高等学校化学学报 ›› 1989, Vol. 10 ›› Issue (9): 925.

• 研究论文 • 上一篇    下一篇

硅胶表面上脂肪酸蒸气吸附膜

赵振国   

  1. 北京大学物理化学研究所
  • 收稿日期:1988-02-02 出版日期:1989-09-24 发布日期:1989-09-24
  • 通讯作者: 金韵

The Surface Films of Aliphatic Acid Vapours on the Silica Gel

Zhao Zhenguo   

  1. Department of Chemistry, Peking University, Beijing
  • Received:1988-02-02 Online:1989-09-24 Published:1989-09-24

摘要: 应用Gibbs方程由甲酸、乙酸和丙酸蒸气在硅胶上的吸附等温线计算了吸附膜的表面压力(π)与每个吸附分子所占面积(σ)间的关系(π~σ图).所得曲线与不溶物在溶液表面上的结果相似,均表现出有“液态扩张膜”“转变膜”和“液态凝聚膜”.不同的是,不溶物只能形成单分子层膜,而硅胶表面上的脂肪酸吸附膜则是多分子层的.蒸气吸附膜由单层向多层的转变,恰与π~σ图上的“液态扩张膜”向“转变膜”的转变相对应.吸附焓(△H)与吸附熵(△S)的计算结果表明,在此转变附近AH和AS发生急剧变化.

关键词: 吸附, 蒸气吸附, 表面膜, 硅胶

Abstract: The relationships between the surface pressure(π) and the area(σ) occupied by each adsorbed molecule on the silica gel were calculated by the Gibbs adsorption equation from the adsorption isotherms of vapours of formic, acetic and propionic acid (at 20℃).The resulting π-σ curves were similar to those of the insoluble films on the sarface of solution, there also exist "the liquid-expanded state", "the liquid-condensed state" and "the intermediate state".The surface films are monomolecu-lar layer on water, but become multimolecular layer on the silica gel at a higher vapour pressure.When the monolayer turns to the multilayer, the liquid-expanded state becomes the intermediate.The enthalpy and entropy of adsorption were culculated from the adsorption isotherms at 20℃ and 30℃.The results show that △Hand △Sgo through a minimum at or near monolayer capacity.Near the minimum the state of the film shows a marked change.

Key words: Adsorption, Adsorption of vapours, Surface film, Silica gel

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