Process design for the recovery of waste refrigerants using deep eutectic solvents

Abstract

The environmental impact on climate change of fluorinated gases (F-gases), used mainly in refrigeration applications, is boosting the search of new recovery processes that would allow their reuse in a circular economy framework. Deep eutectic solvents (DESs) have been recently proposed as alternative absorbents in separation processes because they present several advantages, such as lower price and toxicity, in comparison with other traditional absorbents such as ionic liquids. In this work, the gas solubility of four common F-gases in different choline chloride (ChCl)-based DESs has been studied. In general, the observed gas solubility followed the next trend with the studied DESs: R-32 >R-134a>R-125 >R-143a. The affinity of the DESs for the studied F-gases was higher for ChCl:EG (1:3) than for ChCl:Gly (1:3) (10% H2O). The DESs showed good ideal selectivity for the separation of binary mixtures containing the studied F-gases. A separation process for R-410A (a 50% (w/w) mixture of R-32 and R-125) using two absorption columns was proposed and simulated with Aspen Plus using experimental data. It was found that the DESs were valid to separate R-125 with high purity (>98% w/w) and that in the case of ChCl:Gly (1:3) (10% H2O) it was possible to be recovered with high purity (>98%) and recovery (>98%) both F-gases. This work represents a step forward in the study of alternative absorbents, such as DESs, for the separation of commercial refrigerants (F-gases mixtures) for its further reuse in a circular economy context.