In-situ ultrasonic catalyst rejuvenation in three-phase hydrogenation of xylose

Many catalytic, batchwise three-phase hydrogenations are carried out over Raney Ni catalysts, it being an appropriate choice for several reaction systems, such as manufacturing of various fine chemicals, alimentary industry products and petrochemical compounds. One important drawback of Raney catalysts, usually, is its relatively fast deactivation. In this paper, the usefulness of an integrated ultrasonic treatment of the catalyst is demonstrated in the hydrogenation of xylose to xylitol, resulting to a stable catalyst activity. The underlying reason for the stabilizing effect of the applied ultrasonic field is proposed to consist primarily due to the following phenomena: decontamination of the active sites and creation of fresh active sites, caused by the mechanical stress introduced by the ultrasonic field. (C) 1999 Elsevier Science Ltd. All rights reserved.