Method for preparing chlorophthalic anhydride through gas-liquid micro-interface catalytic oxidation

Abstract

The invention discloses a method for preparing chlorophthalic anhydride through gas-liquid micro-interface catalytic oxidation. According to the method, chlorophthalic anhydride is prepared through catalytic oxidation under normal pressure by taking o-xylene chloride as a raw material, cobalt, manganese and bromine as a composite catalyst, nano graphene as an additive, atomic oxygen as an oxidizing agent and acetic acid as a solvent. The preparation method has the advantages that by adding the nano graphene, the diffusion and dispersion of a gas oxidant are accelerated, a gas-liquid micro-interface system is enhanced, the normal-pressure liquid-phase oxidation reaction is realized, the problem that the traditional oxidation reaction needs to be carried out at high temperature and high pressure is avoided, the product is easy to separate, the catalyst is easy to recover, and the preparation method is suitable for the industrial process.

Description

Technical Field

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

[0002] Chlorophthalic anhydride is currently 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 from 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 gas phase oxidation method of chlorinated o-xylene, but this method has a high reaction temperature, severe carbonization corrosion, and a yield of only about 70%, with low atomic economy, and several industrializations have failed; 3) the liquid phase oxidation method of chlorinated 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 under a pressure of 2.0 to 2.4 MPa and above 190°C to initiate and maintain the reaction. Its yield is generally below 90%, and it is a dangerous process. Its industrialization is increasingly restricted, and the reaction at normal pressure and low temperature will greatly improve the index of safe production. Summary of the invention

[0003] In order to overcome the above-mentioned deficiencies in the preparation of chlorophthalic anhydride, the present invention provides a new scheme for preparing chlorophthalic anhydride by gas-liquid microinterface catalytic oxidation of chloro-o-xylene.

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

[0005] A method for preparing chlorophthalic anhydride by gas-liquid microinterface catalytic oxidation is implemented according to the following steps:

[0006]

[0007] The catalyst is a complex of cobalt salt, manganese salt and bromide;

[0008] The additive is nanographene, the added amount is 0.1-1% of the mass percentage of the solvent, and the scale of the graphene is 1-300nm;

[0009] The preparation and separation process is as follows: chloro-o-xylene, a catalyst, an additive and a solvent are mixed into a reactor, a gas oxidant is introduced, and the mixture is reacted at 90-130° C. for 2-24 hours. When the oxygen concentration in the tail gas reaches 95% of the concentration of the inlet sample, the reaction is stopped, and then distillation and dehydration are performed to obtain chlorophthalic anhydride, and the catalyst and graphene are recovered.

[0010] The cobalt salt described in the above process is one of cobalt acetate, cobalt carbonate, cobalt nitrate, cobalt sulfate, cobalt oxalate, cobalt chloride or cobalt bromide; the manganese salt is one of manganese acetate, manganese carbonate, manganese nitrate, manganese oxalate, manganese chloride, manganese sulfate or manganese bromide; the bromide is hydrobromic acid, 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 solvent is acetic acid, the amount of the additive graphene is 0.01-0.1% of the solvent mass, and the scale of the graphene is 1-300nm.

[0011] The chloro-o-xylene described in the above process includes 3-chloro-o-xylene, 4-chloro-o-xylene or a mixture of the two; its mass percentage is 10% to 30% concentration, and the oxidant content is 20 to 100% oxygen.

[0012] Beneficial technical effects of the present invention:

[0013] The present invention utilizes the nanometer size effect of nanographene materials to rapidly destroy the bubbles expanded in the reaction system, so that the gas introduced rapidly forms small bubbles of microscale, avoiding the formation of large bubbles, which is equivalent to greatly increasing the contact probability of oxygen atoms with chloro-o-xylene and catalyst under the condition of no pressure, thereby improving the efficiency of catalytic reaction, and realizing that the reaction is smoothly carried out at normal pressure in the acetic acid system. Because the reaction can be carried out at normal pressure, the catalytic oxidation reaction can be realized by 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 occurrence of side reactions such as excessive oxidation and serious decarboxylation caused by traditional high temperature and high pressure liquid phase oxidation systems, and improves the safety factor of production. Specific embodiments

[0014] The present invention is specifically described below in conjunction with embodiments, but the present invention is not limited to the scope of the embodiments.

