物理化学学报 >> 1994, Vol. 10 >> Issue (02): 107-113.doi: 10.3866/PKU.WHXB19940204

研究论文 上一篇    下一篇

ZrO2酸碱性质的TPD表征 I. 单组分吸附研究

徐柏庆, 山口力, 田部浩三, 梁娟, 郑禄彬   

  1. 大连理工大学化工学院化学系,大连 116012| 日本国北海道大学理学院化学系;中国科学院大连化学物理研究所,大连 116023
  • 收稿日期:1992-05-18 修回日期:1993-04-23 发布日期:1994-02-15
  • 通讯作者: 徐柏庆

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

摘要:

以NH_3、吡啶、Et_3N、CO_2和苯酚为探针,用TPD-MS方法对ZrO_2催化剂的酸碱性质进行了表征.ZrO_2上碱性探针(NH_3、吡啶和Et_3N)的脱附温度远低于在强酸性SiO_2-Al_2O_3上;而酸性探针CO_2的脱附温度远低于在强碱性MgO上的结果.为ZrO_2的弱酸弱碱性质提供了证明.NH_3吸附IR结果表明ZrO_2表面配位不饱合Zr~(4+)为酸(Lewis酸)中心.NH_3、吡啶和Et_3N与这些酸中心作用的方式和能量分布相似.NH_3和CO_2的TPD谱图均存在三个脱附峰,且相应脱附峰的温度范围相近.表明ZrO_2的酸中心和碱中心具有匹配相当的酸、碱强度,ZrO_2为典型的酸-碱双功能催化剂,在苯酚的TPD过程中,ZrO_2的特征表现为对苯酚的强吸附和对苯酚分解的高活性.文中结合IR结果,对与NH_3和CO_2的脱附相联系的表面吸附物种分别进行了讨论.

关键词: 氧化锆, 酸碱性质, TPD, 酸碱探针, IR

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