Obtaining of 2,2,2-trifluoroethyl-2,2,2-trifluoroacetate via reactive distillation

Reactive distillation is one of the most effective methods for producing esters via the esterification of acids and alcohols. This technique combines chemical reaction with simultaneous separation of the target product within a distillation column. By continuously removing the ester from the reaction zone, it overcomes the chemical equilibrium, shifting the balance toward product formation. The effectiveness of this approach was first demonstrated industrially in the 1980s for methyl acetate production and has since been confirmed in numerous applications.

This study applies reactive distillation to synthesize 2,2,2-trifluoroethyl-2,2,2-trifluoroacetate from 2,2,2-trifluoroethanol and 2,2,2-trifluoroacetic acid. Experiments were carried out in a batch column at atmospheric pressure, using an equimolar feed and 2% sulfuric acid. Under these conditions, the equilibrium ester concentration at the boiling point is only 0.13 mole fraction, as shown in our prior work.

During reactive distillation, the distillate splits into two liquid phases: an aqueous phase (containing dissolved alcohol) and an organic phase. The organic phase consists of a mixture of the target ester and unreacted alcohol, with the ester content exceeding 0.9 mole fraction. This composition arises from two azeotropes present in the system—a heterogeneous azeotrope between the ester and water, and a homogeneous azeotrope between the ester and the alcohol, both boiling near 53.8 °C. Thus, while reactive distillation greatly improves conversion compared to equilibrium, the azeotrope between the ester and the alcohol prevents direct recovery of the pure ester.

To isolate the ester from the organic phase of the distillate, two purification strategies were evaluated: extractive distillation using N-methylpyrrolidone as an entrainer, and liquid-liquid extraction with water. Both methods successfully yielded 2,2,2-trifluoroethyl-2,2,2-trifluoroacetate with a purity exceeding 0.99 mole fraction, demonstrating viable routes for obtaining the high-purity product.