13-16: Recovery of polymerization-grade aconitic acid from acidified cane molasses using ehtyl acetate

Aconitic acid (trans-propene-1, 2, 3- tricarboxylic acid) is the most prevalent organic acid found in sweet sorghum and sugar cane. Aconitic acid content in cane may reach 0.1-0.2% resulting in as much as 3-7% in molasses. It is used in the food processing industry as an acidulant and can be used as a precursor in the organic synthesis of plasticizers. Many routes, including precipitation, adsorption with ion-exchange resins and liquid-liquid extraction have been examined, and most suffer technical or economic limitations.

In this study, recovery of aconitic acid was carried out via liquid-liquid extraction of acidified sugarcane molasses with ethyl acetate (EtOAc). Diluted sugarcane molasses (~40 g/100g refractive dry solids) was acidified to pH 1.3 (H₂SO₄) and extracted (molasses: solvent = 1:3) under six combinations of time and temperature. The conditions ranged from 1-6 hr at either 30 or 40 °C. In order to conserve solvent, the EtOAc was recovered by distillation and reused for subsequent extraction steps.

Under the most efficient set of conditions, 60-80 % (HPLC) of the aconitic acid was recovered as the free acid. The purity of the product is sufficient for the preparation of biodegradable polyesters, which will be polymerized with glycerol (biodiesel process waste) and functionalized with cinnamic acid (pretreatment effluent from the production of cellulosic ethanol). Because molasses and bagasse are both byproducts of the sugarcane industry, the production of polyesters has the potential to further ‘close the cycle’ while adding value to the industry.