Gluconic acid, an important compound in chemical and pharmaceutical industry, can be produced from cellulosic biomass. [1-3] In this study, we combine density functional theory (DFT) calculations and experiments to investigate the catalytic mechanism of the oxidation of glucose to gluconic acid on CuO catalyst. CuO nanoleaves are successfully synthesized and are characterized by XRD, SEM, TEM, NH3-TPD and BET. The catalyst is tested for the glucose oxidation reaction under neutral pH conditions at 2000C in a batch reactor. 100% conversion of Glucose with 67% selectivity towards gluconic acid is achieved within 30 min of reaction time. However, the selectivity for gluconic acid drops significantly after 30 min and XRD patterns shows that CuO is reduced to Cu. The catalyst can be reactivated by high pressure O2 treatment which oxidizes Cu back to CuO. To shed light on the mechanism of glucose oxidation on CuO catalysts, DFT calculations are performed. First-principles calculations reveal that glucose strongly binds to CuO(111) surface via the 3 coordinated surface oxygen atom, which facilitates the C-H dissociation with an activation energy barrier of 87 kJ/mol. The chemisorbed dehydrogenated glucose acts as a reducing agent by combining with the surface lattice oxygen atom to form gluconate, and reduce CuO to Cu. After being reduced, Cu is not active towards glucose oxidation. Due to the lack of lattice oxygen, glucose only binds weakly with Cu(111) surface, and the activation barrier for C-H dissociation increases to 141 kJ/mol. The dehydrogenated glucose can combine with oxygen chemisorbed on Cu(111) to form gluconate; however this step is challenging with a high activation barrier of 138 kJ/mol, consistent with the strong binding of oxygen on Cu(111) surface, reported earlier in the literature. [4] DFT calculations reveal that the surface lattice oxygen of CuO directly participates in the reaction and oxidizes glucose to gluconic acid. The computational results not only provide mechanistic understanding of the reaction mechanism but also explain why the O2 treated catalyst regains its activity for glucose oxidation. References: 1. Mushrif S. H., Vasudevan V., et al., Chem. Eng. Sci. 2014, In press 2. Climent M. J., Corma A. et al., Green Chem. 2011,13, 520–540,. 3. Wang F., Wang Y., et al., Ind. Eng. Chem. Res. 2014, 53, 7939−7946. 4. Soon A., Todorova M. et al. Phys. Rev. B 2006, 73, 165424

Investigating CuO catalyzed oxidation of glucose to gluconic acid using an integrated computational and experimental approach: Insights into the role of lattice oxygen

249th National Meeting (2015)

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