Pressurized Hot Water Flow-through Extraction of Birch Sawdust with Acetate pH Buffer

Abstract

Birch sawdust was extracted with a pressurized hot water (PHW) flowthrough system. The pH of the extract was controlled during extraction by the addition of acetic acid/sodium acetate buffer. Three different pH levels, 4.0, 4.2, and 4.6, were used. Extraction temperatures were 160, 170, and 180 °C, with a constant 4 mL/min flow rate through the 50 mL extraction vessel. During PHW extraction with plain water, the end pH of the extract dropped from 5 to below 3. Buffers kept the pH of the extracts constant during the first 30 min of extraction. Compared to plain water, the use of buffers resulted in a lower yield of xylans during the 170 °C extraction. However, with the buffered system it was possible to obtain xylans from sawdust with a higher molar mass than plain water extraction. Acetic acid/sodium acetate buffer enabled control of the hydrolysis rate of xylans during extraction.

Understanding the role of water during ionic liquid pretreatment of lignocellulose: co-solvent or anti-solvent?

“…Chemical composition, solid recovery, and component removal of switchgrass before and after pretreatment with ionic liquid-water mixtures are summarized in Table 1 20 and thus reduced the extent of xylan solubilization from "auto-hydrolysis" effects, as indicated by the nearly neutral pH of the biomass liquor generated (Table 1).…”

Functionalized galactoglucomannan‐based hydrogels for the removal of metal cations from aqueous solutions

“…Extracted AcGGM from Norway spruce ( Picea abies ) was provided by the Finnish Forest Research Institute (Metla). The extraction conditions were studied and optimized in a previous study for by researchers at the Finnish Forest Research Institute (Metla), and AcGGM was obtained as a solution with a concentration of 30 wt %. To remove impurities and to narrow down the molar mass distribution [low polydispersity (PDI)], the extract was purified.…”

In-line high-temperature pH control during hot-water extraction of wood

“…It was also found that the degradation of hemicellulose chains could somewhat be reduced, but then the hemicellulose yield decreased. Both Song et al (2011a,b) and Kilpeläinen et al (2013) found an optimum of extraction pH around 4 regarding high molar-mass and yield. Since the optimal extraction pH seems to be a rather narrow interval a more precise controlling method is highly needed.…”

“…Their results showed that the molar mass of the extracted hemicelluloses could be preserved to some extent with this passive pH control, but at the expense of the total hemicellulose yield (Song et al, 2011a,b). Another attempt to control pH during hot-water extraction was made with a flow-through extraction system and sodium acetate/acetic acid buffer (Kilpeläinen et al, 2013). It was also found that the degradation of hemicellulose chains could somewhat be reduced, but then the hemicellulose yield decreased.…”