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

Many catalytic, batchwise three-phase hydrogenations are carried out over R aney Ni catalysts, it being an appropriate choice for several reaction syst ems, such as manufacturing of various fine chemicals, alimentary industry p roducts and petrochemical compounds. One important drawback of Raney cataly sts, usually, is its relatively fast deactivation. In this paper, the usefu lness 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 u ltrasonic field is proposed to consist primarily due to the following pheno mena: decontamination of the active sites and creation of fresh active site s, caused by the mechanical stress introduced by the ultrasonic field. (C) 1999 Elsevier Science Ltd. All rights reserved.