Ethyl lactate-water media

Medium Boiling Esters. Esterificatioa of ethyl and propyl alcohols, ethylene glycol, and glycerol with various acids, eg, chloro- or bromoacetic, or pymvic, by the use of a third component such as bensene, toluene, hexane, cyclohexane, or carbon tetrachloride to remove the water produced is quite common. Bensene has been used as a co-solvent ia the preparatioa of methyl pymvate from pymvic acid (101). The preparatioa of ethyl lactate is described as an example of the general procedure (102). A mixture of 1 mol 80% lactic acid and 2.3 mol 95% ethyl alcohol is added to a volume of benzene equal to half that of the alcohol (ca 43 mL), and the resulting mixture is refluxed for several hours. When distilled, the overhead condensate separates iato layers. The lower layer is extracted to recover the benzene and alcohol, and the water is discarded. The upper layer is returned to the column for reflux. After all the water is removed from the reaction mixture, the excess of alcohol and benzene is removed by distillation, and the ester is fractionated to isolate the pure ester. 

There are a eonsiderable number of processes in which ethyl lactate is produced by esterification until a certain amount of water is formed, equilibrium is reached and then ethyl lactate is purified by distillation or other methods. These processes require excess of ethanol to overcome the equihbrium limitations, achieve higher conversions, and, besides, the separation of flic products from the equilibrium mixture is technically difficult, because of mixture of products and unconverted reactants. These are high cost operations. In order to improve ethyl lactate production, an alternative to conventional method consist of combining a separation unit with reaction stage. In the hybrid processes, at least one of die products is continuously removed from the reaction medium so equihbrium is shifted to products formation according to Le Chatelier s principle. In this regard, some reactive separation processes studied for ethyl lactate production are presented below. 

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