The different methods used in the production of fatty alcohols from various sources are (1) hydrolysis of wax esters using animal fats, (2) sodium reduction process using fats and oils, (3) Ziegler process using ethylene, (4) oxo process using olefins,(5) catalytic hydrogenation of fatty acids and methyl esters from fats and oils, and(6) direct hydrogenation of fats and oils. Although not applicable to coconut oil, a brief description of the first method is included. The third and fourth methods use raw materials of petrochemical origin. However, it should be mentioned again that approximately 50% of the world’s supply of fatty alcohols is produced from these two methods.
Hydrolysis of Wax Esters: Fatty alcohol was first obtained from the hydrolysis of wax esters of animal origin, primarily spermaceti from sperm whale. With the worldwide ban on whale hunting, however, this source is no longer available. Spermaceti wax is split by heating with concentrated sodium hydroxide above 573K. The liberated alcohol, approximately 35% yield, is separated by vacuum distillation from the soap and water formed. The product consists essentially of cetyl, oceyl, and arachidyl alcohols.
Sodium Reduction Process: In 1909, Beauvault and Blanc discovered the sodium reduction process of manufacturing fatty alcohols from coconut esters. Fatty alcohol plants established in the 1930s used this process. Although the basic process is relatively simple, actual plant operations in handling the reactants and products are much more complex. The hazards of handling metallic sodium are an additional factor that caused this process to gradually lose out to the catalytic hydrogenation process. Direct Hydrogenation. A more recent process, developed and patented by Henkel , is the direct hydrogenation of natural oils or triglycerides. However, because of the severe conditions employed, a major portion of the valuable glycerin byproduct is also hydrogenated to lower valued propylene glycol and propyl alcohol. The loss of glycerin, the higher consumption of hydrogen gas, and increased use of catalyst do not justify commercial production as yet.
Zieglar Process The Ziegler process builds up ethylene units on triethyl aluminum to the desired average carbon number. The resulting trialkyl aluminum is oxidized with air and then hydrolyzed with water to give the broad mix of even-carbon alcohols from ethanol to eicosanol and higher, which is then fractioned to give lauryl as well as the heavier and lighter alcohols. Therefore, it has to deal with a large amount of co-products.
Natural Process: The manufacture of fatty alcohols from natural oils can be made either through the methyl ester route or fatty acid route. These two methods are both well established and are strongly competitive with each other. Commercial plants around the world use either route.
