(399f) Reaction Pathways for Biomass Derived Furanic Compounds on Ru(001) Surfaces:  a DFT Study

The rapid depletion of fossil fuel resources globally, coupled with a growing energy demand has led to the search for alternative sustainable fuel sources. Fast pyrolysis of lignocellulosic biomass is being considered as an effective and low cost alternative for the production of liquid transportation fuels and chemicals. However, the bio-oil produced from pyrolysis is unsuitable for direct use due to its poor stability and low energy density, arising from its high oxygen content. Hydrodeoxygenation (HDO) is an effective technique for upgrading the bio-oil in a hydrogen rich atmosphere in which the oxygen groups are replaced with hydrogen atoms. Supported Ruthenium catalysts are excellent catalysts for the HDO process^1-3. Insights into the underlying mechanism of the hydrodeoxygentation reaction are essential for controlling the activity and selectivity of the Ru catalyst. In this study, we focus on the potential reactions and products in the catalytic conversion of furfural, a model compound derived from bio-oil, with hydrogen over Ru(001) surface using Density Functional Theory (DFT). The energetics of multiple reaction pathways, including aliphatic side chain and furan ring C-O hydrogenolysis, C-C hydrogenation, C-C scission and the structural rearrangement of furfural to pentane diols and cyclic ketones were analysed. Hydrogenation of the aldehydic side chain of furfural to form furfuryl alcohol and the C_ring-C bond scission are not facile on Ru surfaces since these reactions are associated with high barriers (~200 kJ/mol). In contrast, hydrogenolysis of the C-O bond in the aldehyde side chain and in the furanic ring, has barriers of around 100 kJ/mol. The moderate ring opening barriers provides a low energy reaction pathway for the formation of 1,5 pentane diol, 1,2 pentane diol, cyclopentanone and cyclopentanol which have been observed experimentally on supported Ruthenium catalysts^4-5.

1. Wildschut, J.; Mahfud, F. H.; Venderbosch, R. H.; Heeres, H. J. Ind. Eng. Chem. Res. 2009, 48, 10324â??10334.
2. Wildschut, J.; Melian-Cabrera, I.; Heeres, H. J. Appl. Cat. B. 2010, 99, 298-306.
3. Oh, S.; Hwang, H.; Choi, H. S.; Choi, J. W. Fuel 2015,153, 535-543
4. Elliott, D. C.; Hart, T. R.; Energy and Fuels 2009, 23, 631-637.
5. Nan, W.; Krishna, C. R.; Kim, T-J; Wang, L. J.; Mahajan, D.; Energy and Fuels 2014, 28, 4588-4595