Direct Production of Cyclohexanones from Lignin via Chlorine-Mediated Catalytic Hydroprocessing.

Area of Science:

• Catalysis
• Biomass Conversion
• Green Chemistry

Background:

• Lignin valorization is key for biorefineries.
• Producing cyclohexanones from lignin is challenging due to functional group removal and selective C=O bond retention.
• Existing methods struggle with efficiency and selectivity.

Purpose of the Study:

• To develop an efficient catalytic system for converting lignin into cyclohexanones.
• To overcome the challenges of deoxygenation and selective hydrogenation in lignin conversion.
• To advance the direct synthesis of ketone derivatives from biomass.

Main Methods:

• Utilized a chlorine-modified ZrO2 supported Pd catalyst (Pd-Cl/ZrO2).
• Optimized reaction conditions using poplar reductive catalytic fractionation (RCF) lignin oil.
• Investigated reaction mechanisms using model compound guaiacol.

Main Results:

• Achieved a 34.3 wt% yield of cyclohexanones from poplar biomass under mild conditions (200 °C).
• Demonstrated that trace HCl addition promotes dehydroxylation and milder reaction temperatures.
• Identified that chlorine species on the catalyst suppress aromatic ring hydrogenation and enhance ketone selectivity.

Conclusions:

• The Pd-Cl/ZrO2 catalyst efficiently and selectively converts lignin to cyclohexanones.
• The catalytic system operates under milder conditions, making it suitable for industrial applications.
• This work offers a novel pathway for producing valuable ketone derivatives from lignin, supporting sustainable biorefining.