Sn-MFI molecular sieves: synthesis methods, 29Si liquid and solid MAS-NMR, 119Sn static and MAS NMR studies

Mal, Nawal Kishor; Ramaswamy, V.; Rajamohanan, P. R.; Ramaswamy, A.V.

doi:10.1016/s0927-6513(97)00081-3

Cited by 66 publications

(54 citation statements)

References 13 publications

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“…1) (24), an efficient route to the more thermodynamically stable lactate products is not enabled by the retro-aldol catalysts described above (resulting in triose accumulation and recombination through aldol reactions). Addition of a 1,2-HS cocatalyst [Sn-MFI with Si/Sn = 70 ± 6, fluoride-free synthesis (25)] to a 1 wt% fructose, 0.2 wt% MoO 3 aqueous solution enabled formation of lactic acid at 100°C. However, 1 H NMR data suggest that the lactate formed strong pH-dependent complexes with molybdate species (SI Appendix, Fig.…”

Section: Resultsmentioning

confidence: 99%

Tandem catalysis for the production of alkyl lactates from ketohexoses at moderate temperatures

Orazov

Davis

2015

Proc. Natl. Acad. Sci. U.S.A.

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Retro-aldol reactions have been implicated as the limiting steps in catalytic routes to convert biomass-derived hexoses and pentoses into valuable C2, C3, and C4 products such as glycolic acid, lactic acid, 2-hydroxy-3-butenoic acid, 2,4-dihydroxybutanoic acid, and alkyl esters thereof. Due to a lack of efficient retro-aldol catalysts, most previous investigations of catalytic pathways involving these reactions were conducted at high temperatures (≥160 °C). Here, we report moderate-temperature (around 100 °C) retro-aldol reactions of various hexoses in aqueous and alcoholic media with catalysts traditionally known for their capacity to catalyze 1,2-intramolecular carbon shift (1,2-CS) reactions of aldoses, i.e., various molybdenum oxide and molybdate species, nickel(II) diamine complexes, alkali-exchanged stannosilicate molecular sieves, and amorphous TiO2–SiO2 coprecipitates. Solid Lewis acid cocatalysts that are known to catalyze 1,2-intramolecular hydride shift (1,2-HS) reactions that enable the formation of α-hydroxy carboxylic acids from tetroses, trioses, and glycolaldehyde, but cannot readily catalyze retro-aldol reactions of hexoses and pentoses at these moderate temperatures, are shown to be compatible with the aforementioned retro-aldol catalysts. The combination of a distinct retro-aldol catalyst with a 1,2-HS catalyst enables lactic acid and alkyl lactate formation from ketohexoses at moderate temperatures (around 100 °C), with yields comparable to best-reported chemocatalytic examples at high temperature conditions (≥160 °C). The use of moderate temperatures enables numerous desirable features such as lower pressure and significantly less catalyst deactivation.

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Section: Resultsmentioning

confidence: 99%

Tandem catalysis for the production of alkyl lactates from ketohexoses at moderate temperatures

Orazov

Davis

2015

Proc. Natl. Acad. Sci. U.S.A.

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“…Subsequently, 0.032g of SnCl 4 .5H 2 O (98%, Sigma-Aldrich) dissolved in 0.075 g of distilled water were added drop-wise under stirring and the mixture was stirred for another hour. Afterwards 1 g of NH 4 F dissolved in 0.375 g of distilled water was added to the mixture under vigorous stirring, along with 1.32 mL ethanol. Finally, the mixture was stirred for another 30 min.…”

Section: Catalyst Preparationmentioning

confidence: 99%

“…Afterwards, the powder was filtered, rinsed thoroughly with deionized water and dried overnight at 333 K. Prior to Sn grafting, the powder was activated overnight at 423 K to remove physisorbed water. Then, the activated sample was suspended in dry isopropanol (100 mL g catalyst -1 ) and 27 mmol of SnCl 4 .5H 2 O per g of support was added. The solution was refluxed under N 2 for 7 hours and afterwards filtered, rinsed with isopropanol and dried at 333 K.…”

