Solvent Regeneration in Complex Mixture Using Pervaporation

This study aims to demonstrate the efficiency of dichloromethane (DCM) regeneration from a methanolic effluent by a combination of distillation and membrane pervaporation process. The presence of an azeotrope (MeOH/DCM/water) makes the regeneration of DCM via distillation alone impossible. A process simulation using ProSim software was carried out in order to evaluate the behavior of the azeotropic mixture. Two secondary treatments aiming to purify the DCM contained in the azeotrope were investigated. The first is the washing of the azeotrope with water. ProSim software was used to target the optimal conditions for washing before the experimental test. Residual water was recovered in the organic phase, meaning that the quality specifications for DCM were not reached. The second process studied for DCM purification was a pervaporation step. The feasibility of this had been proven at laboratory scale. The recovered DCM had the quality of a new solvent, and the whole process (distillation + pervaporation) reached a global DCM regeneration yield of 71.8% before optimization. This yield was limited by the distillation of methylal (also called dimethoxymethane) present in the methanolic effluent at the end of the distillation of the azeotrope, a compound retained by the pervaporation membrane. The pervaporation was performed on a hydrophilic Hybsi membrane letting methanol and water pass through and retaining the DCM (membrane surface = 0.15 m(2)). Optimization and scaling up were then carried out with a semi-industrial pervaporation pilot (membrane surface = 1.05 m(2)) which enabled the industrial scale-up. In order to facilitate the steering of the process and to ensure continuous and efficient monitoring of the regeneration operation, online monitoring by near-infrared probe (NIR) had been implemented allowing the composition of the mixture to be determined with an accuracy of +/- 0.05% on each compound. Finally, an assessment had been conducted of the regeneration pathways for methanol recovery at the bottom of the distillation column, for maximizing the regeneration of methanolic effluents by separating heavy compounds and methylal from methanol.

Morgane Le Hir, Adrien Magne, Thomas Clair, Emilie Carretier, Philippe Moulin. Solvent Regeneration in Complex Mixture Using Pervaporation. Organic Process Research and Development, American Chemical Society, 2021, 25 (3), pp.469-485. ⟨10.1021/acs.oprd.0c00442⟩. ⟨hal-03597582⟩

Journal: Organic Process Research and Development

Date de publication: 01-01-2021


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