Catalytic Isomerization/Dehydration of Sugars On Functionalized CNT-Metal Oxide Hybrids At the Liquid-Liquid Interface of Water/Oil Emulsions
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The conversion of C5-C6 sugars into 2-furfural (FA) and 5-hydroxymethylfurfural (HMF) have been considered as key intermediate step in the production of transportation fuels and chemicals from ligno-cellulosic biomass. Typically, the process involves the dehydration reaction of the sugars catalyze by strong acids, albeit this approach results in loss of selectivity due to the instability of the intermediate species in such acidic conditions. An alternative catalytic strategy is the isomerization of the sugars into the xylofuranose and ribose isomers on a basic catalyst, followed by the dehydration reaction on a weak acid. Recently, we have shown that amphiphilic nanohybrid catalysts based on Carbon Nanotubes (CNT) fused to inorganic oxides can stabilize water/oil emulsions and catalyze reactions at the water/oil interface when properly functionalized [1,2,3,4]. In the present contribution we report a new family of amphiphilic-bifunctional catalysts based on sulfonic- and amine- functionalized CNT fused to metal oxides. These nanohybrid materials are able to perform the isomerization and dehydration of the C6-C5 sugars in a biphasic system with high selectivity. Several advantages are obtained when this unique system is used, such as, enhanced mass transfer between the phases, selective conversion of molecules in each of the phases (phase selectivity), direct partitioning and separation of products, leading to substantial simplification of the purification stages.
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