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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 with different Mo contents were prepared by impregnation method.The positron annihilation lifetime (PALS) and doppler broadening (CDB) spectra of these samples were measured to investigate their pore structure and Mo dispersion The electronic lifetime measurement results show that there are two kinds of pores in the Al2O3 carrier.After MoO3 is doped, the Mo atoms mainly enter the macropores of Al2O3 and decrease the volume of the pores.With the Doppler broadening spectrum, the results show that when MoO3 The Doppler broadening spectrum changed significantly when the mass content was only 3%, which showed that Mo was dispersed into the pores of Al2O3 and the electron momentum distribution obtained by the positron measurement changed.When MoO3 content reached 18% After that, the volume of the macropores in Al2O3 decreased to the size corresponding to the pores, and the positron lifetime and Doppler broadening spectrum no longer changed with the content of MoO3, indicating that Mo dispersion gradually reached saturation.