Mechanistic Insight into Lignin Slow Pyrolysis by Linking Pyrolysis Chemistry and Carbon Material Properties

Abstract

As a highly abundant renewable carbon source, lignin can be converted to a variety of advanced carbon materials with tailorable properties through slow pyrolysis. In this study, slow pyrolysis of kraft lignin, for the first time, was investigated with a commercial pyrolysis–gas chromatography–mass spectrometry (Py–GC–MS) system through evolved gas analysis-MS (EGA-MS) and heart-cutting-GC–MS (HC-GC–MS) analyses. These analyses allow recovery and examination of the multiphased gas products generated from thermal decomposition of lignin during slow pyrolysis at a controlled heating rate over a long time course, thus making it possible to link operation conditions, pyrolysis chemistry, and carbon material properties. The overall product distributions, including volatiles and solid products, were quantitatively tracked at different heating rates (2, 20, and 40 °C/min) and different temperature regions (100–200, 200–300, and 300–600 °C). Solid residues were further characterized using a suite of analytical tools, in correlation with the investigation of formation mechanisms of volatiles to reveal the reaction chemistry of lignin during slow pyrolysis and to determine the morphology, pore structure, and interfacial chemical properties. This study provides critical insights into the slow pyrolysis chemistry of lignin and the properties of the resulting carbon material. These results will facilitate a better design and control of the lignin slow pyrolysis process for synthesizing functional carbon materials.

Engineering Lignin-Derived Carbon–Silicon Nanocomposite Electrodes: Insight into the Copyrolysis Mechanism and Process–Structure–Property–Performance Relationships

“…Slow pyrolysis is widely applied in the synthesis of functional carbon materials. The microstructure, the physiochemical and mechanical properties, and the electrochemical performance of the synthesized materials are dependent on the pyrolysis conditions such as temperature and heating rate . It is critical to correlate the pyrolysis conditions with the material properties.…”

“…Table S1 shows the yields of GC–MS detectable volatile compounds and solid residues from copyrolysis of KL and Si NPs at 2 °C/min ramp in the temperature ranges of 100–500 and 500–800 °C, respectively, of which 40 compounds were identified and quantified. For comparison, as shown in Table , the 40 compounds evolved through pyrolysis of KL and KL/Si NPs from 100 to 800 °C at 2 °C/min were classified into seven categories with detailed formation mechanisms of each category from slow pyrolysis according to a previous study . No noticeable difference in both composition and yield could be observed between pyrolysis of KL and KL/Si NPs in the temperature range of 100–500 °C, suggesting that the reactions were more related to lignin pyrolysis although the interactions between Si NPs and lignin-derived carbon may have started playing a role.…”

“…Schematic diagrams of (a) EGA–MS and (b) HC–GC–MS in this study; (c) fast pyrolysis of KL and KL/Si NPs (1:1) at 600 °C; EGA–MS profiles for pyrolysis of (d) KL/Si NPs and (e) KL/SiO NPs from 100 to 800 °C with a 2 °C/min ramp.…”

The pyrolysis of oak with polyethylene, polypropylene and polystyrene using fixed bed and stirred reactors and TGA instrument

“…Thermo-gravimetric Analysis (TGA) can be widely used as a desirable method in assessing the thermal stability of various materials and their mixtures [26,27]. TGA instruments are widely used to study the degradation trend and mechanisms of natural and synthetic polymers and their blends under different conditions [28].…”

“…During wood degradation, hemicellulose and cellulose are degraded at relatively high rates, respectively, while lignin tends to lose weight under low rate during 200e800 C [26]. Under the mechanism of cross-linking and carbonization, a part of the wood structure especially lignin is converted to charcoal [31,32].…”