Plasma-based ozonolysis of lignin waste materials for the production of value-added chemicals

Lignin is the second most abundant and underutilized heterogeneous biopolymer. Current methods, to depolymerize lignin into valuable fuels and chemicals, are facing challenges. The major barriers to the commercialization of these methods are expensive catalysts, energy cost, and difficulty in the separation of a complex mixture of products. Targeted synthesis of chemicals is aimed to get selective compounds that may offer ease of separation. Vanillin is the only chemical that is manufactured commercially from lignin. A facile, highly efficient, room temperature, and metal-free route to the targeted synthesis of vanillin using ozone produced by non-thermal plasma is presented in the current study. The recovered lignin has been characterized by FTIR, SEM/EDX, and HSQC for determining structural changes. The recovered lignin with a loose structure can be further converted into more valuable products. Operational conditions have been investigated to optimize vanillin production. Under optimum conditions, similar to 60% of vanillin (based on GC-MS analysis) was obtained with only 10 min of treatment. The product selectivity has been controlled by reaction time and reactant lignin concentration. The recovered lignin having a partially oxidized structure can be further subject to depolymerization to get more value from this biopolymer.