On mechanism of lignin decomposition – Investigation using microscale techniques: Py-GC-MS, Py-FT-IR and TGA

Abstract Lignin stands the most abundantly available source of renewable aromatic compounds which is generated as a useless waste by-product in numerous industrial processes, e.g., in pulp and paper manufacturing as well as during second-generation ethanol production. The present work aims to investigate the effect of reaction conditions (particularly the reaction atmosphere type) on the composition of the volatiles that evolved during the pyrolysis of lignin. The pyrolytic studies were carried out using coupled microscale techniques, i.e., Py-GC-MS, and Py-FT-IR. The pyrolysis is usually carried out under an inert atmosphere. Herein, there was additionally studied comprehensively the effect of oxidizing (CO2 and air) and reducing atmosphere (H2). There was found a profound impact of the processing temperature on the composition changes of volatiles. A minor effect was noted for the pyrolysis atmosphere on the qualitative composition of the volatiles, but certain quantitative differences between their concentration were observed. Their composition confirmed the complex molecular structure of lignin. Among the identified compounds, there were found phenol derivatives as primary products of cleavage of lignin structures as well as aliphatic oxygen compounds and aromatic hydrocarbons as the products of the secondary decomposition and deoxygenation thereof.