MoO3/Al2O3催化剂中Mo分散的正电子研究  

Positron annihilation study of Mo dispersion in MoO_3/Al_2O_3 catalysts

作　　者：张宏俊[1] 王栋[1] 陈志权[1] 王少阶[1] 徐友明[2] 罗锡辉[2] 

机构地区：[1]武汉大学物理科学与技术学院,武汉430072 [2]中国石化抚顺石油化工研究院,抚顺113001

出　　处：《物理学报》2008年第11期7333-7337,共5页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:10475062);教育部2006年新世纪优秀人才项目资助的课题~~

摘　　要：用浸渍法制备了一系列不同Mo含量的MoO3/Al2O3催化剂.测量了这些样品的正电子湮没寿命谱(PALS)与符合多普勒展宽(CDB)谱,以研究其孔洞结构以及Mo分散.正电子寿命测量结果表明,Al2O3载体中存在两种不同尺寸的孔洞.掺入MoO3之后,Mo原子主要进入Al2O3的大孔中,使孔洞体积减小.符合多普勒展宽谱结果表明,当MoO3的质量含量仅为3%时,多普勒展宽谱即发生了显著的改变.这表明Mo已分散至Al2O3的孔洞中,使得正电子测量所得到的电子动量分布发生改变.在MoO3含量达到18%之后,Al2O3中大孔的体积减小到尺寸与小孔相当,此后正电子寿命和多普勒展宽谱不再随MoO3含量变化,表明Mo分散逐渐达到饱和.A series of MoO3/Al2O3 catalysts was prepared by the impregnation method. The positron annihilation lifetime spectra （PALS） and coincidence Doppler broadening （CDB） spectra of the samples were measured to study the pore structure and dispersion of MoO3. The PALS result shows that there are two types of pores with different size in the AlO3 support. After MoO3 was loaded in the support, Mo species are mainly dispersed inside the large pores of the support, and thus decrease the volume of the large pores. The CDB spectrum shows significant change while MoO3 loading is just 3 %. This indicates that the Mo species are dispersed into the pores, and cause the change of the electron momentum distribution seen by positrons. As the MoO3 loading exceeds 18%, the size of the large pores is decreased to the similar size of the small pores, and the positron annihilation parameters show nearly no change with further Mo loading, which indicates saturation of the dispersion of Mo species.

关 键 词：MoO3/Al2O3催化剂 正电子湮没寿命谱 符合多普勒展宽 Mo分散 

分 类 号：TG111.1[金属学及工艺—物理冶金]