Srilakshmi Chilukoti1, Effendi Widjaja1, Feng Gao1, Huajun Zhang1, Bruce G. Anderson2, J.w Niemantsverdriet2, and Marc Garland1. (1) Process Science and Modelling, Institute for Chemical and Engineering Sciences (ICES), 1 Pesek road, Jurong Island, Singapore, Singapore, (2) Schuit Institute of Catalysis, Chemical Engineering and Chemistry, Eindhoven University of Technology, PO Box 513, 5600 MB, Eindhoven, Netherlands
Band target Entropy Minimization (BTEM) was applied for the analysis of the DRIFTS data measured during CO and NO reaction over Pt/gamma-Al2O3 catalyst under a wide range of experimental conditions. Experiments were designed such that to recover the maximum number of adsorbed species possible for the catalytic system. In order to achieve this DRIFTS spectra were measured in a wide variety of partial pressure ranges of CO (0-8000 ppm) and NO (0-2000 ppm) using temperature range of 50-160°C. The pure component spectra of numerous species adsorbed on both the Pt (primarily a variety of Pt0-CO and Pt2+-CO species) and alumina surface (i.e. nitrates, nitrites, bicarbonates, isocyanates) as well as gas phase species were readily recovered. The pure component spectral estimates of 31 previous known species were obtained. In addition, 8 new and previously unreported spectra are recovered, and many assigned. These include observations of two distinct Pt0-13CO species, even though they contribute less than 0.05% of the total observed DRIFT signal intensity. One important observation of the present study is the detection of formate species on the alumina surface even though hydrogen was not added to the reactant gas stream. It should be noted that some of the vibrational modes of the species not observable in the experimental spectra were only discernable after BTEM analysis. Unlike other self curve resolution techniques BTEM uses no spectral libraries and no a priori information for the pure component spectral recovery. Although the BTEM algorithm has been used repeatedly and successfully for infrared and Raman studies of homogeneous catalytic systems, this is the first time that it has been applied to DRIFTS data from a heterogeneous catalytic system. The present results indicate that BTEM analysis of DRIFTS data is a very promising tool for the study of heterogeneous catalytic in situ spectroscopic data. BTEM performed outstanding when compared with other self-modelling curve resolution techniques of SIMPLISMA and IPCA. Keywords: Spectral reconstruction, Band-Target Entropy Minimization, in situ DRIFTS, Pt/gamma-Al2O3 catalyst, CO and NO reaction.