liquid phase catalyst.pdf

Journal of Catalysis 235 (2005) 139–149 /locate/jcat Active and selective catalyst for liquid phase Beckmann rearrangement of cyclohexanone oxime Chawalit Ngamcharussrivichai a,1 , Peng Wu b , Takashi Tatsumi b,?,2 a Department of Applied Chemistry, Graduate School of Engineering, The University of Tokyo, Hongo, Bunkyo-Ku, Tokyo 113-8656, Japan b Division of Materials Science and Chemical Engineering, Graduate School of Engineering, Yokohama National University, 79-5 Tokiwadai, Yokohama 240-8501, Japan Received 25 February 2005; revised 22 April 2005; accepted 11 July 2005 Available online 25 August 2005 Abstract The effect of acid treatment on the catalytic performance of ultrastable Y catalysts in the Beckmann rearrangement of cyclohexanone oxime has been investigated under liquid phase conditions. Over the catalysts treated under mild conditions, enhanced activity was observed due to an increase in the amount of Br?nsted acid sites, but a considerable amount of extra-framework aluminum (EFAL) with Lewis acidity remained, resulting in a rapid loss of selectivity to ε-caprolactam. Under relatively severe conditions, the extensive removal of EFAL improved the lactam selectivity, although the extraction of framework aluminum resulted in decreased oxime conversion. Pyridine and benzonitrile adsorption studies indicated the presence of at least two different kinds of Lewis acid sites in the catalysts. The relationships between the catalytic performance and Fourier transform infrared spectroscopy suggested that weak Br?nsted acid sites are the active centers for the rearrangement reaction, whereas weak Lewis acid sites due to an extra-framework amorphous phase are responsible for the cyclohexanone formation. Thus the catalyst with weak Br?nsted acid sites and a small amount of acidic EFAL species is active and selective for the liquid phase Beckmann rearrangement of cyclohexanone oxime. ? 2005 Published by Elsevier Inc. Keywords: Beckmann rearrangement; Ultrastable Y; E