Depolymerization of lignin into cycloalkanes over a hydrotalcite-derived NiFe alloy catalyst

Abstract

Herein, an Ni₉Fe₁/NiAlO_z catalyst is reported to be an efficient catalyst for conversion of enzymatic hydrolysis lignin (EHL) and 2-phenethyl phenyl ether (PPE), a lignin dimer model compound. Interspecies electron transfer within the alloy phase enhances the intrinsic hydrogenation activity of Ni, while Fe doping generates abundant interfacial oxygen vacancies (OVs). The combination of H* from high-intensity hydrogen spillover and abundant OVs promotes the depolymerization of EHL into cycloalkanes. Because of this combination, Ni₉Fe₁/NiAlO_z achieves 99.4% of PPE conversion under mild reaction conditions (100 °C, 0.8 MPa H₂, and 3 h) and achieves the yield of cycloalkanes (169.5 mg per g EHL at 300 °C) from EHL that exceeds the theoretical yield. The catalyst is also stable for 6 runs without much deactivation. This strategy provides new insights into the rational design of an efficient and stable transition metal catalyst using a simple preparation method for the valorization of EHL.