复合催化剂PW_n/TiO_2光催化降解甲醛反应的研究

Study on the photodegradation of formaldehyde with PW_n/TiO_2 composite catalysts

合成了PWn TiO2 (n =11,12 )两种复合催化剂,运用FTIR ,TG DTA ,BET比表面积,SEM ,FL等手段对复合催化剂进行了表征,并将其用于甲醛的光催化氧化降解实验.结果表明,PW1 1 TiO2 复合催化剂中的钛醇基团可在PW1 1 的缺位位置发生化学键合作用,导致复合体系中结构的变化,光催化活性较低;PW1 2 TiO2 复合催化体系中不仅保持了PW1 2 完整的Keggin结构,而且,经3 5 0℃焙烧处理后PW1 2 与TiO2 形成载流子的有效迁移,使得复合催化剂具有较高的光催化活性,明显优于纯TiO2 .2种复合催化剂对甲醛的光催化降解反应遵循L H机理,符合一级动力学方程.PW1 2 TiO2 (3 5 0℃焙烧)和PW1 1 TiO2 (3 0 0℃焙烧)为催化剂时,光催化降解的表观反应速率常数分别为0 0 12 43min- 1 ,0 0 0 5 2 14min- 1 .

PW_n/TiO_2 composite catalysts were prepared by the method of sol-gel via calcination technique. Structure characterization was obtained by TG-DTA,FTIR,BET specific surface area, TPR, SEM, FL. Photocatalytic performance of composite catalysts was investigated with formaldehyde as test compound in a static photoreactor made of quartz glass.The results showed that PW_(12)/TiO_2 composite catalyst(calcinated at 350℃)kept complete Keggin structure, and the carriers effectively transferred from TiO_2 to PW_(12), so PW_(12)/TiO_2 composite catalysts had better photocatalysis activity than pure TiO_2 and that ≡Ti-OH may combine with PW_(11) at its lacunary position, leading to structure change, so PW_(11)/TiO_2 composite catalysts had lower photocatalysis activity than PW_(12)/TiO_2. Photocatalysis reactions over two type composite catalysts accorded to L-H mechanism , which had first order kinetic equation. First-order reaction rate constant of PW_(12)/TiO_2 and PW_(11)/TiO_2 were 0.01243min^(-1) and 0.005214min^(-1).