The Manufacturing Of Soap
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Soaps are the sodium or potassium salts of certain fatty acids obtained from the hydrolysis of triglycerides.
Fat + NaOH → glycerol + R–CO2 –Na+
Soap comprises the sodium or potassium salts of various fatty acids, but chiefly of oleic, stearic, palmitic, lauric, and myristic acids.
Manufacturing processes are both batch (in which the triglyceride is steam-hydrolyzed to the fatty acid without strong caustic, and then in a separate step it is converted into the sodium salt) or continuous.
The manufacture of soap (Fig. 1) involves continuous splitting (hydrolysis) and, after separation of the glycerin, neutralization of the fatty acids to soap. The procedure is to split, or hydrolyze, the fat, and then, after separation from the glycerol (glycerin) to neutralize the fatty acids with a caustic soda solution:
(C17H35COO)3C3H5 + 3H2O → 3C17H35COOH + C3H5(OH)5
C17H35COOH + NaOH → C17H35COONa + H2O
In continuous, countercurrent splitting, the fatty oil is deaerated under a vacuum to prevent darkening by oxidation during processing. It is charged at a controlled rate to the bottom of the hydrolyzing tower through a sparge ring (Fig. 2). The oil in the bottom contacting section rises because of its lower density and extracts the small amount of fatty material dissolved in the aqueous glycerol (glycerin) phase. At the same time, deaerated, demineralized water is fed to the top contacting section, where it extracts the glycerol dissolved in the fatty phase. After leaving the contacting sections, the two streams enter the reaction zone where they are brought to reaction temperature by the direct injection of high-pressure steam, and then the final phases of splitting occur. The fatty acids are discharged from the top of the splitter or hydrolyzer to a decanter, where the entrained water is separated or flashed off. The glycerol-water solution is then discharged from the bottom of an automatic interface controller to a settling tank.
Fat + NaOH → glycerol + R–CO2 –Na+
Soap comprises the sodium or potassium salts of various fatty acids, but chiefly of oleic, stearic, palmitic, lauric, and myristic acids.
Manufacturing processes are both batch (in which the triglyceride is steam-hydrolyzed to the fatty acid without strong caustic, and then in a separate step it is converted into the sodium salt) or continuous.
The manufacture of soap (Fig. 1) involves continuous splitting (hydrolysis) and, after separation of the glycerin, neutralization of the fatty acids to soap. The procedure is to split, or hydrolyze, the fat, and then, after separation from the glycerol (glycerin) to neutralize the fatty acids with a caustic soda solution:
(C17H35COO)3C3H5 + 3H2O → 3C17H35COOH + C3H5(OH)5
C17H35COOH + NaOH → C17H35COONa + H2O
In continuous, countercurrent splitting, the fatty oil is deaerated under a vacuum to prevent darkening by oxidation during processing. It is charged at a controlled rate to the bottom of the hydrolyzing tower through a sparge ring (Fig. 2). The oil in the bottom contacting section rises because of its lower density and extracts the small amount of fatty material dissolved in the aqueous glycerol (glycerin) phase. At the same time, deaerated, demineralized water is fed to the top contacting section, where it extracts the glycerol dissolved in the fatty phase. After leaving the contacting sections, the two streams enter the reaction zone where they are brought to reaction temperature by the direct injection of high-pressure steam, and then the final phases of splitting occur. The fatty acids are discharged from the top of the splitter or hydrolyzer to a decanter, where the entrained water is separated or flashed off. The glycerol-water solution is then discharged from the bottom of an automatic interface controller to a settling tank.
