Thermal analysis of spent steam-reforming catalysts

Thermal analysis is a group of techniques in which changes in characteristic properties, of a physical or chemical nature within a substance, are measured as a function of temperature. In catalyst studies, thermal analysis may be used to obtain information on the thermal stability, composition, deactivation, activity and life of a catalyst. The method is especially useful for studying the transformations that occur in or on a catalyst when heated. These transformations include decomposition, phase transition, adsorption, absorption, desorption, dehydration, degradation and solid-state and gas-solid reactions. In this paper, the thermal analysis (TG and DTA) results of spent steam-reforming catalysts are presented. Ni/Al₂O₃ catalysts, which had been in operation in a steam reformer for about 18 months, gave exothermic effects with corresponding weight gain in the temperature range 20-1130 °C. Ni/CaO/Al₂O₃ catalysts, which had been in use for 30 months, however, gave endothermic and exothermic effects with weight loss between 20-850 ° C, and an exothermic effect with weight gain at about 900 ° C. These results and the significant changes observed in the properties of the catalyst along the reformer tube are discussed.