Understanding the Impact of Supercritical Carbon Dioxide on the Delignification Mechanism During Organosolv Pulping: A Model Compound Study

Abstract

The delignification pathways during Organosolv pulping with and without involvement of supercritical carbon dioxide (scCO₂) were studied with lignin model substances. As expected, the degradation rate of all model compounds depended strongly on the temperature, and model compounds carrying a “free” phenolic hydroxyl group were found to be significantly more reactive than their methoxylated, non-phenolic counterparts. Supercritical carbon dioxide was found to enhance the delignification process by lowering the activation energy and accelerating the model substance decay; therefore its application in Organosolv concepts appears reasonable and further studies are proposed. While consumption of the model compounds was accelerated by scCO₂, the formation of stable end products was slowed down, which is explained by the stabilization of intermediates.

Keywords:

• Organosolv
• supercritical carbon dioxide
• delignification
• lignin model compounds
• kinetics

Acknowledgments

The financial support by the Christian Doppler Research Society (CD-laboratory “Advanced Cellulose Chemistry and Analytics”) is gratefully acknowledged.