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

The delignification pathways during Organosolv pulping with and without involvement of supercritical carbon dioxide (scCO(2)) 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 scCO(2), the formation of stable end products was slowed down, which is explained by the stabilization of intermediates.