Method for preparing aromatic carboxylic acid through solvent-free gas-liquid micro-interface catalytic oxidation

Abstract

The invention discloses a method for preparing aromatic carboxylic acid through solvent-free gas-liquid micro-interface catalytic oxidation. According to the method, o-xylene and halide thereof are used as raw materials, cobalt, manganese and bromine are used as composite catalysts, nano graphene, phthalic anhydride and derivatives thereof are used as additives, atomic oxygen is used as an oxidizing agent, and chlorophthalic anhydride is prepared through catalytic oxidation under normal pressure. The method has the advantages that by adding the nano graphene, diffusion and dispersion of a gas oxidizing agent are accelerated, a gas-liquid micro-interface system is strengthened, a normal-pressure liquid-phase oxidation reaction is achieved, and the problem that a traditional high-pressure oxidation reaction is low in safety coefficient is solved. The process product is easy to separate, the catalyst is easy to recover, and the method is suitable for industrial processes.

Description

Technical Field

[0001] The invention relates to a method for preparing aromatic carboxylic acid by solvent-free gas-liquid microinterface catalytic oxidation, and belongs to the category of synthetic chemistry. Background Art

[0002] Phthalic anhydride and its derivatives are important raw materials for basic chemicals and fine chemicals, among which halogenated phthalic anhydride is the key raw material for the preparation of biphenyl dianhydride and various ether anhydrides. The preparation methods that have been tried in industry mainly include: 1) the method of passing chlorine gas through phthalic anhydride, but the product is mainly 4-chlorophthalic anhydride, and there is a large amount of unreacted phthalic anhydride raw material in the obtained product, which is difficult to separate and purify; 2) the method of gas phase oxidation of halogenated o-xylene, but this method has a high reaction temperature, severe carbonization corrosion, and a yield of only about 70%, with low atom economy, and several industrializations have failed; 3) the method of liquid phase oxidation of halogenated o-xylene, which must use an expensive titanium kettle, acetic acid as a solvent, and manganese, cobalt, nickel, bromine, etc. as catalysts. Although the reaction yield is high, the reaction requires high-pressure oxidation and a large amount of low-boiling acetic acid as a solvent. It needs to be above 190°C at a pressure of 2.0 to 2.4 MPa to initiate and maintain the reaction. The yield is about 90%, and the post-treatment and water removal process of acetic acid recovery is complicated and belongs to a dangerous process. Its industrialization is increasingly restricted, and normal pressure reaction will greatly improve the safety index of production. Summary of the invention

[0003] In order to overcome the above-mentioned deficiencies in the preparation of halogenated phthalic anhydride, the present invention provides a new solution for preparing aromatic carboxylic acids by solvent-free gas-liquid microinterface catalytic oxidation.

[0004] In order to achieve the above-mentioned invention task, the present invention adopts the following technical scheme:

[0005] A method for preparing aromatic carboxylic acids by solvent-free gas-liquid microinterface catalytic oxidation is implemented according to the following steps:

[0006]

[0007] In the above o-xylene compound, Y is the element H, Cl or Br;

[0008] The catalyst is a complex of cobalt salt, manganese salt and bromide;

[0009] The additive is nanographene, the addition amount of which is 0.1-1% of the o-xylene compound, and the size of the graphene is 2-150nm;

[0010] The preparation and separation process is as follows: o-xylene compounds, catalysts and additives are mixed into a reactor, gaseous oxygen molecules are introduced at 120°C to 190°C to react for 2-15 hours, the reaction is stopped when the molecular oxygen flow rate in the tail gas is detected to be 95% of the intake air volume, and then distillation and dehydration are performed to obtain phthalic anhydride or halogenated phthalic anhydride, and the catalyst and graphene are recovered.

