A method for preparing antioxidant TMQ and co-producing mesitylene

Abstract

The invention belongs to the technical field of fine chemicals, and provides a method for preparing TMQ and simultaneously co-producing mesitylene. A part of aniline is put into a reactor at one time, and hydrochloric acid is added, stirred and heated to remove water in the hydrochloric acid. After that, after the temperature is raised to the reaction temperature, acetone is continuously introduced into the reactor for reaction, and reaction water is removed while reacting; then the reaction system is sealed, the temperature and pressure are raised for reaction, liquid alkali is added for neutralization, adjusted to alkalinity, water is separated, and the oil phase is distilled to remove unreacted acetone and water and front fractions to obtain TMQ. The front fraction is rectified to obtain mesitylene. The antioxidant TMQ finished product has an effective body content of 45-65% and a mesitylene content of more than 99.0%. Thereby reducing the production cost of mesitylene, reducing energy consumption and material consumption, and is a green and environmentally friendly synthesis process.

Description

Technical Field

[0001] The invention belongs to the technical field of fine chemicals, relates to a preparation method for co-producing an antioxidant TMQ and mesitylene, and is a green and environmentally friendly preparation process. Background Art

[0002] Antioxidant TMQ is a di-, tri-, or tetrapolymer of 2,2,4-trimethyl-1,2-dihydroquinoline, also known as antioxidant RD. It is a ketoamine antioxidant in the form of light yellow to pale yellow particles or flakes. It is mainly used as a rubber antioxidant. The annual domestic demand is 100,000 tons, making it one of the most in-demand rubber antioxidant products in the domestic and international markets.

[0003] The main raw materials for synthesizing the antioxidant TMQ are aniline and acetone (or its derivatives), and the process can be roughly divided into two types: "one-step method" or "two-step method". The process of the "one-step method" is as follows: aniline and acetone undergo condensation and polymerization under the action of a catalyst to directly obtain the antioxidant TMQ polycondensation liquid containing di-, tri-, and tetra-polymers of 2,2,4-trimethyl-1,2-dihydroquinoline, and the TMQ polycondensation liquid is neutralized with liquid alkali, separated from water, and distilled to obtain TMQ. The process of the "two-step method" is as follows: aniline and acetone undergo condensation under the action of a catalyst, and the reaction liquid or the neutralized reaction liquid is distilled or rectified to obtain 2,2,4-trimethyl-1,2-dihydroquinoline, namely, TMQ monomer, and then the TMQ monomer is polymerized under the action of a catalyst to obtain di-, tri-, and tetra-polymers of 2,2,4-trimethyl-1,2-dihydroquinoline, and then neutralized, separated from water, and distilled to obtain the antioxidant TMQ. Sometimes, in order to accelerate the reaction process, solvents such as toluene, xylene, and cyclohexane are added to the reaction. Therefore, the TMQ synthesis method can be divided into "solvent method" or "solvent-free method".

[0004] CN108003095A introduces the commonly used production methods of TMQ: 1) Intermittent kettle method: the raw material aniline and the catalyst are put into the kettle at one time, and the acetone is fed by continuous dripping. The feeding reaction time is generally 2 to 7 hours. Under normal pressure, the reaction temperature is controlled to be 90 to 150 ° C, and the acetone is directly separated and recovered by the fractionation tower on the reactor, and then the acetone is applied to the raw material storage tank. 2) Continuous tower method: aniline and catalyst titanate are continuously fed from the top of the tower, and acetone is fed from the gas phase at the bottom of the tower after vaporization, and continuous reaction is carried out in the tower. Under normal pressure, the reaction temperature is controlled to be 90 to 150 ° C. The material stays in the tower for 3 to 7 hours. The acetone and the water generated during the reaction are evaporated at the same time, and then the acetone is directly separated and recovered by the fractionation tower. At the same time, the antioxidant TMQ polycondensation reaction liquid generated by the reaction continuously flows into the receiving tank at the bottom of the tower. The TMQ polycondensation liquid in the reaction kettle or receiving tank is added with liquid alkali for neutralization, allowed to stand for stratification, the oil phase is distilled, and the antioxidant TMQ finished product is obtained by granulation.

