| As the demand for fabric’s colour continues to increase and the country’s requirements for environmental protection become more stringent,reseachers are paying attention to the investment of new dyes and improvements in existing dye synthesis processes.Reactive black KN-B is one of the most important species of reactive dyes in black chromatography.It is also a kind of most productive azo dyes.It has excellent dyeing performance and wide application,and meets environmental protection requirements in all aspects.In the industry,the conventional stirred tank reactor(STR)is generally used to synthesis the reactive black KN-B by batch production,the time of reaction is long.Besides,STR generally has a large volume,which makes the mass transfer and temperature in some areas are not uniform.All these factors result in the break down of diazonium salt(an intermediate product).Therefore,there are differences in the color,performance,etc.of each batch of products and the yield is also negatively affected.It also poses a threat to the safety of industrial production.As a typical process strengthening equipment,the Rotating Packed Bed(RPB)can effectively improve the mixing and mass transfer efficiency of the liquid-liquid phase,thereby shortening the reaction time.It can also effectively remove the heat through the material circulation and achieve continuous production.Therefore,this subject applies the RPB to the synthesis process of reactive black KN-B,and uses the STR,the RPB+STR reactor series device and the RPB+STR circulation device to synthesis the reactive black KN-B,which laid the foundation for continuous production.In this paper,single factor experiments were used to research the different synthesis process of reactive black KN-B,and The dyes were qualitatively analyzed by UV spectrometer(UV),liquid chromatograph(LC-MS),infrared spectrometer(IR),and quantitative analyzed by spectrophotometry.The following conclusions were obtained:1.Optimum reaction conditions in STR(1)Suitable operating conditions for the diazotization reaction are:STR rotation speed of 600 rpm,reaction time of 30 min,reaction temperature of 10℃,para-ester to hydrochloric acid molar ratio of 1:3,para-ester and nitrous acid;(2)For the acid coupling reaction,the suitable operating conditions are:STR speed of 800 rpm,reaction time of 60 min,temperature of 6-12℃,pH of 1.Under such conditions,the yield can reach more than 90%;(3)For the acid coupling reaction,the suitable operating conditions are:STR rotation speed of 600 rpm,pH of 7.5-8.5,temperature of 12℃,reaction time of 30 min,under this condition,the yield can reach 93.6%.2.Optimum reaction conditions in the RPB+STR series device(material ratio and pH are the same as the STR experiment)(1)The suitable operating conditions for the diazotization reaction are:temperature of 5℃,reaction time of 30 min,and rotational speed of the RPB of 2000 rpm.Under these conditions,the yield can reach 92.9%;(2)The suitable operating conditions for the acid coupling reaction are:temperature of 15℃,reaction time of 75 min,and RPB rotation speed of 2000 rpm.Under this condition,the yield can reach 93.1%;(3)The suitable operating conditions for the alkaline coupling reaction are:temperature of 20“C,the reaction time of 30 min,and the rotational speed of RPB is 1200-1400 rpm.Under this condition,the yield can reach 96.3%.3.The optimum reaction conditions of RPB+STR circulation device(the material ratio and pH are the same as the STR experiment,and the RPB rotational speed is the same as that of the RPB-STR series).(1)The circulation time of the diazotization reaction was 2 min.Under the optimal conditions,the maximum yield can reach 88.7%;(2)The circulation time of the acid coupling reaction was 30 min.Under the optimal conditions,the maximum yield can reach 96.1%;(3)The circulation time of the alkaline coupling reaction was 15 min.Under the optimal conditions,the maximum yield can reach 96.6%.In addition,the paper also evaluated the dyeing performance of the self-made dyes.From the results,the K/S value and color fastness of the self-made dyes are better than that of the dye samples.Combined with actual industrial production,the concentration of the reactants is improved.Experiments show that appropriate increase of reactant concentration can increase the target product yield and product concentration,thus reducing dye wastewater discharge. |
