Catalytic refining lignin into toluene over atomically dispersed Cu/Ni dual sites

Abstract

Lignin refining still suffers from great challenges of selective depolymerization and cleavage of stubborn C‒C linkages. Here, a robust atomically dispersed Cu/Ni-SA@HNC catalyst is fabricated for super-selective hydrogenolysis of lignin and model compounds via an unusual “preferential C_α–C_β bond cleavage in β-O-4 linkages” pathway, affording toluene in yield up to 75.7% from β-O-4 model compounds, and up to 33.7 ± 1.6 wt% (nine parallel experiments) from poplar lignin. The catalyst exhibits high stability, and the scale-up potential is demonstrated by the high space-time yield of toluene (33.7 g·g_cat⁻¹·h⁻¹) in continuous flow reaction of β-O-4 model compound. The origin of the extraordinary selectivity towards C_α–C_β bond cleavage rather than C‒O bond cleavage in β-O-4 model compounds is uncovered. This work conquers the major challenges in lignin valorization by using non-noble dual-metal single-atom catalyst, not only showcasing the application perspective of atomically dispersed catalysts in biopolymer refinery, but also providing a cost-efficient, petroleum independent solution to valuable commodity chemicals.