Facile Utilization of Carbon Dioxide for the Esterification of Potassium Lactate to Butyl Lactate

The utilization of CO₂ is crucial for the sustainable growth of human society. Herein, we present the direct esterification of potassium lactate (KL) with butanol under CO₂ pressurization, resulting in the synthesis of butyl lactate (BL). The pressurized CO₂ reacts with water to generate carbonic acid, thereby facilitating esterification. A single batch reaction yielded 17% of BL, which could be augmented to 36% via two successive operations. Ultimately, through the utilization of a minimal quantity of H₂SO₄ in the final step, the complete conversion of KL to BL was achieved with a selectivity exceeding 99%. The proposed integrated process necessitates approximately 63% less mineral acid compared to conventional lactate separation. An exploration of the effect of various reaction parameters, including reaction temperature, duration, CO₂ pressure, and H₂O content in the KL, was also conducted.