Method and specialized device for tubular diazotization preparation of 2,5-dichlorophenol

Abstract

The invention discloses a method and specialized device for tubular diazotization preparation of 2,5-dichlorophenol. The specialized device comprises a mixer, a tubular reactor and a hydrolysis kettle which are sequentially connected through pipelines, the mixer is connected with a first blending kettle for inputting a mixed solution of 2,5-dichloroaniline and H2SO4 and a second blending kettle for inputting a diazotization reagent separately, the first blending kettle is sequentially connected with a first safety valve, a first metering pump and a first flow meter through a first bottom valve and then connected with the mixer, and the second blending kettle is sequentially connected with a second safety valve, a second metering pump and a second flow meter through a second bottom valve and then connected with the mixer; the first metering pump and the first flow meter form a feedback loop, and the second metering pump and the second flow meter form a feedback loop. An inlet of the hydrolysis kettle is communicated with an outlet of the tubular reactor, a water knockout vessel is installed on the hydrolysis kettle, and a first pulsation damper and a second pulsation damper are arranged on a pipeline between the first blending kettle and the tubular reactor and a pipeline between the second blending kettle and the tubular reactor respectively.

Description

technical field [0001] The invention relates to a method and a special device for preparing 2,5-dichlorophenol by tubular diazotization. Background technique [0002] 2,5-dichlorophenol is the raw material for the synthesis of dicamba (3,6-dichloro-2-methoxybenzoic acid), and its synthesis method is usually based on 2,5-dichloroaniline as the starting material, after heavy Nitriding reaction generates diazonium salt, which can be obtained by high temperature hydrolysis. The diazotization reaction is a batch-type operation mode, and there are many defects in this method: the diazonium salt is unstable and easy to decompose when heated, so the diazotization reaction must strictly control the reaction temperature (generally around 0°C); The chemical reaction is a strong exothermic reaction, and the dropping rate of sodium nitrite must be strictly controlled during the reaction process; the traditional diazotization is a batch production method, and the diazonium salt stays in ...

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Problems solved by technology

The diazotization reaction is a batch-type operation mode, and there are many defects in this method: the diazonium salt is unstable and easy to decompose when heated, so the diazotization reaction must strictly control the reaction temperature (generally around 0°C); The chemical reaction is a strong exothermic reaction, and the dropping rate of sodium nitrite must be strictly controlled during the reaction process; the traditional diazotization is a batch production method, and the diazonium salt stays in the reactor for a long time, which increases the probability of side reactions such as coupling and decomposition The traditional diazotization is a low-temperature reaction, and the ammonium salt is mostly in the state of solid precipitation. At this time, it is a solid-liquid reaction system, and its mass transfer effect is poor. The sodium nitrite solution cannot be quickly mixed into the ammonium salt mixture to achieve uniform mixing at the molecular scale. , increase side reactions, and easily cause safety accidents

A large amount of tar-like waste residue is easily produced during the high-temperature hydrolysis process, which increases the difficulty of post-processing and the pressure on environmental protection

[0003] The methods for preparing 2,5-dichlorophenol by hydrolysis of diazonium salt reported at present include: (1) diazotization is carried out to 2,5-dichloroaniline sulfate with sodium nitrite aqueous solution as diazotizing agent, and partly heavy The nitriding reactant is added into the hydrolysis kettle pre-installed with bottom acid and heated up through the pipeline for hydrolysis (Chemical Production and Technology, 2010, 17 (2): 16-17). The product is taken out by steam distillation during the hydrolysis process, and some heavy The nitriding operation is difficult to control and is not conducive to enlargement; (2) using sodium nitrite solid as a diazotization agent to diazotize 2,5-dichloroaniline sulfate dissolved in 98% sulfuric acid, the obtained diazo liquid is added to Carry out hydrolysis (CN1830943) in the hydrolysis kettle that bottom acid is installed in advance and heat up, this method concentrated sulfuric acid is difficult to recycle and consumption is larger; Sulfate is diazotized in the pipeline, and the obtained diazo solution enters another pipeline for high-temperature hydrolysis (Synthetic Chemistry, 2014, 22(1): 88-90), and the yield is only 85.8%. Many, easy to block the pipeline, difficult to continuous production

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