[0005] Mesitylene, also known as 1,3,5-trimethylbenzene, is an important raw material for organic synthesis. It is used to prepare trimesic acid, as well as antioxidants, epoxy resin curing agents, polyester resin stabilizers, alkyd resin plasticizers, and 2,4,6-trimethylbenzene for the production of reactive brilliant blue, K-3R and other dyes.

[0006] Its main sources: 1) Separated from C9 aromatics. 2) Obtained in the reforming of heavy aromatics, of which mesitylene accounts for about 11.8%. However, since its boiling point (164.7°C) is extremely close to that of o-ethylbenzene (165.15°C), it is difficult to separate by distillation. 3) The isomerization method using mesitylene as raw material, the single-pass yield of 1,3,5-trimethylbenzene obtained by fractionation is 21.6%, and the purity is more than 95%. At the same time, the by-products are 4%-7% of tetramethylbenzene and 9% of xylene. The reaction catalyst is aluminum hydrogen-deficient mordenite: copper: nickel: binder = 85.2:0.5:15. Under this condition, the conversion rate of mesitylene is 46%, the selectivity is 47%, and the single-pass yield of mesitylene is 21.6%. Mitsubishi Gas Company of Japan uses HF-BF3 to separate and isomerize xylene. The byproduct contains high-boiling substances with high concentration of 1,3,5-trimethylbenzene, which can be obtained by distillation and refining. 4) Acetone is dehydrated and synthesized under the catalysis of sulfuric acid, with a yield of 13%-15%. It needs to be 0-5℃, add concentrated sulfuric acid, and place at room temperature for 18-24h. The product is steam distilled to separate 1,3,5-trimethylbenzene, then washed with alkali and water, and the 210℃ fraction is collected by distillation. 15g of metallic sodium is added to this fraction, heated to near boiling point, 2 / 3 of the liquid is evaporated, and the remainder is distilled to 210℃. The 163-167℃ fraction is collected by efficient fractionation to obtain 430-470g of 1,3,5-trimethylbenzene. Summary of the invention

[0007] The purpose of the present invention is to simultaneously produce a high value-added mesitylene product during the preparation of the antioxidant TMQ, thereby improving economic benefits.

[0008] The present invention provides a method for preparing an antioxidant TMQ and co-producing mesitylene. The preparation method is achieved by the following steps:

[0009] Step ①: adding aniline, an acid catalyst, acetone, etc. into a reactor and removing water; or removing water from aniline and an acid catalyst, and then adding acetone;

[0010] Step ②: The material obtained in step ① is heated to a certain temperature, reacted under stirring conditions for a period of time, and then the moisture is removed;

[0011] Step ③: reacting the reaction solution obtained in step ② at a certain temperature and pressure for a period of time;

[0012] Step ④: adding liquid alkali to neutralize the reaction solution obtained in step ③, separating water, distilling the oil phase, and removing acetone, water, and front fractions in sequence to obtain TMQ;

[0013] Step ⑤: The front fraction obtained in step ④ is subjected to rectification and separation to obtain mesitylene, aniline, and kettle liquid containing TMQ monomer in sequence; aniline and TMQ monomer are used in combination.

[0014] Preferably, the acid catalyst is one or more of acidic substances selected from hydrochloric acid, sulfuric acid, benzenesulfonic acid, p-toluenesulfonic acid, oxalic acid, copper halide, titanic acid and titanate ester.

[0015] Preferably, the molecular ratio of aniline, acid catalyst and acetone in step ① is 1:0.1-0.001:6-20.

[0016] Preferably, the molecular ratio of aniline, acid catalyst and acetone in step ① is 1:0.05-0.005:10-15.

[0017] Preferably, the removal of moisture in steps ① and ② refers to controlling the water content in the mixed solution to below 0.3%.

[0018] Preferably, the reaction temperature in step ② is 100-150° C., and the reaction time is 1-10 hours.

[0019] Preferably, the reaction temperature in step ③ is 120-180° C., the reaction time is 1-8 hours, and the reaction pressure is 0.8-4.0 MPa.

