Surface acid–base properties of holmium oxide catalyst: in situ infrared spectroscopy

FT-IR spectroscopy of adsorbed probe molecules of pyridine and CO2, has been used to characterize adsorption sites (acidic and basic sites) on holmium oxide. Ho2O3, was obtained by calcination of holmium nitrate penta hydrate [Ho(NO3)3·5H2O] at 970 K for 1 h in static air. The adsorption and surface reaction of 2-propanol on the test oxide were also examined using IR spectroscopy. The results of adsorbed pyridine and CO2 revealed that the surface of Ho2O3 exposes Lewis acid sites (cus Ho3+) and highly reactive basic sits (O2− and/or OH−). The results also revealed that 2-propanol is irreversibly adsorbed at 300 K giving rise to different surface species. The results revealed that Ho2O3 is a dual functioning catalyst ≥520 K, and that 2-propanol decomposes thereon via dehydration into propene and dehydrogenation into acetone. At ≥570 K, the acetone was used up in a secondary surface reaction, giving rise to gas phase isobutene, methane and carbon dioxide.