The Synthesis And Research Of Benzotriazole Ultraviolet Absorbers

Benzotriazole ultraviolet absorbers because of excellent performance of ultraviolet absorption have been widely used in polymer materials field.2-?2'-Hydroxy-5'-methylphenyl?benzotriazole?BTA?as a classic benzotriazole ultraviolet absorber was loved by people.However,traditional industrial synthesis method of benzotriazoles has caused serious environmental pollution.In order to solve the pollution caused by current production of benzotriazoles,fixed bed was choosen as reactor,the synthesis of BTA by 2-nitro-2'-hydroxy-5'-methylazobenzene?NAB?was choosen a template reaction and investigated over doped Pd solid base-hydrogenation bifunctional catalysts and doped Cu,Co or Ni hydrogenation catalysts,thus green synthetic routes of benzotriazoles were successfully established in this paper.In order to explore the structure-activity relationship of the doped Pd solid base-hydrogenation bifunctional catalysts,different alkali metals?Na,K,Rb and Cs?doped solid base-hydrogenation bifunctional catalysts were designed and prepared.There are two key factors affecting the catalytic performance,one is the distribution of palladium particles,and the other is the dispersion of basic sites that must strictly distribute around the active sites of hydrogenation.And different alkali metal salts could have different impacts on their catalytic performance.In which case,Pd/?-Al₂O₃-KNO₃?The content of Pd was 1%,the content of K was 10%?exhibited the best modifying effect,when the solvent was toluene,the reaction temperature was 60 ^oC,the hydrogen pressure was 2.5MPa,and the feed speed was 0.15 mL/min,the conversion of NAB was 100%,the selectivity of BTA was up to 84.79%.The catalyst could run over 100 h without obvious deactivation.To avoid the high cost of noble metal catalyst,doped Cu,Co or Ni hydrogenation catalysts were designed and prepared.An efficient continuous synthetic technology of BTA from NAB was successfully established.In which case,20%Cu/?-Al₂O₃ had the best performance.The active sites are elementary copper nanoparticles,and the catalytic performance was positively related to the distribution of active sites.When the solvent was toluene,the additional base was triethylamine,the reaction temperature was 120 ^oC,the hydrogen pressure was 2.5 MPa,and the feed speed was 0.15 m L/min,99.52%conversion of NAB and 84.79%selectivity of BTA were obtained.