In situ FTIR study of the adsorption and reaction of ortho-dichlorobenzene over Pd-promoted Co-HMOR

The adsorption and oxidation of 1,2-dichlorobenzene (o-DCB) with 8% O-2/He over Co-HMOR, Pd/Co-HMOR and H-MOR catalyst samples were studied by means of in situ FTIR spectroscopy. Strong o-DCB adsorption takes place on both Co-HMOR and Pd/Co-HMOR at 250 degrees C on Co2+ Lewis acid sites, as indicated by the appearance of a characteristic IR band centered at 1663 cm(-1). o-DCB can also adsorb on these materials through weaker interactions with hydroxyl (Bronsted) acid sites. o-DCB adsorption on such Bronsted acid sites is the only mode of interaction with the parent H-MOR material. Under reaction conditions the 1663 cm(-1) band is no longer detectable in the spectra due to the low concentration of Co2+ sites-which were converted to (Co-OH)(+) and CoOx due to interactions with the water generated by the reaction - and/or the reactivity of the corresponding adsorbed o-DCB species. In the case of Co-HMOR, the presence of gas phase oxygen is necessary for any reaction products to appear, while on Pd/Co-HMOR the onset of the reaction is observed even in the absence of gas phase oxygen, presumably due to the presence of PdO in the sample. (C) 2007 Elsevier Inc. All rights reserved.