Acetic acid concentrations, organic

However, acetic acid fermentation has its limits also. When the concentration of acetic acid in fermenting liquor has reached eight per cent the activity of the acetic acid forming organisms becomes slower and slower and ceases almost altogether when 12 to 14 per cent acid content is reached. 

The weak organic acids such as acetic acid and formic acid both have positive and negative effects on the bioethanol produetion proeess. In fermentations using S. cerevisiae NCYC 2592, an addition of aeetie acid in a concentration of 20 mM increased the ethanol produetivity (unpublished data). The low acetic acid concentrations (lower than 20 mM) did not have an impact on the yeast viability. At fermentations with higher acid concentration, the intracellular pH decreases, requiring plasma membrane ATPase to pump protons out of the cell. The depletion of ATP affected the biomass formation. In comparison with acetic acid, formic acid has a more severe inhibitory effect, which has also been observed in other biosynthesis processes, e.g. succinic acid formation. ... 

Chlorosulfonated polyethylene swells in organic acids. Glacial acetic acid, concentrated butyric acid, and others initiate strong swelling even at room temperature. In dilute organic acids, the service life of CSM is also limited to weeks or months. Most organic acids diffuse easily into CSM glacial acetic acid penetrates a 1 mm thick CSM layer at 20 °C within ten hours [32],... 

Develop the relation (5.2.89) for the acetic acid distribution coefBcient between a nonpolar organic solvent and water. Identify the condition so that k o is independent of the pH, given K i = 1.5 x 10". Identify the aqueous acetic acid concentration beyond which k o changes by more than 10% from the value valid for negligible dimerization. 

If the volumes of the two phases were the same, speculate first about the equilibrium acetic acid concentration in the aqueous phase for each of the four cases. Suggest a way of finding out whether there was any dimerization in the organic phase. Develop an estimate of the dimerization equilibrium constant K, . (Ans. Ki 0.)... 

The more strongly acidic a solution of nitric acid at a given concentration is in a particular organic solvent, the more readily should that solvent support zeroth-order nitration. The values of for solutions of sulphuric acid in nitromethane, sulpholan, and acetic acid show clearly the superiority of nitromethane in this respect. ... 

When acetic anhydride was in excess over nitric acid, acetyl nitrate and acetic acid were the only products. When the concentration of nitric acid was greater than 90 moles %, dinitrogen pentoxide, present as (N02+)(N0a ), was the major product and there were only small traces of acetyl nitrate. With lower concentrations of nitric acid the products were acetic acid, acetyl nitrate and dinitrogen pentoxide, the latter species being present as covalent molecules in this organic medium. A mixture of z moles of nitric acid and i mole of acetic anhydride has the same Raman spectrum as a solution of i mole of dinitrogen pentoxide in 2 moles of acetic acid. 

Various ways of overcoming the PTA oxidation problem have been incorporated into commercial processes. The predominant solution is the use of high concentrations of manganese and cobalt ions (2,248—254), optionally with various cocatalysts (204,255,256), in the presence of an organic or inorganic bromide promoter in acetic acid solvent. Operational temperatures are rather high (ca 200°C). A lesser but significant alternative involves isolation of intermediate PTA, conversion to methyl/)-toluate, and recycle to the reactor. The ester is oxidized to monomethyl terephthalate, which is subsequentiy converted to DMT and purified by distillation (248,257—264). 

After epoxidation a distillation is performed to remove the propylene, propylene oxide, and a portion of the TBHP and TBA overhead. The bottoms of the distillation contains TBA, TBHP, some impurities such as formic and acetic acid, and the catalyst residue. Concentration of this catalyst residue for recycle or disposal is accompHshed by evaporation of the majority of the TBA and other organics (141,143,144), addition of various compounds to yield a metal precipitate that is filtered from the organics (145—148), or Hquid extraction with water (149). Low (<500 ppm) levels of soluble catalyst can be removed by adsorption on soHd magnesium siUcate (150). The recovered catalyst can be treated for recycle to the epoxidation reaction (151). 

Organic acids, including carbon dioxide, lower the wort pH during fermentation. The principal acids formed are lactic, pymvic citric, malic, and acetic acids, at concentrations ranging from 100—200 ppm. The main sulfur compounds formed during fermentation and thek perception thresholds are as follows H2S (5—10 ppb) ethanethiol (5—10 ppb) dimethyl sulfoxide (35—60 ppb) and diethyl sulfide (3—30 ppb). At low levels, these may have a deskable flavor effect at higher levels they are extremely undeskable. Sulfur dioxide also forms during fermentation, at concentrations of 5—50 ppm its presence can be tasted at levels above 50 ppm. 

Because the solution is capable of absorbing one mole of carbon monoxide per mole of cuprous ion, it is desirable to maximize the copper content of the solution. The ammonia not only complexes with the cuprous ion to permit absorption but also increases the copper solubiUty and thereby permits an even greater carbon monoxide absorption capacity. The ammonia concentration is set by a balance between ammonia vapor pressure and solution acidity. Weak organic acids, eg, formic, acetic, and carbonic acid, are used because they are relatively noncorrosive and inexpensive. A typical formic acid... 

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