物理化学学报 >> 1995, Vol. 11 >> Issue (11): 979-984.doi: 10.3866/PKU.WHXB19951105

研究论文 上一篇    下一篇

制备方法对WO3/ZrO2结构的影响

赵璧英,徐献平,高金明,马华容,唐有祺   

  1. 北京大学物理化学研究所,北京 100871
  • 收稿日期:1994-12-16 修回日期:1995-03-14 发布日期:1995-11-15
  • 通讯作者: 赵璧英

The Effect of the Preparation Methods on the Structure of WO3/ZrO2

Zhao Bi-Ying,Xu Xian-Ping,Gao Jin-Ming,Ma Hua-Rong,Tang You-Qi   

  1. Institute of Physical Chemistry,Peking University,Beijing 100871
  • Received:1994-12-16 Revised:1995-03-14 Published:1995-11-15
  • Contact: Zhao Bi-Ying

摘要:

用XRD、比表面测定、LRS定性和定量的方法对用Zr(OH)4和已晶化的ZrO2作载体制得的两类WO3/ZrO2催化剂进行了表征.揭示了样品比表面、载体物相、活性组分的存在状态与制备方法、WO3含量、焙烧温度之间的关系.结果表明,WO3能单层分散在ZrO2上;单层覆盖在Zr(OH)4上的WO3使载体在焙烧时晶粒生长受阻,形成介稳的四方ZrO2,并阻止载体微粒间的烧结,使从Zr(OH)4出发制得的WO3/ZrO2比表面明显增大,在WO3含量达到单层分散容量时以上作用表现得最充分;WO3与Zr(OH)4(或四方ZrO2)在高温(~800℃)可能发生了某种化学结合,开创出超强酸位.用以上观点可对文献中已报导的主要实验事实作出较满意的解释.

关键词: 超强酸, WO3/ZrO2, 喇曼光谱, 单层分散, LRS定量

Abstract:

 WO3/ZrO2 catalysts prepared from Zr(OH)4 and crystallized ZrO2 have been characterized by means of XRD, LRS (qualitative and quantitative), and the specific sufrace area has been measured. The influence of the preparation method, the contents of WO3 in the samples and the calcination tempearture on the specific surface areas of the samples, the phase of support and the structural states of active component has been studied. The results show: (1) WO3 can disperse on ZrO2 as a monolayer; (2) WO3 dispersed on Zr(OH)4 as a monolayer retards the crystalline growth of the support on calcination, makes it crystallizing into a metastable tetragonal modification, and prevents the inter- crystalline sintering between the crystallites of ZrO2. These factors would result in an increase in the specific surface area of WO3/ZrO2 prepared from Zr(OH)4. As the content of WO3 in the sample comes up to its monolayer capacity, this effect is displayed most fully. A chemical reaction can occur between WO3 and Zr(OH)4 (or the tetragonal ZrO2) at a high temperature(800℃),producing some superacid sites on the surface. By these views, the main experimental facts published in the literatures can been interpreted satisfactotily.

Key words: Superacid, WO3/ZrO2, Raman spectroscopy, Monolayer dispersion, Quantitative LRS