Chemical interaction between plasma-excited nitrogen and the surface of HY zeolite

Abstract

The chemical interaction between plasma-excited nitrogen and the HY (decationated Y-type zeolite) surface has been studied by IR spectroscopy, XPS and temperature-programmed desorption (TPD). When the plasma-excited nitrogen was exposed to the HY sample at room temperature, the decrease in the intensities of the OH bands (3650 and 3560 cm^–1) was observed by IR measurement, and, at the same time, the formation of hydrogenated species [NH₃(a) and NH₄⁺(a)] on the HY surface was observed by IR and XPS measurements. After heating the sample at 500 °C, however, mainly N₂ and a little NH₃ were desorbed from the HY surface. Moreover, no hydrogen was desorbed from the HY sample during the TPD run, but the regeneration of the intensities of ν_OH peaks was observed by IR measurement during the heat treatment up to 400°C. The results show that the behaviour of the NH₃(a) and NH₄⁺(a) species formed by the plasma N₂ treatment was different from that in the usual study of ammonia adsorption on HY. The intermediate species [e.g. NH_x(a)(x= 1 or 2)] in the process of raising the temperature were observed by XPS and IR measurements, and the chemical behaviours of these hydrogenated species on the HY surface (surface reaction cycle of the adsorbed nitrogen species) are discussed.