Method for continuous production of 2,5-dimethylphenol, 2,5-dimethylphenol

Abstract

The present invention relates to the field of chemical process technology, disclose a method for continuous production of 2,5-dimethylphenol, 2,5-dimethylphenol, method includes: S1, 2,5-dimethylbenzene sulfonate sodium and strong base are mixed in a rake dryer, milled, sieved, dried, and powder material is obtained; S2, the powder material transfer material is placed in a spiral pipeline reactor for insulation reaction; S3, the material after the insulation reaction is transferred to a quenching tank containing water, and an acidic solution is passed into the quenching tank; S4, the material after quenching is desalted and liquid separated to obtain 2,5-dimethylphenol; wherein the strong base and 2,5-dimethylbenzene sulfonate molar ratio are 1.1-3: 1; the powder material particle size is 1-5 μm, and the acidic solution flow rate is 10-40 kg / h. The method operates continuously, reduces labor costs, and the temperature of the transfer process is uniform, and the purity and yield of 2,5-dimethylphenol can be improved.

Description

Technical Field

[0001] The invention relates to the technical field of chemical process, and in particular to a method for continuously producing 2,5-dimethylphenol and 2,5-dimethylphenol. Background Art

[0002] 2,5-Dimethylphenol is an important pharmaceutical and dye intermediate. It is the main raw material for the preparation of the new lipid-lowering drug Gemfibrozil and the synthetic vitamin E intermediate 2,3,6-trimethylphenol, and has a wide range of uses.

[0003] At present, the main process uses p-xylene sulfonation and alkaline fusion to prepare 2,5-dimethylphenol. The reaction equipment mainly uses a batch reactor. After the reaction is completed, the material is transferred to water for cooling and acidification quenching. However, due to the high freezing point of the generated sodium or potassium salt of 2,5-dimethylphenol, the viscosity increases or partially solidifies when the temperature is lower than 270°C during the material transfer process, resulting in difficulty in material transfer and easy clogging of pipelines. In addition, the heat transfer of the batch reactor is uneven at high temperature, resulting in low reaction conversion rate, large impurities, and low yield. Summary of the invention

[0004] The purpose of the present invention is to overcome the problems of low raw material conversion rate, low purity and yield of 2,5-dimethylphenol in the prior art, and to provide a method for continuously producing 2,5-dimethylphenol and 2,5-dimethylphenol. The method has the characteristics of continuous operation and reduced labor costs, and the temperature during the material transfer process is uniform, and there is no situation where the viscosity of the powder material becomes larger or partially solidified, and the conversion degree of the raw materials is improved. Under the premise of high purity of 2,5-dimethylphenol, its yield can be further improved.

[0005] In order to achieve the above object, the first aspect of the present invention provides a method for continuously producing 2,5-dimethylphenol, characterized in that the method comprises the following steps:

[0006] S1, mixing: mixing, grinding, sieving and drying sodium 2,5-dimethylbenzenesulfonate and a strong base in a rake dryer to obtain a powder material;

[0007] S2, material transfer and heat preservation: the powder material is transferred and placed in a spiral pipe reactor and heat-insulated for reaction;

[0008] S3, acidification quenching: the material after the above insulation reaction is transferred into a quenching tank containing water, and an acidic solution is introduced into the quenching tank for quenching;

[0009] S4, heat preservation and liquid separation: desalting and liquid separation of the quenched material to obtain 2,5-dimethylphenol;

[0010] Wherein, the molar ratio of the strong base to the sodium 2,5-dimethylbenzenesulfonate is 1.1-3:1;

[0011] The particle size of the powder material is 1-5 μm, and the flow rate of the acidic solution is 10-40 kg / h.

[0012] A second aspect of the present invention provides 2,5-dimethylphenol, characterized in that the 2,5-dimethylphenol is prepared by the above method.

