胶溶法制备镧-钡共稳定氧化铝的性能  

Performance of La-Ba Co-modified Alumina Prepared by Peptizing Method

作　　者：张丽娟[1] 董文萍[1] 郭家秀[1] 袁书华[1] 张磊[1] 龚茂初[1] 陈耀强[1] 

机构地区：[1]四川大学化学学院,成都610064

出　　处：《物理化学学报》2007年第11期1738-1742,共5页Acta Physico-Chimica Sinica

基　　金：国家自然科学重点基金(02033303);国家自然科学基金(20273043)资助项目

摘　　要：以硝酸为胶溶剂,两种拟薄水铝石为前驱体,用胶溶法制备了镧-钡共稳定的氧化铝.采用X射线衍射(XRD)、表面分析仪(BET)、氨气程序升温脱附(NH_3-TPD)和NO_2程序升温脱附(NO_2-TPD)技术对所制备的镧改性和镧钡共改性氧化铝的结构特性和表面性能进行了表征.XRD结果表明,改性氧化铝在1273 K焙烧后均以γ- Al_2O_3湘存在.当BaO添加量达到14%(w)时,有少量BaCO_3生成.BET结果表明,在1273 K下焙烧5h后,5%(w)La_2O_3稳定的氧化铝(Ba-0)和5%La_2O_3与8%BaO共同稳定的氧化铝(Ba-8)均具有较大的比表面积,各种氧化铝的吸附等温线表明它们的孔形状均为狭缝型孔和瓶型孔,孔径分布曲线表明,仅有样品Ba-8的孔径分布较宽,孔径为6- 10 nm,其它三种样品的孔径均集中在10 nm;NH_3-TPD结果表明,随着氧化钡添加量的逐渐增多,氧化铝表面的酸量、酸强度逐步减少.NO_2-TPD结果表明,添加BaO后载体对NO_2的吸附量增多,随着BaO含量的增多,体相Ba(NO_3)_2增多.由于样品Ba-8同时具有很好的织构性质、适中的表面酸量和酸强度分布及NO_2吸附脱附能力,使得以它为载体的催化剂具有最好的催化性能,丙烷的起燃温度和完全转化温度分别为526 K和593 K.La-Ba co-modified alumina was prepared from two kinds of pseudo boehmite and HNO3 as peptizer by peptizing method. The structure and surface property of the alumina were characterized by XRD, BET surface area analyzer, NH3-temperature programmed desorption and NO2-temperature programmed desorption technology. XRD results showed that γ-Al2O3 phase existed in all the modified alumina samples after calcination at 1273 K. A little BaCO3 was generated when content of BaO was increased to 14%（w）. BET results showed that both of 5%（w） La2O3- modified and 5% La2O3-8%BaO co-modified alumina （Ba-8） samples exhibited larger specific surface area and pore volume after calcination at 1273 K. N2 adsorption and desorption isotherms of all alumina exhibited that their surface pore structure was slit-shape and ink-shape pores, pore diameter distribution of Ba-8 was broader and centered between 5 and 10 nm, and other samples centered at 10 nm. NH3-TPD results indicated that the larger the BaO doping concentration, the less the acidic amount was. At the same time, surface acidity of alumina apparently became weak. NO2-TPD results showed that BaO doped alumina adsorbed more NO2 than La203 doped, sample Ba-8 adsorbed the most NO2. As sample Ba-8 simultaneously exhibited good textural properties, proper surface acidic amount, acidity and stronger NO2 adsorption capacity, it had the best catalytic performance when it was used as catalyst carder. The temperatures of light-off and complete conversion of Call8 were 526 K and 593 K, respectively.

关 键 词：氧化铝 表面性质 三效催化剂 低贵金属含量 

分 类 号：O614.31[理学—无机化学]