Progress of Cryogenics and Isotopes Separation , ISSN: 1582-2575
2005, Volume 8, Issue 15+16

Particle Size Distribution Function of Supported Gold Catalysts by X-Ray Diffraction

Abstract

Influences of the preparation method and support nature on the structural properties of gold based catalysts are presented. The preparation methods [1, 2] were: impregnation of the support with aqueous solution of HAuCl₄, 3H₂O and homogeneous deposition-precipitation using urea like precipitation agent. The following metal oxides with high specific surface area were used as supports: SiO₂, Al₂O₃, CeO₂, Cr₂O₃, Fe₂O₃, ZrO₂ and TiO₂. The catalytic activity and total surface areas of catalysts were measured. The supported Au catalysts were studied by X-ray diffraction in order to identified the presence of Au and to determine the average particle size, the mean squares of the microstrain, the probability of the faults, the particle size and microstrain distributions functions The values of these parameters are obtained with a fitting method of X-ray lines profile (XRLP) of Au, based on the generalized Fermi function (GFF) facilities [3, 4]. The crystallite sizes and microstrain were obtained by another method based on the whole pattern fitting. The results obtained by these two methods were similar. We have obtained the average of crystallite sizes between 39.2 (Au/Al₂O₃) and 144.9 A (Au/SiO₂) depending on the preparation method and the support nature. The crystallite sizes of Au supported an SiO₂ are considerably bigger than of the others supports. The aim of these studies is to understand the relation between the catalytic activity and the microstructural model [5].