Influence of K2O addition on the aromatization functionality of Al2O3-supported Cr2O3 catalysts in the transformation of isophorone

Alumina-supported unpromoted and K2O-promoted Cr2O3 catalysts were prepared varying the Cr2O3 loading in the range of 5-25 wt.%. These were characterized for total pore area and pore size distribution by mercury porosimetry, X-ray powder diffraction (XRD), electron spin resonance spectroscopy (ESR) and for their total acidity. Transformation of isophorone was carried out on these catalysts, under vapor phase, at atmospheric pressure in the temperature range of 673-808 K. The products obtained are classified into two major groups, one due to decomposition and the other due to aromatization. Efforts have been made to delineate the Cr active species responsible for the aromatization functionality. The influence of K2O on these active species has also been elucidated. It is observed that K2O helps in neutralizing the strong acidity of the catalyst, minimizing the decomposition products while simultaneously enhancing the intrinsic activity of the Cr3+ species towards aromatization. (C) 2001 Elsevier Science B.V. All rights reserved.