[0013] Through the above technical scheme, the 2,5-dimethylphenol and the continuous preparation method thereof provided by the present invention have the characteristics of continuous operation and reduced labor costs, and the temperature during the material transfer process is uniform, and there will be no situation where the viscosity of the powder material becomes larger or partially solidified, thereby improving the conversion degree of the raw materials, and thus being able to improve the yield of 2,5-dimethylphenol while having a higher purity. DETAILED DESCRIPTION

[0014] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0015] A first aspect of the present invention provides a method for continuously producing 2,5-dimethylphenol, characterized in that the method comprises the following steps:

[0016] S1, mixing: mixing, grinding, sieving and drying sodium 2,5-dimethylbenzenesulfonate and a strong base in a rake dryer to obtain a powder material;

[0017] S2, material transfer and heat preservation: the powder material is transferred and placed in a spiral pipe reactor and heat-insulated for reaction;

[0018] S3, acidification quenching: the material after the above insulation reaction is transferred into a quenching tank containing water, and an acidic solution is introduced into the quenching tank for quenching;

[0019] S4, heat preservation and liquid separation: desalting and liquid separation of the quenched material to obtain 2,5-dimethylphenol;

[0020] Wherein, the molar ratio of the strong base to the sodium 2,5-dimethylbenzenesulfonate is 1.1-3:1;

[0021] The particle size of the powder material is 1-5 μm, and the flow rate of the acidic solution is 10-40 kg / h.

[0022] In the present invention, when the particle size of the powder material and the flow rate of the acidic solution meet the above ranges, the continuous operation is smoother and the prepared 2,5-dimethylphenol has higher purity and yield.

[0023] In the present invention, the rake dryer can perform grinding during the drying process, thereby improving production efficiency.

[0024] In the present invention, the spiral pipe reactor can push the material forward during the reaction process, has good transmission performance for materials with high viscosity, and can ensure that the temperature remains uniform and does not decrease during the material transfer process.

[0025] In the present invention, the heat preservation reaction can further convert 2,5-dimethylbenzenesulfonate into 2,5-dimethylphenolate.

[0026] In the present invention, in step S1 and step S2, the strong base is excessive and the reaction system is alkaline, which can prevent the material from becoming viscous or even agglomerated, causing local overheating and resulting in coking or carbonization of the reaction material.

[0027] Furthermore, in step S3, an acidic solution is introduced to maintain the pH of the quenching system at 5-6, so that the system is weakly acidic, and the product 2,5-dimethylphenolate can be completely acidified to 2,5-dimethylphenol.

[0028] According to the present invention, the particle size of the powder material is 2-4 μm, and the flow rate of the acidic solution is 20-30 kg / h.

[0029] According to the present invention, in step S1, the drying conditions include: drying at 110-120° C. for 3-5 hours.

[0030] According to the present invention, the molar ratio of the strong base to the sodium 2,5-dimethylbenzenesulfonate is 1.5-2.1:1.

[0031] In the present invention, the molar ratio of the strong base to the sodium 2,5-dimethylbenzenesulfonate is the feed ratio.

[0032] In the present invention, the molar ratio of the strong base to sodium 2,5-dimethylbenzenesulfonate satisfies the above range, and 2,5-dimethylphenolate can be obtained through a more sufficient reaction, thereby further improving the yield of 2,5-dimethylphenol.

[0033] According to the present invention, the strong base is selected from sodium hydroxide and / or potassium hydroxide.

[0034] Furthermore, the molar ratio of the sodium hydroxide to the potassium hydroxide is 1:(0-3).

[0035] Furthermore, the strong base is sodium hydroxide.

[0036] According to the present invention, the strong base is selected from sodium hydroxide, which can generate a single sodium sulfite salt during the reaction, and is convenient for separation and recovery of the by-product sodium sulfite, thereby increasing the value of the by-product, further increasing the yield of the product and reducing the production cost.

[0037] According to the present invention, the conditions for the heat preservation reaction include: a temperature of 280-350° C. and a time of 1-5 h.

[0038] According to the present invention, the conditions for the heat preservation reaction include: a temperature of 290-310° C. and a time of 1-3 h.

