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CPOTE2020 logo
6th International Conference on
Contemporary Problems of Thermal Engineering
Online | 21-24 September 2020

Abstract CPOTE2020-1060-A

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

Mariusz WĄDRZYK, AGH University of Science and Technology, Poland
Rafał JANUS, AGH University of Science and Technology, Poland
Marek LEWANDOWSKI, AGH University of Science and Technology, Poland
Aneta MAGDZIARZ, AGH University of Science and Technology, Poland

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 or during second-generation ethanol production. However, as lignin is the most thermally stable component of the lignocellulosic biomass, there is still no reasonable technology of its sustainable utilization. One of the most prospective methods to overcome its thermal stability and opening the way of its transformation into value-added chemicals is the pyrolysis process. The aim of the present work is to investigate the effect of reaction conditions on the composition of the volatiles evolved during the pyrolysis of lignin. We especially focused on the assessment of the optimal conditions for the production of low-molecular aromatics i.e. benzene, toluene, which can be easily incorporated into the existing industrial processes. The pyrolytic investigation studies were done using coupled microscale techniques i.e. pyrolysis – gas chromatography/mass spectrometry (Py-GC-MS), and pyrolysis – Fourier Transform Infrared Spectroscopy (Py-FT-IR). For both series, we used a direct mode where the entities formed were directly transferred to analysis. Additionally, the investigations were complemented by performing the TGA of raw material. It allows us to the complementary investigation of the decomposition mechanism. We tested the effect of processing temperature ranging between 300-700 °C on the composition of volatiles evolved during flash pyrolysis. The pyrolysis is usually carried out under an inert atmosphere. Herein, we additionally studied comprehensively the effect of the oxidizing atmosphere (CO2). Subsequently, based on the resultant data, we postulated the likely pathways of the reactions occurring during the decomposition of the raw material. We have found a profound impact of the processing temperature on the composition changes of volatiles. The minor effect was noted for the pyrolysis atmosphere on the qualitative composition of the volatiles but certain quantitative differences between the concentrations of them were observed. Their composition confirmed the complex molecular structure of the lignin. Among the identified compounds we have found phenol derivatives as primary products of cleavage of lignin structures as well as aromatic hydrocarbons as the products of the secondary deoxygenation thereof.

Keywords: Lignocellulosic biomass conversion, Lignin, Pyrolysis, Thermochemical conversion, Waste to biofuels
Acknowledgment: This paper was prepared under the support of the National Science Centre in Poland within the grant number 2019/03/X/ST4/01509. The research was carried out using the infrastructure of the AGH Centre of Energy, AGH University of Science and Technology.