Study of the separation by organic solvent nanofiltration of diluted solutes using commercial, dense and porous membranes and their derivatives by deposition of polyelectrolyte nanolayers

Abstract : The objective of this study was to improve the OSN separation performance of commercial membranes for metathesis applications in which highly diluted catalysts are used. In this work, commercial polymeric membranes were first studied to characterize their performance in organic media using very dilute solute-solvent binary mixtures. Based on a literature review, it was shown that the PERVAP4060 membrane, of which PDMS is the dense active layer, was a promising candidate for organic solvent nanofiltration (OSN). As a porous membrane, the AMS and PAN commercial supports have also been taken into account. In this study, we considered the modification on the surface to improve the separation properties of polymeric OSN membranes. Ar/O2 plasma and/or polyelectrolytes multilayers were used for the preparation of new prototype membranes. Unmodified and modified membranes were tested under OSN conditions using binary feed mixtures. Several highly dilute solutes, organophosphorus ligand R-BINAP, phase transfer catalyst ToABR, and linear alkanes have been studied. Both R-BINAP and ToABR were used in the range of 0.0001 to 0.5% by weight, and most experiments were subsequently performed with 0.05% solute concentrations in toluene. It has been shown that PDMS can retain 80% R-BINAP and about 93% ToABr in toluene. After modification by the LBL deposition, the rejection is improved with the modified PERVAP4060 membranes, leading to an 88% rejection of R-BINAP with a deposit of 10 PAH / PSS polyelectrolyte bilayers at the surface and this rejection being able to reach 95% when the number of bilayers is 20. ToABr rejection increases to 97% with the ten bilayered membranes. The performance of the membrane was studied under different pressures of between 1 and 40 bar; the high rejection, still observed in these OSN conditions, strongly supports a solution-diffusion transfer mechanism through the PDMS. The treatment of ternary mixtures mimicking the catalyst/solute/ solvent mixture corresponding to the hydroformylation has also been studied; no evidence of coupling was detected, and the highest retention remained unchanged. On the other hand, the improvement of the rejection also observed from the porous membranes after modification. The rejection of C44 in the AMS was reached 75% after modification by tention10 bilayers of PDDA / PSS, whereas it was only 25% before modification. In the modified PAN, the rejection of the solutes obtained is in the range of 37 to 50%, whereas it was only 3 to 7% by weight before modification. The disadvantage of the porous membrane, however, is the sharp decrease in flux after the deposition of the multiple layers.
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Mahbub Morshed. Study of the separation by organic solvent nanofiltration of diluted solutes using commercial, dense and porous membranes and their derivatives by deposition of polyelectrolyte nanolayers. Chemical and Process Engineering. Université de Lorraine, 2019. English. ⟨NNT : 2019LORR0089⟩. ⟨tel-02351825⟩

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