The Properties and Synthesis Method of Stearic Acid

wallpapers Industry 2020-09-01

Stearic acid, namely octadecanoic acid, has a structural formula: CH3(CH2)16COOH, produced by the hydrolysis of fats and oils, and is mainly used to create stearates. Each gram is dissolved in 21ml ethanol, 5ml benzene, 2ml chloroform, or 6ml carbon tetrachloride.

Stearic acid is a kind of fatty acid that exists widely in nature. Almost all fats and oils contain stearic acid with varying contents. Stearic acid content is higher in animal fat, such as tallow, which includes 24%, and vegetable oil, which is less. Tea oil is 0.8%, palm oil is 6%, but the content of cocoa butter is as high as 34%. The production methods of industrial stearic acid mainly include fractional distillation and pressing. The decomposing agent is added to the hardened oil and then hydrolyzed to obtain crude fatty acid, washed with water, distilled, and decolorized to bring the finished product. At the same time, by-product glycerol.

(1) Fractional distillation method Add 6t of cottonseed oil-hardened oil, hydrolyzing agent stearic acid cresol sulfonic acid, and stearic acid naphthalene sulfonic acid 120kg into the hydrolysis pot. After passing steam until the oil layer is transparent, add 4200kg of water. Continue heating to boiling, react under normal pressure for 7.5h, clarify for 0.5h, and separate the lower layer of glycerin water. After that, add 120kg of a hydrolyzing agent, add steam to heat the oil layer to be transparent, add 3600kg of water, and react for about 10h. When the mixed acid value reaches 190mgKOH/g or more, it is the end of hydrolysis. After clarification for 0.5h, after separating the glycerin water, add 7g salt and 3600kg water for washing. Use 14 kg of salt and 4200 kg of water for a second washing. It is clarified for 0.5h after the first washing and 2h after the second washing. After the lower layer of acid water is separated, take the upper layer of mixed fatty acid.

Add 2000kg of mixed fatty acids into the distillation kettle for fractional distillation under reduced pressure. The kettle temperature is 250-255°C, the tower temperature is 210-220°C, the maximum temperature is 200-210°C, and the maximum residual pressure is 0.53-0.93kpa. After the balance of feeding, discharging, and discharging is reached, it is transferred to continuous operation, with 100% feeding, 40% discharging, and 60% discharge. The raw material is used to make tertiary stearic acid. After the removed material has an iodine value of less than 2mgl/100g after analysis, 1000kg of stearic acid, and 3kg of 92.5% sulfuric acid are sequentially put into the pickling pot and boiled for washing. After cutting off the sour feet, take 450kg of stearic acid, put it into the decolorizing pot, heat it to 190℃, add 150ml of chemical soda ash, and 11kg of dry clay successively, and then decolorize at about 105℃ under reduced pressure and stirring for about 45min. The first-grade stearic acid is obtained by pressing and filtering, pouring, and forming.

The glycerin water separated in the hydrolysis process is neutralized with lime milk at 80-100°C, and refined glycerin can be obtained through the methods of suction filtration and concentration, press filtration, vacuum distillation, activated carbon decolorization, and press filtration.

(2) Squeezing method Using animal and vegetable oils as raw materials, first-grade stearic acid is obtained by high-pressure hydrolysis, washing, vacuum distillation, pressing, bleaching, and crystallization presence of hydrolyzing agents (such as zinc oxide).

(3) Hydrolyze hardened fat, tallow or goat fat in the presence of decomposer (sulfonated mixture such as benzene and naphthalene), and then undergo acidification, distillation, squeezing, and acid elution to obtain the finished product.

(4) Hydrogenation with oleic acid.

(5) It is made from synthetic fatty acid C10~C20 and C18~C20 fractions of raw materials by melting, pickling (with 1% sulfuric acid) casting, pressing, melting, pickling, dehydration, and crystallization.

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