Ethyl lactate production by reactive distillation – optimization of reaction kinetics and energy efficiency

Background: Ethyl lactate is an environmentally benign solvent, which could substitute petrol-based volatile organic compounds (VOCs) in many applications if production costs are reduced. It is usually produced by the esterification of lactic acid with ethanol – two important chemical building blocks of biorefineries that are available at industrial scale. Reactive distillation is a promising alternative production process, which utilises process intensification to increase energy efficiency and space-time yield by enhancing the reaction kinetics. Methods: In this work, process intensification of ethyl lactate production by means of distillation was analysed with special focus on the efficient separation of water. The feedstock requirements were studied and the process was optimized regarding reaction kinetics in experiments on laboratory level. The preparation of anhydrous starting mixtures for ethyl lactate formation was tested in batch experiments and applied to reactive distillation. The simultaneous distillation was optimized to ensure that the by-product water was separated efficiently and the separation capacity was not limiting the reaction rate. Combined reactive distillation was compared to a serial setup of reactors and distillation steps. Results: It was found that an optimized serial setup can offer similar process intensification at a lower distillate rate compared to simultaneous reactive distillation. Conclusions: The serial setup is more flexible and straight-forward to regulate and scale-up. Based on the experimental results a continuous production process that uses process intensification to reach high ethyl lactate yield and purity was proposed.