Section: Sn-β Deal Via Post-treatment Proceduresmentioning

confidence: 99%

“…Then, 0.5 g of a 37 wt% HCl solution, diluted with 70 g of water, was added and the mixture was stirred for 2 h. Afterwards, 9.0 g of TEOS and 0.302 g of SnCl 4 .5H 2 O dissolved in 1.0 g of water were added dropwise and the mixture was stirred for another 24 h at 313 K to obtain a gel with an approximate composition of 1 SiO 2 :0.02SnO 2 :0.016P123:0.14Cl -:134H 2 O. Finally, the gel was transferred to a Teflon-lined autoclave and was heated for 24 h at 373 K.…”

Section: Sn-sba-15mentioning

confidence: 99%

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Confinement Effects in Lewis Acid-Catalyzed Sugar Conversion: Steering Toward Functional Polyester Building Blocks

et al. 2015

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We report the use of solid Lewis acid catalysts for the conversion of tetrose sugars to four-carbon α-hydroxy acid esters (C4-AHA), which are useful as functional polyester building blocks. Sn-β was by far the most active and selective catalyst, yielding up to 80% methyl vinyl glycolate (MVG), methyl-4-methoxy-2-hydroxybutanoate (MMHB), and α-hydroxy-γ-butyrolactone (HBL) combined at 95% conversion. A very high turnover frequency (TOF) of 330 molC4‑AHA molSn h–1 was attained using Sn-β, a more than 6-fold increase compared with homogeneous SnCl4·5H2O. It is shown that, using different Sn-based catalysts with various pore sizes, the product distribution is strongly dependent on the size of the catalyst pores. Catalysts containing mainly mesopores, such as Sn-MCM-41 or Sn-SBA-15, prefer the production of the more bulky MMHB, whereas microporous catalysts such as Sn-β or Sn-MFI favor the production of MVG. This effect can be further enhanced by increasing the reaction temperature. At 363 K, only 20% MVG is attained using Sn-β, but at 433 K, this increases to 50%. Using a kinetic analysis, it was found that, in microporous catalysts, steric hindrance near the Sn active site in the catalyst pores plays a dominant role in favoring the reaction pathway toward MVG. Moreover, the selectivity toward both products is kinetically controlled.

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“…Notably, the absorption band at approximately 260 nm that is attributed to octahedral Sn 4+ spaces is not observed for the calcined Sn-S MC . On the other hand, the band at 240–250 nm is still in debate, however, penta-coordinated Sn species [30,31], extra-framework Sn species [17], and small tin oxide particles [30,32] have been assigned to the peaks at around 240–250 nm. These results strongly support the idea that Sn 4+ ions were introduced into the Sn-MFI framework as tetrahedrally coordinated states.…”

Section: Resultsmentioning

confidence: 99%

Mechanochemically assisted hydrothermal synthesis of Sn-substituted MFI-type silicates

Kanie

Sakaguchi

Muto

et al. 2018

Science and Technology of Advanced Materials

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Substitution of Al atoms in a zeolite framework by catalytic metal atoms has attracted considerable attention because the catalytic behavior can be tuned by the substituted atoms. In the present study, Sn-substituted MFI-type silicates were synthesized using a hydrothermal reaction of an amorphous Si-O-Sn precursor prepared by mechanochemical grinding of SiO2 and Sn(OH)4. The mechanochemical treatment was found to be a key technique for obtaining the amorphous Si-O-Sn precursor, where tetrahedral Sn4+ species were incorporated into the amorphous matrix. The Sn content in the framework of the MFI-type silicates was successfully controlled by the initial HCl/Si molar ratio of the hydrothermal procedures. Optical reflectance measurements revealed that the Sn4+ ions were dispersedly incorporated into the silicate framework while preserving the initial tetrahedrally coordinated species. Infrared results imply that the resulting Sn-substituted MFI-type silicate has Brønsted acid character. Precise control of the Brønsted and Lewis acid properties by Sn doping is a promising approach to the development of novel types of zeolite-based catalytic materials.

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Sn-MFI molecular sieves: synthesis methods, 29Si liquid and solid MAS-NMR, 119Sn static and MAS NMR studies

Cited by 66 publications

References 13 publications

Tandem catalysis for the production of alkyl lactates from ketohexoses at moderate temperatures

Tandem catalysis for the production of alkyl lactates from ketohexoses at moderate temperatures

Confinement Effects in Lewis Acid-Catalyzed Sugar Conversion: Steering Toward Functional Polyester Building Blocks

Mechanochemically assisted hydrothermal synthesis of Sn-substituted MFI-type silicates

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