NO and CO adsorption studies on transition metal-exchanged silico-aluminophosphate of type 34 catalysts

Adsorption of nitric oxide (NO) and carbon monoxide (CO) and the co-adsorpt ion of (NO+CO) and (CO+NO) over the transition metal-exchanged SAPO-34 have been studied by infrared spectroscopy. Novel manganese; cobalt-, and coppe r-exchanged silico-aluminophosphate of chabazite type catalysts were prepar ed and characterized using techniques such as elemental analysis, X-ray dif fraction, scanning electron microscopy, X-ray photoelectron spectroscopy, a nd nitrogen sorption capacity (BET). Detailed FTIR studies were carried out on the disproportionation reaction o f NO and the decomposition of CO over the Mn-, Co-, Cu-SAPO-34 catalysts. T he IR spectra indicated the formation of various CO/NO species or complexes with active metal species. NO adsorption leads to band formation of at lea st four metal-NO, complexes. In the case of Mn-SAPO-34, the four strong ban ds are attributed to the chemisorbed NO2, metal (NO)(2) (di-nitrosyl) and M n(IT)-NO2 species. The species Mn(II)-NO2 is most abundant, followed by the metal (NO)(2) species. In the case of the Co-SAPO-34, the Co-(NO2) species seemed to be the most abundant followed by the Co-(NO2), and Co-(NO3). Eff ects of the pressure, temperature and evacuation on these NO/CO species hav e been studied. Investigations on the influence of presorbed CO molecule on the adsorption of NO molecules over the catalysts indicated that the pread sorption of CO molecules strongly affects the NO adsorption. The concentrat ion of NO/CO species varies with the NO/CO pressure, reaction temperature a nd evacuation. (C) 2001 Elsevier Science B.V. All rights reserved.