The characterisation of supported cobalt catalysts

The characterisation of a range of supported cobalt catalysts was investigated. The effect of the support as well as the precursor was studied using a combination of characterisation techniques. Catalysts were prepared via aqueous impregnation of silica, alumina and 99% silica + 1% titania with solutions of cobalt nitrate or acetate. B.E.T analysis showed comparable surface areas for all supports investigated. The catalysts were subjected to heat treatments in argon, oxygen and hydrogen to examine the effect of the varying supports and precursors. Differences in the temperatures of decomposition and reduction as well as changes in the composition of the evolved gases, revealed that both support and precursor are both important in determining the stability of the system. Temperature programmed X-ray diffraction was used to determine the phase composition and crystallite size distribution. This confirmed that for all of the catalysts cobalt was present as CO[3]O[4] species as the product of decomposition, and furthermore allowed for determination of cobalt species crystallite size at varying temperatures. Weight loss and thermal events associated with decomposition and reduction were followed using a combination of TGA-DSC. On-line mass spectrometry, allowed for identification of evolved gases. Consequently it was shown that decomposition of supported cobalt catalysts was more complex than the bulk cobalt salts. In addition decomposition of cobalt nitrate supported catalysts were found to be endothermic in contrast to the highly exothermic decomposition of cobalt acetate supported catalysts