Thermal Carbon Analysis Enabling Comprehensive Characterization of Lignin and Its Degradation Products

Abstract

We have developed a novel thermal carbon analysis (TCA) method that provides both carbon mass balance and thermal fractionation profiles. Though not providing chemical structural information, this method enables a comprehensive characterization of both lignin and its degradation products, potential renewable and sustainable feedstocks. TCA is essential as a complement to a qualitative chemical speciation by thermal desorption–pyrolysis gas chromatography–mass spectrometry (TD–Py–GC–MS). Mono- and diaromatic oxygenated compounds were used as model compounds to optimize the method. The influence of various parameters such as solvents, amounts of sample loaded, and temperature ramp configuration, were investigated. A multistep temperature program with TD and pyrolytic temperatures with and without oxygen was employed for analysis of untreated lignin, where up to 55 wt % evolved in the presence of oxygen only, this fraction being unaccounted for by currently used methods. The TCA results were supported by thermogravimetric analysis with a matching heating ramp resulting in a similar mass distribution; however, TCA has the advantage of being selective for carbon. For lignin degradation products, the TD steps of TCA yielded similar recoveries as a solvent extraction followed by GC–MS. Thus, TCA may be used for screening significant product fractions to quantify the previously uncharacterized oligomer/polymer and char fractions.

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

“…At a heating rate of 2 °C/min, two continuous peaks can be observed from the TIT profile at around 220 and 334 °C. A similar trend can be observed from differential thermogravimetric (DTG) 6 and thermal carbon analysis (TCA) curves, 42 where the first peak is primarily related to the release of phenolic monomers and lite-gas molecules (H 2 , CO, and CO 2 ) derived from the cleavage of lateral β-ethers. The extract ion chromatogram of CO 2 (m/z 44) from 100 to 800 °C at a heating rate of 2 °C/min is shown in Figure S1.…”

Quantification of Volatiles from Technical Lignins by Multiple Headspace Sampling-Solid-Phase Microextraction-Gas Chromatography-Mass Spectrometry

“…A study on patterns of volatiles at even higher temperature was conducted by Voeller et al Thermal carbon analysis in combination with thermodesorption-pyrolysis-GC-MS (TD-Py-GC-MS) was used to examine compounds evolving at temperatures from 200 °C up to more than 800 °C. At these temperatures, lignin degradation adds phenolic dimers and oligomers to the group of emitted substances . Kouisni quantified kraft lignin sulfur volatiles via external calibration.…”

“…At these temperatures, lignin degradation adds phenolic dimers and oligomers to the group of emitted substances. 6 Kouisni quantified kraft lignin sulfur volatiles via external calibration. This approach was based on headspace sampling and GC with a sulfur specific detector.…”

Production of Aryl Oxygen-Containing Compounds by the Pyrolysis of Bagasse Alkali Lignin Catalyzed by LaM0.2Fe0.8O3 (M = Fe, Cu, Al, Ti)

“…1 Biomass consists of three major components: cellulose, hemicellulose, and lignin. 2 Cellulose is usually used to produce clean fuels, such as alcohols and methane. 3,4 Hemicellulose can be used as a raw material for xylitol, 5 furfural, 6 adsorbents, 7 etc.…”

“…Biomass has been regarded as an effective alternative for producing fuels and chemicals benefitting from the decreasing generation of pollutants and being carbon dioxide (CO 2 ) neutral . Biomass consists of three major components: cellulose, hemicellulose, and lignin . Cellulose is usually used to produce clean fuels, such as alcohols and methane. , Hemicellulose can be used as a raw material for xylitol, furfural, adsorbents, etc.…”