Capacity, basic neutralization

The various functional properties of neutralizing amines, such as basicity, neutralizing capacity, DR, and volatility often have little or no direct relationship with each other, but all these properties are significantly different at boiler temperatures. This vital consideration is often insufficiently highlighted in manufacturers data sheets. Consequently, some of the commonly available information comparing amines records data at ambient temperatures, making it next to useless. 

The electron-rich oxygen anions exhibit basic electron donor capacity. Basic metal oxides are commonly used for neutralizing or scrubbing acidic gases. Alkaline earth metal oxides have been used for the removal of NOx. The surfaces of cubic alkaline metal oxide such as MgO, CaO, and BaO are dominated by the Lewis basicity of surface oxide anions. The basicity increases down the alkaline earth family as the metal ion radii become larger and the chaige on the metal ion becomes more positive. 

The quantity of free carbon dioxide in water can be calculated from the determination of basic neutralization capacity up to pH 8.3 (BNC8 3, total acidity). In this case, free COj reacts with an alkaline titrant to form hydrogen carbonate (CO2 + OH — HCO ). Provided that the whole basic neutralization capacity up to pH 8.3 consists only of free carbon dioxide, its weight concentration (c(C02)) can be calculated from the following equation ... 

Neutralizing capacity is not the only measure of a required amine feed rate. Once all acidic characteristics have been neutralized, amine basicity becomes the important issue because this raises the pH above the neutralization point, to a more stable and sustainable level. Consequently, in practice we are concerned with the level of amine necessary to raise the condensate pH to a noncorrosive level. This practical amine requirement is difficult to obtain from theoretical calculations because it must take account of the amine volatility, DR, and the boiler system amine recycling factor (as well as temperature). As noted earlier, the basicity of an amine has little or no relationship to its volatility or DR, so that reliable field results are probably a more important guide in assessing the suitability of an amine product than suppliers tables. 

From a practical perspective, DR (along with neutralization capacity and basicity) is one of the most important functional properties of amines and is always referred to when selecting amines for application in a steam-condensate system. Amine DR values vary considerably, however, and for each amine the DR value changes with variation of temperature and pressure. 

FIG. 14 A model for the uptake of weakly basic compounds into lipid bilayer membrane (inside acidic) in response to the pH difference. For compounds with appropriate pki values, a neutral outside pH results in a mixture of both the protonated form AH (membrane impermeable) and unprotonated form A (membrane permeable) of the compound. The unprotonated form diffuse across the membrane until the inside and outside concentrations are equal. Inside the membrane an acidic interior results in protonation of the neutral unprotonated form, thereby driving continued uptake of the compound. Depending on the quantity of the outside weak base and the buffering capacity of the inside compartment, essentially complete uptake can usually be accomplished. The ratio between inside and outside concentrations of the weakly basic compound at equilibrum should equal the residual pH gradient. 

When calcium carbonate goes into solution, it releases basic carbonate ions (COf ), which react with hydrogen ions to form carbon dioxide (which will normally remain in solution at deep-well-injection pressures) and water. Removal of hydrogen ions raises the pH of the solution. However, aqueous carbon dioxide serves to buffer the solution (i.e., re-forms carbonic acid in reaction with water to add H+ ions to solution). Consequently, the buffering capacity of the solution must be exceeded before complete neutralization will take place. Nitric acid can react with certain alcohols and ketones under increased pressure to increase the pH of the solution, and this reaction was proposed by Goolsby41 to explain the lower-than-expected level of calcium ions in backflowed waste at the Monsanto waste injection facility in Florida. 

Antacids are basic compounds that neutralise acid in gastric lumen, have no effect on gastric acid secretion. They are quantitatively compared in terms of their acid neutralizing capacity (ANC), which is defined as the quantity of 1 N HCl (in MEq) that can be brought to pH 3.5 in 15 minutes by a unit dose of antacid preparation. An ideal antacid should be potent in neutralizing acid, inexpensive, not absorbed from GIT and contain negligible amounts of sodium, should be sufficiently palatable to be readily tolerated with repeated dosage and should be free of side effects. An ideal antacid is yet to be developed. 

Claus propositions were summarized as three statements in his more widely read paper of 1856 42 (1) If several equivalents of ammonia (from two to six) combine with an equivalent of certain metal chlorides, neutral substances are formed, in which the basic property of ammonia has been destroyed and simultaneously the ammonia can be neither detected by the usual methods nor eliminated by double decomposition . (2) If the chlorine in these compounds is replaced by oxygen, strong bases are obtained, whose saturation capacity is always determined by the oxygen equivalents contained in them but not by the number of equivalents of ammonia present in them . (3) The number of equivalents of ammonia entering into these substances is not a random one as is evident from a number of facts, it is determined by the number of equivalents of water contained in the hydrates of the metal oxides which can enter into such compounds along with the ammonia . 

Formol titration is a method that estimates amino groups by titration with NaOFI and a phenolphthalein indicator (Vakaleris et ah, 1960). Addition of formaldehyde to the neutralized mixture reduces the pFI by making the amino groups less basic. The amount of NaOFI required to retitrate the mixture has been used as an indicator of proteolysis. Another titrimetric method relies on the increase in buffering capacity of the cheese during ripening and has been applied to study proteolysis in Swiss cheese (Lucey et ah, 1993). 

Both Eqs. 3 and 4 show that hydrogen ion concentration should affect the rate of hemicellulose hydrolysis, but the neutralization capacity of biomass is not always taken into consideration in models reported in the literature. Neutralization is caused by basic minerals containing potassium, sodium, calcium, iron, and other cations present in biomass reacting with sulfuric acid and reducing available hydrogen ions stoichiometrically (17) ... 

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