Temperature influence on the global and local structure of the chromia supported nickel catalysts

The changes induced by the heat treatment on the global and the local structures of the supported nickel catalysts are investigated. The global structure parameters were obtained by processing the X-ray diffraction patterns of the samples using the Scherrer formula. The local structure parameters were determined by X-ray absorption spectra processing. Both types of measurements were carried out using synchrotron radiation. The nickel catalysts supported on chromia were prepared by coprecipitation method. The nickel/chromium atomic percent was 70/30. After preparation, the samples were thermally treated for three hours at 350, 650 and 950°C. A strong correlation between previous catalytic activity information and the global and local structure is evidenced. Also the correlation between the nickel crystallite size and the active metal-oxide support interaction is discussed.