(600bf) Upgrading of Biomass-Derived Aromatics in Aqueous Phase

Biomass, originated through CO₂ fixation by photosynthesis, is inherently oxygen rich[1]. Hence, further upgrading process to eliminate high oxygen content is required. One way to obtain desired biorenewable chemicals from biomass[2] is to design a hybrid process, utilizing high selectivity of biological reactions and high reactivity of thermochemical reactions. One proposed scheme starts from glucose[3], which can be enzymatically converted to an intermediate, myo-inositol[4]. Myo-inositol can be then further thermocatalytically dehydrated to polyols, such as phloroglucinol (1,3,5-trihydroxybenzene), which has potential to produce higher value chemicals, such as phenol and resorcinol.

Nobel metals, such as nickel, platinum, have been widely studied for hydrogenation of C-C, C=C, C-O bonds as well as aromatic molecules [5]. Using a Platinum catalyst, we find that the first step in upgrading phloroglucinol is hydrodeoxygenation to resorcinol and phenol, followed by hydrogenation of the aromatic ring. We show that hydrodeoxygenation is thermodynamically preferred to direct hydrogenation of the aromatic ring through molecular dynamics calculations. We believe that the steric hindrance, caused by the hydrogen bonding between phloroglucinol and surrounding water molecules, inhibits the direct hydrogenation of the aromatic ring. We also use reactive force field potential to model different reaction networks in both the gas and aqueous phase to discover the most probable reaction pathways for phloroglucinol hydrogenation. 

[1] P. H. Raven, R. F. Evert, and S. E. Eichhorn, Biology of plants. (New York: W.H. Freeman and Company Publishers, 2005) p. 124.

[2] A. J. Ragauskas, et al., Science 311, 484 (2006).

[3] S. Atssumi, T. Hanai, and J. C. Liao, Nature 451, 86 (2008).

[4] K. Sanderson, Nature 444, 673 (2006).

[5] J. C. Serrano-Ruiz, and J. A. Dumesic, Green Chem. 11, 1101 (2009).