Method for preparing halogenated phthalic anhydride through micro-interface enhanced catalytic oxidation

Abstract

The invention discloses a method for preparing halogenated phthalic anhydride through micro-interface enhanced catalytic oxidation, which is characterized in that halogenated o-xylene is used as a raw material, cobalt, manganese and bromine are used as composite catalysts, nano-zirconia is used as an additive, atomic oxygen is used as an oxidant, acetic acid is used as a solvent, and chlorophthalic anhydride is prepared through catalytic oxidation under normal pressure. The method has the advantages that by adding the nano-zirconia, diffusion and dispersion of the gas oxidizing agent are accelerated, a gas-liquid micro-interface system is strengthened, normal-pressure liquid-phase oxidation reaction is achieved, the problem that a traditional oxidation reaction needs to be carried out at high temperature and high pressure is solved, product separation is easy, the catalyst is easy to recycle, and the method is suitable for the industrial process.

Description

Technical Field

[0001] The invention relates to a method for preparing halogenated phthalic anhydride by micro-interface enhanced catalytic oxidation, and belongs to the category of synthetic chemistry. Background Art

[0002] Halogenated phthalic anhydride is currently the key raw material for preparing polyimide monomers such as 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 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. However, because a small amount of phenol by-products will be produced during the reaction, it is generally necessary to initiate and maintain the reaction at a pressure of 2.0 to 2.4 MPa and above 190°C, so it is a dangerous process, and its industrialization is increasingly restricted. The use of atmospheric pressure and low-temperature reactions will greatly improve the safety index of production.

[0003] In order to overcome the above-mentioned deficiencies in the preparation of halogenated phthalic anhydride, the present invention provides a new scheme for preparing halogenated phthalic anhydride by micro-interface enhanced catalytic oxidation of halogenated o-xylene, so that the reaction can be carried out under normal pressure or low pressure. Summary of the invention

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

[0005] A method for preparing halogenated phthalic anhydride by micro-interface enhanced catalytic oxidation is implemented according to the following steps:

[0006]

[0007] In the above formula, X is a chlorine or bromine element;

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

[0009] The additive is nano zirconium oxide, the added amount is 0.1-1% of the mass percentage of the solvent, and the size of the zirconium oxide is 1-500nm;

[0010] The preparation and separation process is as follows: halogenated o-xylene, catalyst, additive and solvent are mixed into a reactor, a gaseous oxidant is introduced, and the reaction is carried out at 110-150° C. for 2-20 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 zirconium oxide are recovered.

[0011] The cobalt salt described in the above process is one of cobalt acetate, cobalt chloride or cobalt bromide; the manganese salt is one of manganese acetate, manganese chloride or manganese bromide; the bromide is hydrobromic acid or sodium bromide; wherein the 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, and the amount of the additive zirconium oxide is 0.01-1% of the mass of the solvent.

[0012] The halogenated o-xylene described in the above process includes 3-chloro-o-xylene, 4-chloro-o-xylene or a mixture of the two, 3-bromo-o-xylene, 4-bromo-o-xylene or the two; the mass percentage is 10% to 30% concentration, and the oxidant content is 20 to 100% molecular oxygen gas.

[0013] Beneficial technical effects of the present invention:

[0014] The present invention utilizes the nanometer size effect of nano-zirconia material to quickly destroy the bubbles expanded in the reaction system, so that the gas introduced quickly forms small micro-scale bubbles, avoiding the formation of large bubbles, which is equivalent to greatly increasing the contact probability of oxygen atoms with halogenated o-xylene and catalysts under non-pressurized conditions. At the same time, nano-zirconia has the function of adsorbing and complexing the phenol byproduct produced in the reaction, inhibiting the interference of phenol with the oxidation reaction, thereby improving the efficiency of the catalytic reaction; the reaction can be smoothly carried out under normal low pressure in the acetic acid system, so the catalytic oxidation reaction can be realized by using ceramic or glass reactors, avoiding the use of expensive titanium reactors, and significantly reducing 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 serious side reactions such as decarboxylation caused by excessive oxidation in traditional high-temperature and high-pressure liquid-phase oxidation systems, and improves the safety factor of production.

