The modified hydrophobicity index as a novel method for characterizing the surface properties of titanium silicalites

Weitkamp, Jens; Roland, Eckehart; Thiele, G.

doi:10.1016/s0167-2991(97)80627-1

Cited by 35 publications

(15 citation statements)

References 5 publications

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“…As with defective silanol groups, framework heteroatoms such as Al (in MOR and MFI) and Ti (in MFI) and extraframework alkali cations (in MFI) also behave as hydrophilic centers that can adsorb water; specifically, each Ti center in Ti‐Beta can adsorb two H 2 O molecules . We have synthesized Ti‐Beta‐F, Ti‐Beta‐OH, and Sn‐Beta‐F zeolites and report N 2 , H 2 O, CH 3 OH, and C 2 H 5 OH isotherms on these samples in Figures , respectively.…”

Section: Resultsmentioning

confidence: 99%

Beyond shape selective catalysis with zeolites: Hydrophobic void spaces in zeolites enable catalysis in liquid water

2013

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Zeolites confine active sites within void spaces of molecular dimension. The size and shape of these voids can be tuned by changing framework topology, which can influence catalytic reactivity and selectivity via coupled reaction‐transport phenomena that exploit differences in transport properties among reactants and/or products that differ in size and shape. The polarity and solvating properties of intrazeolite void environments can be tuned by changing chemical composition and structure, ranging from hydrophobic defect‐free pure‐silica surfaces to silica surfaces containing hydrophilic defect sites and/or heteroatoms. Here, we discuss how the polarity of zeolite voids influences catalytic reactivity and selectivity via the partitioning of reactant, product, and solvent molecules between intrazeolitic locations and external fluid phases. These findings provide a conceptual basis for developing selective catalytic processes in aqueous media using hydrophobic zeolites that are able to adsorb organic reactants while excluding liquid water from internal void spaces. © 2013 American Institute of Chemical Engineers AIChE J, 59: 3349–3358, 2013

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Section: Resultsmentioning

confidence: 99%

Beyond shape selective catalysis with zeolites: Hydrophobic void spaces in zeolites enable catalysis in liquid water

2013

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“…High silica zeolites like TS 1 and low Al ZSM 5 belong to such a category of catalysts. Their hydrophobicity, measured by different means such as selective adsorption tests and the Hydrophobic ity Index (HI), was known already at the end of 1970s [6,7]. Actually, surface hydrophobicity was, together with Ti-OOH active species, one of the cornerstones of first hypotheses made on the origin of the activity of TS 1 and, since then, repeatedly proved [8,9].…”

Section: Nature Of the Surface And Its Effectsmentioning

confidence: 99%

The activity of titanium silicalite-1 (TS-1): Some considerations on its origin

Clerici

2015

Kinet Catal

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The high activity of titanium silicate (TS 1) in oxidations with hydrogen peroxide is the result of different factors, directly referable to the MFI structure. The configuration of Ti site (tetrahedral), the nature of active species (Ti-OOH) and the nature of the surface (hydrophobic) are the three factors that are imme diately apparent. Hydrophobicity alone, however, cannot fully explain certain catalytic performances and trends in the oxidation of the olefins, without envisaging a major involvement of porosity. Actually, the molec ular dimensions of pores (ca. 0.55 nm), normally perceived as just a drawback for the limits set to the range of potential substrates, play a relevant and positive role in TS 1 catalysis. The purpose of the paper is to illustrate and discuss these issues, with supporting evidences mostly taken from the oxidation of olefins and alkanes.

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“…In the case of TS-1 the hydrophobicity of the final sample is influenced by the presence of nonframework titanium. 376 Nevertheless, even for hydrophobic Ti-Beta its activity and selectivity are still lower than those for TS-1 for molecules that can diffuse in TS-1. Nevertheless, Ti-Beta gives a higher activity for bulkier reactants.…”

Section: Among Them the Incorporation Of Ti By Direct Synthesis Has Bmentioning

confidence: 99%

Lewis Acids as Catalysts in Oxidation Reactions: From Homogeneous to Heterogeneous Systems

2002

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I. Introduction and Scope 3837 II. Oxidation Strategies 3838 III. Lewis Acids as Oxidation Catalysts 3839 A. Oxidations by Single Electron Abstraction 3839 B. Oxidations by an Assembly of Lewis Acid, Lewis Basic and Redox Centers 3841 1. Vanadium-Based Systems 3842 2. Metal Oxides Other than Vanadium 3844 C. Oxidations via Lewis Acid−Base Adducts 3847 1. Oxidations in Homogeneous Phase 3848 2. Oxidations in Biphasic Fluorous Systems 3854 3. Heteropolyacids as Oxidation Catalysts 3855 4.

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The modified hydrophobicity index as a novel method for characterizing the surface properties of titanium silicalites

Cited by 35 publications

References 5 publications

Beyond shape selective catalysis with zeolites: Hydrophobic void spaces in zeolites enable catalysis in liquid water

Beyond shape selective catalysis with zeolites: Hydrophobic void spaces in zeolites enable catalysis in liquid water

The activity of titanium silicalite-1 (TS-1): Some considerations on its origin

Lewis Acids as Catalysts in Oxidation Reactions: From Homogeneous to Heterogeneous Systems

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