Method for preparing mono-halogenated aromatic hydrocarbon by piston flow continuous halogenation reaction system

Abstract

The invention discloses a method for preparing mono-halogenated aromatic hydrocarbon by using a piston flow continuous halogenation reaction system, which comprises the following steps of: carrying out piston flow continuous catalysis to prepare mono-halogenated aromatic hydrocarbon by using lewis acid or iodine as a catalyst, aromatic hydrocarbon as a reactant and chlorine or bromine as a halogenating agent, compared with a traditional reaction kettle, the efficiency is improved by more than 100 times, the reaction speed is high, the liquid holdup is small, the reaction safety efficiency is high, and the method is suitable for industrial production.

Description

Technical Field

[0001] The invention relates to a method for preparing monohalogenated aromatic hydrocarbons by a plug flow continuous halogenation reaction system, which belongs to the category of synthetic chemistry. Background Art

[0002] Polyimide is one of the polymer materials with the highest heat resistance and light weight and high strength. Halogenated phthalic anhydride obtained by oxidation of halogenated o-xylene is a key raw material for further preparation of various types of dianhydride monomers after coupling or condensation reaction. Halogenated o-xylene is mainly prepared by the halogenation method of o-xylene. The existing halogenated o-xylene preparation process includes: first, chlorine gas is introduced into the tower reactor of o-xylene or bromine is added dropwise for halogenation, but the problem of this method is that after a certain degree of reaction, the generated monohalogenated product is easy to continue to be halogenated, and it is easy to generate dihalogenated by-products; second, o-xylene is halogenated by microfluidic reaction. Although this process method has the characteristics of intrinsic safety, the inner diameter of the microchannel is generally micrometer to centimeter level, and the flux is limited, which affects the output of a single set. It should mainly be used for high-value-added pharmaceutical products priced in "grams" for experiments. For halogenated hydrocarbons with low added value, the cost-effectiveness of investment is not high, and it is difficult to make a profit after large-scale production. Summary of the invention

[0003] In order to overcome the problem of large liquid holding capacity and potential danger of kettle halogenation reaction system and the problem of easy occurrence of polyhalogenation, the present invention provides a method for monohalogenated aromatic hydrocarbons using a piston flow continuous halogenation reaction system. By using a composite catalyst and utilizing the small liquid holding capacity and efficient radial stirring of the piston continuous flow reaction system, the halogenating agent is quickly mixed with the aromatic hydrocarbons and a tiny gas-liquid or liquid-liquid interface catalytic micro-reaction environment is formed. By controlling the unidirectional flow of the reactants, the residence time of the reactants in the reactor is reduced, and the probability of producing polyhalogenated aromatic hydrocarbon by-products is reduced. This not only increases the safety factor of the process, but also reduces the occurrence of side reactions, thereby improving the reaction efficiency and the yield of monohalogenated aromatic hydrocarbons.

[0004] In order to achieve the above-mentioned invention task, the present invention adopts the following technical scheme: a method for preparing monohalogenated aromatic hydrocarbons by a plug flow continuous halogenation reaction system, wherein the process specifically comprises the following steps:

[0005] 1) Mix a certain proportion of raw aromatic hydrocarbons and the composite catalyst, and pass the mixture into a piston flow reactor reaction module through a metering pump, and control the aromatic hydrocarbon liquid flow rate to 0.1-40 mol / min;

[0006] 2) simultaneously, the halogenating agent is introduced into the reaction module of the plug flow reactor through a metering pump, and the flow rate of the halogenating agent is controlled at 0.09 to 36 moL / min, and the temperature of the reaction module is controlled at 15 to 60° C.;

[0007] 3) After the reactants stay in the module for 5 seconds to 3 minutes, the reaction products flow out from the reactor outlet, and the hydrogen halide gas is separated by a gas-liquid separator and absorbed by alkaline solution;

[0008] 4) The remaining liquid is washed with water three times, and the monohalogenated aromatic hydrocarbons and aromatic hydrocarbon raw materials are separated by distillation, and the unreacted aromatic hydrocarbons are recovered for reuse.

