Evidence for Monatomic Platinum Species in H-ZSM-5 from FTIR Spectroscopy of Chemisorbed CO

FTIR study of the electronic metal–support interactions on platinum dispersed on silica modified with titania

“…The band at 2128 cm 1 was studied extensively by others. 19 It was reported that at a high temperature of reduction the band at 2128 cm 1 decreases its intensity. This band was mainly assigned to carbon monoxide coordinated to Pt ions.…”

“…This band was mainly assigned to carbon monoxide coordinated to Pt ions. 19 The band at higher wavenumber (2189 cm was assigned to carbon monoxide physically adsorbed 18 or coordinated to titanium ions.…”

Pt speciation on ZSM-5 by IR of probes co-adsorption and chemometric analysis

“…This band is characteristic of CO adsorbed on electron deficient platinum species [10,11,15,22,23]. After air ageing, the metal dispersion is more affected than after exposure to inert and reductive atmospheres at the same temperature (during 5 h).…”

“…The activity of these metal centres depends on many parameters, such as the preparation method (metal precursor, zeolite acidity and thermal treatment), the level of Pt unsaturation and the metal location [6][7][8][9]. Indeed, the metal speciation on zeolites can be rather complex, since the metal atoms could be mainly found as grafted cations in exchange position of the crystalline framework [10,11] and/or as supported nanoparticles.…”

“…Important additional information is then also available such as dispersion, metal coordination and support interactions in the case of Pt nanoparticles [8,9,[12][13][14][15][16][17]. But the spectroscopic data interpretation becomes rather difficult when Pt atoms are also found in exchange positions (mono-atomic species) on the same metal catalyst, simply because the respective IR components are overlapping [10]. Differentiation between Pt in exchange position and platinum oxide using CO is also not obvious, since a part of the IR feature (m CO ) of Pt d+ (CO) n complexes may fall in the same region than for CO ads on Pt oxide.…”