Facile synthesis of a high-performance titanosilicate catalyst with controllable defective Ti(OSi)₃OH sites

Abstract

A novel TS-1 (TS-1S) catalyst with newly-generated defects, i.e. Ti(OSi)3OH species, which exhibits the highest reactivity among different Ti species, is constructed in an ingenious strategy. This also provides a promising way to effectively tune the intrinsic nature of Ti active centres in other titanosilicates.

Hollow core–shell structured TS-1@S-1 as an efficient catalyst for alkene epoxidation

“…The IR spectra in the hydroxyl region (Fig. 4c) demonstrated that HCS-TS had more Ti-OH groups, with an obvious absorption band at 3676 cm À1 , whereas it was difficult to be detected in TS-1 and H-TS-1, 22 consistent with the peak of 235 nm formed in UV-vis spectra. Furthermore, the absorption band at 3500 cm À1 was attributed to hydrogen-bonded silanol nests.…”

“…5D ). 22,25,45,49 The above results implied the existence of open tetra-coordinated titanium (Ti(OSi) 3 OH) species in HCS-TS. 22 …”

“…22,25,45,49 The above results implied the existence of open tetracoordinated titanium (Ti(OSi) 3 OH) species in HCS-TS. 22 UV resonance Raman spectroscopy was applied to further identify the newly formed "TiO 6 " species in HCS-TS P , which triggered the UV-Vis absorption band at 260 nm (Fig. 3d).…”

“… 38 Notably, the peak at 210 nm widened obviously and a stronger absorption band at 235 nm was observed for HCS-TS, which was ascribed to Ti(OSi) 3 OH active sites. 22 Additionally, a new absorption band at 260–280 nm was detected in HCS-TS P , which was believed to be “TiO 6 ” species in octahedral coordination. 15,39 Compared with TS-1, the ratio of I 960 / I 550 further decreased after the second step of crystallization ( Table 1 ), implying the partial transformation of “TiO 4 ” species to different titanium active sites in HCS-TS and HCS-TS P .…”

“…Selective dissolution of Si species around Ti(OSi) 4 sites of TS-1 could directionally construct active Ti(OSi) 3 OH species. 22 Interestingly, the Ti species with other coordination environments, such as Ti(V) species and the Ti(VI) species surrounded with nearby Si vacancies, could also take responsible for a superior catalytic activity in various Ti-catalyzed reactions. 10,23,24 Wu et al successfully synthesized TS-1 + with stable sixcoordination Ti species ("TiO 6 "), it showed a superior activity in the oxidation of propylene to propylene oxide with the TON value increasing about 2-3 times than TS-1.…”