Titania as an Early Transition Metal Oxide with a High Density of Lewis Acid Sites Workable in Water

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• 作者：Kiyotaka Nakajima ; Ryouhei Noma ; Masaaki Kitano ; Michikazu Hara
• 刊名：The Journal of Physical Chemistry C
• 出版年：2013
• 出版时间：August 8, 2013
• 年：2013
• 卷：117
• 期：31
• 页码：16028-16033
• 全文大小：350K
• 年卷期：v.117,no.31(August 8, 2013)
• ISSN：1932-7455

文摘

Anatase TiO₂ prepared by a simple sol鈥揼el reaction of Ti(i-pro)₄ was studied as an early transition metal oxide with Lewis acid sites workable in water. Fourier transform infrared (FT-IR) measurements revealed that TiO₂ has a significantly higher density of effective Lewis acid sites in water than niobic acid (Nb₂O₅路nH₂O), a heterogeneous water-tolerant Lewis acid, because most Lewis acid sites on TiO₂ can maintain Lewis acidity even in the presence of water, which is in contrast to those on Nb₂O₅路nH₂O. TiO₂ as an easily separable and reusable heterogeneous catalyst that exhibits higher catalytic performance for the transformation of pyruvaldehyde into lactic acid and the allylation of benzaldehyde with tetraallyltin in water than Nb₂O₅路nH₂O, and the catalytic activity of TiO₂ is comparable to that of scandium trifluoromethanesulfonate (Sc(OTf)₃), a highly active homogeneous water-tolerant Lewis acid, despite the lower amount of effective Lewis acid sites. The high catalytic performance of TiO₂ for these reactions can be attributed to a high density of Lewis acid sites that can function in water.