Does the Zn2+ Species Introduced into H-ZSM-5 Zeolite Affect the Strength of Brønsted Acid Sites?

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)

Abstract

To clarify the issue on Brønsted acidity enhancement by the presence of zinc species in H-ZSM-5 zeolite (G.D. Qi, et al., Angew. Chem.-Int. Edit. 2016, 55, 15826), the influence of Zn2+ cationic species, introduced into the zeolite, on the strength of Brønsted acid sites (BAS) has been analyzed by solid-state NMR and FTIR techniques using trimethylphosphine (TMP) and CO as probe molecules. Comparative analysis of the acidity for H-ZSM-5 and Zn2+/H-ZSM-5 zeolites has been performed. TMP adsorbed on both zeolite samples exhibits same signals at 6.3 and −4.5 ppm in 1H and 31P MAS NMR spectra, respectively, assigned to protonated TMP. FTIR spectroscopy has shown that both zeolite samples, H-ZSM-5 and Zn2+/H-ZSM-5, display the same red frequency shift (ΔνOH⋅⋅⋅CO=−318 cm−1) of the O−H stretching band and the same blue frequency shift (ΔνCO=+32 cm−1) of the CO stretching band for CO adsorption complex with BAS. The results obtained do not provide any evidence for the existence of some specific BAS with enhanced acid strength for Zn2+-exchanged zeolite compared to the strength inherent to pure acid-form zeolite. It is thus inferred the strength of BAS in H-ZSM-5 zeolite is not affected by the modification of the zeolite with Zn2+ cationic species.

Original languageEnglish
Pages (from-to)478-487
Number of pages10
JournalChemCatChem
Volume12
Issue number2
DOIs
Publication statusPublished - 18 Jan 2020

Keywords

  • Brønsted acid sites
  • FTIR spectroscopy
  • solid-state NMR
  • zeolite
  • zinc
  • HYDROXYL-GROUPS
  • surface
  • heterogeneous catalysis
  • nanoreactor
  • Superaerophilic
  • DISSOCIATIVE ADSORPTION
  • METHANE ACTIVATION
  • PROTON AFFINITY
  • CARBON-MONOXIDE
  • LIGHT PARAFFINS
  • BRONSTED ACID SITES
  • TRIMETHYLPHOSPHINE OXIDE
  • STRETCHING BANDS
  • bursting
  • STATE NMR

Fingerprint Dive into the research topics of 'Does the Zn<sup>2+</sup> Species Introduced into H-ZSM-5 Zeolite Affect the Strength of Brønsted Acid Sites?'. Together they form a unique fingerprint.

Cite this