阅读说明：本技术 一种复合催化剂及制备偏苯三酸酐的方法 (Composite catalyst and method for preparing trimellitic anhydride ) 是由 柯伯留 柯伯成 罗建立 周晔 石埕阳 徐小买 柯美松 柯海宝 方珩徽 于 2021-07-28 设计创作，主要内容包括：一种复合催化剂,包括醋酸钴、醋酸锰、四溴乙烷、醋酸锆；复合催化剂中各成分按重量比,醋酸钴∶醋酸锰∶四溴乙烷∶醋酸锆＝1:0.3～5:0.3～5:0.3～5；一种制备偏苯三酸酐的方法,以偏三甲苯为原料,醋酸为溶剂,该法使用上述复合催化剂,空气为氧化剂；按重量比,偏三甲苯∶醋酸∶复合催化剂＝1:2.5～10:0.01～0.08,制备方法：在混合釜中将原料按比例计量搅拌混合,并升温溶解；将混合物料转入氧化釜,通入空气加压,反应的温度控制在160～220℃,压力控制在0.6～2.2Mpa,在成酐釜中将氧化物料脱水成粗酐,产生的稀醋酸送入精馏釜提浓回用。本发明解决了传统生产方法偏三甲苯转化率较低,副反应较多,从而得到的成品中杂质较多从而影响最终产品外观和色号的问题。(A composite catalyst comprises cobalt acetate, manganese acetate, tetrabromoethane and zirconium acetate; the composite catalyst comprises the components of, by weight, cobalt acetate, manganese acetate, tetrabromoethane and zirconium acetate in a ratio of 1: 0.3-5; a method for preparing trimellitic anhydride takes trimellitic benzene as raw material and acetic acid as solvent, the method uses the composite catalyst and air as oxidant; according to the weight ratio, the pseudocumene, the acetic acid and the composite catalyst are 1: 2.5-10: 0.01-0.08, and the preparation method comprises the following steps: the raw materials are weighed, stirred and mixed in a mixing kettle according to a proportion, and are heated and dissolved; transferring the mixed material into an oxidation kettle, introducing air for pressurization, controlling the reaction temperature at 160-220 ℃ and the pressure at 0.6-2.2 Mpa, dehydrating the oxidation material into crude anhydride in an anhydride forming kettle, and feeding the generated dilute acetic acid into a rectifying kettle for concentration and recycling. The invention solves the problems that the traditional production method has low pseudocumene conversion rate and more side reactions, so that the appearance and the color number of a final product are influenced because more impurities exist in the obtained finished product.)

1. The composite catalyst is characterized by comprising cobalt acetate, manganese acetate, tetrabromoethane and zirconium acetate; the composite catalyst comprises the components of cobalt acetate, manganese acetate, tetrabromoethane and zirconium acetate in a weight ratio of 1: 0.3-5.

2. A process for producing trimellitic anhydride from trimellitic anhydride, wherein trimellitic anhydride is used as a starting material and acetic acid is used as a solvent, characterized in that the composite catalyst of claim 1 is used and air is used as an oxidizing agent; according to the weight ratio, the pseudocumene, the acetic acid and the composite catalyst are 1: 2.5-10: 0.01-0.08, and the preparation method mainly comprises the following steps:

(1) mixing: metering the pseudocumene, the acetic acid and the composite catalyst in proportion in a mixing kettle, starting stirring and mixing, and heating to ensure that the pseudocumene and the solvent are mutually dissolved;

(2) and (3) oxidation: transferring the mixed material into an oxidation kettle, introducing air for pressurization, controlling the reaction temperature at 160-220 ℃, controlling the pressure at 0.6-2.2 Mpa, and finishing the oxidation reaction when the oxygen content of tail gas reaches 15-20%;

(3) anhydride formation: dehydrating the oxidized material in an anhydride forming kettle to form crude anhydride, sending dilute acetic acid generated in the anhydride forming process into a rectifying kettle, concentrating and recycling;

(4) and (3) rectification: and (4) decompressing and rectifying the crude anhydride in a rectifying still to remove byproducts, thus obtaining the finished product of trimellitic anhydride.

3. The process for producing trimellitic anhydride according to claim 2, wherein in the mixing step, the temperature in the mixing vessel is controlled to be 60 to 120 ℃.

