Probing the Incorporation of Ti(IV) into the BEA Zeolite Framework by XRD, FTIR, NMR, and DR UV−jp810722bis

Abstract

The method (Dzwigaj, S., et al. Chem. Commun. 1998, 87) proposed earlier to incorporate V(V) ions into the BEA zeolite framework at the solid−liquid interface from V precursors in aqueous solution has been successfully extended to the solid−gas interface and titanium, with TiCl4 vapor as the precursor. The use of TiCl4 vapor has the advantage to restrict the speciation of titanium to this single species and to lead to a significant amount of Ti (∼5 Ti wt %) determined by chemical analysis. The incorporation of Ti into the SiBEA zeolite framework is evidenced by XRD. The reaction of TiCl4 vapor with H-bonded and terminal SiO−H groups of vacant T-atom sites is monitored by FTIR, 29Si MAS NMR, 1H−29Si CP MAS NMR and 1H MAS NMR. The presence of tetrahedral Ti(IV) as the main titanium species is evidenced by diffuse reflectance UV−vis. A possible pathway for the formation of framework tetrahedral Ti(IV) in TiSiBEA is proposed.