Identification of SH groups in zeolite-supported HDS catalysts by FTIR spectroscopy

NiNaY zeolite (prepared by ion exchange of NaY) and CoHY zeolite (prepared by impregnation of HY) were studied by Fourier Transform Infrared (FTIR) spectroscopy and by the thiophene hydrodesulfurization (HDS) catalytic reaction. The metal- (Ni or Co) loading in the nonsulfided zeolites correlated with the Lewis acidity (determined by pyridine adsorption) indicating a high dispersion level of Ni or Co species. Following sulfidation of the zeolites by H-2/H2S at 373 K two kind of SH band were observed in the IR spectra: the broad band at 2520 cm(-1) was assigned to H2S hydrogen bonded to the strong Bronsted acid sites (SiOHAl groups), the sharp band at 2580 cm(-1) was assigned to H2S coordinatively bound to the Lewis acidic cationic sites. These SH bands were not identified during sulfidation above 473 K, but the similar catalytic activities and product selectivities after sulfidation either at 373 K or at 673 K indicate that SH groups bonded to strong Bronsted acid sites are present and should play a role in HDS catalysts working under industrial conditions. (C) 1997 Elsevier Science B.V.