An XRD, FTIR and TPD Investigation of NO2 Surface Adsorption Sites of δ, γ Al2O3 and Barium Supported δ, γ Al2O3.

In this paper an XRD, FTIR and TPD investigation of NO₂ surface adsorption sites of δ, γ Al₂O₃ and barium supported δ, γ Al₂O₃ is reported. Aim of this study is to bring additional light on the surface structures involved in NOx adsorption. Two samples of barium supported aluminas have been prepared and aged at 800 °C. These samples were characterised in comparison with the relative alumina support. The XRD characterisation of these samples shows the presence of barium carbonate and barium aluminate supported on alumina. The comparison of the FTIR spectra, before and after NO₂ adsorption, has revealed the formation, upon NO₂ contact, of a complex variety of nitrate and nitrite groups. The thermal desorption of nitrate and nitrite species has been simultaneously studied by means of FTIR spectroscopy and by TPD technique. By comparing the structural, adsorptive and spectroscopic results obtained on alumina and on barium supported alumina samples, a hypothesis on the basic sites active in NO₂ adsorption and of the possible decomposition paths induced by thermal heating are proposed. [ABSTRACT FROM AUTHOR]