This work presents recent developments on improving the performance of the HDO reaction of HMF to DMF in the presence of secondary alcohols able to provide in-situ generated H2. To effectively implement the conversion of biomass-derived sugars such as glucose and fructose to useful fuels and chemicals the process of sugar dehydration needs to be integrated with the downstream HDO reaction of HMF. As part of the RAPID (Rapid Advancement of Process Intensification Deployment) initiative at the University of Delaware a microchannel reactor is being developed capable of transforming glucose to DMF in a biphasic system. The microchannel concept enables the rapid extraction of HMF from the aqueous phase (where sugar dehydration takes place) to the organic phase (with the organic alcohol solvent providing the H2 equivalents necessary to reduce HMF to DMF). However, the rate of sugar dehydration is significantly faster than the corresponding rate of HDO to DMF. As such, a superior HDO catalyst needs to be synthesized capable of efficiently dehydrogenating the alcohol solvent, as well as performing the HDO reaction at rates equivalent to the sugar dehydration, all while remaining exclusively within the organic phase, thus necessitating a hydrophobic character. In a first step, a carbon support with hydrophobic character was identified via water vapor adsorption, followed by wet impregnation with the Ru precursor and testing in a neat alcohol environment. Interestingly, the chosen catalysts showed a product distribution vastly different from the standard commercial Ru/C catalyst. Rather than to the hydrophobicity, this was attributed to the presence of acid sites on the carbon support that were able to modulate the reaction chemistry in the presence of alcohol facilitating higher selectivities towards DMF than were obtainable on the conventional catalyst. While the impact of hydrophobicity appeared, in a first instance, to be of no consequence on the reaction outcome, the presence of water in the system nonetheless was shown to have a significant effect in affecting the overall selectivity towards DMF. The implications of this and other considerations for the design of an effective catalyst will be discussed.

Role of the support and the solvent on the transfer hydrodeoxygenation of HMF to DMF on carbon supported ruthenium catalysts.

2019 Spring National Meeting

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