4. The process according to claim 2, wherein the temperature of the vessel for forming trimellitic anhydride in the step of forming trimellitic anhydride is controlled to 160 to 220 ℃.

5. The process according to claim 2, wherein the temperature of the rectifying still is controlled to 200 to 280 ℃ and the degree of vacuum is 10 to 20mmHg in the rectifying step.

6. The process according to claim 2, wherein the mixing vessel, the oxidizing vessel, the anhydride-forming vessel and the rectifying vessel are all made of titanium.

Technical Field

The invention relates to the field of chemical synthesis, in particular to a composite catalyst and a method for preparing trimellitic anhydride.

Background

Trimellitic anhydride (TMA), also known as 1, 2, 4-benzenetricarboxylic anhydride for short, is white or yellowish acicular crystals in appearance. Trimellitic anhydride contains carboxylic acid and anhydride structures in molecular structures, has chemical properties of benzoic acid and phthalic anhydride, can react with alcohol to generate ester or polyester, reacts with alkali to generate salt, reacts with ammonia (amine) to generate amide-imide, and performs condensation reaction with hydrocarbon under the action of a catalyst, so that the trimellitic anhydride has wide application in the aspects of producing PVC resin plasticizers, polyimide resin paints, water-soluble alkyd resins, epoxy resin curing agents, impregnants for low-voltage and pulse power containers, cinematograph films, water treatment agents, surfactants and the like.

At present, the production method of trimellitic anhydride includes a batch operation method and a continuous operation method. The Chinese patent No. 02143030.6 discloses a method for producing trimellitic anhydride by a continuous oxidation process. It uses pseudocumene as raw material, acetic acid as solvent and cobalt acetate, manganese acetate, tetrabromoethane or hydrogen bromide as catalyst. The method comprises the following technical processes: (1) the continuous oxidation reaction process of the mixed materials; (2) anhydride forming process; (3) refining; (4) slicing or granulating; (5) and (5) solvent recovery process. The method adopts a continuous oxidation technology and an advanced refining technology, and is suitable for large-scale industrial production compared with an intermittent oxidation technology. The defects that the self-inhibition effect is generated in the presence of the catalyst, namely, the produced partial oxidation product and the catalyst form a complex to cause the activity of the catalyst to be passivated, so that the yield of the trimellitic anhydride is limited within the range of 65-75 percent, and the maximum obstacle is formed in further improving the yield of the trimellitic anhydride.

The Chinese patent application No. 200410041379.7 proposes a method for continuously producing trimellitic anhydride by stepwise catalytic oxidation. The method adopts pseudocumene as a raw material, low-element aliphatic carboxylic acid as a solvent and cobalt, manganese and bromine as catalysts. The method is realized by adopting a method of continuously and secondarily adding the catalyst. The production process comprises the following steps: (1) a step-by-step catalytic continuous oxidation process; (2) crystallization and liquid-solid separation; (3) anhydride forming process; (4) refining; (5) and (5) solvent recovery process. Compared with the domestic general intermittent oxidation production process, the method has the characteristics of low production labor intensity, stable product quality, high safety, high product yield and the like, effectively solves the problems of unstable product quality, difficult operation and low product acid value and yield in the domestic existing production process, and is suitable for large-scale industrial production. The step-by-step catalytic oxidation is continuously carried out in two reaction kettles connected in series, in fact, the method that a single kettle is continuously connected into double kettles is not an ideal continuous method, and the defects are concentrated in that: 1. optimization of continuous operation cannot be realized, and because the oxidation conditions of three methyl groups on a trimellitic nucleus are different, the fixed operation conditions do not accord with the basic rule of oxidation; 2. the conversion rate of the pseudocumene is low, and the yield is influenced. And the production method has more side reactions, so that the obtained finished product has more impurities, the impurities can influence the appearance and the color number of the finished product, and the color number of the product is generally more than 130.