[0015] Example 1

[0016] In a 500mL glass reactor, 140g 4-chloro-o-xylene (1moL), 0.3g cobalt acetate catalyst, 0.1g manganese acetate, 1g tetrabromoethane, 0.325g graphene with a diameter of about 2-5nm, and 325g acetic acid are added and heated to 120°C. Oxygen with a purity of 100% is introduced at a flow rate of 270mL / min. The temperature is controlled at 120°C for reaction for 6 hours. When the flow rate of oxygen in the tail gas is detected to be ~256mL / min, ventilation is stopped, acetic acid is recovered under the condition of heating to 140°C, and reduced pressure distillation is performed at 200-220°C to collect 176g 4-chlorophthalic anhydride, with a molar yield of 96% and a melting point of ~96°C. The residual organic matter, catalyst and graphene in the glass reaction do not need to be purified and can be directly used for the next batch of oxidation reactions.

[0017] Example 2

[0018] In a 500mL glass reaction tube, 140g 3-chloro-o-xylene (1moL), 0.4g cobalt acetate catalyst, 0.15g manganese acetate, 1.5g tetrabromoethane, 0.325g graphene with a diameter of about 10-50nm, 525g acetic acid are added, heated to 100°C, and oxygen with a purity of 100% is introduced at a flow rate of 240mL / min. The temperature is controlled at 100°C for reaction for 10 hours. When the flow rate of oxygen in the tail gas is detected to be 230mL / min, the oxygen is stopped, the temperature is raised to 140°C and acetic acid is distilled off, and reduced pressure distillation is performed at 200-220°C to collect 170g 3-chlorophthalic anhydride, with a molar yield of 93% and a melting point of 125°C. The residual organic matter, catalyst and graphene in the glass reaction do not need to be purified and can be directly used for the next batch of oxidation reactions.

[0019] Example 3

[0020] In a 500mL glass reaction tube, 14g of a mixed 3-, 4-chloro-o-xylene mixture (0.1moL, 0.45 / 0.55), 0.04g of catalyst cobalt acetate, 0.015g of manganese acetate, 0.3g of sodium bromide, 0.125g of graphene with a diameter of about 2-70nm, and 425g of acetic acid are added, heated to 90°C, air is introduced at a flow rate of 100mL / min, the temperature is gradually raised to 130°C, and the reaction is carried out for 8 hours. When the concentration of tail gas oxygen is detected to be 20%, the oxygen is stopped, the acetic acid is evaporated off under the condition of heating to 140°C, and then vacuum distillation is carried out at 200-220°C to collect and obtain 17.9g of a 3- and 4-chlorophthalic anhydride mixture, with a molar yield of 98% and a melting point of 98°C; the residual organic matter, catalyst and graphene in the glass reaction do not need to be purified and can be directly used for the next batch of oxidation reactions.

[0021] The above is a detailed introduction to the preparation of chlorophthalic anhydride by gas-liquid micro-interface catalytic oxidation of chloro-o-xylene 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 principle of the present invention, several improvements and modifications can be made to the present invention, such as using other bromotoluene, bromo-o-xylene, chlorotoluene, toluene, xylene, etc. as reactants. These improvements and modifications also fall within the scope of protection of the present invention.

Claims

1. A method for preparing chlorophthalic anhydride by gas-liquid microinterface catalytic oxidation, the preparation process is as follows: The catalyst is a complex of cobalt salt, manganese salt and bromide; The preparation and separation process is as follows: chloro-o-xylene, a catalyst, a solvent and a nano-graphene additive are mixed and added into a reactor, a gas oxidant is introduced, and the reaction is carried out at 90° C. to 130° C. for 2-24 hours. When the oxygen content in the tail gas is detected to be above 95% of the content of the inlet sample, the reaction is stopped, and then distillation and dehydration are performed to obtain chlorophthalic anhydride, and the catalyst is recovered.

2. A method for preparing chlorophthalic anhydride by gas-liquid microinterface catalytic oxidation according to claim 1, characterized in that: The cobalt salt is one of cobalt acetate, cobalt carbonate, cobalt nitrate, cobalt sulfate, cobalt oxalate, cobalt chloride or cobalt bromide; the manganese salt is one of manganese acetate, manganese carbonate, manganese nitrate, manganese oxalate, manganese chloride, manganese sulfate 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. A method for preparing chlorophthalic anhydride by gas-liquid microinterface catalytic oxidation according to claim 1, characterized in that: The chloro-o-xylene includes 3-chloro-o-xylene, 4-chloro-o-xylene or a mixture of the two, and the concentration of the chloro-o-xylene in the reaction system is 10-30%; the gas oxidant content is 20-100% of molecular oxygen; the solvent is acetic acid, the amount of the additive graphene is 0.01-0.1% of the solvent mass, and the scale of the graphene is 1-300nm.

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