High-temperature effects on a CoMoAl 2O 3 catalyst

Abstract

The effects of high-temperature firing in air on a hydrotreating catalyst were investigated by X-ray diffraction, X-ray fluorescence, X-ray photoelectron spectroscopy, and scanning electron microscopy. The firing process did not cause any loss of cobalt or molybdenum from the catalyst. However, changes in the distribution of cobalt, molybdenum, silicon, and calcium were observed in the outer and fractured surfaces of the catalyst pellets. Also, the chemical states of cobalt and molybdenum were altered by the firing process. The crystal structure of the alumina support was found to be in the η form for temperatures up to 800 °C. Between 800 ° and 900 °C a transformation to the α form occurred with concurrent segregation of cobalt, molybdenum, calcium, and silicon into isolated inclusions.