[0009] The aromatic hydrocarbons are o-xylene, p-xylene, m-xylene and toluene;

[0010] The composite catalyst is a combination of ferric chloride, ferric bromide, aluminum chloride or iodine and phenothiazine-10-carbonyl chloride;

[0011] The halogenating agent is chlorine or bromine.

[0012] Furthermore, the molar ratio of the catalyst ferric chloride, ferric bromide, aluminum chloride or iodine to phenothiazine-10-carbonyl chloride is 1:0.1-1.

[0013] Furthermore, the piston flow continuous reaction system is 2 to 4 reaction modules connected in series, or 2 to 4 reaction modules connected in parallel, and the liquid holding capacity of each module is 100 ml to 10 liters; the dosage of the composite catalyst is 0.01 to 1% of the mass fraction of aromatics; and the alkali solution is a sodium hydroxide or sodium carbonate aqueous solution with a concentration of 5 to 20%.

[0014] Beneficial technical effects of the present invention:

[0015] The invention discloses a technology for preparing monohalogenated aromatic hydrocarbons by piston flow continuous halogenation. The unidirectional flow feature facilitates rapid removal of product, avoids the generation of polyhalogenated byproducts in traditional kettle-type halogenation reactions to the greatest extent, and improves the yield of monohalogenated aromatic hydrocarbons.

[0016] The piston continuous flow reaction system has a smaller liquid holding capacity than the traditional tower reactor, has the inherent safety feature, small equipment footprint, and high stirring efficiency (such as attached Figure 3 ), especially suitable for the fast-reaction aromatic halogenation reaction; a set of industrial-scale piston continuous flow reaction system similar to CofloreATR has an annual output more than 3 times higher than that of the tower kettle with the same space occupation, which is in line with the development trend of chemical production pursuing intrinsic safety under the new situation. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The present invention is a flow chart of a method for preparing monohalogenated aromatic hydrocarbons using a plug flow continuous halogenation reaction system.

[0018] Figure 2 It is a production equipment for preparing monohalogenated aromatic hydrocarbons using a plug flow continuous halogenation reaction system.

[0019] Figure 3The radial stirring effect diagram of the reaction module of the plug flow reaction system

[0020] The present invention is specifically described below in conjunction with embodiments, but the present invention is not limited to the scope of the embodiments.

[0021] Example 1

[0022] In a 200-liter batching tank, 106 kg (1000 mol) of o-xylene and a composite catalyst of ferric chloride (5 g) and (8 g) phenothiazine-10-carbonyl chloride are mixed, and the o-xylene is pumped into two series reaction modules with a liquid holding capacity of 3 liters at a flow rate of 530 g (5 mol) / min by a metering pump. At the same time, liquid chlorine is introduced into the series reaction modules at a flow rate of 310 g (4.5 mol) / min. The temperature of the reaction modules is controlled at 25°C, and the reactants stay in the modules for 30 seconds. After flowing out of the second reaction module, hydrogen chloride gas is separated through a gas-liquid separator. The remaining liquid is washed with water three times and distilled. The component collected at 140°C is the raw material o-xylene, and the component collected at 195°C is 133.5 kg of monochloro-o-xylene, with a yield of 95% (calculated based on the introduction of liquid chlorine). The unreacted o-xylene is recovered and reused; the byproduct hydrogen chloride is 1000 kg Absorbed by 10% sodium carbonate solution.

[0023] Example 2

[0024] In a 200-liter batching tank, 88 kg (1000 mol) of toluene and a composite catalyst of aluminum chloride (4 g) and phenothiazine-10-carbonyl chloride (4 g) are mixed, and the toluene is pumped into three series reaction modules with a liquid holding capacity of 1 liter by a metering pump at a flow rate of 88 g (1 mol) / min. At the same time, bromine is introduced into the series reaction modules at a flow rate of 128 g (0.8 mol) / min. The temperature of the reaction modules is controlled at 60°C. The reactants stay in the modules for 2 minutes. After flowing out of the second reaction module, hydrogen bromide gas is separated through a gas-liquid separator. The remaining liquid is washed with water three times, and the component at 110°C is collected by distillation as raw material toluene, and 158 kg of monobromotoluene at 179-185°C is obtained, with a yield of 94%. Unreacted toluene is recovered and reused; the byproduct hydrogen bromide is absorbed by 1500 kg of 10% sodium hydroxide solution.

