Pure component spectral analysis of surface adsorbed species measured under real conditions. BTEM-DRIFTS study of CO and NO reaction over a Pd/γ-Al2O3catalyst

Abstract

The adsorption of NO and CO was studied on an alumina-supported palladium catalyst by in situdiffuse reflectance infrared spectroscopy (DRIFTS). The temperature range was 50–160 °C and a wide variety of partial pressures was used. The band-target entropy minimization (BTEM) algorithm was applied to the DRIFTS data sets resulting in the pure component spectra of numerous species adsorbed on both the Pd (primarily a variety of Pd–CO and Pd–NO species, in various oxidation states and coordinations) and alumina surface species (i.e. nitrates, nitrites, carbonates, bicarbonates, formates, and isocyanates) as well as gas phase species. Twenty seven previously known species were identified as well as three new and previously unreported or previously unassigned spectra. The present study indicates that BTEM can be meaningfully applied to Pd/Al₂O₃DRIFTS in order to provide enhanced spectroscopic analysis. Moreover, the present results are compared in detail with the recent BTEM analysis of CO and NO adsorption on Pt/Al₂O₃ using DRIFTS (Phys. Chem. Chem. Phys. 2008, 10, 3535).