http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
Recovery of carboxylic acids from fermentation broth via acid springing
A proprietary technology owned by Texas A&M University, named the MixAlco Process, can process biodegradable wastes (e.g., paper fines, municipal solid waste, sewage sludge, and industrial biosludge) to obtain carboxylic acids and mixed alcohol fuels as downstream products. The process uses a mixed culture of naturally occurring microorganisms, found in natural habitats such as the rumen of cattle and marine and terrestrial swamps, to convert biomass wastes into a mixture of carboxylic acids. As the microorganisms digest the biomass and convert it into a mixture of carboxylic acids, the pH must be controlled. This is done by adding a buffering agent (e.g., calcium carbonate), thus a mixture of carboxylate salts is produced. Carboxylic acids can be recovered from the carboxylate salts directly through a process known as 'acid springing.' This process mixes carboxylate salts (e.g., Ca(Ac)2) with carbon dioxide (CO2) and a low-molecular-weight tertiary amine (R3N) to precipitate calcium carbonate (CaCO3). The low-molecular-weight tertiary amine carboxylate (R3NHAc) remains in the liquid. Then, this liquid is mixed with tri-nivoctylamine (R3N) and distilled. During distillation, tertiary amine carboxylate can be thermally decomposed into the amine itself, which is recycled, and carboxylic acids. Theoretically, no chemicals are consumed or wastes produced during this process. Essentially, the 'acid springing' process consists of precipitation and thermal conversion. The research described in this thesis focuses on choosing a proper lowmolecular-weight tertiary amine suitable for the process and determining the optimal temperature for thermal conversion. Because the fermentation broth mainly contains calcium acetate (more than 80% by weight), an aqueous solution of reagent-grade calcium acetate is used for research purposes instead of fermentation broth. Then, the actual fermentation broth is used to verify the conclusions. A 0.3-L pressure vessel reactor was designed and made for precipitation and a distillation bench was prepared for thermal conversion. The recovery effectiveness was evaluated by gas chromatography (GC) and a pH test. The results indicated that tributylamine is the best choice among several kinds of low-molecular-weight tertiary amine. The optimal temperature for concentrating tributyl ammonium acetate is about 110 oC, and the optimal temperature for recovering acetic acid from tributyl ammonium acetate is about 170 oC. The corresponding optimal temperatures for the process dealing with fermentation broth are 110 and 190 oC.
Title from author supplied metadata (automated record created 2010-03-12 12:08:51).
Master of Science Texas A&M University 2008 http://hdl.handle.net/1969.1/ETD-TAMU-2008-12-153