Ambient Pressure Microwave-Driven Catalytic Conversion of Lignin to Phenolic Blend for Soy Protein Adhesive Application

This work presents the first report on microwave-driven catalytic lignin depolymerization in the liquid phase at ambient pressure utilizing glycerol as the solvent. This process is notably swift, accomplishing approximately 89% lignin conversion in just 15 min. The process is efficient since solvents are recyclable, catalysts are regenerable, and there is no need for pressurized hydrogen. The phenolic blend was retained during its dissolution in the glycerol solvent, which was later vented from the hot-press cross-linking process with soy protein to create adhesives. The results from the single lap tests indicated a strong correlation between the bonding strength and solid content levels. The current formulation demonstrated that a solid content level of 68 wt % resulted in greater bonding strength than the commercial soy protein adhesive, which contains 34 wt % solid content. This study outlined a method for quickly transforming lignin waste into a phenolic blend at ambient pressure. The phenolic mixture can substitute a significant amount of soy protein, while improving the bonding strength of the soy-based adhesive.

Transforming waste lignin into a value-added phenolic blend for enhancing the bonding strength of soy protein adhesive.