this embodiment are high.
[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.
Claims
1. A method for preparing ethyl p-aminobenzoate, characterized in that: The following steps are involved: S1, adding p-nitrobenzoic acid and ethanol to a reactor, adding concentrated sulfuric acid dropwise and heating to carry out esterification reaction to prepare ethyl p-nitrobenzoate; S2, post-treating the ethyl p-nitrobenzoate obtained in step S1; S3, adding ethyl p-nitrobenzoate and ethanol obtained by the post-treatment of step S2 to a hydrogenation reactor, adding a catalyst, passing nitrogen and hydrogen in sequence, and finally heating the reaction in a hydrogen atmosphere to obtain ethyl p-aminobenzoate; S4. Post-treating the ethyl p-aminobenzoate obtained in step S3 to obtain the final target product.
2. The method for preparing ethyl p-aminobenzoate according to claim 1, wherein: In step S1, the amount of p-nitrobenzoic acid used is 150.75-184.25 kg, the amount of ethanol used is 450-550 L, and the amount of concentrated sulfuric acid used is 47.5-52.5 L.
3. The method for preparing ethyl p-aminobenzoate according to claim 1, wherein: In step S1, the temperature of the esterification reaction is 65-75° C., and the reaction time is 3 h.
4. The method for preparing ethyl p-aminobenzoate according to claim 1, wherein In step S2, the specific operation of the post-treatment is: recovering part of the ethanol by atmospheric distillation to maintain the fluidity of the material, then washing with 450-550 L of water at a temperature of 45-55° C., cooling to 0° C. and then centrifuging to obtain a wet product of ethyl p-nitrobenzoate.
5. The method for preparing ethyl p-aminobenzoate according to claim 1, wherein: In step S3, the amount of ethyl p-nitrobenzoate is 355.5-434.5 kg, and the amount of ethanol is 1035-1265 L.
6. The method for preparing ethyl p-aminobenzoate according to claim 1, wherein: In step S3, the catalyst is a Pd / C catalyst diluted with ethanol, wherein the amount of ethanol used is 103.5-126.5 L, and the amount of Pd / C catalyst used is 2.85-3.15 kg.
7. The method for preparing ethyl p-aminobenzoate according to claim 1, wherein: In step S3, nitrogen is introduced to 0.2 MPa to purge the reactor three times, and then vented. Then, hydrogen is introduced to 0.3-0.7 MPa to purge the nitrogen in the reactor three times.
8. The method for preparing ethyl p-aminobenzoate according to claim 1, wherein: In step S3, the reaction temperature is 55-65° C. and the reaction time is 3 h.
9. The method for preparing ethyl p-aminobenzoate according to claim 1, wherein In step S4, the specific operation of the post-treatment is: filtering to recover the catalyst, then performing reduced pressure distillation on the filtrate to recover part of the ethanol to maintain the fluidity of the material, finally cooling to 0°C and centrifuging, and finally vacuum drying to obtain the target product.
10. The method for preparing ethyl p-aminobenzoate according to claim 9, wherein: The temperature for reduced pressure distillation is 75-85°C, and the temperature for vacuum drying is 55-65°C.