Amorphous Ti species in titanium silicalite-1: Structural features, chemical properties, and inactivation with sulfosalt

Su, Junfeng; Xiong, Guang; Zhou, Juncheng; Liu, Wenhuan; Zhou, Danhong; Wang, Guiru; Wang, Xiangsheng; Guo, Hongchen

doi:10.1016/j.jcat.2011.12.006

Cited by 101 publications

(92 citation statements)

References 42 publications

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“…In view of the present X-ray diffraction study, which does not exclude a small fraction of sixfold coordinated Ti ions in ULE, we assign the weak Raman feature at $685 cm À1 to the symmetric stretching vibration of TiO 6 octahedral units. Raman bands at about 700 cm À1 in Tisubstituted zeolites 32 and at 684 cm À1 in cobalt-doped TiO 2 thin films 33 were also associated with sixfold coordinated Ti 4þ ions in Ti-O-Ti arrangements.…”

Section: Raman and Infrared Spectroscopy On Pristine Ulementioning

confidence: 91%

Femtosecond laser-induced transformations in ultra-low expansion glass: Microstructure and local density variations by vibrational spectroscopy

Efthimiopoulos

Πάλλες

Richter

et al. 2018

Journal of Applied Physics

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We report X-ray diffraction, resonance Raman, and infrared (IR) results on pristine ultra-low expansion (ULE) glass, a binary titanosilicate glass with 5.67 mol. % TiO2. ULE processing by femtosecond (fs) laser radiation leads to nanograting writing and photo-darkening for imaging and data storage. We investigate here the vibrational/structural changes induced by fs laser irradiation of ULE at 515 nm. Optical imaging revealed the formation of micro-cavities, and Raman mapping showed molecular oxygen trapped in such cavities of laser-irradiated ULE glass. While titanium in the pristine glass was found predominantly in tetrahedral Ti4+ sites highly dispersed in the silicate matrix, Raman and IR reflectance spectroscopy on laser-irradiated ULE indicated the formation of Ti3+ sites; Ti3+ octahedral sites are formed in the shells of cavities and aggregate in amorphous Ti2O3-type clusters, while the glass around and below cavities contains Ti3+ tetrahedral sites dispersed in the silicate network. Laser-processed ULE glass was found to also exhibit local restructuring of the silicate matrix. Shifts of the strong IR band at about 1080–1100 cm−1 were translated into changes of the average Si-O-Si bond angle in the laser-transformed areas and found to reflect local density variations; the average local density increases relative to silica glass up to about 8% in the shells of micro-cavities and decreases by about 0.5% in the surrounding material. Chemical processes were proposed to account for photo-darkening and the local structural transformation effect in the probed areas of the fs laser-processed ULE glasses.

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Section: Raman and Infrared Spectroscopy On Pristine Ulementioning

confidence: 91%

Femtosecond laser-induced transformations in ultra-low expansion glass: Microstructure and local density variations by vibrational spectroscopy

Efthimiopoulos

Πάλλες

Richter

et al. 2018

Journal of Applied Physics

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“…Figure (A) shows the Raman spectra of Ti‐rich TS‐1 zeolite ((NH 4 ) 2 CO 3 /SiO 2 molar ratio of 0.3), (a) calcined, (b) acid‐treated(1 mol/L), calcined. The peaks at 144 and 637 cm −1 (line a) are due to the presence of anatase TiO 2 , the peaks at 700 cm −1 is due to the amorphous Ti species on the surface of s‐TS‐1(0.3) . After acid washing of s‐TS‐1(0.3) zeolite, the peaks at 144 cm −1 , 637 cm −1 and 700 cm −1 were disappeared (line b), indicating that the anatase TiO 2 and amorphous Ti species were washed away from s‐TS‐1‐m (0.3).…”

