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

Petri Kilpeläinen, Veikko Kitunen, Andrey Pranovich, Hannu Ilvesniemi, Stefan Willför

Abstract


Birch sawdust was extracted with a pressurized hot water (PHW) flow-through 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.

Keywords


Pressurized hot water extraction; Flow-through; pH buffer; Birch; Sawdust; Xylan

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