Selective depolymerization of lignosulfonate via hydrogen transfer enhanced in an emulsion microreactor

Area of Science:

• Chemical Engineering
• Polymer Chemistry
• Sustainable Chemistry

Background:

• Lignosulfonate, a byproduct of the paper industry, is an abundant source of aromatic compounds.
• Current methods for lignosulfonate depolymerization often lack efficiency and selectivity.
• Valorization of lignosulfonate is crucial for a circular bioeconomy.

Purpose of the Study:

• To develop an efficient emulsion microreactor for lignosulfonate conversion.
• To investigate the selective depolymerization of lignosulfonate via hydrogen transfer.
• To enhance the production of volatile phenolic monomers from lignosulfonate.

Main Methods:

• Construction of an emulsion microreactor utilizing the self-surfactivity of lignosulfonate.
• Employing industrial Raney Nickel as a catalyst and isopropanol as a hydrogen donor.
• Conducting the hydrogen transfer reaction under mild conditions (473 K for 2.0 h).

Main Results:

• Achieved a remarkable process intensification effect on lignosulfonate depolymerization.
• Obtained 116.1 mg/g⁻¹ of volatile phenolic monomers, doubling yields compared to non-emulsion processes.
• Isolated 39.3 mg/g⁻¹ of 4-ethyl guaiacol, a valuable chemical feedstock.
• Observed automatic phase separation post-reaction for easy product enrichment and separation.

Conclusions:

• The emulsion microreactor demonstrates significant process intensification for lignosulfonate conversion.
• This method offers a highly efficient route to valuable phenolic monomers, including 4-ethyl guaiacol.
• The system shows promise for other lignin sources and highlights the importance of the hydrogen donor.