超声波辅助共沉淀法制备大比表面积TiO_2-Al_2O_3复合载体

分别以氨水、碳酸氢铵、尿素为沉淀剂,AlCl3为铝源,采用超声波辅助共沉淀法制备了TiO2-Al2O3复合载体;考察了沉淀剂对TiO2-Al2O3复合载体结构性能的影响;采用FTIR、XRD、N2吸附-脱附法、SEM等手段对所制得的复合载体进行了表征。表征结果显示,TiO2-Al2O3复合载体中TiO2为锐钛矿型,Al2O3为γ-Al2O3晶型,采用氨水和碳酸氢铵为沉淀剂提高了锐钛矿TiO2的热稳定性,加入十六烷基三甲基溴化铵有利于增大载体的孔径和孔体积。其中以碳酸氢铵为沉淀剂制得的TiO2-Al2O3复合载体的结构性能最好,主要是因为碳酸氢铵是一种缓冲溶液,释放NH4+的速率较慢,该复合载体的孔径达30.9nm、孔体积达2.19mL/g、比表面积达284m2/g。

Preparation of TiO2-Al2O3 Composite Support with High Specific Surface Area by Ultrasound-Assisted Co-Precipitation Method

TiO2-Al2O3 composite supports,which could be used in preparation of hydrorefining catalysts,were synthesized from AlCl3 and NH4HCO3(or NH3·H2O and(NH2)2CO) as the precipitant by co-precipitation method combined with ultrasonic dispersion.Effects of the precipitants on the properties of the TiO2-Al2O3 composite supports were studied.The products were characterized by means of FTIR,XRD,N2 adsorption-desorption and SEM.The results showed that TiO2 and Al2O3 in the TiO2-Al2O3 composite supports existed in the forms of anatase phase and γ-Al2O3 respectively,NH4HCO3 and NH3·H2O improved the thermal stability of the anatase phase,and adding cetyltrimethylammonium bromide was conducive to increases of the pore diameter and the pore volume.Among the three precipitants,the support prepared by precipitation with NH4HCO3 solution had the best structural properties,because NH4HCO3 was a buffer solution which released NH+4 with a slow speed.The pore diameter,the pore volume and the specific surface area of the above TiO2-Al2O3 composite support were 30.9 nm,2.19 mL/g and 284 m2/g.