Engineering distinct structure-interface of sub-nano alumina domains on silica for acidic amorphous silica-alumina towards bio-refining

Zichun Wang, Robert Buechel, Yijiao Jiang, Lizhuo Wang, Haimei Xu, Patrice Castignolles, Marianne Gaborieau, Olivier Lafon, Jean-Paul Amoureux, Michael Huang, Alfons Baiker*, Jun Huang*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

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Abstract

Amorphous silica–aluminas (ASAs) are important solid catalysts and supports for many industrially essential and sustainable processes, such as hydrocarbon transformation and biorefining. However, the wide distribution of acid strength on ASAs often results in undesired side reactions, lowering the product selectivity. Here we developed a strategy for the synthesis of a unique class of ASAs with unvarying strength of Brønsted acid sites (BAS) and Lewis acid sites (LAS) using double-flame-spray pyrolysis. Structural characterization using high-resolution transmission electron microscopy (TEM) and solid-state nuclear magnetic resonance (NMR) spectroscopy showed that the uniform acidity is due to a distinct nanostructure, characterized by a uniform interface of silica–alumina and homogeneously dispersed alumina domains. The BAS population density of as-prepared ASAs is up to 6 times higher than that obtained by classical methods. The BAS/LAS ratio, as well as the population densities of BAS and LAS of these ASAs, could be tuned in a broad range. In cyclohexanol dehydration, the uniform Brønsted acid strength provides a high selectivity to cyclohexene and a nearly linear correlation between acid site densities and cyclohexanol conversion. Moreover, the concerted action of these BAS and LAS leads to an excellent bifunctional Brønsted–Lewis acid catalyst for glucose dehydration, affording a superior 5-hydroxymethylfurfural yield.
Original languageEnglish
Pages (from-to)262-271
Number of pages10
JournalJACS Au
Volume1
Issue number3
DOIs
Publication statusPublished - 19 Feb 2021

Bibliographical note

Copyright 2021 American Chemical Society. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.

Keywords

  • Amorphous silica−alumina
  • Brønsted and Lewis acidities
  • double-flame-spray pyrolysis
  • glucose conversion
  • cyclohexanol dehydration
  • solid-state NMR

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