Simultaneous SO{sub 2}/NO{sub x} abatement using zeolite supported-copper. Progress report, April 1--June 30, 1996

The authors have continued the investigation of the adsorption of NO on the Cu/{gamma}-alumina samples and have begun the study of the interaction of NO with sulfated Cu/{gamma}-alumina. The interaction of NO with a sulfated surface is extremely important, since the copper sites in the most popular NO reduction catalyst, Cu/ZAM-5, also adsorb SO{sub 2}, and the catalyst is poisoned by SO{sub 2}. It may be possible to determine whether the poisoning mechanism is due to a chemical effect, or some other effect, and investigate measures which might alleviate the deleterious effects of surface sulfation on the adsorption/reduction process. The results for NO interacting with the sulfated surface do not appear to result in the formation of any new species, but do show a dramatic change in the relative amounts of the NO species formed on the surface. The sulfation of the copper species apparently forces the copper species to remain as Cu{sup 2+}, which gives rise to a strong band at 1850 cm{sup {minus}1}, shifted to lower frequency from the 1863 cm{sup {minus}1} absorption found for the unsulfated catalyst, but which is still probably due to the formation of a Cu{sup 2+}/NO complex, given the small frequency shift. Two other infrared absorption bands observed for NO adsorbed on the un-sulfated catalyst are observed in the current study only weakly, and are due to the formation of adsorbed NO{sub 2}, the NO oxidation product formed when Cu{sup 2+} is reduced to Cu{sup +}, and to the Cu{sup +}/NO{sup {minus}} complex. The relatively intense absorption due to the Cu{sup 2+}/NO complex and the weak absorptions due to adsorbed NO{sub 2} and the Cu{sup +}/NO{sup {minus}} complex indicate that little reduction of the copper has taken place. Stabilization of the Cu species as Cu{sup 2+} by the sulfate apparently prevents participation of the surface copper species in the redox cycle. To the authors` knowledge this is the first reported infrared spectroscopic study of NO interacting with a sulfated Cu/{gamma}-alumina catalyst