67 Activity and deactivation of HDS catalysts: Studying the active phase using CO as a probe molecule

Publisher Summary This chapter investigates the initial deactivation of several hydrodesulfurization (HDS) catalysts using infrared spectroscopy using CO as a probe molecule (IR-CO). The chapter discusses the IR spectra of CO adsorbed on a freshly sulfided Mo/A1 2 O 3 catalyst at increasing CO pressure. Three prominent bands can be distinguished—the one at 2153 cm -1 , which adsorbs CO weakly, is attributed to the hydroxyl groups on the alumina surface. Two other bands with a high CO adsorption strength, at 2105 and 2064 cm -1 , are attributed to coordinatively unsaturated Mo 2+ sites located at the edges and comers of the MoS 2 slabs, respectively. The chapter reveals the IR spectra of 10 mbar CO adsorbed on the conventional NiMo/Al 2 O 3 catalyst after being exposed to thiophene for different reaction times. Again, the interaction of CO with the support is evidenced by a band at 2153 cm -1 . The thiophene treated catalysts show a broad band at 2080 cm -1 , which is attributed to promote active sites responsible for the enhanced HDS activity.