NH3-TPD AND XPS STUDIES OF RU AL2O3 CATALYST AND HDS ACTIVITY/

The effects of pretreatment of catalyst on its surface properties and the HDS activity of a 0.49% Ru/AI(2)O(3) catalyst were studied in a si ngle-pass, differential microreactor. The surface properties of the ca talyst were measured by NH3-TPD and XPS analysis. The Ru/Al2O3 catalys t was pretreated in three ways: reduced in H-2 (Ru-R catalyst), oxidiz ed in air and subsequently reduced in H-2 (Ru-OR catalyst), or sulfide d in H2S/H-2 (Ru-S catalyst). Three types of peaks (low, middle, and h igh temperatures) were observed in the NH3-TPD study. The predominant high-temperature peak was observed for both the Ru-OR and Ru-S catalys ts, pretreated at 300 degrees C. Mass spectrometry showed that the hig h-temperature peak in NH3-TPD consisted of N-2 and H-2 formed from the decomposition of NH3 on the ruthenium sites. NO adsorption of unsatur ated Ru species was related to the low-temperature peak in the NH3-TPD . The XPS analysis showed that the peaks at 279.9 eV, 280.6 eV, and 28 2.5 eV were ascribed to metallic ruthenium, RuO2, and RuO3, respective ly. The low-, middle-, and high-temperature peaks were assigned to RuO 2, acid sites on alumina, and metallic Ru, respectively. Metallic ruth enium was effective in the HDS of thiophene and the decomposition of N H3.