Title:
New Heterogeneous Catalysts for Converting Sugars in Aqueous Media
New Heterogeneous Catalysts for Converting Sugars in Aqueous Media
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Author(s)
Davis, Mark E.
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Abstract
The isomerization of glucose into fructose is a large-scale reaction for the production of
high-fructose corn syrup and recently is being considered as an intermediate step in the
possible route of biomass to fuels and chemicals. Here, it is shown that a large-pore
zeolite that contains tin (Sn-Beta) is able to isomerize glucose to fructose in aqueous
media with high activity and selectivity. Specifically, a 10 wt% glucose solution
containing a catalytic amount of Sn-Beta (1:50 Sn:glucose molar ratio) gives product
yields of approximately 46% (w/w) glucose, 31% (w/w) fructose, and 9% (w/w)
mannose after 30 and 12 minutes of reaction at 383 K and 413 K, respectively. This
reactivity is also achieved when a 45 wt% glucose solution is converted. The Sn-Beta
catalyst can be used for multiple cycles, and the reaction stops when the solid is
removed, clearly indicating that the catalysis is occurring heterogeneously. With
isotopically labeled glucose, it is demonstrated (1H and 13C MAS NMR spectroscopy) that
the isomerization reaction catalyzed by Sn-Beta in water proceeds by way of an
intramolecular hydride shift, confirming that framework tin centers in Sn-Beta act as
Lewis acids in aqueous media. Most importantly, the Sn-Beta catalyst is able to perform
the isomerization reaction in highly acidic, aqueous environments with equivalent activity
and product distribution as in media without added acid. This enables Sn-Beta to couple
isomerizations with other acid-catalyzed reactions, including hydrolysis/isomerization or
isomerization/dehydration reaction sequences, including starch to fructose and glucose to
5-hydroxymethylfurfural (HMF).
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Date Issued
2011-03-10
Extent
52:20 minutes
Resource Type
Moving Image
Resource Subtype
Lecture