[0020] Preferably, in step ④, the oil phase is distilled, and the gas phase temperature before removal of the fraction is 60-150°C, the liquid phase temperature is 110-180°C, and the pressure is 0.1-2.0 kPa.

[0021] Preferably, the main components of the front fraction obtained in step ④ are aniline content 0.3-1.0%, mesitylene content 35.0-76.0%, and TMQ monomer content 5.0-18.0%.

[0022] Preferably, the main components of the TMQ obtained in step ④ are 45-58% of di-, tri- and tetramers of 2,2,4-trimethyl-1,2-dihydroquinoline, 0.0-0.05% of aniline, 0-0.3% of isopropyl diphenylamine, 0% of mesitylene, 0% of TMQ monomer, and a softening point of 85-98°C.

[0023] Preferably, the content of mesitylene obtained in step ⑤ reaches 99.5%. The content of impurity aniline is 0.0-0.05%.

[0024] Preferably, the kettle liquid containing TMQ monomer mainly consists of: 0-20% mesitylene, 65.0-90.0% 2,2,4-trimethyl-1,2-dihydroquinoline, 0-5.0% primary amine, 0-3.0% isopropyldiphenylamine, and 0.0-3.0% 2,2,4-trimethyl-1,2-dihydroquinoline dimer.

[0025] Beneficial Effects

[0026] In the process of preparing the antioxidant TMQ, the present invention controls different reaction conditions through staged reaction, and simultaneously co-produces a high value-added mesitylene product, thereby providing improved economic benefits. Compared with the traditional processes of separation of C9 aromatics, reforming of heavy aromatics and isomerization, the present invention has the following advantages: ① the raw materials aniline and acetone are bulk commodities, low in price and easily available; ② conventional acid catalysts are used, which are widely available, and the wastewater generated is easy to handle; ③ the process is simple, TMQ and mesitylene are co-produced; ④ the distillation method is easy to separate, and the mesitylene product has a higher purity. DETAILED DESCRIPTION

[0027] The synthesis method of the present invention is described in detail below in conjunction with the embodiments. It should be noted that, in the case of no conflict, the embodiments in this application and the features described in the embodiments can be combined with each other. The present invention will be described in detail below in conjunction with the embodiments.

[0028] The method for preparing rubber antioxidant TMQ and co-producing mesitylene of the present invention comprises the following steps: a portion of aniline and hydrochloric acid are added to a reaction kettle at one time, and the temperature is stirred and heated to remove water in the hydrochloric acid. After the temperature is raised to the reaction temperature, acetone is continuously introduced into the reaction kettle for reaction, and reaction water is removed during the reaction. After that, the reaction system is sealed, heated and pressurized, and reacted for a period of time under stirring, and then the pressure is released, liquid alkali is added for neutralization, the temperature is adjusted to alkalinity, water is separated, and the oil phase is distilled to remove unreacted acetone and water and a front fraction to obtain TMQ. The front fraction is rectified to obtain mesitylene, aniline, and a kettle liquid containing a TMQ monomer. The aniline and the kettle liquid containing a TMQ monomer are used together.

[0029] The TMQ polycondensation reaction liquid is obtained, and the TMQ polycondensation liquid in the intermediate tank is added with liquid alkali for neutralization, and the liquid is allowed to stand for stratification. The oil phase is kept under a vacuum of -0.098 MPa, and the material temperature is controlled at 200-240 °C, and the unreacted raw material aniline, unpolymerized TMQ monomer, etc. are distilled and recovered for use in the reaction. After the kettle material is cooled, the finished product of the antioxidant TMQ is obtained by granulation, and the effective body content in the product reaches 52-63%.

[0030] The reaction time of aniline and acetone in the reactor is 4 to 6 hours, and the temperature of the reactor is controlled at 105 to 140°C; the molar ratio of aniline to acetone is 1:2 to 6, and the molar ratio of catalyst to aniline is 0.01 to 0.3 to 1. The acetone fractionation tower on the reactor is used to directly separate and recover the acetone and discharge the reaction water, and then the acetone is applied to the raw material storage tank.