Section: Resultsmentioning

confidence: 99%

Synthesis of Hierarchical Titanium‐Rich Titanium Silicalite‐1 Zeolites and the Highly Efficient Catalytic Performance for Hydroxylation of Phenol

et al. 2019

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Improving the framework titanium (Ti) of titanium silicalite-1 (TS-1) zeolites and creating inter-crystalline mesoporosity are two ways to enhance the catalytic properties of TS-1 for hydroxylation of phenol. Most researches only used one of the ways. In this study, we successfully synthesized of hierarchical Titanium-Rich (Ti-rich) TS-1. Ti-rich TS-1 was synthesized in the presence of ammonium carbonate ((NH 4 ) 2 CO 3 ). The framework Ti content of TS-1 zeolites synthesized by different content of (NH 4 ) 2 CO 3 was studied by X-ray fluorescence (XRF), Fourier transform infrared spectra (FTIR) and ultraviolet visible spectra, the framework Ti content was significantly increased by using (NH 4 ) 2 CO 3 as crystallization-mediating agent. The synthesized samples were evaluated in hydroxylation of phenol. When the molar ratio of ammonium carbonate and tetraethyl orthosilicate in the synthesis gel was 0.2, the molar ratio of Si/Ti reached 34.43 and the Ti-rich TS-1 shows the optimum catalytic activity in hydroxylation of phenol. The post-modification with aqueous solution of tetrapropylammonium hydroxide (TPAOH) was used to further improve the diffusion property. Compared with the parent TS-1, the secondary pore volume was all increased. The developed hierarchical Ti-rich TS-1 zeolites were also assessed in hydroxylation of phenol. It was confirmed that hierarchical Ti-rich titanium silicalite-1 zeolites can improve the catalytic activity in phenol conversion considerably.

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“…The EDS analysis showed maximum amount of Ti content (Si/Ti=99.0) for TS‐1‐mt possibly as a result of contribution of solid silica as precursor in the synthesis mixture (Table S2 and Figure S8). The UV‐vis spectra of all the TS‐1 samples shows strong absorption bands at λ=210‐220 nm, indicating the presence of Ti framework species which is responsible for selective oxidation reaction (Figure S9) . The TS‐1‐mt showed higher absorption bands at 240–260 nm; howerver, TS‐1 and TS‐1‐m showed absorption at λ=310‐330 nm coressponding to anatase TiO 2 phase.…”

Section: Resultsmentioning

confidence: 99%

Efficient Synthesis of Titaniosilicalite‐1 Zeolite Nanoparticles Under Solvent‐free Conditions for the Oxidation of Dibenzothiophene: Impact of Silica Precursor

Shakeri

2019

ChemistrySelect

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Various silica precursors of tetraethyl orthosilicate (TEOS), mesocellular silica foam (MCF), and a combination of TEOS and MCF are investigated under solvent-free conditions to achieve efficient TS-1 catalyst. The obtained TS-1 catalysts were characterized by powder XRD, FTIR, diffusive reflectance UV-Vis, FE-SEM, TEM, N 2 sorption, DLS, and EDS. The TS-1 synthesized by combination of TEOS and MCF possesses smaller crystal size, higher yield of solid materials, and enhanced Ti incorporation than that obtained by either only MCF or TEOS. The average particle size of TS-1 catalysts synthesized by using MCF, TEOS, and the combination of TEOS and MCF were about 350, 170, and 105 nm, respectively. The yield of solid TS-1 by using MCF, TEOS, and the combination of TEOS and MCF were 0.28, 0.80, and 1.20 g-TS-1/g-TPAOH, respectively. Oxidation of 1000 ppm of the bulky substrate of dibenzothiophene (DBT; kinetic diameter 0.9 nm) by TS-1 synthesized by combination of TEOS and MCF was about two times higher than that by the TS-1 catalyst prepared either by TEOS or MCF. Furthermore, oxidation of 5000 ppm of DBT (equally to 5 separate batches) by this catalyst resulted in full conversion in 24 h. Consequently, the use of combination of TEOS and amorphous silica of MCF as silica precursor under solvent-free conditions is a practical approach to prepare efficient TS-1 catalyst.

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Amorphous Ti species in titanium silicalite-1: Structural features, chemical properties, and inactivation with sulfosalt

Cited by 101 publications

References 42 publications

Femtosecond laser-induced transformations in ultra-low expansion glass: Microstructure and local density variations by vibrational spectroscopy

Femtosecond laser-induced transformations in ultra-low expansion glass: Microstructure and local density variations by vibrational spectroscopy

Synthesis of Hierarchical Titanium‐Rich Titanium Silicalite‐1 Zeolites and the Highly Efficient Catalytic Performance for Hydroxylation of Phenol

Efficient Synthesis of Titaniosilicalite‐1 Zeolite Nanoparticles Under Solvent‐free Conditions for the Oxidation of Dibenzothiophene: Impact of Silica Precursor

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