XPS characterization of a synthetic Ti‐containing MFI zeolite framework: the titanosilicalites, TS‐1

Abstract

Following a previous investigation on micro-and mesoporous titanosilicates, we have here deepened the XPS and Xray-excited Auger electron spectroscopy (XAES) studies on the surface properties of microporous titanosilicalites-1 (TS-1) and reference silicalites-1 (S-1), both characterized by the MFI framework type. The aim was that of complementing the information already obtained on these compounds with other techniques such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), dielectric relaxation spectroscopy (DRS), electron spin resonance (ESR), and quantomechanical calculations. Notwithstanding the expected low photoelectron intensity due to the very low solubility of Ti (IV) ions in the MFI framework, an accurate XPS curve-fitting procedure and the simultaneous use of the XPS and Auger signals (Wagner plot) have made possible, both qualitatively and quantitatively, the distinction of two Ti (IV) sites: the framework tetrahedral species -Ti (IV) substituting Si (IV) -and the Ti(IV) tetrahedral species grafted to surface hydroxyl groups. Both species are prone to convert into octahedrally coordinated Ti (IV) species as a consequence of interaction with water and other ligands.

Usefulness of alkoxyltitanosiloxane for the preparation of mesoporous silica containing a large amount of isolated titanium

“…We expect that the titanium environment of TMS-TS3 is more electropositive and the Ti-O bond is more ionic than that of TMS-MP. Because microporous titanium silicate TS-1, which is active for epoxidation of olefins, shows a high Ti (2p) binding energy [42,43], TMS-TS3 may be useful as a catalyst for similar oxidation reaction of bulk olefins. Fig.…”

Optimization of hydrogen storage capacity in silica-supported low valent Ti systems exploiting Kubas binding of hydrogen

“…All binding energies (BEs) were referenced to the C 1s hydrocarbon peak at 284.8 eV. In addition, the XPS spectrum of trimethyl Ti-HMS has a shoulder in the binding energy (BE) range of Ti(III) chemical state at 456.2 eV [21], suggesting that decomposition to a lower valent Ti species may have occured.…”

Regeneration of Deactivated Hollow Titanium Silicalite Zeolite from Commercial Ammoximation Process by Encapsulating Amorphous TiO2-SiO2Nanoparticles inside Zeolite Crystal

“…To confirm the chemical status of Ti species in the crystal surface, the regenerated HTS, as well as fresh and deactivated HTS zeolites, were characterized by X‐ray photoelectron spectroscopy (XPS), as shown in Figure . In principle, the peaks at around 461 eV and 459 eV in the Ti 3 d 3/2 XPS spectra of TS‐1 zeolite are attributed to the framework Ti species and extra‐framework Ti species, respectively . In our previous work, we have confirmed the aggregation of Ti species on zeolite surface (with the formation of acidic Ti‐rich nanoparticles) by using multiple characterization methods .…”

“…In principle, the peaks at around 461 eV and 459 eV in the Ti 3d 3/2 XPS spectra of TS-1 zeolite are attributed to the framework Ti species and extraframework Ti species, respectively. [26][27][28] In our previous work, we have confirmed the aggregation of Ti species on zeolite surface (with the formation of acidic Ti-rich nanoparticles) by using multiple characterization methods. [29] But, compared to deactivated HTS zeolite, the regenerated HTS zeolite possess higher proportion of framework Ti species in zeolite surface, which is almost the same as that of fresh HTS zeolite.…”