STUDIES OF THE REDUCTION AND REOXIDATION PROCESSES OF ND4PDO7

It has been demonstrated that Nd4PdO7, when exposed to a gas mixture o f CO and He, fully decomposes to Nd2O3 and nano-sized Pd-particles, wh ich are found on the surfaces of the micron-sized Nd2O3 particles. Thi s material, known to exhibit catalytic activity for oxidation of CO an d hydrocarbons, and reduction of NO, can be reoxidised to Nd4PdO7 by h eat treatment at 1085 degrees C in air for a short period of time, i.e . when utilised as catalyst this material can easily be regenerated if it has become aged. The reduced material has been studied in scanning and transmission electron microscopes (SEM and TEM) equipped with ele ment analysis facilities, and characterised by X-ray powder diffractio n (XRPD) studies. A wet-chemistry method for extraction of the nanopar ticles formed has been developed, based on selective dissolution of Nd 2O3, and the bare Pd-particles have been characterised by XRPD, SEM an d TEM studies. The reduction and reoxidation of Nd4PdO7 material was m onitored in a thermogravimetric setup. Nd4PdO7 decomposed in air to Nd 2O3 and Pd at 1185 degrees C, which is approximate to 50 degrees C hig her than the previously reported decomposition temperature. (C) 1998 E lsevier Science B.V.