Biocatalytic intensified process for the synthesis of neopentyl glycol dicaprylate/dicaprate

Abstract

Emollient esters are widely used ingredients in the cosmetics industry. Their chemical synthesis requires the use of high temperatures and polluting acid catalysts, resulting in environmentally unfriendly processes. This paper describes, for the first time, the biocatalytic synthesis process of the cosmetic ingredient neopentyl glycol dicaprylate/dicaprate (INCI name), a mixture of branched diesters with excellent emollient properties. The co-esterification of the acids with the alcohol is carried out in a solvent-free system, using the biocatalyst Lipozyme®435, a commercial immobilized derivative of Candida antarctica lipase B marketed by Novozymes. Process intensification has been approached by acting on three different aspects. Firstly, the use of solvent-free systems provides higher yields by operating with smaller reactor volumes. Secondly, the inhibition of the enzymatic activity caused by caprylic and capric acids has determined the need to implement a new reaction strategy consisting in the use of a fed-batch reactor, in which the acid is added to the reactor using a peristaltic pump in order to maintain an optimal acid concentration that minimizes the inhibition effects. Finally, the reusability of the biocatalyst used has been verified, allowing it to be used in at least five consecutive reaction cycles without noticeable loss of activity. All this results in an efficient synthesis process with a process productivity of 0.15 kg product/L reactor·h and a biocatalyst productivity of 167.09 kg product/kg biocatalyst. Only 6 h are needed, operating in a fed-batch reactor at 80 °C, to obtain a product with 92.5% purity. In addition, the most commonly used sustainability indicators have been calculated, reflecting that the biocatalytic process developed for the synthesis of neopentyl glycol dicaprylate/dicaprate complies with many of the principles of “green chemistry” and is suitable for future implementation on an industrial scale.