Adipic acid, hexamethylenediamine (HMDA) and ε -caprolactam are the basic monomers for the production of the most important polyamides 6 and 66. As shown, they are derived from benzene or butadiene as C6 sources. Hydrogenation and oxidation produce cyclohexanone, which is further converted to adiponic acid and HMDA, or to ε -caprolactam by oxime (Weissermel et al., 1994).
These routes, though, are well established in industry and run efficiently.
Synthesis of these monomers from renewable resources has attracted extensive attention in academia and industry. The suggested approaches all start with carbohydrates, such as glucose.
Frost et al. (1996, 1997) first published a method for the production of adipic acid from glucose fermentation.
Genomatica (2015) (Burgard et al., 2010) recently announced bioengineered microorganisms capable of producing adipic acid.
Rennovia reported a novel chemical route for the catalytic conversion of glucose to adipic acid via gluconedioic acid, as shown in Figure 8 (ICIS, 2010).
Adipic acid, as shown in Figure 9, is a C6 platform chemical that can be converted to adipic dionitrile (ADN) through a chemical process through amidation and dehydration. Adiponitrile is produced by hexamethylenediamine (HMDA) (Voit et al., 2001) and aminohexanitrile (Mares et al., 1998; Eiermann et al., 1999; Ebel et al., 2001), which can be converted to ε -caprolactam (Buysch et al., 1996; Ritz et al., 1997).
Alternatively, hexamethylenediamine and ε -caprolactam can be produced from bioylpropylene or butadiene (Tomilov et al., 1967; Weissermel et al., 1994) (sections 2.1.3.1 and 2.1.3.2). Starting with bio-acrylonitrile or bio-butadienedionitrile can be obtained. As described in section 2.1.4.1, adiponitrile is used as a starting structural unit for hexamethylenediamine and ε -caprolactam (Buysch et al. 1996; Ritz et al., 1997).
Another route to exploit natural synthetic properties starts with the amino acid lysine. Lysine is commercially produced on a large scale through fermentation, mainly for feed (Izumi et al., 1978). ε -caprolactam can be converted into caprolactam derivatives by lysine cyclization, followed by deamination (Frost, 2009).
