(167g) Aqueous-Phase Hydrodeoxygenation Activity of Pd/ZrO2 Catalysts

Aqueous-phase Hydrodeoxygation Activity of Pd/ZrO₂ Catalysts

Changjun Liu^†, Oscar Marin^†, Ayman M. Karim ^*‡, Heather Brown^‡ and Yong Wang ^*†,‡

^† The Gene & Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman Washington 99164, United States

^‡ Institute for Interfacial Catalysis, Pacific Northwest National Laboratory, Richland, Washington 99352, United States

Keywords: Aqueous-phase hydrodeoxygenation, bifunctional catalyst, biomass, zirconia

To meet the increase in worldwide energy demand, new processes that use a sustainable resource such as lignocellulosic biomass need to be developed ¹. A common step in all the processes that currently exist for the thermochemical conversion of biomass to liquid fuels/chemicals, (e.g. liquefaction fast pyrolysis/catalytic fast pyrolysis, and aqueous phase conversion of carbohydrates), is oxygen removal by hydrodeoxygenation (HDO). Our focus is on the aqueous phase HDO of sugar streams generated from the hydrolysis of biomass. Well-developed hydrolysis processes are capable of deconstructing the cellulose and hemicellulose in lignocellulose into their corresponding sugars (e.g., glucose, fructose, xylose, and et al.) and separate them from lignin². Selective removal of oxygen from these biomass-derived compounds (monoses/polyols) is one of the key challenges in converting them into fuels and valuable chemicals³. Bifunctional catalysts with appropriate metallic and acidic sites were found capable of catalyzing the aqueous-phase HDO of polyols⁴. Wide ranges of Pt promoted solid acid catalysts have been tested⁵. However, in order to improve the selectivity to mono-oxygenates further understanding of the HDO reaction mechanism is required.

In this work, Pd/ZrO₂ catalysts promoted by various metal oxides (SnO₂, MoO₃, WO₃) were studied in the aqueous-phase hydrodeoxygenation of polyols with focus on its selectivity to C-O cleavage and C-C cleavage. Ethylene glycol and glycerol were used as model compounds of polyols to simplify the reaction routes and products. The interaction between Pd and WO₃-ZrO₂, the effects of palladium particle size, and the promotion effect of three metal oxides in aqueous-phase HDO of polyols were elucidated. The structures of the catalysts were characterized by CO FTIR and in situ XAFS. Addition of Sn was found to affect the Pd structure and accessibility due to PdSn alloy formation. The effect of the reaction conditions on the Pd and Sn structure and oxidation state will be discussed and correlated with the reaction pathways.

 *Corresponding author

References

1.      Huber, G. W.; Dale, B. E., Grassoline at the Pump. Sci.Am. 2009, 301 (1), 52-56.

2.      (a) Huber, G. W.; Iborra, S.; Corma, A., Synthesis of transportation fuels from biomass:  chemistry, catalysts, and engineering. Chemical Reviews 2006, 106 (9), 4044-4098; (b) Sun, Y.; Cheng, J., Hydrolysis of lignocellulosic materials for ethanol production: a review. Bioresource technology 2002, 83 (1), 1-11.

3.      Chen, L.; Zhu, Y.; Zheng, H.; Zhang, C.; Zhang, B.; Li, Y., Aqueous-phase hydrodeoxygenation of carboxylic acids to alcohols or alkanes over supported Ru catalysts. Journal of Molecular Catalysis A: Chemical 2011, 351 (0), 217-227.

4.      (a) Huber, G. W.; Cortright, R. D.; Dumesic, J. A., Renewable alkanes by aqueous-phase reforming of biomass-derived oxygenates. Angewandte Chemie International Edition 2004, 43 (12), 1549-1551; (b) Li, N.; Huber, G. W., Aqueous-phase hydrodeoxygenation of sorbitol with Pt/SiO2-Al2O3: Identification of reaction intermediates. Journal of Catalysis 2010, 270 (1), 48-59.

5.      Li, N.; Tompsett, G. A.; Zhang, T.; Shi, J.; Wyman, C. E.; Huber, G. W., Renewable gasoline from aqueous phase hydrodeoxygenation of aqueous sugar solutions prepared by hydrolysis of maple wood. Green Chemistry 2011, 13 (1), 91-101.