2025 AIChE Annual Meeting

(572e) Non-Noble Based Hydrotalcite Catalysts for Catalytic Depolymerization of High-Molecular-Weight Lignin to SAF-Range Hydrocarbons

Authors

Sung Bong Kang, School of Earth Sciences and Environmental Engineering, Gwangju Institute of Science and Technology
Charles M. Cai, University of California
Arthur Ragauskas, University of Tennessee
Chang Geun Yoo, State University of New York College of Environmen
Lignin, the most abundant aromatic biopolymer on Earth, represents a promising renewable feedstock for aromatic and cyclic hydrocarbons. Despite its high energy density and chemical functionality, its effective conversion into high-performance fuels has been limited by its heterogeneity and recalcitrance to depolymerization. The valorization of lignin into liquid fuels could significantly enhance the carbon and energy efficiency of biomass conversion processes. In particular, the production of sustainable aviation fuels (SAFs) from lignin-derived naphthenic and cycloalkanes has gained increasing attention. However, selective depolymerization of the high-molecular-weight-lignin (HMWL) into stable, fuel-range hydrocarbons remains a significant challenge.

In this study, we introduce a series of hydrotalcite-like copper-based porous metal oxide (CuPMO) catalysts, tailored for the depolymerization of HMWL lignin into SAF-range naphthenic and cycloalkanes via the thermic oxygen removal (AOR)—a non-hydrogenate lignin depolymerization strategy that employs supercritical alcohol as both solvent and hydrogen donor under thermochemical conditions.

The CuPMO catalysts were synthesized by a co-precipitation method, systematically varying both the Mg2+/Al3+ molar ratios (0.5–3) and Cu loadings (10–20 wt.%). The catalysts are denoted as CuxPMOy, where x represents the Cu loading and y indicates the Mg2+/Al3+ molar ratio. The catalytic depolymerization and deoxygenation performance of the CuxPMOy series catalysts was evaluated in AOR reactor under supercritical methanol (<350 ℃), without external hydrogen, using HMWL obtained from CELF (co-Solvent enhanced lignocellulosic fractionation) pretreatment. The crystal structure and chemical state of the catalyst were characterized by BET, XRD and XPS analysis. And the reducibility and basicity of the catalysts were measured by the temperature programming method (H2-TPR and CO2-TPD).

The catalytic behavior and physicochemical characteristics of the CuPMO catalysts varied noticeably with changes in Mg2+/Al3+ molar ratio and Cu loading. These compositional differences influenced key properties such as acid–base balance, surface area, and metal dispersion. As a result, the catalysts exhibited tunable acid–base properties, high surface area, and excellent metal dispersion, which contributed to high selectivity toward cycloalkanes and cyclohexyl alcohols with efficient deoxygenation.

This work offers a practical and economically viable pathway for lignin valorization toward SAF production by employing a non-noble metal-based CuPMO catalytic platform. The process is compatible with existing biorefinery infrastructure, thereby enhancing its scalability and potential for commercial deployment. Comprehensively, these findings highlight the promise of Cu-based catalysts as a cost-effective and scalable solution for producing SAF-comparable fraction from lignin.