Preparation method for synthesizing 2,4-dichloroaniline from 2,4-dichloronitrobenzene

Abstract

The invention provides a preparation method for synthesizing 2,4-dichloroaniline from 2,4-dichloronitrobenzene. The preparation method comprises the following steps: feeding 2,4-dichloronitrobenzene, solvent and catalysts into a reaction kettle; feeding hydrogen into the reaction kettle for 6 to 16 hours at 20 to 100 DEG C at 3 to 30MPa while stirring, wherein the pressure in the reaction kettle is controlled within 4 to 25MPa; stopping feeding the hydrogen, reducing the temperature, and filtering the catalysts out at the normal pressure when the pressure in the reaction kettle starts to increase slowly; then, distilling 90% of the total solvent at the normal pressure; detecting the amino value of the product, i.e., 2,4-dichloroaniline, and indicating that the finished product is qualified if the amino value thereof is higher than or equal to 99%, wherein the weight percentage of the liquid material, i.e., 2,4-dichloronitrobenzene, is higher than or equal to 99%; the solvent is particularly alcohol and methylbenzene the carbon number of which are smaller than or equal to 4; the catalysts are particularly palladium-carbon series catalysts, Raney nickel and inhibitory amino dechlorination catalysts; and the hydrogen is a commercial product with the content of hydrogen being higher than or equal to 99.5%. The invention has the characteristics of simple technological operation, simple treatment after reduction destination, short production period, three-waste emission avoidance, environmental pollution prevention, high device utilization rate, high product yield, good product quality and the like.

Description

technical field [0001] The invention relates to the field of organic synthesis intermediates, in particular to a method for preparing high-quality 2.4-dichloroaniline through high-pressure hydrogenation reduction of 2.4-dichloronitrobenzene under Pd / C catalytic conditions. Background technique [0002] 2.4-Dichloroaniline is an important intermediate in organic synthesis, and is mainly used as a raw material for the synthesis of anti-infective drug ciprofloxacin, pesticide fungicide amide azole, herbicide (PUMA) and dyes. In recent years, due to the increase in the use of its downstream products, its production and sales have increased accordingly. Chlorinated aromatic hydrocarbon aniline is generally prepared by reduction of chlorinated aromatic hydrocarbon nitro compounds, the main ways are: iron powder reduction method, alkali sulfide or hydrazine hydrate reduction method, electrochemical reduction method and catalytic hydrogenation reduction method. Among them, iron powd...

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Problems solved by technology

Chlorinated aromatic hydrocarbon aniline is generally prepared by reduction of chlorinated aromatic hydrocarbon nitro compounds, the main ways are: iron powder reduction method, alkali sulfide or hydrazine hydrate reduction method, electrochemical reduction method and catalytic hydrogenation reduction method. Among them, iron powder reduction method The process is simple, the equipment investment is small, and the production is easy to control, but it produces a large amount of amine-containing waste liquid and waste residue, causing serious environmental pollution. After reduction, the post-treatment process is likely to cause dechlorination, thus making the product quality unstable.

The reduction route of soda sulfide or hydrazine hydrate has problems such as long process, many wastes, and poor product quality; although the electrolytic reduction process is a clean process, it has high energy consumption and large investment in equipment

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