Electrocatalytic conversion of G-type and S-type phenolic compounds from different tree species in a heteropolyacid fluidized system

Han, Shuangmei and Zhang, Xiaolei and Wang, Ruizhen and Wang, Kui and Jiang, Jianchun and Xu, Junming (2023) Electrocatalytic conversion of G-type and S-type phenolic compounds from different tree species in a heteropolyacid fluidized system. Chemical Engineering Journal, 452 (Part 2). 139299. ISSN 1385-8947 (https://doi.org/10.1016/j.cej.2022.139299)

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Abstract

The electrocatalytic hydrodeoxygenation (ECH) of lignin typical model compounds and lignin-derived oil from different tree species into (alkyl)-cyclohexane and (alkyl)-cyclohexanol in the fluidized electrocatalysis system were investigated in this research. The selected model compounds include two G-type compounds: eugenol (EO) and guaiacol (GO), and two S-type compounds: 4-allyl-2,6-dimethoxyphenol (4-DMP) and 2,6-dimethoxyphenol (2,6-DMP). This ECH system consisted of phosphotungstic acid (PW12) electrolyte, catalyst that suspended in the electrolyte, and NaBH4 reductant in the cathode. The results showed that 4-DMP could be converted using Pt/C as the catalyst at 25 mA/cm2 current density and 80°C for 60 min, with higher faradaic efficiency of 90% and the selectivity of PCH and 4-PCH was 62% and 20%, respectively. For CO bond cleavage, the DFT calculations showed that, for EO, GO, and 4-DMP, the C-OCH3 bond will be firstly broken, while for 2,6-DMP, it is preferred that C-OH bond will be firstly broken. It was found that G-type (EO, GO) was more easily hydrodeoxygenated than S-type (4-DMP, 2,6-DMP) compounds, with the reaction rate in the order of GO > EO > 2,6-DMP > 4-DMP, indicating that the allyl group had a negative effect on the electrocatalytic conversion. Furthermore, it was also found that the complete conversion of lignin-derived oil monomers of pine (mainly G-type) and poplar (mainly S-type) can be achieved, with the yield of target products (PCH and 4-PCH) of 64% and 43%, respectively. Overall, this work innovatively integrates biomass refining and electrocatalytic upgrading, which provides a green and environmentally friendly solution for lignin conversion and utilization.

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