Research On The Preparation Technology Of 2-amino-4-acetamidoanisole

2-Amino-4-acetamidoanisole(AMA)is an important intermediate in the disperse dye industry,it can be used to produce more than ten kinds of dyes such as Disperse Blue,Disperse Violet and Disperse Yellow dyes.The traditional preparation process of 2-amino-4-acetylaminoanisole was based on chlorobenzene as the starting material,which underwent two nitration and two reduction reactions,resulting in a long reaction course,high pollution and high risk of reaction process.Based on these industry problems,this paper adopted a new production process using 2,4-dinitrochlorobenzene(DNBC)as the starting material to prepare AMA.After etherification reaction,catalytic hydrogenation reduction reaction and selectivity acetylation reaction would prepare AMA with high purity and yield.The first step was the etherification reaction.Methanol was used as the reaction solvent,and alkali substances such as sodium hydroxide were used as acid neutralizing agents for the reaction with 2,4-dinitrochlorobenzene.The influence of the addition of methanol,alkali types,sodium hydroxide dosage,sodium hydroxide injection speed and crystallization process on the purity and yield of the final product was studied.The best reaction conditions were temperature69℃,2,4-dinitrochlorobenzene: methanol: sodium hydroxide=1:19:1(molar ratio).30%sodium hydroxide methanol solution was added to the reaction mixture with an injection rate of1.5 m L/min.Finally,the reaction solution was cooled naturally to room temperature and then cooled quickly,the pale yellow acicular 2,4-dinitroanisole crystal would be obtained with the purity of more than 99% and the yield of more than 97%.The second step was the hydrogenation reduction using Pd/C as the catalyst.The influence of solvent types,stirring speed,temperature,hydrogen pressure,catalyst addition and catalyst cycle index on the hydrogenation reduction reaction was studied.When the rotation speed reached 500 r/min,the reaction entered the intrinsic region.The best reaction conditions were tetrahydrofuran reaction environment,temperature 90°C,hydrogen pressure 2.5 MPa,5% Pd/C,and 0.8% catalyst dosage.The kinetic model of the reaction was determined by Matlab fitting,and the reaction rate constant and adsorption constant were obtained.The reaction activation energy and adsorption heat were calculated by the Arrhenius equation.The results showed that the activation energy of the catalytic hydrogenation reaction process was 18 ～ 29 k J/mol,and the heat of adsorption is-18 ～-26 k J/mol.After the hydrogenation reduction was completed,the conversion of 2,4-dinitroanisole was more than 99%,and the reaction solution was directly used for the next selective acetylation reaction without any subsequent treatment.The third step was the selective acetylation reaction.The influence of solvent,reaction temperature,type of acidifying reagent,dosage of acetic acid,dosage of acylating reagent acetic anhydride,type and dosage of acid binding agent,recrystallization solvent on the purity and yield of the product AMA were researched.The best reaction conditions were tetrahydrofuran reaction environment,temperature-5°C,and 0.99 eq.(molar equivalent)of acetic anhydride.After the reduced pressure distillation and recrystallization,the ash black powder of 2-amino-4-acetamidoanisole was obtained with the purity of more than 98% and the yield of 91.9%.