Formation and surface characterization of thulium oxide catalysts

Abstract

Thulium oxide, Tm₂O₃, was obtained as a final product of the thermal decomposition of Tm(CH₃COO)₃·4H₂O. The decomposition steps up to 800°C were characterized by TG, DTA, XRD, SEM, GC-MS and gas- and solid-phase IR spectroscopy. The results showed that Tm(CH₃COO)₃ ·4H₂O dehydrates completely in two overlapping steps at 90 and 110°C and decomposes to Tm₂O₃ at 540°C through a non-crystalline intermediate Tm(OH)(CH₃COO)₂ at 350°C, Tm(O)(CH₃COO) at 375°C and Tm₂O₂CO₃ at 400°C. The oxides obtained at 600 and 800°C were subjected to texture analysis and pyridine adsorption. The results revealed that the oxide obtained at 600°C has a higher surface area of 49.7 m² g⁻¹ with larger pores than that obtained at 800°C (S_BET=32.8 m² g⁻¹). On the other hand, the oxide obtained at 600°C has a basic surface character and contains at least two different Lewis acid sites as indicated from pyridine adsorption. The gaseous decomposition products as identified by gas-phase IR and GC-MS are water vapour, acetic acid, ketene, acetone and methane.