Formation of 5-(Hydroxymethyl)furfural by Stepwise Dehydration over TiO2 with Water-Tolerant Lewis Acid Sites

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• 作者：Ryouhei Noma ; Kiyotaka Nakajima ; Keigo Kamata ; Masaaki Kitano ; Shigenobu Hayashi ; Michikazu Hara
• 刊名：Journal of Physical Chemistry C
• 出版年：2015
• 出版时间：July 30, 2015
• 年：2015
• 卷：119
• 期：30
• 页码：17117-17125
• 全文大小：484K
• ISSN：1932-7455

文摘

The reaction mechanism for the formation of 5-(hydroxymethyl)furfural (HMF) from glucose in water over TiO₂ and phosphate-immobilized TiO₂ (phosphate/TiO₂) with water-tolerant Lewis acid sites was studied using isotopically labeled molecules and ¹³C nuclear magnetic resonance measurements for glucose adsorbed on TiO₂. Scandium trifluoromethanesulfonate (Sc(OTf)₃), a highly active homogeneous Lewis acid catalyst workable in water, converts glucose into HMF through aldose鈥搆etose isomerization between glucose and fructose involving a hydrogen transfer step and subsequent dehydration of fructose. In contrast to Sc(OTf)₃, Lewis acid sites on bare TiO₂ and phosphate/TiO₂ do not form HMF through the isomerization鈥揹ehydration route but through the stepwise dehydration of glucose via 3-deoxyglucosone as an intermediate. Continuous extraction of the evolved HMF with 2-sec-butylphenol results in the increase in the HMF selectivity for phosphate/TiO₂, even in highly concentrated glucose solution. These results suggest that limiting the reactions between HMF and the surface intermediates improves the efficiency of HMF production.