[0039] In the present invention, the insulation is achieved by introducing a high-temperature molten salt having a temperature of 360-380°C into the jacket of the spiral pipe reactor to ensure that the temperature of the insulation reaction is 280-350°C, which can make the insulation more uniform and ensure that the temperature is maintained between 280-350°C during the material transfer process to avoid pre-cooling and bonding of the materials.

[0040] According to the present invention, the quenching tank contains 1-3 volume % of water based on the volume of the material after the insulation reaction.

[0041] In the present invention, the quenching tank contains 1-3 volume % of water based on the volume of the material after the insulation reaction, which can effectively disperse the inorganic salts and 2,5-dimethylphenol generated during the neutralization process.

[0042] According to the present invention, the acidic solution is selected from at least one of an inorganic acid solution, an aqueous sulfur dioxide solution and an aqueous carbon dioxide solution.

[0043] Furthermore, the inorganic acid solution is selected from dilute hydrochloric acid and / or dilute sulfuric acid.

[0044] Furthermore, the inorganic acid solution is an aqueous sulfur dioxide solution.

[0045] According to the present invention, the pH of the quenching process is maintained at 5-6.

[0046] According to the present invention, the desalination method is selected from at least one of centrifugal separation, filter pressing and suction filtration.

[0047] According to the present invention, the temperature of the liquid separation is 80-95°C.

[0048] In the present invention, when the temperature of the liquid separation satisfies the above range, 2,5-dimethylphenol can be kept in a liquid state, which is convenient for static separation.

[0049] Furthermore, the temperature of the liquid separation is 80-85°C.

[0050] A second aspect of the present invention provides 2,5-dimethylphenol, characterized in that the 2,5-dimethylphenol is prepared by the above method.

[0051] According to the present invention, the yield of 2,5-dimethylphenol is not less than 90.9%, and the purity is not less than 94%.

[0052] Furthermore, the yield of the 2,5-dimethylphenol is not less than 94.9%, and the purity is not less than 97.9%.

[0053] According to one embodiment of the present invention, the method comprises the following steps:

[0054] S1, mixing: 200-210 kg of sodium 2,5-dimethylbenzenesulfonate and 60-80 kg of strong base are mixed in a rake dryer, and then ground, sieved and dried to obtain a powder material with a particle size of 1-5 μm, wherein the molar ratio of the strong base to the sodium 2,5-dimethylbenzenesulfonate is 1.1-3:1;

[0055] S2, material transfer and heat preservation: the powder material is transferred and placed in a spiral pipe reactor and kept at 280-350°C for 1-5h;

[0056] S3, acidification quenching: the material after the above insulation reaction is transferred to a quenching tank, wherein the quenching tank contains 1-3 volume % of water based on the volume of the material after the insulation reaction, and an acidic solution is introduced into the quenching tank at the same time, the flow rate is controlled to be 10-40 kg / h, and the pH value of the quenching process is maintained at 5-6;

[0057] S4. Liquid separation under heat preservation: desalt the quenched material and separate the liquid at 80-85° C. to obtain 2,5-dimethylphenol.

[0058] The present invention will be described in detail below through examples. In the following examples, the raw materials 2,5-dimethylbenzenesulfonic acid, acid, and base used are all commercially available;

[0059] The purity of 2,5-dimethylphenol was measured by liquid chromatography;

[0060] The yield of 2,5-dimethylphenol was calculated by actual yield / theoretical yield*100%.

[0061] Example 1

[0062] S1. Put 208 kg of sodium 2,5-dimethylbenzenesulfonate and 60 kg of sodium hydroxide into a rake dryer in sequence, grind and sieve into a powder with a particle size of 2 μm, and dry at 110° C. for 5 hours to obtain a powder material, wherein the molar ratio of sodium hydroxide to sodium 2,5-dimethylbenzenesulfonate is 1.5:1;

[0063] S2. Discharge the powder material evenly into the spiral pipe reactor and keep it at 290° C. for 2 h.

[0064] S3, after the insulation is completed, quenching is carried out in a quenching tank at 290°C, wherein the quenching tank contains 1 volume % of water based on the volume of the powder material after insulation, and then sulfur dioxide aqueous solution is introduced, the flow rate is controlled to be 20 kg / h, and the system pH is 5;

[0065] S4. The quenched material was centrifuged for desalting and allowed to stand at 80°C for liquid separation to obtain 115.9 kg of 2,5-dimethylphenol with a yield of 95% and a purity of 97.9%.

