Control of Ti active-site microenvironment in titanosilicate catalysts and its effect on oxidation pathways

Yu, Yunkai; Wang, Rui; Liu, Wei; Chen, Zhen; Liu, Haoxin; Huang, Xingliang; Tang, Zijie; Liu, Yueming; He, Min

doi:10.1016/j.apcata.2020.117953

Cited by 19 publications

(16 citation statements)

References 79 publications

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“…According to the result of Gaussian simulation, 48 the kinetic size of 1,2‐epoxyhexane molecules is 0.76 × 0.31 nm, which means that 1,2‐epoxyhexane is favor to adsorb on the external surface of TS‐1. Hence, the 1,2‐epoxyhexane is over‐oxidized immediately to n‐valeraldehyde (Figure 5B) because CTS‐1 contains higher percentage of external Ti‐sites according to the results of (QUI + ACN) DRIFTS and 1 H MAS NMR 25 . On the contrary, the silica islands‐deposited ITS‐1 exhibits low conversation of 1,2‐epoxyhexane due to the reduced percentage of external Ti‐sites.…”

Section: Resultsmentioning

confidence: 98%

“…Hence, the 1,2-epoxyhexane is overoxidized immediately to n-valeraldehyde (Figure 5B) because CTS-1 contains higher percentage of external Ti-sites according to the results of (QUI + ACN) DRIFTS and 1 H MAS NMR. 25 On the contrary, the Therefore, the silica islands-deposited strategy is helpful to improve the selectivity of 1,2-epoxyhexane in the 1-hexene epoxidation.…”

Section: Catalytic Performance Of 1-hexene Epoxidation Reactionmentioning

confidence: 99%

“…To date, much work has been focused on modulating the Ti-sites environment of TS-1. [22][23][24][25] For example, different Ti species (e.g., tetrahedral-coordinated, pentahedral-coordinated, octahedrallycoordinated) can lead to a significant change in catalytic performance.…”

Section: Introductionmentioning

confidence: 99%

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Silica islands regulated external Ti‐site environment of TS‐1 for enhanced performance of 1‐hexene epoxidation

Yuan

Fan

et al. 2022

AIChE Journal

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Rational regulation of the local environment of Ti-sites in TS-1 harbors tremendous industrial and scientific significance to epoxidation reactions. Herein, we report a facile and environment-friendly strategy to boost catalytic selectivity by covering the Tisites on an external surface of TS-1 (ITS-1) without sacrificing activity of internal Ti sites. By a quantitative analysis of d 3 -acetonitrile and quinoline-DRIFTS, 1 H MAS NMR and XPS, it is found that the percentage of external Ti-sites decreased from 11% to 6% after depositing surface silica islands. This successfully inhibits ringopening reaction of 1,2-epoxyhexane on catalyst surface, as demonstrated by slower kinetic decomposition rate of 1,2-epoxyhexane. Compared with conventional TS-1 catalyst, selectivity of 1,2-epoxyhexane over ITS-1 catalyst significantly increased from 83.5% to 98.5% while maintaining high 1-hexene conversion. Furthermore, overmuch surface silica coverage only leads to extremely low conversion (2%) due to inhibition of mass transfer. This work paves the way for rational construction of Ti-containing catalysts for 1-hexene epoxidation.

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Section: Resultsmentioning

confidence: 98%

Section: Catalytic Performance Of 1-hexene Epoxidation Reactionmentioning

confidence: 99%

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Silica islands regulated external Ti‐site environment of TS‐1 for enhanced performance of 1‐hexene epoxidation

Yuan

Fan

et al. 2022

AIChE Journal

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“…The number and coordination environment of Ti in the framework determine the catalytic performance of TS-1 zeolite. [30][31][32][33][34] Some small-molecule additives (e.g., (NH 4 ) 2 CO 3 , (NH 4 ) 2 SO 4 and 1,3,5-benzenetricarboxylic acid) and polymers (e.g., PAA) have been utilized to lower the pH of the system or solidify the gel, allowing the rate of Ti entering the framework to match with the rate of nucleation and crystallization to increase the titanium content of TS-1. [35][36][37][38] With the help of CGMs (e.g., ethanol and amino acids), TS-1 zeolite with high activity mono-nuclear hexacoordinated titanium (TiO 6 ) was prepared.…”

Section: Introductionmentioning

confidence: 99%

“…The number and coordination environment of Ti in the framework determine the catalytic performance of TS-1 zeolite. 30–34 Some small-molecule additives ( e.g. , (NH 4 ) 2 CO 3 , (NH 4 ) 2 SO 4 and 1,3,5-benzenetricarboxylic acid) and polymers ( e.g.…”

Section: Introductionmentioning

confidence: 99%

Impact of a polymer modifier on directing the non-classical crystallization pathway of TS-1 zeolite: accelerating nucleation and enriching active sites

et al. 2022

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Ti-MWW Catalysts for Propylene Oxide Production: Influence of Si/Ti Ratio and Calcination Conditions

et al. 2023

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Titanium silicates of MWW structures with different Si/Ti ratios were prepared via hydrothermal synthesis using piperidine as the structure directing agent and boric acid as the crystallization agent. All the syntheses resulted in highly crystalline materials independent of the Si/Ti ratio. The observed morphology showed MWW-like well-defined thin hexagonal platelets. The synthesized Ti-MWW materials exhibited higher surface areas and partial meso-porosity compared to the commercial TS-1 catalyst. The coordination of the Ti-species was investigated by UV–vis- and IR-spectroscopy. The MWW titanium silicates were tested for the catalytic performance in the epoxidation of propylene in a laboratory-scale trickle bed reactor to compare their clear different physico-chemical properties with the commercial TS-1. The synthesized Ti-MWW materials showed significantly higher catalytic activities, up to 3.5 times, using acetonitrile as the solvent and enhanced epoxide selectivities partially up to 100% in methanol unlike TS-1. The effect of the Ti content in the MWW and the calcination conditions were investigated in propylene epoxidation, revealing the beneficial effect of a lower calcination temperature and an increased Ti content on the activity. The catalytic results were correlated with the physico-chemical properties of the synthesized materials. Graphical Abstract

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Control of Ti active-site microenvironment in titanosilicate catalysts and its effect on oxidation pathways

Cited by 19 publications

References 79 publications

Silica islands regulated external Ti‐site environment of TS‐1 for enhanced performance of 1‐hexene epoxidation

Silica islands regulated external Ti‐site environment of TS‐1 for enhanced performance of 1‐hexene epoxidation

Impact of a polymer modifier on directing the non-classical crystallization pathway of TS-1 zeolite: accelerating nucleation and enriching active sites

Ti-MWW Catalysts for Propylene Oxide Production: Influence of Si/Ti Ratio and Calcination Conditions

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