The Chemical Structure of Sebacic Acid
Sebacic Acid is a castor-derived fatty acid and a precursor to various esters such as dioctyl sebacate, dibutyl sebacate, and dimethyl sebcate. While the price is often tied to the castor crop yield each year, many consumers of Sebacic Acid have become curious about how the chemical is produced from its castor oil feedstock.
Although sebacic acid can be synthesized from phenols and cresols, castor oil oxidation is considered a more green and cost competitive method of sebacic acid production. First, the castor oil undergoes transesterification followed by steam cracking to yield ricinoleic acid. This is accomplished by heating the castor oil to a high temperature (about 250°C) and mixing it with an alkali such as molten caustic soda. The ricinoleic acid is then cleaved by caustic digestion to give capryl alcohol (2-octanol) and sebacic acid. This method produces a fairly low yield of sebacic acid, and so further purification methods are used to result in higher purity yields.
An alternative production of sebacic acid results in using adipic acid as a starting point. In this process, high purity sebacic acid results from an electro oxidation process. This process was first developed by by Asahi Chemical Industry in Japan and was also piloted by BASF in Germany. First, adipic acid is partially esterified to form monomethyl adipate. Through electrolysis of the potassium salt of moneomethyl adipate dissolved in methanol and water, dimethyl sebacate is created. The dimethyl sebcate then is hydrolyzed to form sebacic acid.