[0066] Example 2

[0067] The method is consistent with that in Example 1, except that in step S2, the temperature is kept at 305° C. for 2 h, and 116.1 kg of 2,5-dimethylphenol is obtained with a yield of 95.2% and a purity of 98.3%.

[0068] Example 3

[0069] The method is consistent with that of Example 1, except that in step S1, the amount of sodium hydroxide used is 80 kg, and the molar ratio of sodium hydroxide to sodium 2,5-dimethylbenzenesulfonate is 2:1. 116.3 kg of 2,5-dimethylphenol is obtained, with a yield of 95.3% and a purity of 98.1%.

[0070] Example 4

[0071] The method is consistent with that in Example 1, except that in step S1, the amount of sodium hydroxide used is 80 kg, wherein the molar ratio of sodium hydroxide to sodium 2,5-dimethylbenzenesulfonate is 2:1, and in step S2, the temperature is kept at 305° C. for 2 h to obtain 115.8 kg of 2,5-dimethylphenol with a yield of 94.9% and a purity of 98.2%.

[0072] Example 5

[0073] The method is consistent with that of Example 1, except that 40 kg of sodium hydroxide and 56 kg of potassium hydroxide are used as the base, the molar ratio of sodium hydroxide to potassium hydroxide is 1:1, and the molar ratio of sodium hydroxide + potassium hydroxide to sodium 2,5-dimethylbenzenesulfonate is 2:1. 115.1 kg of 2,5-dimethylphenol is obtained, with a yield of 94.3% and a purity of 98%.

[0074] Example 6

[0075] The method was consistent with that of Example 1, except that the temperature was kept at 305° C. for 5 h. 113.1 kg of 2,5-dimethylphenol was obtained with a yield of 92.7% and a purity of 96.2%.

[0076] Example 7

[0077] The method was consistent with that of Example 1, except that the temperature was kept at 325° C. for 2 h. 113 kg of 2,5-dimethylphenol was obtained with a yield of 92.6% and a purity of 96%.

[0078] Example 8

[0079] The method is consistent with that in Example 1, except that in step S3, dilute sulfuric acid is introduced to obtain 112.8 kg of 2,5-dimethylphenol with a yield of 92.4% and a purity of 96.1%.

[0080] Example 9

[0081] S1. Put 208 kg of sodium 2,5-dimethylbenzenesulfonate and 60 kg of sodium hydroxide into a rake dryer in sequence, grind and sieve into a powder with a particle size of 4 μm, and dry at 120° C. for 3 h to obtain a powder material, wherein the molar ratio of sodium hydroxide to sodium 2,5-dimethylbenzenesulfonate is 1.5:1;

[0082] S2. Discharge the powder material evenly into the spiral pipe reactor and keep it at 290° C. for 2 h.

[0083] S3, after the insulation is completed, the material is transferred to a quenching tank at 290°C for quenching, wherein the quenching tank contains 3% by volume of water based on the volume of the material after the insulation reaction. A sulfur dioxide aqueous solution is introduced, the flow rate is controlled to be 40 kg / h, and the system pH is 6;

[0084] S4. The quenched material was centrifuged for desalting and allowed to stand at 85°C for liquid separation to obtain 113.2 kg of 2,5-dimethylphenol with a yield of 92.7% and a purity of 96.3%.

[0085] Example 10

[0086] The method is consistent with that in Example 1, except that in step S3, the flow rate of the aqueous sulfur dioxide solution is controlled to be 40 kg / h, and 115.1 kg of 2,5-dimethylphenol is obtained with a yield of 94.3% and a purity of 97%.

[0087] Embodiment 11

[0088] The method is consistent with that of Example 1, except that in step S3, the material is transferred to a quenching tank for quenching, wherein the quenching tank contains 0.5 volume % of water based on the volume of the material after the insulation reaction. 111 kg of 2,5-dimethylphenol is obtained with a yield of 90.9% and a purity of 94%.