[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 2000mL glass reaction tube, 140g 4-chloro-o-xylene (1moL), 0.3g cobalt acetate catalyst, 0.1g manganese acetate, 1g sodium bromide, 0.325g zirconium oxide with a diameter of about 2-50nm, 325g acetic acid are added and heated to 130°C, oxygen with a purity of 100% is introduced at a flow rate of 270mL / min, and the temperature is controlled at 130°C 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 177g 4-chlorophthalic anhydride, with a molar yield of 97% and a melting point of 96°C; the residual organic matter, catalyst and zirconium oxide in the glass reaction do not need to be purified and can be directly used for the next batch of oxidation reactions.

[0018] Example 2

[0019] In a 2000mL 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, 0.325g of zirconium oxide with a diameter of about 50-100nm, 525g of acetic acid are added, heated to 100°C, oxygen with a purity of 100% is introduced at a flow rate of 240mL / min, the temperature is controlled at 120°C for 10 hours, and 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 and obtain 216g of 3-bromophthalic anhydride, with a molar yield of 95% and a melting point of 132°C; the organic matter, catalyst and zirconium oxide remaining in the reaction do not need to be purified and can be directly used for the next batch of oxidation reactions.

[0020] Example 3

[0021] In a 2000mL glass reaction tube, 18.5g of a mixed 3-, 4-bromo-o-xylene mixture (0.1moL, 0.25 / 0.75), 0.04g of cobalt acetate catalyst, 0.015g of manganese acetate, 0.3g of sodium bromide, 0.125g of zirconium oxide with a diameter of about 50-100nm, 100g of acetic acid are added, heated to 110°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 7.4 hours. When the concentration of tail gas oxygen is detected to be 20%, the oxygen is stopped, the temperature is raised to 140°C to remove acetic acid, and then vacuum distillation is carried out at 200-210°C to collect and obtain 22.3g of a 3- and 4-bromophthalic anhydride mixture with a molar yield of 98% and a melting point of 125°C; the residual organic matter, catalyst and zirconium oxide in the glass reaction do not need to be purified and can be directly used for the next batch of oxidation reactions.

[0022] The above is a detailed introduction to the micro-interface enhanced catalytic oxidation of chloro-o-xylene to prepare chlorophthalic anhydride 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, 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 halogenated phthalic anhydride by microinterface enhanced catalytic oxidation, characterized in that: The preparation process is as follows: In the above formula, X is chlorine or bromine; The catalyst is a complex of cobalt salt, manganese salt and bromide; The additive is nano zirconium oxide; The preparation and separation process is as follows: halogenated o-xylene, catalyst, solvent and nano zirconium oxide additive are mixed and added into a reactor, a gas oxidant is introduced, and the reaction is carried out at 110° C. to 150° C. for 2-20 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 halogenated phthalic anhydride, and the catalyst is recovered.

2. A method for preparing halogenated phthalic anhydride by microinterface enhanced catalytic oxidation according to claim 1, characterized in that: The cobalt salt is one of cobalt acetate, cobalt chloride or cobalt bromide; the manganese salt is one of manganese acetate, manganese chloride or manganese bromide; the bromide is hydrogen bromide or sodium bromide; 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 halogenated phthalic anhydride according to claim 1, characterized in that: The halogenated o-xylene includes 3-chloro o-xylene, 4-chloro o-xylene or a mixture of the two and 3-bromo o-xylene, 4-bromo o-xylene or a mixture of the two, and the concentration of the halogenated 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 zirconium oxide is 0.01-1% of the solvent mass, and the size of the zirconium oxide is 1-500nm.

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