Acta Phys. -Chim. Sin. ›› 1994, Vol. 10 ›› Issue (02): 107-113.doi: 10.3866/PKU.WHXB19940204

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Characterization of Acid-base Property of ZrO2 by Thermal Desorption: I. TPD Studies of Acid and Base Probes

Xu Bai-Qing, Yamaguchi Tsutomu, Tanabe Kozo, Liang Juan,  Zheng Lu-Bin   

  1. Department of Chemistry, School of Chemical Engineering, Dalian University of Technology, Dalian 116012| Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo 060, Japan; Dalian Institute of Chemical Physics, Academia Sincia, Dalian 116023
  • Received:1992-05-18 Revised:1993-04-23 Published:1994-02-15
  • Contact: Xu Bai-Qing

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Abstract:

Acid-base properties of ZrO_2 pretreated at 873 K have been studied in relation to a typical acidic SiO_2-Al_2O_3 and a typical basic MgO catalysts by exadring the TPD behavior of NH_3, CO_2, pyridine, Et_3N, and phenol. The weakly acidic property of ZrO_2 is evidenced by a much lower desorption temperature of NH_3 in comparison with that of SiO_2-Al_2O_3, and its weakly basic property by a much lower desorption temperature of CO_2 in comparison with that of MgO. NH_3, pyridine and Et_3N show similar TPD profiles though decomposition of CH_3CN occurs in the TPD process of Et_3N. It is shown by the IR of adsorbed NH_3 that the acid sites on ZrO_2 are Lewis acidic in nature, and some of them can become more acidic in strength at elevated temperature. Three TPD peaks on the TPD profiles of NH_3 and CO_2-peaks. It is concluded from these observations that the strength of the acid and base sites on ZrO_2 are well matched, and that ZrO_2 is a typical acid-base bifunctional catalyst. A discussion on the relation between the adsorbed surface species and the desorption of NH_3 and CO_2 is given based on the IR results of adsorbed NH_3 and CO_2, respectively.
In the TPD profile of phenol, the feature of ZrO_2 is characterized by a relative difficulty for phenol desorption and an easiness for phenol decomposition.

Key words: Zirconium dioxide, Acid-base property, Acid and base probes, TPD, IR