Pressurized hot water extraction of Scots pine sapwood: effect of wood size on obtained treatment products

Abstract

The efficiency of hot water extraction (HWE) is dependent on the size of treated wood. While previous research regarding this size-effect has focused on HWE treating sawdust and wood chips, this study investigated its effect on wood blocks with precise dimensions and a broad range of treatment conditions. Scots pine (Pinus sylvestris L.) sapwood samples with dimensions of 10 × 10 × 20 mm 3 and 25 × 25 × 50 mm 3 (R × T × L) were HWE treated at 130-170°C for 40-200 min using liquid-to-solid ratios of 4-20. Our results showed that wood mass loss, which was primarily caused by the decomposition of hemicelluloses, was larger when using small samples. This was mainly assigned to a higher quantity of acetone-soluble decomposition products that remained within the large samples, due to longer distances for diffusion and mass transfer from the wood blocks to the extraction liquid. In line with wood mass loss differences, the amount of dissolved compounds (i.e., carbohydrates) in the extraction liquid at different treatment severities was dependent on the wood size, while the liquid-to-solid ratio had only modest effects. However, composition changes of the extraction liquid, in particular changes in the proportion of poly-and monocarbohydrates with increasing treatment severity, were similar for both sample sizes.

Effect of drying on the hydroxyl accessibility and sorption properties of pressurized hot water extracted wood

“…In line with previous studies (e.g. Kyyrö et al 2020;Nitsos et al 2016;Wikberg et al 2015), HWE treatment caused a decrease in hemicellulose content and an increase in cellulose and lignin content due to the preferential degradation of hemicelluloses (Table 1). Slightly larger contents of cellulose and hemicelluloses and lower contents of lignin were recorded for the never-dried sample group than…”

“…Treating wood with pressurized hot water within the temperature range of 100-240 °C causes the preferential cleavage and extraction of hemicellulosebased carbohydrates, which simultaneously increases cellulose and lignin content in the solid residue (Wikberg et al 2015;Nitsos et al 2016;Kyyrö et al 2020). Pressurized hot water extraction (HWE) reduces the concentration of accessible OH groups (OH acc ), and consequently, the moisture content of the treated wood (Boonstra and Tjeerdsma 2006).…”

Approaching Highly Leaching-Resistant Fire-Retardant Wood by In Situ Polymerization with Melamine Formaldehyde Resin

“…The negative value of WPG may be due to the wood being degraded by hot water, leading to an increase in extractives during leaching that was performed according to EN 84. 37 The standard deviations of 0-30MF and 8-30 MF specimens were relatively high resulting in low statistical differences before and after water leaching. Nevertheless, the WPG difference of 0-30MF and 8-30MF specimens was quite similar compared to the 8-0MF specimen, which is due to the hydrophobic cured MF resin providing good water resistance.…”

“…Figure b shows that the increased WPG of the 8-0MF specimen was completely lost after water leaching due to the hygroscopicity of the FRs. The negative value of WPG may be due to the wood being degraded by hot water, leading to an increase in extractives during leaching that was performed according to EN 84 . The standard deviations of 0-30MF and 8-30 MF specimens were relatively high resulting in low statistical differences before and after water leaching.…”

Kraft pulping of softwood chips with mild hot water pre-hydrolysis to understand the effects of wood chip thickness

“…Chip size influences pre-hydrolysis, delignification, post-pulping fiber separation, and subsequent fiber properties (Borlew and Miller 1970;Grace and Malcolm 1989;Niskanen 1998;Gullichsen and Fogelholm 2000;Song et al 2008;Rissanen et al 2014a,b;Kyyrö et al 2020). Mass transfer within wood chips during pulping is mainly by diffusion.…”