Method for preparing 2,5-dimethoxy-4-chloroaniline by hydrogenation reduction

Abstract

The invention provides a method for preparing 2,5-dimethoxy-4-chloroaniline by hydrogenation reduction, which comprises the following steps: (1) beating and dissolving a raw material of 2,5-dimethoxy-4-chloro nitrobenzene; (2) adding a catalyst and the material into a hydrogenation reactor, performing a relatively high temperature high pressure hydrogenation reaction in the early stage of the reaction; (3) transferring the material in the reaction of step (2) into a relatively low temperature low pressure reaction state; (4) after the reaction is complete, filtering the catalyst; (5) cooling and precipitating the material; (6) performing pressure filtration and precipitating the material to obtain the product. In the invention, the reduction process of 2,5-dimethoxy-4-chloroaniline is controlled to have two stages of a high temperature high pressure stage and a low temperature low pressure stage, which effectively controlled the dechlorination reaction, and realizes the selective reduction of nitro groups. Hydrogen reduction is adopted instead of iron powder reduction, which avoids the generation of a lot of iron mud, and reduces environment pollution.

Description

technical field [0001] The invention relates to a method for preparing haloaniline through hydrogenation reduction of halogenated nitrobenzene, in particular to a method for preparing 2,5-dimethoxy-4-chloroaniline through hydrogenation reduction. Background technique [0002] As an important chloroaniline, 2,5-dimethoxy-4-chloroaniline is an important organic pigment intermediate, which can be used to prepare permanent yellow HR (dye index number C.I.Pigment Yellow83 (21108)) And permanent peach red FBB-B (dye index number C.I.Pigment Red 146 (12485)), used for advanced ink and plastic products. At present, the industrial production of 2,5-dimethoxy-4-chloroaniline in the world adopts iron powder reduction process, which has high energy consumption, large amount of waste water, and activated carbon decolorization of the product. The process route Long, the production process is cumbersome, and a large amount of iron sludge is produced, which causes serious pollution to the ...

AI Technical Summary

Problems solved by technology

The hydrogenation process of Raney nickel is often used to passivate the activity of the catalyst by adding dehalogenation inhibitors. The disadvantage of this method is that the introduction of additives cannot effectively prevent the loss of halogens, and the reaction selectivity is relatively poor; Without additives, the product often needs to be post-treated to improve the purity, the production cost is high, and the quality is difficult to guarantee

The hydrogenation process using Pt / C, due to the high price of Pt / C catalyst, makes the product cost too high to participate in the market competition