Study of Fe-silicalite catalyst for the N2O oxidation of benzene to phenol

A set of Fe-silicalite samples of MFI structure have been prepared by the h ydrothermal technique, followed by steaming and by further chemical treatin g of the solid. After characterisation by nitrogen adsorption/desorption. X -ray diffraction (XRD), scanning electron microscopy-electron probe micro a nalysis (SEM-EPMA), the samples have been tested as catalysts for the oxida tion of benzene to phenol by N2O. The best performing catalyst has been stu died also by temperature programmed desorption-mass spectrometry and temper ature programmed reaction-mass spectrometry (TPD-TPR-MS), after pre-adsorpt ion of both reactants and products. It was found that phenol forms when N2O is adsorbed first, followed by benzene. Almost no phenol formation was obs erved when adsorbing benzene before N2O. Furthermore, on this catalyst N2O decomposed since 50 degreesC or less, forming gaseous N-2 and adsorbed oxyg en, which started to become available for the oxidation of benzene since 10 0-200 degreesC. However, the so formed phenol remained adsorbed onto the ca talyst. It desorbed within the 225-425 degreesC temperature range, with a m aximum around 300 degreesC. (C) 2001 Elsevier Science B.V. All rights reser ved.