Effect of Transition Metal Catalyst On Lignin Oxidation During Alkaline Hydrogen Peroxide Pretreatment

Biomass lignocellulose can be used as feedstock for bioethanol production, and a pretreatment is necessary for achieving high ethanol yield and economical feasibility. As a method to increase enzyme digestibility of biomass by selective delignification, alkaline hydrogen peroxide (AHP) pretreatment has been proposed and studied. The lignin recalcitrance in lignocellulose biomass can be removed by H₂O₂ oxidation and the enzymatic hydrolysis efficiency of the polysaccharides can be greatly improved. However, a big issue with AHP pretreatment is the high cost of hydrogen peroxide during the pretreatment, and the selectivity of the oxidant need to be improved, i.e. to achieve highest pretreatment efficiency with low level of H₂O₂ loading.

In 1890s, Fenton discovered that iron ion can catalyze the oxidation of organic substrate by hydrogen peroxide. Since then, research has been done on the application of transition metal catalysts in catalyzing the phenol contaminant in wastewater and pulp bleaching. It is desired that catalyst can enhance selective electron transfer from lignin substrate to the oxidant and improve the selectivity of delignification reactions to unproductive side reactions.