[0089] Comparative Example 1

[0090] The method is consistent with that of Example 1, except that in step S1, the material generated from sodium 2,5-dimethylbenzenesulfonate and sodium hydroxide is ground into a material with a particle size of 6 μm. Finally, 109 kg of 2,5-dimethylphenol is obtained with a yield of 89.3% and a purity of 93.7%.

[0091] Comparative Example 2

[0092] The method is consistent with that in Example 1, except that in step S3, the flow rate of the sulfur dioxide aqueous solution is controlled to be 60 kg / h, and 108.3 kg of 2,5-dimethylphenol is obtained with a yield of 88.8% and a purity of 93.9%.

[0093] Comparative Example 3

[0094] The method is consistent with that in Example 1, except that step S1 is not performed, 208 kg of sodium 2,5-dimethylbenzenesulfonate and 60 kg of sodium hydroxide are directly discharged into the spiral pipe reactor without screening, mixed evenly, and then kept warm for reaction. The other steps are consistent to obtain 107.1 kg of 2,5-dimethylphenol with a yield of 87.8% and a purity of 92.7%.

[0095] Comparative Example 4

[0096] 208 kg of sodium 2,5-dimethylbenzenesulfonate and 80 kg of sodium hydroxide were added to a 500 L batch reactor in sequence, and the mixture was kept at 305°C for 2 hours. After the heat preservation, in order to prevent the material from condensing, the temperature was kept at 305°C and the material was transferred to a quenching tank containing an aqueous solution of sulfur dioxide for quenching, the pH was adjusted to 5, and then the mixture was centrifuged for desalination and allowed to stand at 80°C for separation to obtain 111.2 kg of 2,5-dimethylphenol, with a yield of 91.1% and a purity of 94.3%.

[0097] Comparative Example 5

[0098] 208 kg of sodium 2,5-dimethylbenzenesulfonate and 60 kg of sodium hydroxide were added to a 500 L batch reactor in sequence and kept at 290°C for 2 hours. After the insulation, in order to prevent the material from condensing, the temperature was kept at 290°C and transferred to a quenching tank containing an aqueous solution of sulfur dioxide for quenching, the pH was adjusted to 5, and then centrifuged for desalination and allowed to stand at 80°C for separation to obtain 110 kg of 2,5-dimethylphenol with a yield of 90.1% and a purity of 94.1%.

[0099] Comparative Example 6

[0100] 208 kg of sodium 2,5-dimethylbenzenesulfonate and 80 kg of sodium hydroxide were added to a 500 L batch reactor in sequence and kept at 320°C for 2 hours. After the heat preservation, the material was directly transferred to a quenching tank containing a sulfur dioxide aqueous solution at 260°C for quenching, the pH was adjusted to 5, and then centrifuged for desalination and allowed to stand at 80°C for separation to obtain 108.9 kg of 2,5-dimethylphenol, with a yield of 89.2% and a purity of 93.5%.

[0101] Comparative Example 7

[0102] 208 kg of sodium 2,5-dimethylbenzenesulfonate and 80 kg of sodium hydroxide were added to a 500L batch reactor in sequence and kept at 320°C for 2 hours. After the insulation, at 200°C, the material was completely solidified and could not be transferred. The sulfur dioxide aqueous solution was directly added to the reactor for quenching, soaked for 24 hours, stirred, adjusted to pH 5, and then centrifuged for desalination and allowed to stand at 80°C for separation to obtain 103.7 kg of 2,5-dimethylphenol, with a yield of 85% and a purity of 91.7%.

[0103] Comparative Example 8

[0104] The method is consistent with that of Example 1, except that in step S1, the amount of sodium hydroxide used is 37 kg, wherein the molar ratio of sodium hydroxide to sodium 2,5-dimethylbenzenesulfonate is 0.9:1. 105 kg of 2,5-dimethylphenol is obtained, with a yield of 86% and a purity of 87%.

