The Origin of Molecular Mobility During Biomass Pyrolysis as Revealed by In situ ¹H NMR Spectroscopy

Abstract

The thermochemical conversion of lignocellulosic biomass feedstocks offers an important potential route for the production of biofuels and value-added green chemicals. Pyrolysis is the first phenomenon involved in all biomass thermochemical processes and it controls to a major extent the product composition. The composition of pyrolysis products can be affected markedly by the extent of softening that occurs. In spite of extensive work on biomass pyrolysis, the development of fluidity during the pyrolysis of biomass has not been quantified. This paper provides the first experimental investigation of proton mobility during biomass pyrolysis by in situ (1)H NMR spectroscopy. The origin of mobility is discussed for cellulose, lignin and xylan. The effect of minerals on cellulose mobility is also investigated. Interactions between polymers in the native biomass network are revealed by in situ (1)H NMR analysis.

Lignin pyrolysis reactions

“…The chemical structures of the pyrolysis products of lignins have been evaluated by gas chromatography/mass spectrometry (GC/MS) [10][11][12], nuclear magnetic resonance (NMR) [12][13][14][15][16][17][18] and infrared (IR) spectroscopic [15,[19][20][21] analyses, along with pyrolysis directly coupled with GC/MS [22][23][24][25][26][27][28][29][30][31][32][33][34][35] and IR [19,[36][37][38][39] (Py-GC/MS, Py-IR). Aromatic methoxy groups are stable during the primary pyrolysis stage and become very reactive in the temperature range of 400-450 °C.…”

Characterization of Miscanthus pyrolysis by DRIFTs, UV Raman spectroscopy and mass spectrometry

“…To better understand the effect of Misc composition on its thermal degradation, cellulose (Cel-misc), holocelluloses (Holomisc) (i.e. cellulose and hemicelluloses) and lignin (Lig-misc) biopolymers were extracted from Misc following the procedure previously described by Dufour et al [12]. Table 1 shows characteristics of raw Miscanthus in terms of ultimate analysis and the main components of the organic fraction.…”

“…An efficient energy conversion of such biomass resources demands an accurate knowledge of their detailed chemical behavior during degradation. Therefore, many analytical techniques have been used to characterize and to understand biomass pyrolysis by analyzing the solid residue (the biochar) after pyrolysis or in-situ (e.g., FT-IR, Raman and NMR) [11][12][13][14][15][16]. Among the FT-IR techniques, DRIFTs (Diffuse Reflectance Infrared Fourier Transform Spectroscopy) have demonstrated to be an efficient analytical tool to study biomass chemical modification for ex-and in-situ analyses [16,17].…”

“…Despite the difference between the two apparatus, the product yield from the furnace follow the thermogravimetric weight loss curve. For details on thermal degradation and pyrolysis characteristics of Miscanthus, please refer to Dufour et al[12] and Dorge et al[5].…”

Identification of the fractions responsible for morphology conservation in lignocellulosic pyrolysis: Visualization studies of sugarcane bagasse and its pseudo-components

“…Two interesting studies on the morphological changes of biomass (Miscanthus) and its pseudo-components during pyrolysis have been published by Dufour, et al [24,25]. In the first, the authors used 1 H MNR, to monitor changes to each pseudo component during devolatilization with slow heating rates.…”