The application of CRTA and linear heating thermoanalytical techniques to the study of supported cobalt oxide methane combustion catalysts

Two combined thermal analysis-mass spectrometry techniques have been used t o ascertain the effects of various support materials on the preparation and subsequent combustion activity of supported cobalt oxide catalysts. Both t echniques used small sample masses in order to minimise temperature and pre ssure gradients throughout the sample during reaction as the sample tempera ture was increased at a linear heating rate. Temperature-programmed reducti on (TPR) techniques employed not only reveal reduction, but also distinguis h it from the adsorption (or evolution) of the H-2 and the loss of absorbed water. The thermally induced decomposition of supported and unsupported co balt nitrate hexahydrate was studied using a solid insertion probe mass spe ctrometer (SIP-MS) system operating under high vacuum. The su port material was found to affect the decomposition process significantly. In particular , the decomposition of cobalt nitrate dispersed on gamma -Al2O3 occurred vi a a markedly altered process in comparison with the unsupported nitrate. Th e ZrO2 and CeO2 supports both exhibited less pronounced effects on the deco mposition process. After calcination of dispersed cobalt nitrate species, m ethane combustion activity was found to be much lower for alumina-supported samples relative to the other supports used. A combined temperature-progra mmed reduction-mass spectrometry (TPR-MS) technique was used to elucidate a correlation between catalyst activity and reducibility. The reduction of a Co3O4/CeO2 catalyst was also studied under constant rate thermal analysis (CRTA) conditions. (C) 2001 Elsevier Science B.V. All rights reserved.