Dehydration of Fructose to 5-Hydroxymethylfurfural Over Zeolite Catalysts with Carbon As Adsorbent

Cellulose-based biomass comprised of five-carbon (e.g. xylose) and six-carbon sugars (glucose) is an abundant, renewable resource that can be utilized to produce fuels and chemical feedstocks. One pathway for the conversion of cellulose-based biomass involves the dehydration of fructose to 5-hydroymethyl furfural (HMF) which can be used to the production of high value polymers such as polyurethanes and polyamides, as well as biofuels. Homogeneous mineral acids, such as hydrochloric acid, are being used to convert fructose to HMF, which is corrosive, toxic and suffers from other serious drawbacks, such as difficult separation and recycling of catalysts and product contamination. Furthermore, HMF can easily be further rehydrated to form levulinic and formic acid under continued exposure to the homogeneous acid catalysts. In order to increase the selectivity of HMF, biphasic reactor system has been developed and shown increased selectivity towards HMF with the organic solvent in situ extracting the HMF from the water phase. These organic extraction solvents are, however, generally hazardous and are required in great volume to perform the extraction. A system that uses environmentally benign heterogeneous acid catalysts (e.g. zeolites) and extraction techniques would be beneficial for this process. In this study, we develop a one pot process in which heterogeneous acid catalysts performs the dehydration of fructose and the produced HMF is protected from further rehydration by adsorbing on carbon materials. In addition to being environmentally benign, these heterogeneous catalysts and adsorbents do not require energy intensive separations processes to retrieve the HMF or recycle the catalyst. It is found that fructose can be hydrolyzed over different zeolite catalysts in water at 100°C to 165°C. HMF can be selectively adsorbed on carbon materials in the presence of fructose. The adsorption capacity of HMF on carbon materials can be varied with the carbon microstructures. The reaction results indicate that both the conversion of fructose and selectivity to HMF can be increased by adding the carbon materials into the reaction. The selectivity of HMF can be increased two times compared to the one without using adsorbents.