Acidity characterization of rare-earth-exchanged Y zeolite using P-31 MAS NMR

作者：Yu Shanqing^*; Tian Huiping

来源：Chinese Journal of Catalysis, 2014, 35(8): 1318-1328.

DOI：10.1016/S1872-2067(14)60149-2

• Y zeolite
• Rare earth
• Acid site
• Solid-state P-31 NMR

Detailed qualitative and quantitative information on the effects of rare-earth (RE) cations on the types (Bronsted and Lewis), strengths, and distributions of acid sites on Y zeolite was studied by solid-state P-31 magic-angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy, using adsorbed trimethylphosphine oxide (TMPO) and tributylphosphine oxide (TBPO) as probe molecules. A total of seven P-31, resonance peaks, with P-31 NMR/TMPO chemical shifts at delta = 78, 70, 65, 62, 58, 55, and 53, corresponding to sites with different acid strengths, were identified. The peaks at delta = 78 and 70 arose from external and internal acid sites, the peaks at delta = 65, 62, 58, and 53 were from internal Bronsted acid sites, and the peak at delta = 55 was from internal Lewis acid sites. With increasing RE content, the number of medium strength Bronsted acid sites (delta = 62 and 58) increased significantly, whereas those of strong Bronsted acid sites (delta = 65) and weak Lewis acid sites (delta = 55) decreased. These experimental results were explained in terms of the influence of framework Al, extra-framework Al, and RE cations on the Y zeolite acidity.

• 出版日期2014-8
• 单位中国石油化工股份有限公司石油化工科学研究院