[0031] Example 1

[0032] Polycondensation reaction: In a 1000ml reactor, add 460ml aniline and 10ml 31% hydrochloric acid, stir and heat to 110℃, maintain for 2h, remove the water in the hydrochloric acid, and detect the water content of 0.5%. Maintain at 110℃, and continuously introduce 1600ml acetone (acetone and aniline molar ratio is 1:3.5) at a rate of 200mL / h to carry out polycondensation reaction. The water produced during the reaction and the excess acetone can be recovered by the distillation tower connected to the reactor at the same time, and the water produced by the reaction can be separated. The water content of the reaction liquid is detected to be 0.5%.

[0033] High-pressure reaction: the reaction solution was transferred to an autoclave, and 1600 mL of acetone (the molar ratio of acetone to aniline was 1:3.5) was added, the reaction temperature was controlled at 150°C, and the reaction was stirred for 3 hours. At this time, the system pressure was 1.9 MPa. After the pressure was reduced, the temperature was reduced to 100°C, and 24 ml of 16% sodium hydroxide solution was added for neutralization. The water was separated and the oil phase was distilled at normal pressure to remove acetone and water. Then, negative pressure distillation was performed. Under a vacuum of -0.098 MPa, i.e., 2000 Pa, the material temperature was controlled at 180°C, 470 g of the front fraction was extracted, and 332 g of TMQ finished product was obtained. The components of the distillate before testing are: aniline content 0.3%, mesitylene 72.5%, TMQ monomer content 19.3%; the main components of the TMQ finished product are: 2,2,4-trimethyl-1,2-dihydroquinoline di-, tri-, and tetra-polymer content 48.58%, aniline content 0.01%, isopropyl diphenylamine content 0.11%, mesitylene content 0.00%, TMQ monomer content 0.25%, softening point 88.6℃;

[0034] Distillation: Under normal pressure, the front fraction was distilled by a packed distillation column, the reflux ratio was controlled to 5, the kettle temperature was 180-210°C, and the 165-169°C fraction was collected to obtain 325g of 1,3,5-trimethylbenzene (mesitylene) with a content of 99.0%, and the impurity aniline content was 0.02%. The remaining kettle liquid was 142g, and its main components were 13.5% mesitylene, 73.3% TMQ monomer content, 1.0% primary amine content, 0.8% isopropyl diphenylamine content, and 2.5% 2,2,4-trimethyl-1,2-dihydroquinoline dimer content. The kettle liquid was used as a recovered raw material in the polycondensation reaction.

[0035] Example 2

[0036] Polycondensation reaction: In a 1000ml reactor, add 460ml aniline and 10ml 31% hydrochloric acid, stir and heat to 110℃, maintain for 3h, remove the water in the hydrochloric acid, and detect the water content of 0.2%. Maintain at 130℃, and continuously introduce 1600ml acetone (acetone and aniline molar ratio is 1:3.5) at a rate of 200mL / h to carry out polycondensation reaction. The water produced during the reaction and the excess acetone can be recovered by the distillation tower connected to the reactor at the same time, and the water produced by the reaction can be separated. The water content of the polycondensation reaction liquid is detected to be 0.5%.

[0037] High-pressure reaction: the reaction solution was transferred to an autoclave, and 2000 mL of acetone was added. The reaction temperature was controlled at 180°C and the reaction was stirred for 5 hours. At this time, the system pressure was 3.5 MPa. After the pressure was reduced, the temperature was reduced to 100°C, and 24 ml of 16% sodium hydroxide solution was added for neutralization. The water was separated and the oil phase was distilled at normal pressure to remove acetone and water. Then, negative pressure distillation was performed. Under a vacuum of -0.099 MPa, i.e., 1000 Pa, the material temperature was controlled at 180°C, 512 g of the front fraction was extracted, and 349 g of TMQ finished product was obtained. The components of the distillate before detection were: aniline content 0.03%, mesitylene 78.8%, TMQ monomer content 16.5%; the main components of the TMQ finished product were: 2,2,4-trimethyl-1,2-dihydroquinoline di-, tri- and tetra-polymers content 45.12%, aniline content 0.00%, isopropyl diphenylamine content 0.08%, mesitylene content 0.00%, TMQ monomer content 0.34%, and softening point 92.4℃.

