Alcohols
Conversion of natural fats and oils
Reduction of methyl esters
Coconut and palm kernel oils and tallow fat (a by-product of the rendering industry) are the major feed materials for this route to alcohols. The compositions of the fatty acids present in the triglycerides that compose the major raw materials are as follows:
Fatty Acid Composition of Coconut Oil, Palm Kernel Oil and Tallow (percent by weight)
| Chain Length | Coconut Oil | Palm Kernel Oil | Tallow |
|---|---|---|---|
| Saturated | |||
| C6 | 0-0.8 | 0-1.5 | -- |
| C8 | 5-9 | 3-5 | -- |
| C10 | 6-10 | 3-7 | -- |
| C12 | 44-52 | 40-52 | 0-0.2 |
| C14 | 13-19 | 14-17 | 2-8 |
| C16 | 8-11 | 7-9 | 24-37 |
| C18 | 1-3 | 1-3 | 14-29 |
| C20+ | 0-0.4 | 0-1 | 0-1.2 |
| Range | 88.5-95 | 78-86.5 | 42-57 |
| Unsaturated | |||
| C14 | -- | -- | 0.4-0.6 |
| C16 | 0-1 | 0-1 | 1.9-2.7 |
| C18 | 5-10.5 | 13.5-21 | 41-55 |
| Range | 5-11.5 | 13.5-22 | 43-58 |
SOURCE: D. Swern, Bailey's Industrial Oil and Fat Products, 3rd ed., Intersceince Publishers, New York, 1964, pp. 176 and 192.
The triglycerides are first subjected to ester interchange with excess methanol using an alkaline catalyst:
The resulting methyl esters are subjected to distillation and then may be converted to alcohols, alkanolamides or fatty acids, or they may be used in the production of other derivatives. The by-product glycerin is normally refined and sold.
Hydrogenation of the methyl esters to alcohols is performed continuously at pressures above 3,000 psi using a copper chromite catalyst:
Most of the methanol is recovered in the process and is recycled for use in the ester exchange step. The alcohol product (95% overall yield from the triglyceride) is fractionated to eliminate small amounts of high-boiling impurities and to give the desired cuts of alcohols.
When copper chromite catalyst is used, all double bonds are hydrogenated, a process that is satisfactory for most applications. This process is employed to produce detergent-range alcohols by most manufacturers, including some of the world's largest detergent producers such as P&G, Henkel Group and Kao Corporation.
Reduction of fatty acids
Fats and oils may be hydrolyzed to the corresponding fatty acids and subsequently reduced catalytically to the alcohols. Variations in catalysts and operating conditions permit retention of double bonds, if desired. Until 1991, the former Sherex Chemical Company, Inc. (now part of Witco Corporation) used its own variation of this method to produce oleyl and tallow alcohols from the corresponding fatty acids. CONDEA Chemie GmbH of Germany and United Coconut Chemicals Inc. in the Philippines produce saturated fatty alcohols by direct reduction of acids.
Saponification of esters
Production of fatty alcohols by saponification of sperm whale oil was once a source of detergent alcohols. However, this process has been largely eliminated by restrictions on hunting the sperm whale. The alcohols are no longer isolated from this source on a commercial basis in the United States or Western Europe, and Japan has also terminated nearly all of its production of alcohols from sperm oil.
Wool grease is another potential source of detergent alcohols, but it is usually refined only to produce lanolin, even though saponification can give an alcohol fraction. Amerchol Corporation (a part of Union Carbide Corporation) in the United States does produce a very small volume of alcohol from lanolin (less than one million pounds), but its production is largely consumed captively.