Characterization and analysis of torrefied wood

Abstract

This study investigated chemical decomposition of lignocellulosic components in the course of torrefaction under isothermal conditions for durations up to 5 hours. The goal was a better understanding of the behaviour of biomass, at both short and long residence times, which is important for innovation in the chemical and bioenergy industries. Gaseous and solid-phase decomposition products of cellulose, xylan, and two lignins, were studied following torrefaction at three temperatures (220, 250, and 280 °C) for a continuous recording of mass loss and emission of volatiles over 5 hours. Two decomposition stages were revealed for xylan, with a notable release of CO that increased with treatment temperature. 4-O-methyl glucurono-units on the side chains of xylan degraded first, and acetyl groups and macromolecule fragments accounted for the second degradation, starting at 250 °C. The primary production of acetic acid occurred at 280 °C. For the two lignins, decomposition reactions predominated at lower temperatures, while rearrangement prevailed at 280 °C. The emission of phenol was a clear distinction between the two. Cellulose was thermally stable at short times under all treatments, but it decomposed dramatically afterwards, especially at 280 °C.

Pretreatment of biomass by torrefaction

“…After torrefaction, the stalk will have lost most of its water while some low molecular weight volatile organic compounds and long-chain polysaccharides decompose. Lignin pyrolysis produces mainly charcoal [13].…”

“…Additionally, the solid products become brittle, fragile and cylindrical or spherical in shape. As the solid products lose most of their moisture and their volatile matter, their energy density increases and the charcoal even has a hydrophobic character [5,8,13].…”

“…[5,13]. As the pyrolysis temperature increases, the liquid product yield increases and it has a darker color.…”

Wood polypropylene composites prepared by thermally modified fibers at two extrusion speeds: mechanical and viscoelastic properties

“…These reactions lead to a modified lignin, which is more hydrophobic and rigid than the original one . The hydrophobic character of the retified wood is elevated and the amount of volatile components is lowered (Jaziri et al 1987;Bourgois and Guyonnet 1988;Bourgois et al 1989). The expectation is that this pre-treatment will improve the interfacial compatibility of wood and PP.…”

Analytical Techniques as a Tool to Understand the Reaction Mechanism

“…Although the low-temperature thermal pretreatments have been studied earlier [110][111][112][113], the amount of publications on torrefaction has been relatively small. However, the number of publications has increased rapidly in the last few years due to the recognition that the thermal pretreatment has economic importance in the development of efficient biomass conversion technologies.…”