Synthesis of TS-1 Molecular Sieves Using a New Ti Source

Borin, Mario F.; Silva, Teresa da; Felisbino, Romilda Fernandez; Cardoso, Dilson

doi:10.1021/jp060703o

Cited by 23 publications

(14 citation statements)

References 15 publications

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“…This method saves time (12 h) and provides a relatively mild condition. From then on, many works focused on improving the synthesis procedure and catalytic performance of TS-1 by changing titanium and silicon sources, − tuning templates, , and adding additives. , For cutting down the cost of TS-1, many researchers tried to use tetrapropylammonium bromide (TPABr) as the template, due to the high cost of TPAOH . However, the decrease of basicity and introduction of Br – usually make the crystal size larger, and this will further lead to a poorer catalytic performance.…”

Section: Introductionmentioning

confidence: 99%

Role of Supports in the Tetrapropylammonium Hydroxide Treated Titanium Silicalite-1 Extrudates

Zuo

Hong

et al. 2015

Ind. Eng. Chem. Res.

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Titanium silicalite-1 (TS-1) was extruded with silica and alumina supports, and then the extrudates were treated with dilute tetrapropylammonium hydroxide (TPAOH) solution. The treated TS-1 extrudates were characterized and evaluated in the epoxidation of propene. The two supports exhibited different properties after the treatment. The dissolution of silicon, forming hollows in the TS-1 crystals, preferably occurred when alumina support was used. The inhibition of generation of hollows in the silica supported TS-1 arose from the dissolution and recrystallization of silica support. The crystallization of support also led to the unblocking of inherent micropores, which was beneficial for improving the catalytic performance. Alumina support showed a different result. A very small amount of aluminum was inserted into the framework of TS-1, but the small amount of framework Al caused a sharp increase of the acid amount, and thus a low selectivity of propene oxide and poor catalyst stability in propene epoxidation.

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Section: Introductionmentioning

confidence: 99%

Role of Supports in the Tetrapropylammonium Hydroxide Treated Titanium Silicalite-1 Extrudates

Zuo

Hong

et al. 2015

Ind. Eng. Chem. Res.

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“…An increase in the unit cell volume proportional to the amount of metals introduced into the zeolite framework has been previously reported. 22,23 The unit cell volume expansion and symmetry change of the MFI type zeolite are due to distortion of the framework to accommodate Mo atoms with an ionic radius larger than Si. 24 The space group transition and volume expansion observed for Mo-MFI-D provide additional evidence for the incorporation of molybdenum atoms into the framework of the MFI type zeolite.…”

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confidence: 99%

Direct Evidence for Single Molybdenum Atoms Incorporated in the Framework of MFI Zeolite Nanocrystals

et al. 2019

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Direct evidence of the successful incorporation of atomically dispersed molybdenum (Mo) atoms into the framework of nanosized MFI zeolite is demonstrated for the first time. Homogeneous distribution of Mo with a size of 0.05 nm is observed by scanning transmission electron microscopy high-angle annular dark-field imaging (STEM-HAADF). 31P magic-angle spinning nuclear magnetic resonance (MAS NMR) and Fourier-transform infrared (FT-IR) spectroscopy, using trimethylphosphine oxide (TMPO) and deuterated acetonitrile as probe molecules, reveal a homogeneous distribution of Mo in the framework of MFI nanozeolite, and the presence of Lewis acidity. 31P MAS NMR using TMPO shows probe molecules interacting with isolated Mo atoms in the framework, and physisorbed probe molecules in the zeolite channels. Moreover, 2D 31P–31P MAS radio frequency-driven recoupling NMR indicates the presence of one type of Mo species in different crystallographic positions in the MFI framework. The substitution of framework Si by Mo significantly reduces the silanol defect content, making the resulting zeolite highly hydrophobic. In addition, the insertion of Mo into the MFI structure induces a symmetry lowering, from orthorhombic (Pnma), typical of high silica MFI, to monoclinic (P21/n), as well as an expansion of unit cell volume. The novel material opens many opportunities of catalysts design for application in mature and emerging fields.

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“…One can see that the crystallinities for the specimens exhibit an order F > G > E > C > D > B > A . Since the Ti–O bond is longer than the Si–O bond, the incorporation of Ti(IV) into the framework of TS-1, replacing Si(IV), would result in the expansion of the TS-1 cell. ,, The linear relationship between the content of framework Ti, x f , and unit cell volume of TS-1, v , can be usually expressed as follows: v = 5345.6 + 19.7 x normalf x normalf = n Ti / ( n Ti + n Si ) where n Ti and n Si denote respectively the molar numbers of Ti and Si in the framework of TS-1. Table lists the unit cell parameters and volumes obtained by the XRD determination, and contents of framework Ti, calculated on the basis of the above expressions, for the specimens B – G .…”

Section: Resultsmentioning

confidence: 99%

“…The intensity of the band at ∼230 nm, which is indicative of the content of framework Ti, exhibits approximately an order F > G > E > D > C > B > A, being consistent with that determined by XRD. The band at ∼320 nm is usually assigned to anatase, 33,34 and that at ∼270 nm is caused by the non-tetra-coordinated Ti, e.g., the partially condensed hexa-coordinated Ti species, 53 the site-isolated Ti species in penta-or octahedral coordination, 54 or even the Ti species partially coordinated with water molecules. 34,55 Both the anatase and non-tetra-coordinated Ti belong to extraframework Ti species.…”

Section: Industrial and Engineering Chemistry Researchmentioning

confidence: 99%

Synthesis of High-Performanced Titanium Silicalite-1 Zeolite at Very Low Usage of Tetrapropyl Ammonium Hydroxide

Huang

Zhang

Liu

et al. 2013

Ind. Eng. Chem. Res.

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A novel method for the synthesis of high-performanced titanium silicalite-1 (TS-1) zeolite at a very low usage of tetrapropylammonium hydroxide (TPAOH) was developed in this work. The method involved a temperature-programmed hydrothermal crystallization (TPHC) of a batch with a TPAOH/SiO 2 molar ratio of as low as 0.05, being 5 times smaller than that employed in the conventional synthesis, in which the TPAOH was entirely provided by a TS-1 precursor sol. The characterizations of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), diffuse reflectance ultraviolet− visible spectroscopy (DR UV−vis), and scanning electron microscopy (SEM) indicated that the TS-1 synthesized via the novel method possessed a uniform crystal size of ∼0.3 μm, a very high crystallinity and a considerably large content of framework Ti (2.33 mol %). The TS-1 had been employed as the catalyst for the ammoximation of cyclohexanone, of which the influencing factors were systematically investigated. It was shown that the TS-1 synthesized via the novel method possessed a very high performance, which is even better than for those synthesized via the conventional method both in this work and in the literature work.

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Synthesis of TS-1 Molecular Sieves Using a New Ti Source

Cited by 23 publications

References 15 publications

Role of Supports in the Tetrapropylammonium Hydroxide Treated Titanium Silicalite-1 Extrudates

Role of Supports in the Tetrapropylammonium Hydroxide Treated Titanium Silicalite-1 Extrudates

Direct Evidence for Single Molybdenum Atoms Incorporated in the Framework of MFI Zeolite Nanocrystals

Synthesis of High-Performanced Titanium Silicalite-1 Zeolite at Very Low Usage of Tetrapropyl Ammonium Hydroxide

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