Structure and reactivity of single site Ti catalysts for propylene epoxidation

Lü, Zheng; Liu, Xiaoyang; Zhang, Bin; Gan, Zhuoran; Tang, Siwen; Ma, Lu; Wu, Tianpin; Nelson, George J.; Qin, Yong; Turner, C. Heath; Yu, Lei

doi:10.1016/j.jcat.2019.07.051

Cited by 41 publications

(22 citation statements)

References 55 publications

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“…We are not aware of any other examples of tetrahedral coordination in titanium oxide with such large bond lengths. This combination of low coordination numbers and long Ti–O bonds contributes to the low density of the resulting titanium oxide films. ,− Additional analysis of the EXAFS data to extract information about the second coordination sphere proved unreliable but did point to low (1 to 2) Ti–O–Si or Ti–O–Ti coordination numbers (Supporting Information Tables S2 and S3), consistent with the isolated nature of the initial titanium oxide subunits as they grow out of the silica nucleation centers.…”

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confidence: 92%

Nucleation and Initial Stages of Growth during the Atomic Layer Deposition of Titanium Oxide on Mesoporous Silica

et al. 2020

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A chemical approach to the deposition of thin films on solid surfaces is highly desirable but prone to affect the final properties of the film. To better understand the origin of these complications, the initial stages of the atomic layer deposition of titania films on silica mesoporous materials were characterized. Adsorption–desorption measurements indicated that the films grow in a layer-by-layer fashion, as desired, but initially exhibit surprisingly low densities, about one-quarter of that of bulk titanium oxide. Electron microscopy, X-ray diffraction, UV/visible, and X-ray absorption spectroscopy data pointed to the amorphous nature of the first monolayers, and EXAFS and 29Si CP/MAS NMR results to an initial growth via the formation of individual tetrahedral Ti–oxide units on isolated Si–OH surface groups with unusually long Ti–O bonds. Density functional theory calculations were used to propose a mechanism where the film growth starts at the nucleation centers to form an open 2D structure.

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confidence: 92%

Nucleation and Initial Stages of Growth during the Atomic Layer Deposition of Titanium Oxide on Mesoporous Silica

et al. 2020

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“…76,77 Such an atomic-level understanding will provide valuable guidance in designing and preparing advanced catalysts. 24,[78][79][80][81][82][83][84][85][86] Moreover, in situ and operando studies concerning the dynamic changes during the catalytic reactions are required to further reveal the mechanism involved in catalysis. Compared with SACs made by wet chemistry that are indeed closer to practical applications, single atoms fabricated by physical deposition on ultrathin oxide lms (surface free energy approach) provide better-dened models for fundamental studies, especially for local and dynamic characterization studies, of practical catalysts.…”

Section: Summary and Perspectivesmentioning

confidence: 99%

A perspective on oxide-supported single-atom catalysts

Zhou

et al. 2020

Nanoscale Adv.

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“…The measurement of propylene epoxidation was discussed previously. [34] Briefly, it was carried out in a quartz tubular reactor with an inner diameter of 10 mm and at normal pressure using a mixture of 0.15 g catalyst of 60-80 mesh size and 1.5 g quartz sand of 25-35 mesh size as diluent. A thermocouple was placed to the quartz tube wall where the catalyst resides to directly measure the reaction temperature.…”

Section: Catalytic Activity Measurementmentioning

confidence: 99%

Gold Catalysts Synthesized Using a Modified Incipient Wetness Impregnation Method for Propylene Epoxidation

et al. 2020

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Propylene epoxidation in the presence of oxygen and hydrogen were measured for a series of Au/TS-1 catalysts prepared by a modified incipient wetness impregnation (mIWI) method. This method enables precise control of the Au : Ti ratio in the Au/TS-1 catalysts. The optimized Au/TS-1 catalyst exhibited 12 % propylene conversion, 87 % PO selectivity, and 25 % hydrogen efficiency. The particle size of gold nanoparticles prepared by the modified IWI was between 2 and 3 nm, as demonstrated by XRD patterns, STEM images, and X-ray absorption spectroscopy at the Au L 3 edge. XPS spectra showed that the surface species on the catalysts were similar. UV-Vis spectra suggested that in the modified IWI method, the chlorine ligands in Au(Cl) 4 À were replaced by hydroxyl groups, which contributes to form small gold nanoparticles. Kinetic studies showed that the active sites of Au(mIWI)/TS-1 are similar to the Au(DP)/TS-1 prepared by deposition precipitation.

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Structure and reactivity of single site Ti catalysts for propylene epoxidation

Cited by 41 publications

References 55 publications

Nucleation and Initial Stages of Growth during the Atomic Layer Deposition of Titanium Oxide on Mesoporous Silica

Nucleation and Initial Stages of Growth during the Atomic Layer Deposition of Titanium Oxide on Mesoporous Silica

A perspective on oxide-supported single-atom catalysts

Gold Catalysts Synthesized Using a Modified Incipient Wetness Impregnation Method for Propylene Epoxidation

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