The Chinese patent application No. 200410072953.5 discloses a method for producing trimellitic anhydride by continuously oxidizing anhydride in a stirring type multi-kettle way, which takes trimellitic benzene as a raw material, acetic acid as a solvent, tetrabromoethane as an accelerant and cobalt acetate and manganese acetate as catalysts. An oxidation reaction kettle with a stirring device is connected in series by three to four stages, the temperature in the kettle is 160-260 ℃, and the pressure is 0.08-0.12Mpa (absolute pressure). Adding the materials into oxidation reaction kettles at different levels according to the proportion, continuously feeding the mixed materials into a multistage series reaction kettle with stirring by virtue of pump force through pipeline connection, and carrying out liquid-phase continuous oxidation, anhydride formation and refining while stirring to obtain the trimellitic anhydride. The multi-kettle continuous oxidation production avoids frequent operation of temperature and pressure rise and fall, the reaction process is stable, and the corrosion to equipment and the environmental pollution are reduced; high quality, low consumption, safety and reliability. The multi-kettle continuous oxidation is a relatively ideal production method, but some technical details are not properly processed, which is shown in the following steps:

1. air is connected in parallel to enter the reaction kettles at all levels, the air utilization rate is low, most of the air is wasted, and if the air is connected in series from the reaction kettle at the next level, the air is fully utilized.

2. The content of tail gas of each stage of reaction kettle is controlled within 0.8-15%, but the oxygen content of tail gas after multi-kettle mixing is controlled below 8%, so that the possibility of explosion cannot be prevented, and the strict control of the oxygen content of the outlet of each stage of reaction kettle below 8% is correct.

Disclosure of Invention

The invention aims to solve the technical problem of the prior art, provides a novel method for preparing trimellitic anhydride, and solves the problems that the traditional production method has low conversion rate of trimellitic anhydride and more side reactions, so that the appearance and the color number of a final product are influenced due to more impurities in the obtained finished product.

The technical scheme adopted by the invention for solving the technical problems is as follows:

the invention provides a composite catalyst, which comprises cobalt acetate, manganese acetate, tetrabromoethane and zirconium acetate; the composite catalyst comprises the components of cobalt acetate, manganese acetate, tetrabromoethane and zirconium acetate in a weight ratio of 1: 0.3-5.

The invention also provides a method for preparing trimellitic anhydride, which takes trimellitic benzene as a raw material and acetic acid as a solvent, uses the composite catalyst of claim 1, and utilizes air as an oxidant; according to the weight ratio, the pseudocumene, the acetic acid and the composite catalyst are 1: 2.5-10: 0.01-0.08, and the preparation method mainly comprises the following steps:

mixing: metering the pseudocumene, the acetic acid and the composite catalyst in a mixing kettle according to a proportion, starting stirring and mixing, and heating to ensure that the pseudocumene and the solvent are mutually dissolved;

an oxidation step: transferring the mixed material into an oxidation kettle, introducing air for pressurization, controlling the reaction temperature at 160-220 ℃, controlling the pressure at 0.6-2.2 Mpa, and finishing the oxidation reaction when the oxygen content of tail gas reaches 15-20%;

anhydride forming step: dehydrating the oxidized material in an anhydride forming kettle to form crude anhydride, sending dilute acetic acid generated in the anhydride forming process into a rectifying kettle, concentrating and recycling;

a rectification step: and (4) decompressing and rectifying the crude anhydride in a rectifying still to remove byproducts, thus obtaining the finished product of trimellitic anhydride.

Further, in the mixing step, the temperature in the mixing kettle is controlled to be 60-120 ℃.

Further, in the step of forming the anhydride, the kettle temperature of the anhydride forming kettle is controlled to be 160-220 ℃.

Further, in the rectification step, the temperature of the rectification kettle is controlled to be 200-280 ℃, and the vacuum degree is 10-20 mmHg.

Preferably, in order to prevent the corrosion of equipment, the mixing kettle, the oxidation kettle, the anhydride forming kettle and the rectifying kettle are all made of titanium.

The invention has the beneficial effects that: the method for preparing the trimellitic anhydride by using the composite catalyst has the advantages that the composite catalyst used in the method can effectively reduce side reactions in the oxidation process, the decarboxylation reaction is reduced, the reaction process is more stable, the production efficiency is improved, and the production cost is reduced; meanwhile, the yield of the trimellitic anhydride is high, and the appearance and the color number of a final product can be well guaranteed.

The invention will be explained in more detail below with reference to the drawings and examples.

Drawings

FIG. 1 is a process flow diagram of the process for producing trimellitic anhydride according to the present invention.

