物理化学学报 >> 2002, Vol. 18 >> Issue (02): 142-146.doi: 10.3866/PKU.WHXB20020210

研究论文 上一篇    下一篇

改性Y分子筛的酸碱性能及吸附性能的研究

周灵萍;邓量;寇元;李宣文   

  1. 北京大学化学与分子工程学院,北京 100871
  • 收稿日期:2001-08-13 修回日期:2001-10-30 发布日期:2002-02-15
  • 通讯作者: 周灵萍 E-mail:zhou_ling_ping@hotmail.com

Studies on Acidity and Basicity and Adsorption of Modified Y Zeolites

Zhou Ling-Ping;Deng Liang;Kou Yuan;Li Xuan-Wen   

  1. College of Chemistry & Molecular Engineering, Peking University,Beijing 100871
  • Received:2001-08-13 Revised:2001-10-30 Published:2002-02-15
  • Contact: Zhou Ling-Ping E-mail:zhou_ling_ping@hotmail.com

摘要: 吡啶、吡咯、苯、甲苯、乙苯作为探针分子,在Li+, Na+, K+, Cs+改性的Y型分子筛上进行吸附,用TPD及IR方法系统地研究了不同碱金属离子改性的Y型分子筛的酸碱性能和吸附性能的变化. 结果表明,按Li、Na、K、Cs的顺序, 随着碱金属离子半径的增大, 其L酸酸强度依次减弱,L碱的强度逐渐增强.由于改性Y型分子筛所含碱金属离子的不同,其对芳烃的吸附的强弱及吸附量的大小亦不同.随着骨架外的阳离子的半径逐渐增大,碱的强度逐渐增强,与芳烃的作用愈强烈,导致TPD脱附峰温增高及芳烃和侧链上的C-H伸缩振动谱带向低波数位移愈多.由于位阻的原因,对含同一种碱金属离子的分子筛来说,随着芳烃侧链C数的增加,芳烃的吸附量逐渐减小.

关键词: 改性八面沸石, TPD, FTIR, 表面酸碱性, 芳烃吸附

Abstract: The acidity and basicity of alkali cation exchanged Y zeolites were investigated systematically using pyridine and pyrrole as the TPD and IR spectroscopic probe respectively. It was found that the overall Lewis basicity in the modified Y zeolites increased and the Lewis acidity in the modified Y zeolites decreased as the cation was exchanged from LiY to CsY in the alkali cation series. The adsorption of benzene, toluene and ethylbenzene on Y zeolites modified by alkali cations were also studied comparatively by IR spectroscopy and TPD. The following results were obtained: (1)The adsorption of pyridine on modified Y zeolites could also be used to characterize the acidity and basicity of alkali cation exchanged Y zeolites; (2) The C-H stretching frequencies of aromatic ring, of CH3 on the side-chain of toluene, and of -CH2- on the side-chain of ethylbenzene shifted towards lower wavenumber as the cation was exchanged from LiY to CsY; (3)The adsorption strength and the amount of sorbed aromatics on modified Y zeolites were related to the basicity of alkali cation exchanged Y zeolites.

Key words: Modified Y zeolites, TPD, FTIR, Surface acidity and basicity, Aromatic hydrocarbon adsorption