[0011] The cobalt salt described in the above process is one of cobalt acetate, cobalt carbonate, cobalt chloride or cobalt bromide; the manganese salt is one of manganese acetate, manganese carbonate, manganese chloride or manganese bromide; the bromide is hydrogen bromide, sodium bromide or tetrabromoethane, wherein the element molar ratio of cobalt: manganese: bromine is =1-10:2-8:2-10, and the mass percentage concentration of the catalyst in the reaction system is 0.01-0.5%. The additives include a combination of graphene and phthalic anhydride or a combination of graphene and chlorophthalic anhydride or a combination of graphene and bromophthalic anhydride, wherein the amount of graphene is 0.1-1% of the o-xylene compound, and the particle size is 2-150nm; the amount of phthalic anhydride or halogenated phthalic anhydride is 10-25% of the mass of the o-xylene compound, and the halogenated phthalic anhydride includes 4-chlorophthalic anhydride, 3-chlorophthalic anhydride, 4-bromophthalic anhydride or 3-bromophthalic anhydride.

[0012] The o-xylene compounds described in the above process are o-xylene, brominated o-xylene and chloro-o-xylene; wherein brominated o-xylene includes 3-bromo-o-xylene and 4-bromo-o-xylene, or a mixture of the two; chloro-o-xylene includes 3-chloro-o-xylene and 4-chloro-o-xylene, or a mixture of the two; and the oxidant is molecular oxygen with a concentration of 20 to 100%.

[0013] Beneficial technical effects of the present invention:

[0014] The present invention utilizes the nanometer size effect of nanographene materials, and in the gas-liquid phase reaction process, rapidly destroys the bubbles expanded in the reaction system, so that the gas oxygen introduced rapidly forms small bubbles of microscale, and avoids the formation of large bubbles, which is equivalent to greatly increasing the contact probability of oxygen atoms, reactants and catalysts under the condition of no pressure, thereby improving the efficiency of catalytic reaction, and realizing the smooth progress of the reaction at normal pressure. Because the reaction can be carried out at normal pressure, the catalytic oxidation reaction can be realized using ceramic or glass reactors, avoiding the use of expensive titanium reactors, and can greatly reduce fixed asset investment. The present invention uses air and oxygen of different concentrations as oxidants, which are cheap and easy to obtain, avoids the traditional high temperature and high pressure liquid phase oxidation system causing excessive oxidation to cause serious side reactions such as decarboxylation, and improves the safety factor of production. Specific embodiments

[0015] The present invention is specifically described below in conjunction with embodiments, but the present invention is not limited to the scope of the embodiments.

[0016] Example 1

[0017] In a 500mL glass reaction tube, 140g 4-chloro-o-xylene (~1moL), 0.3g cobalt acetate catalyst, 0.1g manganese acetate, 1g tetrabromoethane, 1.4g graphene with a diameter of about 2-10nm, and 30g 4-chlorophthalic anhydride were added, and the mixture was heated to 120°C. Oxygen with a purity of 100% was introduced at a flow rate of 360mL / min. The temperature was gradually controlled to 150°C within 60 minutes, and the reaction was continued for ~3 hours. When the flow rate of oxygen in the tail gas was detected to be 340mL / min, the ventilation reaction was stopped, the temperature was raised to 200-220°C, and reduced pressure distillation was performed to collect 206.5g of 4-chlorophthalic anhydride. After removing the added 30g chlorophthalic anhydride, the product had a molar yield of 96% and a melting point of ~96°C. The recovered catalyst and graphene can be used directly.

[0018] Example 2

[0019] In a 500mL glass reaction tube, 185g of 3-bromo-o-xylene (1moL), 0.4g of catalyst cobalt acetate, 0.15g of manganese acetate, 1.5g of tetrabromoethane, 0.20g of graphene with a diameter of about 10-150nm, and 20g of 4-bromophthalic anhydride were added, and the mixture was heated to 130°C, and oxygen with a purity of 100% was introduced at a flow rate of 240mL / min. The temperature was controlled to react at 180°C for 5 hours. When the flow rate of oxygen in the tail gas was detected to be 230mL / min, the ventilation reaction was stopped, and the mixture was heated to 200-220°C for vacuum distillation to collect and obtain 213.4g of 3-bromophthalic anhydride. After removing the added 20g of bromophthalic anhydride, the molar yield of 3-bromophthalic anhydride was calculated to be 94%; the residual organic matter, catalyst and graphene in the glass reaction tube did not need to be purified and were directly used for the next batch of oxidation reactions.

