Study On The Synthesis Of Benzotriazole Ultraviolet Absorbent By Catalytic Hydrogenation

Benzotriazole ultraviolet absorbers have extremely important application value in the fields of medicine,polymer materials,cosmetics,etc.due to their unique properties,and their synthetic routes have become research hotspot in this field.According to literature and experimental research,In this paper,a method for preparing three benzotriazole ultraviolet absorbers by diazotization reaction,coupling reaction and catalytic hydrogenation reduction reaction is designed,namely 2-?2'-hydroxy-5'-methylphenyl?benzotriazole?UV-P?,2-?2'-hydroxy-3',5'-dicumylphenyl?benzotriazole?UV-234?,2-?2'-hydroxy-5'-tert-octylphenyl?benzotriazole?UV-329?,and further screening and optimization of process reaction conditions is also conducted.The structure characterization and performance analysis of azo intermediates and target products were carried out by ¹H NMR,¹³C NMR,IR,MS,DG,UV and the process of catalytic hydrogenation reduction was tested online by in-situ infrared.The main research scope was carried out as following:1.Diazo coupling reaction:Azo intermediates are synthesized by performing diazo and coupling reactions at a reaction temperature of 0-5?and a p H of 7-9 using o-nitroaniline and substituted phenol compounds in a molar ratio of 1:1.Finally,2-?2'-hydroxy-5'-methylphenyl?azobenzene,purity 85%,yield 74%;2-?2'-hydroxy-3',5'-dicumylphenyl?azobenzene,purity 80%,yield 67%;2-?2'-hydroxy-5'-t-octylphenyl?azobenzene,purity 90%,yield 80%.The wastewater after the coupling reaction can be recycled and applied 3-5 times,saving about 20%of water.This method conformed to the tenets of energy saving,emission reduction,environmental protection,and cost-effectiveness.2.Catalytic hydrogenation reduction reaction:Through the screening of catalysts,solvents and basic additives,as well as the selection and optimization of reaction conditions such as reaction time,pressure,temperature,mass ratio or and solvent,and finally,the optimum reaction conditions are optimized by orthogonal and parallel experiments.The optimal reaction conditions for the preparation of UV-P by catalytic hydrogenation:pressure1.0 MPa,temperature 50?,m?Pd/C?:m?azo intermediate?=l:40,toluene volume 10m L,yield 61%Or more;the optimal reaction conditions for catalytic hydrogenation to produce UV-234:pressure 1.25 MPa,temperature 60?,m?Pd/C?:m?azo intermediate?=l:20,toluene volume 14 m L,yield about 50%or more;the optimal reaction conditions for catalytic hydrogenation to produce UV-329:pressure 1.25 MPa,temperature 60?,m?Pd/C?:m?azo intermediate?=l:20,toluene volume 12 m L;The yield is up to more than 90%,and the repeatability is good.3.Structural characterization and performance analysis:Through ¹H NMR,¹³C NMR,IR,MS,DG,UV and other analytical test methods,it can be found that the molecular weight of UV-234 and UV-P increase by 222,and the thermal stability increases by more than91?;Compared with UV-P,the molecular weight of UV-329 is increased by 98,and the thermal stability is increased by more than 40?.Compared with UV-329,the molecular weight of UV-234 is increased by 124,and the thermal stability is increased by more than51?.In addition,the vibration absorption wavelength range of NO₂ groups is1550-1500cm^-1 and 1365-1330cm^-1.The dynamic reaction process of catalytic hydrogenation reduction can be monitored online by in-situ infrared,and the optimal reaction times for the synthesis of UV-P,UV-234 and UV-329 by catalytic hydrogenation reduction are determined to be 5-7 h,4-6 h and 5-8 h,respectively.In conclusion,this article prepared three types of UV-P,UV-234 and UV-329benzotriazole ultraviolet absorbers through diazotization reaction,coupling reaction and catalytic hydrogenation reduction reaction.The reaction mechanism is clearer and easier to understand,the synthesis process is simpler and easier to implement,and waste water treatment is more energy-saving and environmentally friendly.Finally,an energy-saving,environmentally friendly,simple and efficient process route was designed to further promote the development of catalytic hydrogenation reduction methods in the synthesis of ultraviolet absorbers and lay the foundation for the industrialization of the method.