Acta Phys. -Chim. Sin. ›› 1994, Vol. 10 ›› Issue (01): 1-5.doi: 10.3866/PKU.WHXB19940101

• Communication •     Next Articles

Adsorption of Na+ onto γ-Alumina Studied by Solid-state 23Na and 27Al NMR Spectroscopy

Deng Feng, Du You-Ru, Ye Zhao-Hui, Kong Yu-Hua   

  1. Laboratory of Nuclear Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics, The Chinese Academy of Science, Wuhan 430071; Huibei Institute of Chemistry, Wuhan 430071
  • Received:1993-08-30 Revised:1993-10-05 Published:1994-01-15
  • Contact: Du You-Ru


The adsorption of Na~+ on γ-alumina surface at four coverages of Na_2CO_3 (5%, 10%, 15%, and 20% wt/wt) was characterized by solid-state ~(23)Na and ~(27)Al NMR spectroscopy. The experimental results suggest that two distinct adsorbed species are present on alumina surface: surface species and surface salts. At lower coverages of Na_2CO_3 (5% and 10%), a surface species is predominant, in which the Na~+ cations are associated with the oxygen atoms of γ-alumina. With increasing the loading level to 15%, a second adsorbed species begins to appear which is attributed to the surface salt, Na_2CO_3, deposited on the solid surface. Further adsorption of Na_2CO_3 leads to an increase in the amount of surface salt while the amount of surface species remains unchanged. ~1H-~(27)Al CP/MAS experiments give the evidence that some Na~+ cations in the form of surface species are coordinated with the Br~(‥)onsted acid sites of γ-alumina. This may be the main driving force that improves appreciably the catalytic efficiency of Na_2CO_3/γ-Al_2O_3 catalyst.

Key words: Adsorption, γ-alumina, 23Na MAS NMR, 1H—27Al CP/MAS NMR