Sodium hypochlorite steaming process

The refining process most commonly used involves treatment with hot aqueous alkaH to convert free fatty acids to soaps, followed by bleaching, usually with hydrogen peroxide, although sodium chlorite, sodium hypochlorite, and ozone have also been used. Other techniques include distillation, steam stripping, neutralization by alkaH, Hquid thermal diffusion, and the use of active adsorbents, eg, charcoal and bentonite, and solvent fractionation... 

As in the Raschig process, aqueous caustic reacts with chlorine to make sodium hypochlorite solution. The urea solution is prepared by dissolving urea in water with the addition of steam to provide the heat needed for the endothermic dissolution. The temperature is kept at about 5°C for 43 percent urea solution. Glue is added at a ratio of 0.5g/Uter of solution to inhibit side reactions. The urea and hypochlorite solutions are added to the hydrazine reactor at a ratio of 1 4, and the reaction temperature is allowed to rise to 100°C. The crude product contains approximately 35 g N2H4/liter and can be refined in the same steps as used for the Raschig process. 

Commercially, most cellulose is extracted from wood by one of two methods, the kraft (sulfate) process or the steam explosion process. The product of these reactions is wood pulp, which consists primarily of cellulose. In the kraft process, wood chips are treated with a solution of sodium hydroxide (NaOH) and sodium sulfide (Na2S) at temperatures of about 175°C (35o°F) for two to six hours. This process usually results in a yield of about 40 to 45 percent wood pulp. The pulp is then treated with a bleaching agent, such as calcium or sodium hypochlorite (Ca(0Cl)2 or NaCIO) or chlorine dioxide (C102) to remove the color of lignin and other impurities. 

The production of chlorpicrin (trichloronitromethane) can be used to illustrate the process. Here, 11.2 parts of nitromethane is added slowly to about 700 parts of a 10 per cent sodium hypochlorite solution under agitation at 20-25 0. After all the nitromethane has been introduced, stirring is continued until the temperature falls. A yield of 96 per cent of trichloronitromethane is obtained when the crude product is distilled with steam. 

In another process, acid is added to reduce the pH of a sodium hypochlorite solution to less than 5.5. The solution is sprayed into a stream of inert gas to make fine droplets or distilled. The vapor stream is adsorbed into water to make a hypochlorous acid solution with low salt. Solutions of hypochlorous acid or sodium hypochlorite can also be stripped in a column against a current of chlorine, steam, and air at 95-100°C. The exit gases are condensed to form hypochlorous acid solutions that are free of chloride. Similarly, a hydroxide solution is circulated downward through a stripping column against a stream of chlorine and an inert gas above 60°C. The effluent gas is condensed to form a salt-free solution of hypochlorous acid. Hypochlorous acid can also be made... 

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