An improved synthetic method for preparing o-phenylenediamine by reduction of o-nitroaniline

Abstract

The invention relates to an improved synthetic method for preparing o-phenylenediamine by reducing o-nitroaniline. The method comprises adding o-nitroaniline and sodium sulfide according to the molar ratio of 1:1.5-2 into a reaction vessel, injecting water, controlling the weight ratio of sodium sulfide to water to be 1:1-20, controlling the reaction temperature to be 50-150 DEG C, reacting for 1-5 h, crystallizing and separating o-phenylenediamine, so as to obtain reaction waste water; concentrating the reaction waste water to obtain a solid residue; performing medium-temperature calcining on the residue, concretely adding an inorganic base into the residue and controlling the temperature of medium-temperature calcining to be 300-600 DEG C; performing high-temperature calcining on the residue, concretely mixing with carbon powder, and controlling the temperature of high-temperature calcining to be 900-1200 DEG C; and performing separation filtering, concretely using water to dissolve the post-calcined product, filtering and recovering superfluous carbon powder and obtaining a filtrate which is a sodium sulfide aqueous solution. The method realized continuous efficient wastewater processing, is beneficial for reducing discharge of ' three wastes (waste gas,waste water and industrial residue) ', reduces safe production risk, improves sodium sulfide recovery rate, and is relatively suitable for large-scale production of o-phenylenediamine in industry.

Description

technical field [0001] The invention relates to a synthesis method of o-phenylenediamine, in particular to a synthesis method for preparing o-phenylenediamine by reduction of o-nitroaniline, so as to realize green and safe recycling of reaction products. Background technique [0002] O-phenylenediamine is an important organic chemical intermediate. In addition to being used in the production of dyes, it is also the main raw material for systemic fungicides such as pesticides carbendazim, benomyl, and (methyl) thiophanate. It is also a developer , Leveling agent and surfactant, etc. are important raw materials. [0003] At present, there are several routes for the synthesis of o-phenylenediamine, and two of the more important routes are as follows: [0004] First, the patent CN 102633653 reports a method for preparing o-phenylenediamine by catalytic hydrogenation of o-nitroaniline, using o-nitroaniline as a raw material, alcohol as a solvent, and nickel as a catalyst, at a h...

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Problems solved by technology

[0008] In this process, the reduction reaction of o-nitroaniline is relatively mature, but the wastewater recovery process is not yet perfect, and the actual content of sodium sulfide in actual industrial production is low (50-60%) and the complexity of the components of aniline reduction wastewater ( Containing sodium sulfate, sodium thiosulfate, sodium sulfite, sodium thiocyanate and a small amount of aniline organic compounds) and other factors, when the waste water mixture directly reacts with carbon powder in a high-temperature environment heated by microwave instantaneously, it is easy to produce suffocation, stench, Acidic and corrosive toxic gas, the solution formed by absorbing the gas with sodium hydroxide solution includes: sodium carbonate, sodium hydrogen sulfide, sodium sulfite and sodium cyanide, indicating that the waste gas contains highly toxic gases hydrogen sulfide and hydrogen cyanide, and there are obvious Security risks

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