Online investigation of lignin depolymerization via reactor-integrated electrospray ionization high-resolution mass spectrometry

Abstract

Depolymerization of lignin can yield phenolic monomeric platform molecules, but depolymerization and repolymerization are proposed as concurrent processes, which greatly limit the yield of monomeric products. Molecular-level characterization of heavy intermediates during depolymerization process is crucial for developing efficient methods to depolymerize raw lignin into monomers. In this study, a reactor-integrated negative-ion electrospray ionization high-resolution mass spectrometry was used to real-time analyze the lignin depolymerization process under operando conditions. Elemental composition, structural information as well as time-resolved evolution of a series of dimers and oligomers were obtained, which is hard to achieve with traditional GC-MS methods. The real-time evolution profiles of monomers, dimers, and oligomers reveals a possible repolymerization process during lignin depolymerization. These results provide insight into the complex lignin depolymerization process.