Spatially Orthogonal Metal-Zeolite Catalysts for One-Step Phenol Synthesis from Birch Lignin Oil

Area of Science:

• Catalysis
• Renewable Energy
• Chemical Engineering

Background:

• Current phenol production relies on the energy-intensive cumene process using fossil resources.
• Lignin, a renewable aromatic source, offers a sustainable alternative but faces challenges in direct conversion to phenol.
• Existing methods struggle with low reactivity of syringyl (S)-type lignin monomers and integrating essential catalytic steps like demethoxylation and dealkylation.

Purpose of the Study:

• To develop a novel catalyst for the direct, one-step conversion of lignin to phenol.
• To overcome the limitations of poor syringyl monomer reactivity and catalyst deactivation.
• To achieve high yields and stability in producing phenol from renewable lignin sources.

Main Methods:

• Development of a spatially orthogonal metal-zeolite catalyst.
• Utilizing highly enriched Molybdenum (Mo⁰) sites for selective methoxy removal from lignin monomers.
• Employing a silica-encapsulated HZSM-5 zeolite structure to protect acid sites and prevent coking.

Main Results:

• The catalyst achieved selective methoxy removal from both guaiacyl (G)- and S-type lignin monomers via Mo⁰ sites and hydrogen spillover.
• The encapsulated HZSM-5 nanosheets preserved Brønsted acid sites for efficient dealkylation, preventing catalyst deactivation.
• Near-quantitative conversion of both monomer types was achieved, enabling the first direct one-step phenol production from birch lignin oil with high yield and stability.

Conclusions:

• The developed metal-zeolite catalyst successfully addresses the challenges of direct lignin-to-phenol conversion.
• This breakthrough offers a stable and efficient route for producing phenol from renewable lignin biomass.
• The findings pave the way for sustainable chemical manufacturing, reducing reliance on fossil fuels.