Catalytic combustion of hexane over transition metal modified zeolites NaX and CaA

Hexane deep oxidation was studied over NaX and CaA zeolites modified by ion exchange with transition metals (Mn2+, Co2+, Fe3+), the percentage of ion exchanged, determined by ICP-MS, varying between 39 and 98%. Parent and exchanged zeolites were characterized by Xray diffraction (XRD), N-2 physisorption, temperature-programmed reduction (TPR), oxygen and ammonia temperature-programmed desorption (TPD) and inverse gas chromatography (IGC). Catalytic activities were evaluated through the recording of light-off curves in a pulsed microreactor, catalytic activity being correlated with physicochemical properties of the solids (crystallinity, surface acidity, adsorption properties and morphological parameters). As general trend, CaA zeolites are more active than NaX zeolites. Mn-exchanged CaA zeolite was the most active catalyst for hexane oxidation, whereas the addition of Fe to the zeolites leads to strong chemical and morphological changes in the parent zeolite. (c) 2004 Elsevier B.V. All rights reserved.