The effect of water on the acidity of TiO₂ and sulfated titania

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• 作者：Apoorva P. Kulkarni and Darrin S. Muggli
• 关键词：Sulfated titania ; TPD ; Isopropylamine ; Brø ; nsted ; Lewis ; Ammonia ; Pyridine ; DRIFTS ; Acidity
• 刊名：Applied Catalysis A: General
• 出版年：2006
• 出版时间：11 April 2006
• 年：2006
• 卷：302
• 期：2
• 页码：274-282
• 全文大小：607 K

文摘

Temperature-programmed desorptions (TPD) of isopropylamine (IPA), NH₃, and pyridine were compared with diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) of pyridine to determine the effect of H₂O on the acidities of three titania catalysts. Brønsted acidity increased in the following order: Degussa P-25 TiO₂ < TiO₂ synthesized in our laboratory (p-TiO₂) < sulfated titania (SO₄²⁻/TiO₂). Although the traditional interpretation of pyridine infrared spectra showed an apparent increase in Brønsted acidity upon treating SO₄²⁻/TiO₂ with H₂O, IPA TPD spectra showed that H₂O displaced IPA from approximately one-third to one-half of the Brønsted sites. Similarly, H₂O treatment prior to TPD displaced significant amounts of both NH₃ and pyridine. The primary effect of H₂O is displacement of strongly adsorbed basic probe molecules from Brønsted sites, rather than the conversion of Lewis sites to Brønsted sites.