Study On Continuous Preparation Method Of Azo Reactive Dyes

With its excellent dyeing properties,azo dyes account for more than 70%of the dye category,and are widely used.Azo-type reactive dyes take into account the bright colors of reactive dyes,and have the advantages of good resistance to rubbing,washing,and fastness to sunlight.They are a class of dyes with very commercial value.In the actual production of traditional azo-type reactive dyes,the batch reactor is used as the production mode of the reactor.The reactor equipment is huge,and the mass transfer and heat transfer cannot achieve good production conditions.This leads to the by-products that are easily mixed into the dye produced,which causes differences between batches of dyes and reduces the quality of the dye.The batch-type production method has a long production cycle,which is bound to increase the production cost of the dye.The thesis focuses on continuous diazotization reaction and continuous coupling reaction.First,select target dyes:reactive yellow M-5G,reactive red M-3B,and reactive blue-black KN-B.Then,the optimal synthesis route of dye intermediates was determined through orthogonal experiments.At the same time,the low-temperature reaction calorimeter EASY-MAX402 produced by METTLER TOLEDO was used to investigate the thermal effect of the common 8 types of aromatic ammonia in the diazotization reaction.Separate coupling----,the thermal effect of the coupling reaction was also measured.According to the current experimental results,it can be seen that most of the aromatic ammonia diazotization exotherm is between 25 KJ/mol-120 KJ/mol.The heat of coupling reaction is between 30KJ/mol-120 KJ/mol.These data provide heat exchange data support for the subsequent continuous diazotization reaction and continuous coupling reaction.In addition,considering the relatively high viscosity of the dicondensate diazonium salt,the paper also measured the viscosity of the target dye intermediate diazonium salt.Based on the above experimental results,a pipeline reaction device for continuous production was introduced in the follow-up test.During the trial production of the continuous pipeline reactor,it was found that the spiral shear propulsion pipeline reactor of the equipment The diazotization of the milky turbid liquid system is superior to the batch reaction diazotization.The diazotization efficiency is about90%,and the quality of the diazonium salt is better than the batch reaction.At the same time,it is fed through the coupled feed inlet after screening.The equipment can completely complete the coupling reaction of the condensate diazonium salt.For diazotization of 5%mass concentration of dicondensate solution,the diazotization efficiency is more than 90%.Compared with batch reaction,this tubular reactor does not show advantages.The reason is that when the diazo component is a clear solution,the batch reaction can be quickly and evenly mixed,and there will be no coating,so for the diazotization reaction of this system,the tubular reactor fails to reflect Advantage.The tubular reactor has a diazotization efficiency of95%-98%for a 10%mass concentration of dicondensate.The thesis also improved the traditional diazotization end point detection reagent-Erich reagent.Erich reagent is 4-dimethylaminobenzaldehyde alkyd solution,which can react with aromatic amine at room temperature to show color.It is often used to determine the end point of the diazotization reaction,but the traditional Ehrlich reagent is too sensitive(detection limit of 10^-4 mol/L by visual inspection in the laboratory),when a small amount of aromatic amine remains in the solution It can still react with it and develop color,but in industrial production,when the diazotization reaction efficiency is?98%,it can be judged that the diazotization reaction is over,which makes the continuous flow production of diazotization reaction The reagent reagent color test is inaccurate to judge the reaction efficiency.The paper invented a test paper for quickly testing the efficiency of diazotization.Since the amino group in the aromatic amine reacts with the aldehyde group of benzaldehyde to form a colored Schiff base,whether the diazotization is finished is determined by the color development or not Through the monitoring of the color development time,using the difference in the reactivity of different aromatic aldehydes and the difference in the concentration of the lower limit of the color development,the concentration range of the aromatic amine to be measured can be accurately judged,and the diazotization efficiency can be calculated after a simple conversion.