FTIR investigations of the adsorption and disproportionation of NO on Cu-exchanged silicoaluminophosphate of type 34

Abstract

Novel copper exchanged silicoaluminophosphates of chabazite type catalyst have been prepared. Conventional techniques such as elemental analysis, X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, nitrogen sorption capacity (BET) have been employed for the characterization of the materials. X-Ray photoelectron spectroscopy results identified the presence of both Cu^I and Cu^II species on the catalyst. A detailed FTIR study was carried out on the disproportionation reaction of nitric oxide over the Cu-SAPO-34 catalyst. The spectra indicated the formation of nitrous oxide, mono- and di-nitrosyl complexes of Cu^I and of Cu^II and nitrate species. The types of NO sites on the Cu-SAPO-34 are similar to those seen on other copper exchanged zeolites, in particular Cu-ZSM-5. Effects of the pressure, temperature and evacuation on these nitric oxide species have been studied. The concentration and distribution of NO complexes varies with the NO pressure, reaction temperature and evacuation. The adsorption of nitric oxide on the copper exchanged silicoaluminophosphate have been compared with the copper exchanged high silica pentasil zeolite catalyst under identical experimental conditions.