FTIR STUDY OF ADSORPTION AND REACTION OF SO2 AND H2S ON NA SIO2/

The adsorption of SO2, H2S and mixtures of SO2/H2S on silica or silico n carbide supported sodium catalysts has been studied by infrared spec troscopy. A unique feature of this work has been the acquisition of lo w wave number data in the region from 700 to 450 cm(-1) where these su pports are optically transparent to IR radiation, thus giving access t o the spectral range associated with SOx deformation modes. The spectr al assignments have been proposed taking into account the spectra of d ifferent SxOyn- salts in solution or as solids. Some spectra of these ions have been revised (Na2S2O4) or recorded for the first time (Na2S3 O6). The adsorption of SO2 leads mainly to disulfrte (bands at 657 and 560 cm(-1)) and sulfite (635 and 495 cm(-1)) species. The adsorption of H2S alone produced NaSH species. SO2 reacted with chemisorbed H2S t o yield a stable thiosulfate species (680 cm(-1)). In the reverse sequ ence, H2S reacted with chemisorbed SO2 to yield thiosulfate and an int ermediate which has been tentatively identified as a polythionate SmO6 2- (645 cm(-1)). Thiosulfate, polythionate, water and sulfur were gene rated when an excess of a 2/1 mixture of H2S/SO2 was contacted with th e catalyst, indicating significant activity towards the Claus reaction , 2H(2)S+SO2-->3/nS(n)+2H(2)O. (C) 1998 Elsevier Science B.V.