The synthesis of hierarchical lamellar zeolites with a controlled meso-/microporous morphology and acidity is an expanding area of research interest for a wide range of applications. Here, we report a one-step synthesis of a hierarchical meso-/microporous lamellar MFI–Sn/Al zeolite ( i.e. , containing both Lewis acidic Sn- and Al-sites and a Brønsted acidic Al–O(H)–Si site) and its catalytic application for the conversion of glucose into 5-(ethoxymethyl)furfural (EMF). The MFI–Sn/Al zeolite was prepared with the assistance of a diquaternary ammonium ([C 22 H 45 –N + (CH 3 ) 2 –C 6 H 12 –N + (CH 3 ) 2 –C 6 H 13 ]Br 2− , C 22-6-6 ) template in a composition of 100SiO 2 /5C 22-6-6 /18.5Na 2 O/ x Al 2 O 3 / y SnO 2 /2957H 2 O ( x = 0.5, 1, and 2; y = 1 and 2, respectively). The MFI–Sn/Al zeolites innovatively feature dual meso-/microporosity and dual Lewis and Brønsted acidity, which enabled a three-step reaction cascade for EMF synthesis from glucose in ethanol solvent. The reaction proceeded via the isomerization of glucose to fructose over Lewis acidic Sn sites and the dehydration of fructose to 5-hydroxymethylfurfural (HMF) and then the etherification of HMF and ethanol to EMF over the Brønsted acidic Al–O(H)–Si sites. The co-existence of multiple acidities in a single zeolite catalyst enabled one-pot cascade reactions for carbohydrate upgrading. The dual meso-/microporosity in the MFI–Sn/Al zeolites facilitated mass transport in processing of bulky biomass molecules. The balance of both types of acidity and meso-/microporosity realized an EMF yield as high as 44% from the glucose reactant.
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Catalytic behavior of hexaphenyldisiloxane in the synthesis of pyrite FeS 2
Functional small molecules afford opportunities to direct solid-state inorganic reactions at low temperatures. Here, we use catalytic amounts of organosilicon molecules to influence the metathesis reaction: FeCl 2 + Na 2 S 2 → 2NaCl + FeS 2 . Specifically, hexaphenyldisiloxane ((C 6 H 5 ) 6 Si 2 O) is shown to increase pyrite yields in metathesis reactions performed at 150 °C. In situ synchrotron X-ray diffraction (SXRD) paired with differential scanning calorimetry (DSC) reveals that diffusion-limited intermediates are circumvented in the presence of (C 6 H 5 ) 6 Si 2 O. Control reactions suggest that the observed change in the reaction pathway is imparted by the Si–O functional group. 1 H NMR supports catalytic behavior, as (C 6 H 5 ) 6 Si 2 O is unchanged ex post facto . Taken together, we hypothesize that the polar Si–O functional group coordinates to iron chloride species when NaCl and Na 2 S 4 form, forming an unidentified, transient intermediate. Further exploration of targeted small molecules in these metathesis reaction provides new strategies in controlling inorganic materials synthesis at low-temperatures.
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- Award ID(s):
- 1653863
- NSF-PAR ID:
- 10244139
- Date Published:
- Journal Name:
- Chemical Communications
- Volume:
- 56
- Issue:
- 64
- ISSN:
- 1359-7345
- Page Range / eLocation ID:
- 9186 to 9189
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/D0CC03397A
