Abstract
BackgroundHot water hydrolysis process is commercially applied for treating wood chips prior to pulping or wood pellet production, while it produces hydrolysis liquor as a by-product. Since the hydrolysis liquor is dilute, the production of value-added materials from it would be challenging.ResultsIn this study, acidification was proposed as a viable method to extract (1) furfural and acetic acid from hot water hydrolysis liquor and (2) lignin compounds from the liquor. The thermal properties of the precipitates made from the acidification of hydrolysis liquor confirmed the volatile characteristics of precipitates. Membrane dialysis was effective in removing inorganic salts associated with lignin compounds. The purified lignin compounds had a glass transition temperature (Tg) of 180–190 °C, and were thermally stable.ConclusionsThe results confirmed that lignin compounds present in hot water hydrolysis liquor had different characteristics. The acidification of hydrolysis liquor primarily removed the volatile compounds from hydrolysis liquor. Based on these results, a process for producing purified lignin and precipitates of volatile compounds was proposed.
Highlights
Hot water hydrolysis process is commercially applied for treating wood chips prior to pulping or wood pellet production, while it produces hydrolysis liquor as a by-product
It is seen that the wood chips contained 17.0, 47.2, 3.9, 2.8, and 26.5 wt% of hemicelluloses, cellulose, extractives, acid-soluble lignin, and acid-insoluble lignin, respectively
The hydrolysis liquor produced in this work had an acidic pH of 3.2–3.6 implying that the acetyl groups attached to wood chips were partly removed and converted to acetic acid during hydrolysis process [4, 33]
Summary
Hot water hydrolysis process is commercially applied for treating wood chips prior to pulping or wood pellet production, while it produces hydrolysis liquor as a by-product. In a forest biorefining process, cellulose can be produced as dissolving pulp, while lignin and hemicelluloses are converted to other value-added products [1, 2]. Hot water hydrolysis process is commercially used for extracting hemicelluloses from wood chips. It was reported that hydrolysis liquor contains hemicelluloses and some lignin that can be used in the production of value-added products [3]. Hot water hydrolysis process can be carried out prior to pulping process [4, 5] or in wet torrefaction process [6] In both processes, the hydrolyzed wood chips are transferred to the steps
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