Study On Synthesis Technology Of Disperse Orange 25

Disperse orange 25 is a kind of e-type disperse dye with very low water solubility,which is mainly used in polyester fiber dyeing.The dye forms stable hydrogen bond with the fiber in the dyeing process,which makes it have excellent heat resistance,leveling and dyeing fastness and become one of the most productive azo dyes in China.In industry,disperse orange 25 is mainly produced by intermittent operation,and the performance of each batch of dyes is uneven.Due to the strong exothermic characteristics and thermal instability of diazotization and coupling reaction in the synthesis process,once mixed unevenly,it is easy to generate heat accumulation,which makes the diazonium salt intermediate decompose,which not only affects the product quality,but also may cause explosion accidents.Rotating packed bed is a new process-intensification device,which is widely used in rapid reaction system.It can shear and disperse liquid through strong centrifugal force,thus enhancing mass transfer and molecular mixing process.In addition,the synthesis of disperse dyes is a fast liquid-liquid reaction,therefore,the rotating packed bed will be used in the synthesis process of disperse orange 25 to realize its continuous production.In this paper,kinetics of diazotization was studied using stopped-flow spectrometer,and the complex reaction mechanism of diazotization was discussed.In addition,the process of disperse orange 25 was studied using RPB series STR.The main conclusions are as follows:(1)The kinetic equation of diazotization of p-nitroaniline was deduced and its kinetic parameters were determined.The Arrhenius equation and the expression of diazotization rate of p-nitroaniline were obtained.The arrheniuse quation is:k=6.95×108exp(-4545.47/T)The reaction rate expression is:-dc/dt=6.95×108 exp(-45454.47/T)cAcB(2)The optimal process conditions were determined,and the stirring speed of diazotization and coupling reaction was 500 rpm.The reaction time was 20 min and 1.5 h,and the reaction temperature was 9 and 7?,respectively.In addition,the molar ratio of p-nitroaniline:hydrochloric acid:sodium nitrite was 1:2.8:1.07,and the pH of coupling reaction was 2.0.Under the above conditions,the yield of disperse orange 25 dye can reach 99.3%,and the average particle size can reach 480 nm.(3)The optimal process conditions of RPB series STR reactor were determined.The cycle flow rate of diazotization and coupling reaction was 300 ml/min.The cycle time was 8 and 10 min respectively,and the RPB speed was 1600 and 2000 rpm respectively.Under the above conditions,the yield of disperse orange 25 dye can reach 92.0%,and the average particle size can reach 80 nm.