[0020] Example 3

[0021] In a 500mL glass reaction tube, 106g of o-xylene, 0.4g of catalyst cobalt acetate, 0.15g of manganese acetate, 3g of sodium bromide, 0.5g of graphene with a diameter of about 2-70nm, and 20g of phthalic anhydride are added, and the mixture is heated to 120°C. Air is introduced into the bottom of the kettle at a flow rate of 1000mL / min, and the temperature is gradually raised to 190°C. The mixture is reacted for 6.5 hours. When the concentration of oxygen in the tail gas is detected to be 20%, the ventilation reaction is stopped, the temperature is raised to 190-210°C, and reduced pressure distillation is performed to collect 162.5g of phthalic anhydride. After removing the added 20g of bromophthalic anhydride, the molar yield of phthalic anhydride is 96%, and the melting point is 131°C. The residual organic matter, catalyst and graphene in the glass reaction do not need to be purified and are directly used for the next batch of oxidation reactions.

[0022] The above is a detailed introduction to the method for preparing corresponding carboxylic acids by gas-liquid microinterface catalytic oxidation of o-xylene and its halides provided by the present invention. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present invention, the present invention can also be improved and modified in a number of ways. For example, the oxidation of p-xylene, m-xylene, toluene and other aromatic methyl compounds to prepare corresponding aromatic carboxylic acids, these improvements and modifications also fall within the scope of protection of the present invention.

Claims

1. A method for preparing aromatic carboxylic acids by solvent-free gas-liquid microinterface catalytic oxidation, the preparation process is as follows: In the above o-xylene compound structure, Y is the element H, Cl or Br; The catalyst is a complex of cobalt salt, manganese salt and bromide; The preparation and separation process is as follows: o-xylene or its halogenated product, catalyst and additive are mixed and added into a reactor, gaseous oxygen molecules are introduced at 120°C to 190°C to react for 2-15 hours, and the reaction is stopped when the molecular oxygen flow rate in the tail gas is detected to be 95% of the intake air volume to obtain aromatic carboxylic acid, which is then distilled and dehydrated to obtain phthalic anhydride or halogenated phthalic anhydride, and the catalyst is recovered.

2. A method for preparing aromatic carboxylic acids according to claim 1, characterized in that: The cobalt salt is one of cobalt acetate, cobalt carbonate, cobalt chloride or cobalt bromide; the manganese salt is one of manganese acetate, manganese carbonate, manganese chloride or manganese bromide; the bromide is hydrogen bromide, sodium bromide or tetrabromoethane; wherein the element molar ratio of cobalt: manganese: bromine is 1-10: 2-8: 2-10, and the mass percentage concentration of the catalyst in the reaction system is 0.01-0.5%.

3. According to claim 1, a method for preparing aromatic carboxylic acids by solvent-free gas-liquid microinterface catalytic oxidation, characterized in that: The o-xylene compound is o-xylene, brominated o-xylene and chloro-o-xylene; wherein brominated o-xylene includes 3-bromo-o-xylene and 4-bromo-o-xylene, or a mixture of the two; chloro-o-xylene includes 3-chloro-o-xylene and 4-chloro-o-xylene, or a mixture of the two; and the gas oxidant is molecular oxygen with a concentration of 20 to 100%.

4. According to claim 1, a method for preparing aromatic carboxylic acids by solvent-free gas-liquid microinterface catalytic oxidation, characterized in that: The additive includes a combination of graphene and phthalic anhydride, or a combination of graphene and chlorophthalic anhydride, or a combination of graphene and bromophthalic anhydride, wherein the amount of graphene is 0.1-1% of the o-xylene compound, and the particle size is 2-150 nm; the amount of phthalic anhydride or halogenated phthalic anhydride is 10-25% of the mass of the o-xylene compound, and the halogenated phthalic anhydride includes 4-chlorophthalic anhydride, 3-chlorophthalic anhydride, 4-bromophthalic anhydride or 3-bromophthalic anhydride.

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