Confirmation of the isomorphous substitution by Sn atoms in the framework positions of MFI-typed zeolite

Xia, Changjiu; Liu, Yujia; Lin, Min; Peng, Xinxin; Zhu, Bin; Shu, Xingtian

doi:10.1016/j.cattod.2018.02.056

Cited by 25 publications

(24 citation statements)

References 30 publications

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“…Two shoulders (332 and 416 cm -1 ) are attributed to the perturbation of Si-O-Si vibrations linked to the presence of neighboring Mo-O-Si species, or possibly Mo-O-Si vibrations. 17 This result is further supported by the presence of a broad band at 1105 cm -1 in the FTIR spectrum of sample Mo-MFI-D, corresponding S3). The two samples differ substantially: (i) sample Mo-MFI-D contains Mo atoms in the MFI framework and no oxide phase, with a negligible amount of isolated silanols (3745 cm -1 ), and (ii) sample Mo-MFI-P contains molybdenum oxide and silanols as shown by FTIR (Figure S4).…”

Section: Supporting Informationmentioning

confidence: 59%

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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Section: Supporting Informationmentioning

confidence: 59%

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

et al. 2019

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“…Figure 2 shows the relationship between the ionic radius of T ions (rT IV , Å) and the unit cell volume (V, Å 3 ) of HZSM zeolites. Relationship between the radius of Т ions (rT IV , Å) and the unit cell volume (V, Å 3 ) of (H)ZSM (Data from [98][99][100][101][102][103][104][105][106][107][108][109][110][111][112][113]).…”

Section: Hzsm-5 Zeolitesmentioning

confidence: 99%

“…Figure 2.Relationship between the radius of Т ions (rT IV , Å) and the unit cell volume (V, Å 3 ) of (H)ZSM (Data from[98][99][100][101][102][103][104][105][106][107][108][109][110][111][112][113]). …”

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confidence: 99%

Design of MFI Type Aluminum- and Titanium-Containing Zeolites

2021

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HZSM-5 (MFI type) of composition (Hx)[Al3+xSi12−xO24] × wH2O and nanocomposites NA/HZSM-5, NA:M/HZSM-5 (NA—nanoscale anatase; M = V, Ni, Ag) with Si/Al = 12, 25, 40, 300 (sp.gr. Pnma or P21/n; z = 8), as well as zeolites [(Ti4+xSi12−xO24] × wH2O (TS) with Si/Ti = 47, 53, 73.5 (sp.gr. Pnma) were studied by XRPD, XAS, FTIR-spectroscopy, BET, XPS, SEM, EDX, TPD, UV–VIS-spectroscopy, UV–DRS, and chemiluminescence methods. The results obtained together with photocatalytic, adsorption, antimicrobial, catalytic properties were analyzed using crystallochemical concepts and literature data. It was shown that NA or NA:M introduction into HZSM-5 leads, respectively, to the photodegradation of MeO dye in the UV region or difenoconazole in the visible range, and contributes to the appearance in the dark of adsorption (almost complete extraction of P(V), As(V), and Se(V) from aquatic environment) and bacteriostatic properties in respect to Staphylococcus epidermidis, Bacillus antracoides, and Escherichia coli for NA:Ag/HZSM-5(40, 300). The presence of titanium ions in NA nanoparticles on the HZSM-5 surface improves the catalytic activity in ethanol and propane (the best performance for NA/HZSM-5(25) and NA/HZSM-5(40), respectively) conversion. Determination of the composition (surface and bulk) and structure (statistical and local) of TS zeolites together with the found correlations made it possible to propose new catalysts in the reactions of propane, ethanol, and allyl chloride conversion.

