Abstract
Lee (1993) has shown that tertiary amines are able to hics. extract water from low-concentration calcium acetate and sodium acetate solutions. This thesis extends the previous work to include calcium propionate and butyrate. Amine extraction may be used to selectively remove water from a fermentation broth thus concentrating calcium acetate, propionate, and butyrate. Compared to competing technologies that extract undissociated acids from a volatile fatty acid fermentation broth, extracting water with tertiary amines allows for higher pH levels in the broth resulting in greater productivity. Specifically, triethylamine and N,N-diethyl-methylamine in a 1:2 volumetric mixture are superior to any other examined mixture or single amine for extracting water at 40[]C, the proposed fermentation temperature (Lee, 1993; Davison et al., 1966, 1967). Once the acid salts have been concentrated, a variety of techniques are available to convert the concentrated salts into other products such as ketones, alcohols, and acids. At low temperatures, the low-molecular-weight amine mixture has a high affinity for water. By raising the temperature 20 to 25[]C, the water separates from the amine allowing for convenient solvent regeneration of the amine. The distribution coefficients, [] , measure the selectivity of concentrating calcium salts in the aqueous phase. The distribution coefficients generally vary as follows: [] thus, there is less selectivity as the aliphatic group increases in size. The amine mixture was used to extract water from actual fermentation broth to determine whether possible surfactants in the broth interfere with the extraction. Prior to extraction, the fermentation broth was adjusted to pH 11.5 by adding a small amount of lime. The high pH precipitate protein which can be recycled to the fermentor or collected for animal feed. Through 15 extraction runs, no degradation of the amine was observed.
Gaskin, David J (1997). Concentrating aqueous volatile fatty acid salt solutions using a tertiary amine mixture. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1997 -THESIS -G375.