 | |
| Names | |
|---|---|
| IUPAC name Lithium 12-hydroxyoctadecanoate | |
| Identifiers | |
3D model (JSmol) | |
| ChemSpider | |
| ECHA InfoCard | 100.028.669 |
| UNII | |
| |
| |
| Properties | |
| C18H35LiO3 | |
| Molar mass | 306.42 g·mol−1 |
| Appearance | White powder |
| Melting point | > 200 °C (392 °F; 473 K) |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Lithium 12-hydroxystearate (C18H35LiO3) is achemical compound classified as alithium soap. In chemistry, "soap" refers to salts offatty acids. Lithium 12-hydroxystearate is a white solid. Lithium soaps are key component of manylubricating greases.
Lithium 12-hydroxystearate exhibits highoxidation stability and adropping point up to around 200 °C. Most greases used today in motor vehicles, aircraft, and heavy machinery containlithium stearates, mainly lithium 12-hydroxystearate.[1] Greases can be made with the addition of several different metallic soaps. Some greases are prepared fromsodium,barium,lithium, andcalcium soaps. Lithium soap greases are preferred for their water resistance, and their oxidative and mechanical stability. Depending on the grease, they also have good performance at high or low temperatures, but not both.
To produce lithium 12-hydroxystearate,lithium hydroxide and 12-hydroxystearic acid are combined in an aqueous medium. With vigorous stirring, dilute monohydrate lithium hydroxide is gradually added to a dispersion of the fatty acid in water heated to slightly below boiling.[2] Since these lithium soaps are difficult to filter, they are collected byspray drying. For applications, lithium 12-hydroxystearate is usually dispersed in synthetic oils such assilicone oil andester oil. The synthetic oils are preferred for their greater stability and ability to perform at extreme temperatures.
12-hydroxystearic acid is prepared by thehydrogenation ofcastor oil, followed bysaponification withsodium hydroxide and acidification withhydrochloric acid.[3] This process convertsricinoleate moieties in castor oil triglycerides to 12-hydroxystearate, withstearate as a byproduct fromdehydration of thehydroxy acid followed by hydrogenation. Lithium soaps manufactured fromhydrogenated castor oil typically contain a mixture of lithium 12-hydroxystearate andlithium stearate.
