CHARACTERIZATION AND ACTIVITY OF PRASEODYMIUM OXIDE CATALYSTS PREPARED IN DIFFERENT GASES FROM PRASEODYMIUM OXALATE HYDRATE - MICROSCOPIC, THERMOGRAVIMETRIC AND IR SPECTROSCOPIC STUDIES

PrO1.833 and Pr2O3 catalysts have been obtained as final decomposition products of Pr-2 (C2O4)(3) . 10H(2)O in different gases (O-2, N-2, and H-2). The decomposition processes were characterized by thermogravimetric (TG) and differential thermal analysis (DTA), X-ray diffraction (XRD) and IR spectroscopy of the solid-phase products. The results indicate that the compound dehydrates in three steps at 100, 150 and 380 degrees C and that the anhydrous oxalate decomposes at 445 degrees C to form two phases of Pr2O2(CO3) depending upon the atmosphere used for the reaction. On further heating PrO1.833 is formed at 550 degrees C in O-2 and at 650 degrees C in N-2. In contrast, Pr2O3 was formed at 650 degrees C in H-2. Surface area measurements and scanning electron microscopy (SEM) have shown that PrO1.833 produced at 700 degrees C has a different surface area depending on the gas used: 43 and 64 m(2) g(-1) for O-2 and N-2, respectively. The surface area of Pr2O3 formed in H-2 is 59 m(2) g(-1). The texture of the catalyst has been found to depend upon the decomposition atmosphere. IR spectroscopy has been used to analyse (qualitatively and quantitatively) the gas-phase reaction products between room temperature and 400 degrees C from the dehydrogenation and dehydration reactions of propan-2-ol over PrO1.833 and Pr2O3, catalysts. The results revealed that Pr2O3 is a selective dehydration catalyst at 275 degrees C, decomposing propan-2-ol into propene (ca. 80%). However, PrO1.833 is a dual function dehydration/dehydrogenation catalyst.