Chemistry and ecotoxicity of heat-treated pine wood extractives

Abstract

Pine (Pinus pinaster) wood was heat treated in an autoclave for 2-12 hours at 190-210 ºC.Hemicelluloses were the first compounds affected by the treatment. In general, the sugar decrease was higher for arabinose and galactose followed by xylose and mannose. Lignin started to degrade for small mass losses but at a slower rate than hemicelluloses, and cellulose only degraded significantly for severe treatments. Almost all of the original extractives disappeared and new compounds arose like anhydrosugars and phenolic compounds. The compounds that might leach from heat treated wood were mainly those identified in the water and ethanol extracts, all of which were not harmful at the existing concentrations, thereby reinforcing the wood heat treatment as an environmental benign process.

Effect of the Brazilian thermal modification process on the chemical composition of Eucalyptus grandis juvenile wood: Part 1: Cell wall polymers and extractives contents

“…This result is in accordance with those of other studies of Eucalyptus species (Brito et al 2008, Esteves, Graça andPereira 2008) and other species (Esteves et al 2011, Hill 2006, Kamdem et al 2002, Mohareb et al 2012.…”

“…Although the averages of insoluble lignin content did not differ between untreated wood and the treatments at 140 and 160 °C, it is reported in the literature that lignin degradation also occurs at these temperatures (Esteves et al 2008, Esteves et al 2011, Fengel and Wegener 1989, Hill 2006, Sundqvist 2004). So, it is possible that some degradation of lignin occurred in the present study, but at a small level when compared to the degradation of hemicelluloses and the increase in extractives content.…”

“…The thermal modification temperatures used in this work (140, 160 and 180 °C) were not high enough to cause mass loss of cellulose, according to previous information in the literature (Esteves, Graça and Pereira 2008;Esteves, Videira and Pereira 2011;Fengel and Wegener 1989;Sundqvist 2004). Therefore, it is assumed that the process did not cause cellulose degradation, so the difference of holocellulose content among the treatments is believed to be attributed basically to the mass loss of hemicelluloses, which are the most thermally labile compounds of the cell wall structure (Fengel and Wegener 1989, Hill 2006, Stamm 1964, Sundqvist 2004).…”

“…It is extensively reported in the literature that the extractives content of thermally modified wood increases compared to untreated wood due to degradation of hemicelluloses and lignin (Esteves et al 2008, Esteves et al 2011, Fengel and Wegener 1989, Hill 2006, Mohareb et al 2012, Stamm 1964, Sundqvist 2004. In this particular situation, as can be seen in Table 1, the increase in the total extractives content of thermally modified wood occurred more by hemicelluloses degradation than by lignin degradation.…”

Effect of Vacuum Heat Treatment on the Chemical Composition of Larch Wood

“…Heat treatment avoids the use of toxic chemicals and therefore does not have the same deleterious effects on the environment as chemical treatments. However, the major disadvantage of heat treatment is that the resultant decrease in bending strength causes an increased likelihood of breakage (Esteves et al 2011). In recent years, several industrial heat treatment processes have been used: stream treatment in Finland (Viitanen et al 1994), a combination of steam and heated air treatment in the Netherlands (Tjeerdsma et al 1998), and oil treatment in Germany (Rapp 2001).…”