Method for preparing mononitrotoluene by continuously adiabatically nitrifying toluene at high temperature

Abstract

The invention relates to a method for preparing mononitrotoluene by continuously adiabatically nitrifying toluene at high temperature, and belongs to the technical field of chemical production. The method comprises the following steps: diluting concentrated sulfuric acid into dilute sulfuric acid; adding concentrated nitric acid into a dilute sulfuric acid solution to prepare a sulfuric acid solution of nitric acid, namely a mixed acid solution, continuously, quickly and uniformly mixing the toluene and the mixed acid solution, and carrying out continuous high-temperature reaction under an adiabatic condition to obtain a reactant solution; and carrying out liquid separation treatment on the reactant solution to obtain an organic phase and an acid phase, and carrying out alkali washing andwater washing on the organic phase to obtain the mononitrotoluene. The method is based on a continuous technology, the dilute sulfuric acid is used as a solvent, fuming nitric acid is used as a nitration reagent, high-temperature high-selectivity single nitration of the toluene is achieved through continuous heat insulation, the toluene conversion rate is larger than 99.9%, the purity of the mononitrotoluene is larger than 99%, and the content of dinitrotoluene by-products is smaller than 1%. The method belongs to a chemical intrinsically safe process, and has the advantages of greenness, energy conservation and high efficiency.

Description

technical field [0001] The invention relates to a method for preparing mononitrotoluene by continuous adiabatic high-temperature nitration of toluene, which belongs to the technical field of chemical production. Background technique [0002] Mononitrotoluene is an important fine chemical intermediate, including three isomers of o-nitrotoluene, m-nitrotoluene and p-nitrotoluene, and is widely used in pharmaceutical, pesticide and dye industries. For example, p-nitrotoluene is used to make DSD acid, p-methylaniline and TNT, o-nitrotoluene is used to make o-methylaniline and TNT, and m-nitrotoluene is used to make m-methylaniline. At present, the designed production capacity of mononitrotoluene in China is as high as 370,000 tons per year. [0003] Toluene mononitration reaction route is as follows: [0004] [0005] At present, industrial production mainly adopts batch or continuous tank-type processes. For example, Chinese patent application CN101805264 discloses a conti...

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Problems solved by technology

[0005] At present, industrial production mainly adopts batch or continuous tank-type processes. For example, Chinese patent application CN101805264 discloses a continuous tank-type low-temperature mononitrotoluene preparation method. The patent application proposed by the applicant (patent application number 201910269638.8, named " A method for preparing mononitrotoluene by adiabatic nitration") adopts an intrinsically safe intermittent adiabatic nitration technology. The main problems of the above-mentioned existing two preparation methods are as follows: (1) in the still-type nitration, the reaction kettle lasts The liquid volume is large, and when danger occurs, the hazard is greater; (2) The heat transfer area of ​​the reactor is small, and the heat transfer efficiency is low, which does not match the rapid nitrification reaction with high heat of reaction; (3) The reactor adopts an inner coil to increase Heat exchange area, maintain low temperature reaction process to control the production of impurities, high energy consumption; (4) Once the heat exchange system of the reactor stops working due to mechanical or other failures, the temperature of the reaction system will immediately lose control and cause an explosion

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