Revealing Brønsted acidic bridging SiOHAl groups on amorphous silica-alumina by ultra-high field solid-state NMR

Zichun Wang, Kuizhi Chen, Yijiao Jiang, Julien Trebosc, Wenjie Yang, Jean-Paul Amoureux, Ivan Hung, Zhehong Gan, Alfons Baiker, Olivier Lafon*, Jun Huang*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)

Abstract

Amorphous silica–aluminas (ASAs) are important acidic catalysts and supports for many industrially essential and sustainable processes. The identification of surface acid sites with their local structures on ASAs is of critical importance for tuning their catalytic properties but still remains a great challenge and is under debate. Here, ultrahigh magnetic field (35.2 T) 27Al-{1H} D-HMQC (dipolar-mediated heteronuclear multiple-quantum correlation) two-dimensional NMR experiments demonstrate two types of Brønsted acid sites in ASA catalysts. In addition to the known pseudobridging silanol acid sites, the use of ultrahigh field NMR provides the first direct experimental evidence for the existence of bridging silanol (BS: SiOHAl) acid sites in ASAs, which has been hotly debated in the past few decades. This discovery provides new opportunities for scientists and engineers to develop and apply ASAs in various reaction processes due to the significance of BS in chemical and fuel productions based on its strong Brønsted acidity.

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Original languageEnglish
Pages (from-to)11563-11572
Number of pages10
JournalJournal of Physical Chemistry Letters
Volume12
Issue number47
DOIs
Publication statusPublished - 2 Dec 2021

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