Non-conventional sol-gel synthesis for the production of boron-alumina catalyst applied to the vapour phase Beckmann rearrangement

In the past few years. vapour phase Beckmann rearrangement of cyclohexanone-oxime to caprolactam has been investigated in depth and a wide variety of catalysts has been studied. To date a large number of experiments concerning non-zeolitic supported boron oxides have been carried out. In the present work, we report on boria-alumina catalysts where the boron is part of the catalyst lattice. these catalysts being tested for the cyclohexanone-oxime vapour phase rearrangement to caprolactam. These catalysts are obtained by the sol-gel route using (NH4)(2)B4O7 as the source of boron, which has never been used before in B/Al sol-gel synthesis. The local environment of catalysts was characterised by solid state Al-27- and B-11-MAS-NMR and their structure by X-ray powder diffraction; the acidity was determined by TPD of ammonia. The effect of B/Al ratio and the role of different polar agents in the feed were also investigated by catalytic tests. (C) 2003 Elsevier Science B.V. All rights reserved.