Detailed Description

As shown in figure 1, a method for preparing trimellitic anhydride takes trimellitic benzene as a raw material and acetic acid as a solvent, and uses a composite catalyst and air as an oxidant; according to the weight ratio, the pseudocumene, the acetic acid and the composite catalyst are 1: 2.5-10: 0.01-0.08;

the composite catalyst comprises cobalt acetate, manganese acetate, tetrabromoethane and zirconium acetate; the composite catalyst comprises the components of cobalt acetate, manganese acetate, tetrabromoethane and zirconium acetate in a weight ratio of 1: 0.3-5. It should be noted that if the amount of the composite catalyst is too much, the composite catalyst will be over oxidized, and the reaction will be violent and difficult to control, resulting in the problem of increased by-products. Zirconium acetate can obviously reduce the occurrence of decarboxylation reaction during the oxidation reaction, so that the reaction process tends to be more stable, and finally the yield of trimellitic anhydride is obviously improved.

The main method for preparing trimellitic anhydride by using the composite catalyst comprises the following steps:

mixing: metering the pseudocumene, the acetic acid and the composite catalyst in a mixing kettle according to a proportion, stirring and mixing, and heating to 60-120 ℃ to enable the pseudocumene, the solvent and the composite catalyst to be mutually soluble;

an oxidation step: transferring the mixed material into an oxidation kettle, introducing air for pressurization, controlling the reaction temperature to be 160-220 ℃, controlling the pressure to be 0.6-2.2 Mpa, and finishing the oxidation reaction when the oxygen content of tail gas reaches 15-20%;

anhydride forming step: controlling the temperature of an anhydride forming kettle at 160-220 ℃, dehydrating an oxidation material in the anhydride forming kettle to form crude anhydride, sending dilute acetic acid generated in the anhydride forming process into a rectifying kettle, concentrating and recycling;

a rectification step: controlling the kettle temperature of the rectifying kettle at 200-280 ℃ and the vacuum degree at 10-20 mmHg, and decompressing and rectifying the crude anhydride in the rectifying kettle to remove byproducts, thereby obtaining a finished product of trimellitic anhydride.

Example 1:

firstly, 200kg of pseudocumene, 600kg of acetic acid and 14kg of composite catalyst are added into a mixing kettle, wherein 2.2kg of cobalt acetate, 6.6kg of manganese acetate, 4.2kg of tetrabromoethane and 1kg of zirconium acetate are added into the composite catalyst, stirring and mixing are started, the temperature is raised to 80 ℃, and the pseudocumene and the solvent are mutually dissolved;

transferring the mixed material into an oxidation kettle, introducing air for pressurization, controlling the reaction temperature at 210 ℃, controlling the pressure at 1.8Mpa, controlling the reaction time at 70 minutes, and finishing the oxidation reaction when the oxygen content of the tail gas reaches 15-20%;

then controlling the temperature of an anhydride forming kettle at 180 ℃, dehydrating the oxidized material in the anhydride forming kettle to form crude anhydride, sending the dilute acetic acid generated in the anhydride forming process into a rectifying kettle, concentrating and recycling;

a rectification step: controlling the kettle temperature of a rectifying kettle at 200-280 ℃ and the vacuum degree of 10-20 mmHg, decompressing and rectifying the crude anhydride in the rectifying kettle to remove byproducts, obtaining 248.8kg of finished trimellitic anhydride, and measuring the color number to be 120 by utilizing a platinum-cobalt colorimetric method.

Example 2:

firstly, 200kg of pseudocumene, 600kg of acetic acid and 12kg of composite catalyst are added into a mixing kettle, wherein 1.5kg of cobalt acetate, 3kg of manganese acetate, 3kg of tetrabromoethane and 4.5kg of zirconium acetate are added into the composite catalyst, stirring and mixing are started, the temperature is raised to 80 ℃, and the pseudocumene and the solvent are mutually dissolved;

transferring the mixed material into an oxidation kettle, introducing air for pressurization, controlling the reaction temperature at 180 ℃, controlling the pressure at 1.0Mpa, controlling the reaction time at 90 minutes, and finishing the oxidation reaction when the oxygen content of the tail gas reaches 15-20%;

then controlling the temperature of an anhydride forming kettle at 180 ℃, dehydrating the oxidized material in the anhydride forming kettle to form crude anhydride, sending the dilute acetic acid generated in the anhydride forming process into a rectifying kettle, concentrating and recycling;

a rectification step: the temperature of the rectifying still is controlled at 240 ℃, the vacuum degree is 15mmHg, the crude anhydride is decompressed and rectified in the rectifying still to remove by-products, 250.2kg of finished trimellitic anhydride is obtained, and the color number is 110 by utilizing a platinum cobalt colorimetric method.