[0025] Example 3

[0026] In a 100-liter batching tank, 53 kilograms (500 mol) of m-xylene and a composite catalyst of iodine (6 g) and (3 g) phenothiazine-10-carbonyl chloride are mixed, and toluene is pumped into four parallel reaction modules with a liquid holding capacity of 1 liter by a metering pump at a flow rate of ~352 g (4 mol) / min. At the same time, liquid chlorine is introduced into the parallel reaction modules by a metering pump at a flow rate of 199 g (2.8 mol) / min. The temperature of the reaction module is controlled at ~20° C. The reactants stay in the module for 25 seconds before flowing out, and hydrogen chloride gas is separated through a gas-liquid separator. The remaining liquid is washed with water three times, and the component at ~140° C. is collected by distillation as raw material toluene, and 67 kilograms of monochloro-m-toluene at ~179~180° C. The yield is 96%, and the unreacted m-xylene is recovered and reused; the byproduct hydrogen chloride is absorbed by 700 kg of 15% sodium carbonate solution.

[0027] The above is a detailed introduction to the method for preparing monohalogenated aromatics by a piston continuous flow catalytic reaction system provided by the present invention. Specific examples are used in this article 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 one of the characteristics of the piston continuous flow reaction is the smaller amplification effect. Therefore, for ordinary technicians in this technical field, without departing from the principle of the present invention, the present invention can also be improved and modified, such as flux amplification, etc., without departing from the principle of the present invention. These improvements and modifications also fall within the scope of full protection of the present invention.

Claims

1. A method for preparing monohalogenated aromatic hydrocarbons by a plug flow continuous halogenation reaction system, wherein the process specifically comprises the following steps: 1) Mix a certain proportion of raw aromatic hydrocarbons and the composite catalyst, and pass the mixture into a piston flow reactor reaction module through a metering pump, and control the aromatic hydrocarbon liquid flow rate to 0.1-40 mol / min; 2) simultaneously, the halogenating agent is introduced into the reaction module of the plug flow reactor through a metering pump, the flow rate of the halogenating agent is controlled at 0.09 to 36 moL / min, and the temperature of the reaction module is controlled at 15 to 60° C.; 3) After the reactants stay in the module for 5 seconds to 3 minutes, the reaction products flow out from the reactor outlet, and the hydrogen halide gas is separated by a gas-liquid separator and absorbed by alkaline solution; 4) The remaining liquid is washed with water three times, and the monohalogenated aromatic hydrocarbons and aromatic hydrocarbon raw materials are separated by distillation, and the unreacted aromatic hydrocarbons are recovered for reuse. The aromatic hydrocarbons are o-xylene, p-xylene, m-xylene and toluene; The composite catalyst is a combination of ferric chloride, ferric bromide, aluminum chloride or iodine and phenothiazine-10-carbonyl chloride; The halogenating agent is chlorine or bromine.

2. A method for preparing monohalogenated aromatic hydrocarbons in a plug flow continuous halogenation reaction system according to claim 1, characterized in that: The molar ratio of the catalyst ferric chloride, ferric bromide, aluminum chloride or iodine to phenothiazine-10-carbonyl chloride is 1:0.1-1.

3. A method for preparing monohalogenated aromatic hydrocarbons in a plug flow continuous halogenation reaction system according to claim 1, characterized in that: The piston flow continuous reaction system comprises 2 to 4 reaction modules connected in series or in parallel, and the liquid holding capacity of each module is 100 ml to 10 liters; the concentration of the composite catalyst is 0.01 to 1% of the mass fraction of aromatic hydrocarbons; and the alkali solution is a sodium hydroxide or sodium carbonate aqueous solution with a concentration of 5 to 20%.

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