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“…Pyridine adsorption FT-IR spectroscopy is currently a commonly adopted method for determining the type and number of acid sites of Sn-containing zeolites and molecular sieves. According to the literature reports [30][31][32][33][34][35][36][37], the Sn-containing zeolites and molecular sieves mainly have Lewis acid sites, and they usually give pyridine absorption bands in the range of 1450 to 1455 cm −1 and 1610 to 1615 cm −1 . These bands are often accompanied by another important band at 1490 cm −1 , which is generally considered as the contribution of pyridine adsorbed on both Brønsted acid sites and Lewis acid sites.…”

Section: Acidity Of the Sn-containing Defective S-1 Zeolitementioning

confidence: 99%

Effect of Stannic Species Modification on the Acidity of Silicalite-1 and Its Enhancement in Transforming Ethylenediamine to Heterocyclic Amines

et al. 2020

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In this study, a series of SnO 2 modified zeolite catalysts (Snx-S-1; x is the weight percentage of Sn) were prepared with SnCl 2 and a defective Silicalite-1 (S-1) zeolite via facile deposition-precipitation method. It was found that the stannic species modified all-silica zeolite catalysts were active for the intermolecular condensation of ethylenediamine (EDA) to 1, 2-Diazabicyclo [2, 2, 2] octane (TEDA) and piperazine (PIP). The best catalyst Sn6-S-1 (6 wt.% Sn loading) showed 86% EDA conversion and 93% total selectivity to TEDA and PIP. By contrast, the defective S-1 zeolite parent showed only approximately 9% EDA conversion under the same conditions. With the help of catalyst characterization techniques including hydroxyl vibration and pyridine adsorption FT-IR spectroscopy (transmission mode), the enhancement of the catalytic activity of the SnO 2 modified zeolite catalysts (Snx-S-1) was mainly attributed to the formation of mild Lewis acid sites in the siliceous zeolite. Both the hydroxyl nests of the defective S-1 zeolite and the dispersed SnO 2 clusters should be the important factors for the formation of mild Lewis acid sites on the modified zeolite. Based on the catalytic performance of the modified zeolite in the conversion of EDA to PIP and TEDA, it is inferred that the mildly acidified defective S-1 zeolite by the SnO 2 deposition modification might become a very active and durable catalyst for reactions involving strongly alkaline reactants and products.Catalysts 2020, 10, 211 2 of 16 hydroxyl groups) of H-ZSM-5 zeolite. For this reason, some modification methods such as alkali metal ion modification [7] and dealumination [9], etc. have been proposed to weaken the strength of acidic sites in H-ZSM-5. However, such efforts often cause negative effects such as worse diffusivity due to pore channel blocking. In 2003, titanium silicalite-1 (TS-1) was patented for the reaction of EDA to TEDA and PIP [10]. Later, people conducted a detailed study on the intermolecular condensation of EDA to make PIP and TEDA over TS-1 zeolite [11]. Silicalite-1 (S-1) zeolite is an aluminum-free crystalline silicate with the same MFI topological framework as the Al-containing ZSM-5 zeolite and Ti-containing silicate zeolite (TS-1). It is well known that the presence of defective sites in S-1 lattice can form mild acidity (silanol nests). The defective S-1 zeolite has been reported as an active Beckmann rearrangement catalyst [12][13][14][15]. However, previous study indicated that the defective S-1 zeolite itself was not very active and selective for the reaction of EDA to TEDA and PIP, giving only 19.5% EDA conversion and 7.5% TEDA selectivity [11]. This implies that the acidity of defective S-1 is too weak to be an efficient catalyst for the conversion of EDA.In recent years, Sn-β zeolite has attracted increasing attention because its isolated framework Sn is an active Lewis acid site for many reactions, including Baeyer-Villiger oxidation, sugar isomerization, and Meerwein-Ponndorf-Verley reaction [16,17]. Sn-MFI zeol...

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Confirmation of the isomorphous substitution by Sn atoms in the framework positions of MFI-typed zeolite

Cited by 25 publications

References 30 publications

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

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

Design of MFI Type Aluminum- and Titanium-Containing Zeolites

Effect of Stannic Species Modification on the Acidity of Silicalite-1 and Its Enhancement in Transforming Ethylenediamine to Heterocyclic Amines

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