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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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Zeolite‐Based Catalysts for Conversion of Oxygenated Polymer Waste by Positron Annihilation
Abstract Positron Annihilation Lifetime Spectroscopy (PALS) has been employed to investigate the catalysts HZSM‐5 and MESO−Y, which play a pivotal role in catalyzing and upgrading plastics, with a primary focus on oxygenated polymers, thereby transforming existing plastic materials into simpler, higher‐quality value‐added products. In this study, PALS was systematically compared with other complementary analytical techniques. The research outcomes have successfully demonstrated the efficacy of PALS in elucidating the morphology and topology of zeolites at micro/meso‐meter scales. The first experiment focuses on H‐ZSM‐5 zeolite subjected to treatments involving polyurethane and polypropylene. The second experiment delves into H‐ZSM‐5 zeolites with varying Si/Al ratios, both before and after conversion. The third experiment investigates Y zeolites that are surfactant templated to induce meso‐porosity, examining their fresh state as well as their post‐conversion condition. The PALS analysis was supplemented by BET (Brunauer‐Emmett‐Teller) analysis and NMR (Nuclear Magnetic Resonance) spectroscopies. Notably, PALS exhibits superior sensitivity, at the sub‐nanometer scale, suggesting its potential as a preferred complementary method for catalysis studies. In conclusion, the integration of PALS into the repertoire of analytical tools enhances our understanding of catalyst behavior and catalytic processes, offering valuable insights for the advancement of plastic recycling and catalysis research.
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- Award ID(s):
- 2052817
- PAR ID:
- 10487601
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- ChemCatChem
- Volume:
- 16
- Issue:
- 4
- ISSN:
- 1867-3880
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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