Acta Phys. -Chim. Sin. ›› 2006, Vol. 22 ›› Issue (10): 1233-1237.doi: 10.1016/S1872-1508(06)60058-2

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Base-induced Brönsted Acid Sites on Dealuminated HY Zeolite: A Solid-state NMR Spectroscopy Study

HU Wei;LUO Qing;LI Shen-Hui;SHEN Wan-Ling;YUE Yong;DENG Feng   

  1. State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, P. R. China
  • Received:2006-04-20 Revised:2006-05-27 Published:2006-10-11
  • Contact: DENG Feng E-mail:dengf@wipm.ac.cn

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Abstract: Using trimethylphosphine(TMP) and d5-pyridine (deuterated pyridine) as the basic probe molecules, the concentrations of Brönsted acid sites on both HY zeolite and dealuminated HY zeolite have been quantitatively determined using solid-state 1H and 31P magic-angle spinning(MAS) NMR. After the adsorption of the probe molecules, the concentration of Brönsted acid sites on the dealuminated HY zeolite increases by about 25%, whereas the parent HY sample remains almost unchanged. The increase in the concentration of Brönsted acid sites is due to the appearance of base-induced Brönsted acid sites in the dealuminated HY zeolite. The terminal SiOH in the vicinity of the aluminum atom is “induced” to form a bridging hydroxyl group (SiOHAl) in the presence of the basic probe molecules. The mechanism of formation of the induced Brönsted acid sites has also been discussed.

Key words: HY zeolite, NMR, Dealumination, Probe molecule, Induced Brö, nsted acid site