A kind of method for preparing difluorobenzene by tubular double nitriding reaction

Abstract

A method for preparing difluorobenzene by a tubular diazotization reaction comprises the following steps: mixing a material phenylenediamine, a hydrochloric acid aqueous solution and a fluorboric acid aqueous solution and storing the mixture into a first storage tank, storing a material sodium nitrite aqueous solution into a second storage tank, respectively conveying the above materials into a mixer through a transfer pump and mixing and adding the mixture into a tubular reactor, carrying out a diazotization reaction at 0-100 DEG C for reaction residence time of 1-150 s, cooling the reaction mixture obtained after the reaction to minus 5-minus 10 DEG C, filtering to obtain wet diazonium salt and a filtrate, drying the wet diazonium salt, pyrolyzing by a pyrolysis kettle, collecting a target fraction, and distilling to obtain difluorobenzene. The method of the invention has advantages of high product yield, less ''three wastes (waste gas, waste water and industrial residue) '', simple operation and good safety, and is very suitable for industrial production.

Description

(1) Technical field [0001] The invention relates to a method for preparing difluorobenzene by tubular double nitriding reaction. (2) Background technology [0002] Difluorobenzene is an important fine chemical intermediate, which is widely used in the fields of medicine and pesticides. For example, m-difluorobenzene can be used to synthesize difluorobenzene salicylic acid, fluoroquinolone antibacterial agents, fluorine-containing phenyl insecticides, etc.; Difluorobenzene can be used to synthesize liquid crystal materials. There are many kinds of synthetic methods of difluorobenzene reported in the literature, which can be divided into: (1) halogen exchange method according to different starting materials: WO2001081274A1, US20050096489 and WO2008073471A1 etc. have reported using chlorobenzene or fluorobenzene as raw materials, CsF, CuF 2 Fluorides are used as fluorinating agents to carry out halogen replacement under high temperature and high pressure conditions. Although...

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Problems solved by technology

And o-phenylenediamine prepares p-difluorobenzene through Schiemann reaction and there is no report yet

[0003] The method of preparing difluorobenzene by using phenylenediamine through the Schman reaction is relatively cheap and easy to obtain, but the traditional kettle-type diazotization process has disadvantages that are difficult to overcome: first, the diazotization reaction is a strong exothermic reaction, and phenylenediamine The diazotization reaction releases more heat, and the diazonium salt is unstable and easy to decompose at high temperature; the mass transfer and heat transfer efficiency in the kettle process is low, which is likely to cause high local concentration and temperature. To solve the above problems, it is necessary to slowly drop diazotization Reagents, or external forced cooling, which greatly reduces production efficiency and consumes a lot of energy

Secondly, phenylenediamine has two amino groups, and intramolecular or intermolecular coupling side reactions are prone to occur during the diazotization process, which affects the yield.

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