Determination of metal crystallite size and morphology in supported nickel catalysts

Abstract The application of H2 chemisorption, X-ray diffraction (XRD) line broadening, and transmission electron microscopy (TEM) to the determination of metal crystallite size and size distribution in Ni SiO 2 , Ni Al 2 O 3 , and Ni TiO 2 catalysts having wide ranges of nickel loadings and dispersions was investigated. Average crystallite diameters estimated from H2 chemisorption and TEM were found to be in very good agreement over wide ranges of metal dispersion and loading in the Ni SiO 2 system and in good agreement for a 15% Ni Al 2 O 3 ; poor agreement was evident in the Ni TiO 2 system, the results suggesting that H2 adsorption was suppressed. In the few samples where it was possible to obtain information from XRD, the estimates of crystallite diameter were generally in good or fair agreement with those from H2 chemisorption or TEM. The specific limitations of these three techniques in determination of nickel crystallite size and their application to the study of sintering and metal support interactions in supported nickel catalysts are presented and discussed.