(703c) Catalytic Strategy for Conversion of Triacetic Acid Lactone (TAL) to Potassium Sorbate

This study has proposed a new method for producing potassium sorbate (KS) from triacetic acid lactone (TAL), a biomass-derived chemical, which can be biologically synthesized from glucose. KS is widely used as a preservative in various foods, pharmaceuticals, and other industrial applications. This approach has a higher yield to KS from TAL than the previous method that produced sorbic acid from TAL. Sorbic acid used alone had limited value due to its low water solubility; use of water-soluble KS can overcome this problem. So far, KS has been manufactured by converting sorbic acid with potassium hydroxide. Therefore, we have proposed a new approach for producing KS rather than making sorbic acid as an intermediate. TAL-derived KS by hydrogenation, dehydration, and ring-opening & hydrolysis reactions. TAL can be fully hydrogenated over 10wt% Pd/Al₂O₃ to give close to quantitative yields of HMP (95% yield). This study has carried out dehydration of 4-hyrdoxy-6-methyl 2H-Pyran-2-one (HMP) over solid catalysts, and then the obtained parasorbic acid (PSA) at the yield of 86% with respect to TAL. Moreover, we have developed a kinetic model for the dehydration of HMP to PSA. The obtained PSA was reacted with an equal molar amount of KOH. Here, KOH was used as a reactant of the ring-opening hydrolysis reaction. The overall yield of the TAL-derived KS was calculated to 72.1%. The KS molecule was analyzed by 1H NMR and 13C NMR spectra. The difference in THF solubility between the KS product and impurities enabled us to purify the KS product by simply extracting with THF, and the purity of KS product was measured to be >95% by HPLC analysis and 1H NMR spectra. Furthermore, the synthesized KS has shown similar antifungal activity with commercial potassium sorbate.