[0105] Table 1

[0106]

[0107] a: The molar ratio refers to the molar ratio of the strong base to sodium 2,5-dimethylbenzenesulfonate; b: The water content refers to the water content in the quenching tank based on the volume of the material after the insulation reaction; c: The flow rate refers to the flow rate of the acidic solution.

[0108] Table 2

[0109] Comparative Example <![CDATA[Molar ratio a > Insulation temperature / ℃ Insulation time / h Transfer temperature / ℃ 4 2:1 305 2 305 5 1.5:1 290 2 290 6 2:1 320 2 260 7 2:1 320 2 200

[0110] Table 3

[0111]

[0112]

[0113] It can be seen from the results of the examples and comparative examples in Tables 1-3 that Examples 1-11 using the method of the present invention have good technical effects, wherein the purity of 2,5-dimethylphenol is maintained at 94% or above, and the yield can reach 90.9% or above.

[0114] Among them, Examples 1-4 meet the preferred technical solutions of the present invention, and have significantly better effects, further improving the yield of 2,5-dimethylphenol while improving its purity. Specifically, the purity of 2,5-dimethylphenol is not less than 97.9%, and the yield is not less than 94.9%.

[0115] It can be seen that the method provided by the present invention has the characteristics of continuous operation and reduced labor costs, and the temperature during the material transfer process is uniform, and there will be no situation where the viscosity of the powder material becomes larger or partially solidified, which can improve the conversion degree of the raw materials, thereby improving the yield of 2,5-dimethylphenol while having a higher purity.

[0116] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for continuously producing 2,5-dimethylphenol, characterized in that: The method comprises the following steps: S1, mixing: mixing, grinding, sieving and drying sodium 2,5-dimethylbenzenesulfonate and a strong base in a rake dryer to obtain a powder material; S2, material transfer and heat preservation: the powder material is transferred and placed in a spiral pipe reactor and heat-insulated for reaction; S3, acidification quenching: the material after the above insulation reaction is transferred into a quenching tank containing water, and an acidic solution is introduced into the quenching tank for quenching; S4, heat preservation and liquid separation: desalting and liquid separation of the quenched material to obtain 2,5-dimethylphenol; Wherein, the molar ratio of the strong base to the sodium 2,5-dimethylbenzenesulfonate is 1.1-3:1; The particle size of the powder material is 1-5 μm, and the flow rate of the acidic solution is 10-40 kg / h; The quenching tank contains 1-3 volume % of water based on the volume of the material after the insulation reaction.

2. The method according to claim 1, wherein: The particle size of the powder material is 2-4 μm, and the flow rate of the acidic solution is 20-30 kg / h.

3. The method according to claim 1 or 2, wherein: The molar ratio of the strong base to the sodium 2,5-dimethylbenzenesulfonate is 1.5-2.1:

1.

4. The method according to claim 1 or 2, wherein: The strong base is selected from sodium hydroxide and / or potassium hydroxide.

5. The method according to claim 4, wherein: The molar ratio of the sodium hydroxide to the potassium hydroxide is 1:(0-3).

6. The method according to claim 4, wherein: The strong base is sodium hydroxide.

7. The method according to any one of claims 1-2, 5-6, wherein: The conditions of the heat preservation reaction include: temperature of 280-350° C. and time of 1-5 h.

8. The method according to claim 7, wherein: The conditions of the heat preservation reaction include: temperature of 290-310° C. and time of 1-3 h.

9. The method according to any one of claims 1-2, 5-6, and 8, wherein: The acidic solution is selected from at least one of an inorganic acid solution, a sulfur dioxide aqueous solution and a carbon dioxide aqueous solution.

10. The method according to claim 9, wherein: The inorganic acid solution is selected from dilute hydrochloric acid and / or dilute sulfuric acid.

11. The method according to any one of claims 1-2, 5-6, and 8, wherein: Keep the pH during the quenching process at 5-6.

12. The method according to any one of claims 1-2, 5-6, 8, and 10, wherein: The desalination method is selected from at least one of centrifugal separation, filter pressing and suction filtration; And / or, the temperature of the liquid separation is 80-85°C.

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