| CPC C07C 67/54 (2013.01) [B01D 19/00 (2013.01); B01J 19/0046 (2013.01); C07C 67/08 (2013.01); B01J 2219/00452 (2013.01); B01J 2219/0059 (2013.01)] | 12 Claims | 

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               1. A system for producing a diester-based composition, the system comprising: 
            a first reactor in which an esterification reaction of dicarboxylic acid and alcohol is performed; 
                a first reflux unit connected to the first reactor and selectively separating unreacted alcohol from a mixed gas generated during the esterification reaction, and then refluxing the separated unreacted alcohol to the first reactor, wherein the first reflux unit comprises: 
                1) a first reflux column directly connected to the first reactor and receiving the mixed gas and unreacted alcohol in a liquid state and then transferring the mixed gas to a first pre-condenser and the unreacted alcohol in a liquid state to the first reactor; 
                2) the first pre-condenser directly connected to the first reflux column and condensing a portion of the unreacted alcohol in the mixed gas from the first reflux column; 
                3) a gas-liquid separation device directly connected to the first pre-condenser and receiving the mixed gas and the unreacted alcohol in a liquid state which is condensed from the portion of the unreacted alcohol, and then transferring the mixed gas to a first condenser and the unreacted alcohol in a liquid state to the first reflux column; 
                4) the first condenser directly connected to the gas-liquid separation device and condensing the mixed gas from the gas-liquid separation device; and 
                5) a first layer-separator directly connected to the first condenser and separating alcohol and water in a condensate and then transferring an alcohol layer to the gas-liquid separation device and discharging a water layer. 
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