(438d) Enhanced Electrochemical Hydrodeoxygenation of Bio-Oil Model Compounds Using Bimetallic Platinum Catalysts

The production of renewable fuels has become necessary as fossil fuels continue to deplete past the point of no return.¹ Bio-oils derived from the fast pyrolysis of biomass represent a promising source of renewable and sustainable, carbon-neutral chemicals and fuels. Pyrolysis oils, however, struggle from low yields and increased heteroatom content.² To solve this problem a second upgrading step is needed which increases the fuel’s hydrogen content and removes heteroatoms. Conventional oil upgrading has been done through thermochemical processes using high temperatures (>300 °C) and high-pressure hydrogen (10-20MPa).³ Electrochemical hydrodeoxygenation (EC-HDO) is a promising method for upgrading biomass derived oxygenates into biofuels at near ambient conditions without the need for external hydrogen (H2).3 Though initial results on electrocatalytic upgrading have been promising few researchers report appreciable yields of fully deoxygenated products and the efficiency remains low at high current densities.³

This work presents the upgrading of phenol and guaiacol as bio-oil model compounds. EC-HDO of phenol and guaiacol were investigated in a custom electrochemical cell (H-Cell), wherein the anode and cathode are separated by a Nafion® 117 membrane. Preliminary results on the EC-HDO of phenol using a lab synthesized PtRu-C catalyst showed that after 4 hours of electrolysis at -0.46 V vs Ag/AgCl cyclohexane selectivity reaches 31%. Further EC-HDO experiments were performed using lab synthesized Pt and Ru catalysts to investigate the role of active metal on cyclohexane selectivity. These results (figure 1) showed that the lab synthesized PtRu catalyst produced the highest cyclohexane selectivities (31%), highest conversion (100%) and efficiencies (35%). Additional experiments on EC-HDO of guaiacol showed that using the lab synthesized PtRu-C catalyst resulted in a cyclohexane selectivity of 34%. Our preliminary results indicate that the addition of metals to Pt-C catalysts can increase phenol EC-HDO performance and cyclohexane selectivity. Our current work is focused on the development of new bimetallic catalysts for the enhancement of cyclohexane productions such as PtCo, PtNi, and PtCu. Additionally, experimental results will be presented using guaiacol as a model compound to show how the bimetallic catalysts affect the EC-HDO of various functional groups.

References

(1) Zhang, X.; Lei, H.; Chen, S.; Wu, J. Catalytic Co-Pyrolysis of Lignocellulosic Biomass with Polymers: A Critical Review. Green Chemistry. 2016. https://doi.org/10.1039/c6gc00911e.

(2) Zhang, B.; Zhong, Z.; Min, M.; Ding, K.; Xie, Q.; Ruan, R. Catalytic Fast Co-Pyrolysis of Biomass and Food Waste to Produce Aromatics: Analytical Py-GC/MS Study. Bioresour. Technol. 2015, 189. https://doi.org/10.1016/j.biortech.2015.03.092.

(3) Chen, G.; Liang, L.; Li, N.; Lu, X.; Yan, B.; Cheng, Z. Upgrading of Bio-Oil Model Compounds and Bio-Crude into Biofuel by Electrocatalysis: A Review. ChemSusChem. 2021. https://doi.org/10.1002/cssc.202002063.