Alkaline refining

Sodium hydroxide appears to be the most important alkali employed in commercial operations, and two general methods for its use are of importance. One method employs dilute, sodium hydroxide solutions at elevated temperatures, and the other uses concentrated solutions at low temperatures. In the hot, alkaline refining process, temperature, time, concentration of alkali, and consistency of pulp may be varied over wide limits. The literature contains only a limited amount of data showing the effect of alkaline treatment on sulfite-pulp composition. However, from the available data, certain principles are apparent. 

When certain softwoods are pulped by the sulfite process, the resulting pulp usually contains a considerable proportion of uronic acid anhydride which cannot be removed entirely in subsequent alkaline refining. When the sulfate process is used on softwoods, a pulp which is free from uronic acid anhydride may be obtained. This important difference between the sulfite and sulfate pulps from softwoods does not apply to hardwoods, which, when pulped by either process, still retain a considerable proportion of uronic acid anhydride in the final product. 

TABLE 33. Desirable Quality of Freshly Produced Intermediate and Final Products in Alkaline Refining of Palm Oil (48,50). 

Both figures are corrected for moisture and insoluble impurities in the crude oil. In alkaline refining, the term acid oil factor (AOF) is sometimes used ... 

Process control Proper processing conditions (dosage of processing aids, temperature, pressure/vacuum, flow rate, etc.) must be closely adhered to and monitored to ensure the oil is processed correctly and to minimize undesirable side reactions. In order to assess process efficiency, the oil losses through spent clay or soapstock (as in the case of alkaline refining only) must also be monitored. 

Vegetable oil refinery lipid, feed grade (33.7), is obtained in the alkaline refining of a vegetable oil for edible use. It consists predominantly of the salts of fatty acids, glycerides, and phosphates. It may contain water and not more than 22% ash on a water-free basis. It is to be neutralized with acid before use in commercial feed. Includes IFN 4-05-078 (vegetable oil refinery lipid). 

The first example demonstrates the formulations of a 50% soy oil alkyd for baking enamels. The preliminary selection of ingredients would be alkaline refined soy oil, phthalic anhydride (PA), and pentaerythritol. The basis for calculation is 1 mole of PA. From Table 5, the excess OH recommended at 50% oil length is 25%. Therefore, the quantity of PE required, in equivalents, would be... 

These alkaline degradations can cause a loss of up to 25% (usually 10-20 %) of aZp/to-cellulose during alkaline refining of pulps. 

KT21. Soapstock is recovered via the alkaline refinement process of oilseeds and contains phosphorus lipids, hydrateable and nonsaponifiable compounds, soaps of FFA, vitamins A and E, as well as carotenoid pigments. In their work, condensed corn-soluble basal medium was initially fed with biodiesel glycerol water but when the dissolved oxygen level rose above 10%, the medium was fed with sunflower soapstock. A shift in the monomer compositions from 3-hydroxydecanoate to 3-hydroxyoctanoate was observed when the medium was fed with sunflower soapstock. The final PHA also contained 3-hydroxytetradecanoate and 3-hydroxytetradecenoate monomers with a CDW and PHA content of 17 g/1 and 17%, respectively. 

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