Catalytic performance of metal oxide-loaded Ta-ilerite for vapor phase Beckmann rearrangement of cyclohexanone oxime

Abstract

Ta-ilerite and Me/Ta-ilerite (Me = Pt, Pd) catalysts have been prepared using pillaring and impregnation methods, and tested as a catalyst for vapor phase Beckmann rearrangement of cyclohexanone oxime to E-caprolactam. It was found that Pt and I'd metal oxides played a very important role in improving the catalytic performance of Ta-ilerite. Me/Ta-ilerite catalysts showed higher lactam selectivities and yields than Ta-ilerite catalyst. Particularly, Pt/Ta-ilerite catalyst exhibited a relatively strong resistance for the deactivation of catalyst with time. These results were due to the changes of acid site distribution due to the metal loading on the Ta-ilerite. Pt oxide loading increased the number of relatively weak acid sites, while Pd oxide loading increased the number of medium acid sites. The results from NH3-TPD and the catalytic reaction demonstrated that weak acid sites were favorable for high catalytic efficiency in this catalyst system. (C) 2004 Elsevier B.V. All rights reserved.