Example 3:

firstly, 200kg of pseudocumene, 750kg of acetic acid and 8kg of composite catalyst are added into a mixing kettle, wherein 1.3kg of cobalt acetate, 2.5kg of manganese acetate, 1kg of tetrabromoethane and 3.2kg of zirconium acetate are added into the composite catalyst, stirring and mixing are started, the temperature is raised to 80 ℃, and the pseudocumene and the solvent are mutually dissolved;

transferring the mixed material into an oxidation kettle, introducing air for pressurization, controlling the reaction temperature at 200 ℃, controlling the pressure at 1.5Mpa, controlling the reaction time at 80 minutes, and finishing the oxidation reaction when the oxygen content of the tail gas reaches 15-20%;

then controlling the temperature of an anhydride forming kettle at 180 ℃, dehydrating the oxidized material in the anhydride forming kettle to form crude anhydride, sending the dilute acetic acid generated in the anhydride forming process into a rectifying kettle, concentrating and recycling;

a rectification step: the temperature of the rectifying still is controlled at 240 ℃, the vacuum degree is 15mmHg, the crude anhydride is decompressed and rectified in the rectifying still to remove by-products, 252kg of finished trimellitic anhydride is obtained, and the color number is 100 by utilizing a platinum cobalt colorimetric method.

Example 4:

firstly, 200kg of pseudocumene, 750kg of acetic acid and 6kg of composite catalyst are added into a mixing kettle, wherein in the composite catalyst, 0.9kg of cobalt acetate, 1.3kg of manganese acetate, 1.2kg of tetrabromoethane and 2.6kg of zirconium acetate are stirred and mixed, and the temperature is raised to 80 ℃ to ensure that the pseudocumene and the solvent are mutually dissolved;

transferring the mixed material into an oxidation kettle, introducing air for pressurization, controlling the reaction temperature at 190 ℃, controlling the pressure at 1.2Mpa, controlling the reaction time at 80 minutes, and finishing the oxidation reaction when the oxygen content of the tail gas reaches 15-20%;

then controlling the temperature of an anhydride forming kettle at 180 ℃, dehydrating the oxidized material in the anhydride forming kettle to form crude anhydride, sending the dilute acetic acid generated in the anhydride forming process into a rectifying kettle, concentrating and recycling;

a rectification step: controlling the temperature of a rectifying still at 240 ℃ and the vacuum degree at 15mmHg, decompressing and rectifying the crude anhydride in the rectifying still, removing byproducts from the distillate to obtain 251.4kg of finished trimellitic anhydride, and measuring the color number of the trimellitic anhydride to be 100 by utilizing a platinum-cobalt colorimetric method.

Example 5:

firstly, 200kg of pseudocumene, 500kg of acetic acid and 4kg of composite catalyst are added into a mixing kettle, wherein 1.2kg of cobalt acetate, 1.2kg of manganese acetate, 0.9kg of tetrabromoethane and 0.7kg of zirconium acetate are added into the composite catalyst, stirring and mixing are started, the temperature is raised to 80 ℃, and the pseudocumene and the solvent are mutually dissolved;

transferring the mixed material into an oxidation kettle, introducing air for pressurization, controlling the reaction temperature at 210 ℃, controlling the pressure at 2.1Mpa, controlling the reaction time at 90 minutes, and finishing the oxidation reaction when the oxygen content of the tail gas reaches 15-20%;

then controlling the temperature of an anhydride forming kettle at 180 ℃, dehydrating the oxidized material in the anhydride forming kettle to form crude anhydride, sending the dilute acetic acid generated in the anhydride forming process into a rectifying kettle, concentrating and recycling;

a rectification step: controlling the temperature of a rectifying still at 240 ℃ and the vacuum degree at 15mmHg, decompressing and rectifying the crude anhydride in the rectifying still, removing byproducts from the distillate to obtain 251kg of finished trimellitic anhydride, and measuring the color number to be 110 by utilizing a platinum-cobalt colorimetric method.

While the process and system for producing trimellitic anhydride of the present invention have been described with reference to the accompanying drawings, it is to be understood that the invention is not limited in its application to the details of the process and system, and that various modifications and variations can be made without departing from the spirit or scope of the invention.