[0038] Distillation: Under normal pressure, the front fraction was distilled by a packed distillation column, the reflux ratio was controlled to 7, the kettle temperature was 180-210°C, and the 165-169°C fraction was collected to obtain 365g of 1,3,5-trimethylbenzene (mesitylene) with a content of 99.5%, and the impurity aniline content was 0.04%. The remaining kettle liquid was 140g, and its main components were 8.3% mesitylene, 85.3% TMQ monomer content, 1.0% primary amine content, 0.4% isopropyl diphenylamine content, and 4.5% 2,2,4-trimethyl-1,2-dihydroquinoline dimer content. The kettle liquid was used as a recovered raw material in the polycondensation reaction.

[0039] Example 3

[0040] The main operating conditions are the same as those in Example 1, but sulfuric acid is used as a catalyst to obtain 386g of TMQ finished product. The components of the front fraction are as follows: aniline content 0.03%, mesitylene 85.8%, TMQ monomer content 12.5%; the main components of the TMQ finished product: 2,2,4-trimethyl-1,2-dihydroquinoline di-, tri-, and tetramer content 56.1%, aniline content 0.00%, isopropyl diphenylamine content 0.18%, mesitylene content 0.00%, TMQ monomer content 0.04%, softening point 95.5°C; under normal pressure conditions, the front fraction is rectified by a packed distillation column, the reflux ratio is controlled to 5, the kettle temperature is 180-210°C, and the 165-169°C fraction is collected to obtain 465g of 1,3,5-trimethylbenzene (mesitylene) with a content of 99.1%, and the impurity aniline content is 0.004%.

[0041] Embodiment 4-9

[0042] The experimental method of Example 2 was used. Under the condition that other conditions remained unchanged, the product quality of TMQ and trimethylbenzene was investigated by changing the type of acid catalyst and the ratio of acetone to aniline, and different reaction temperatures and reaction times. The results are shown in the following table.

[0043] .

[0044] 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, such as changing the type of acid catalyst and reaction temperature / time, different reaction modes, such as intermittent and continuous, etc. Any modification, equivalent substitution, improvement, etc. (such as using acetone derivatives, aniline derivatives, intermediates of the reaction between aniline and acetone, etc.) 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 antioxidant TMQ and co-producing mesitylene, characterized in that: The following steps are involved: Polycondensation reaction: in a 1000ml reactor, add aniline and isopropyl titanate, stir and heat to 110°C, maintain for 3h, remove moisture, and detect the water content to be 0.2%; maintain at 150°C, continuously introduce acetone at a rate of 200mL / h, and carry out polycondensation reaction for 6h. The water produced during the reaction and the excess acetone can be recovered and the water produced by the reaction can be separated by a distillation tower connected to the reactor; the water content of the polycondensation reaction liquid is detected to be 0.2%; the volume ratio of aniline, tetraisopropyl titanate and acetone is 1:0.02:10; High-pressure reaction: the reaction liquid is transferred to an autoclave, and acetone is added, the volume ratio of acetone to aniline is 1:10; the reaction temperature is controlled to 160°C, and the reaction is stirred for 8 hours, at which time the system pressure is 2.3MPa. After the pressure is reduced, the temperature is reduced to 100°C, 24ml of liquid alkali and 16% sodium hydroxide solution are added for neutralization, water is separated, and the oil phase is distilled at normal pressure to remove acetone and water, and then enters negative pressure distillation, under a vacuum of -0.099MPa, i.e. 1000Pa, the material temperature is controlled to 180°C, and the front fraction is extracted to obtain TMQ finished product; Distillation: Under normal pressure, the front fraction is distilled by a packed distillation column, the reflux ratio is controlled to 7, the kettle temperature is 180-210℃, and the 165-169℃ fraction is collected to obtain 1,3,5-trimethylbenzene (mesitylene) with a content of 99.6%. The kettle liquid is used as a recovered raw material in the polycondensation reaction.