Chemometric analysis of diffuse reflectance spectra of CoA zeolites : spectroscopic fingerprinting of Co2+-sites

A new method for spectroscopic fingerprinting is proposed for Co2+ in zeolite A. The method is based on the use of different mathematical (GRAMS) and chemometrical techniques (PGA and SIMPLISMA) which were applied on series of diffuse reflectance spectra of CoA zeolite as a function of the Go-content and taken after dehydration at 400 degrees C. Two Co2+ species could be determined, which were assigned to trigonal and tetrahedral coordination at the hexagonal windows. Their relative concentrations as a function of the Co-loading were determined