Monday, May 4, 2009
9-47
Mixed Culture Acidogenic Fermentation and Acid Extraction from Pre-Pulping Wood Extract
Pre-pulping extraction is a means of deriving a hemicellulose-rich process stream from the front end of a kraft pulp mill. When the extraction is carried out using green liquor, pulp quality and quantity can be retained while still releasing hemicellulose and acetic acid for recovery as bioprocessing feedstock or chemical products. Acetic acid is naturally present in the extract and its concentration can also be increased through conversion of hemicellulose sugars to organic acids. Either source may provide sufficient value to justify recovery and purification. In this study, mixed culture acidogenic fermentation was done on green liquor pre-pulping liquor and a liquid-liquid extraction method was applied to separate organic acids from the same hardwood extract.
We determined the production levels of carboxylic acids using mesophilic and thermophilic cultures with green liquor salts and calcium carbonate as the buffering agents. Conditions of combined extraction and fermentation conditions were assessed to determine optimal yields of carboxylic acids. The organic acid removal process utilized a solution of trioctylphosphine oxide (TOPO) and un-decane contacted with the wood extract. TOPO has strong hydrogen bonding acceptor properties that induce the carboxylic acid to transfer to the extract phase. The two phases are immiscible and separate gravimetrically. Distillation is used to separate organic acids from the solvent phase, which is recycled back to the extraction. Results present the extraction and recovery efficiencies.
We determined the production levels of carboxylic acids using mesophilic and thermophilic cultures with green liquor salts and calcium carbonate as the buffering agents. Conditions of combined extraction and fermentation conditions were assessed to determine optimal yields of carboxylic acids. The organic acid removal process utilized a solution of trioctylphosphine oxide (TOPO) and un-decane contacted with the wood extract. TOPO has strong hydrogen bonding acceptor properties that induce the carboxylic acid to transfer to the extract phase. The two phases are immiscible and separate gravimetrically. Distillation is used to separate organic acids from the solvent phase, which is recycled back to the extraction. Results present the extraction and recovery efficiencies.
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