Process-Decoupled Operando Molecular Characterization of Liquid-Phase Lignin Depolymerization by Online...

Area of Science:

• Chemical Engineering
• Materials Science
• Biomass Conversion

Background:

• Lignin, an abundant biopolymer, is underutilized due to its complex structure.
• Catalytic depolymerization of lignin is challenging due to structural heterogeneity and limited intermediate accessibility.

Purpose of the Study:

• To investigate the molecular-level details of alkali Kraft lignin depolymerization.
• To elucidate structure-reactivity relationships during catalytic depolymerization using advanced analytical techniques.

Main Methods:

• Utilized a decoupled double-bed flow-through reactor for spatial separation of reactions.
• Integrated online high-resolution mass spectrometry (HRMS) for real-time product analysis.
• Employed van Krevelen diagrams and tandem MS for detailed structural elucidation.

Main Results:

• Online HRMS resolved thousands of molecular species, from monomers to heptamers.
• Catalytic hydrogenolysis significantly reduced polymer degree and unsaturation.
• Identified extensive hydrogenation, partial deoxygenation, and cleavage of β-O-4 linkages, with C-C linkages largely preserved.

Conclusions:

• Online HRMS is a powerful operando tool for studying lignin depolymerization.
• Flow-through conditions suppress recondensation and promote depolymerization.
• Provided molecular-level insights for efficient biomass valorization.