超临界流体干燥法制备纳米TiO_2-ZnO复合催化剂及其对苯酚降解的光催化性能

Preparation of Nanosized TiO_2-ZnO Composite Catalyst and Its Photocatalytic Performance for Degradation of Phenol

以TiCl4和Zn(NO3 ) 2 ·6H2 O为原料 ,采用溶胶 凝胶法结合超临界流体干燥法制备了纳米级TiO2 ZnO(7～ 10nm)复合催化剂 ,并用XRD和TEM等手段进行了表征 .以苯酚光催化降解为模型反应对所制备催化剂的催化性能进行了评价 .结果表明 ,与单组分TiO2 及普通干燥法制备的TiO2 ZnO催化剂相比较 ,纳米TiO2 ZnO复合粒子的光催化活性有较大提高 .用超临界干燥法制备的催化剂具有粒径小、分布窄、比表面积大、分散性好和光催化活性高等特点 .采用超临界流体干燥法可直接制得纳米TiO2 (锐钛矿型 ) ZnO(非晶态 )复合催化剂 ,可实现干燥、晶化一步完成 .复合催化剂中ZnO的最佳掺入量为x(ZnO)=0 8% .超临界流体干燥法是制备纳米材料的一种新技术 ,具有产物容易收集和溶剂可回收利用等优点 .

Nanosized TiO 2-ZnO (7～10 nm) composite catalyst was prepared from TiCl 4 an d Zn(NO 3) 2·6H 2O by sol-gel and supercritical fluid drying (SCFD) methods . The structural properties of the catalyst were characterized by means of XRD a nd TEM techniques. The catalytic activity was evaluated by photocatalytic degr adation of phenol as a model reaction. The results indicated that the photocatal ytic activity of the nanosized TiO 2-ZnO composite catalyst was improved great ly compared with both single-component TiO 2 and TiO 2-ZnO composite catalys t prepared by common drying method. The catalyst prepared by SCFD method possess es many excellent properties such as small particle diameter, narrow size distri bution, large specific surface area, good dispersibility and high photocatalytic activity. It was found that the drying and crystallization of anatase TiO 2 an d non-crystalline ZnO could be achieved in one step by SCFD technique. The opti mum ZnO doping concentration (mole fraction) is 0 8%. The SCFD method is a nove l process and technique to prepare nanosized materials, and it is the advantage that the products are easy to be collected and the solvent can be recycled and r eused.