Solvent recycle with imperfect membranes: A semi-continuous workaround for diafiltration

Abstract

For separation of a two-component mixture, a three-stage organic solvent nanofiltration (OSN) process is presented which comprises of a two-stage membrane cascade for separation with a third membrane stage added for integrated solvent recovery, i.e. solvent recycling. The two-stage cascade allows for increased separation selectivity whilst the integrated solvent recovery stage mitigates the otherwise large solvent consumption of the purification. This work explores the effect of washing the solvent recovery unit at intervals in order to attain high product purities with imperfect solvent recovery membranes possessing less than 100 % rejection of the impurity. This operation attains a purity of 98.7 % through semi-continuous operation with two washes of the solvent recovery stage, even when imperfect membranes are used in a closed-loop set-up. This contrasts favourably with the 83.0 % maximum purity achievable in a similar set-up with a single continuous run. The process achieves slightly lower (-0.7 %) yield of around 98.2 % compared to a continuously operated process without solvent recovery but consumes approx. 85 % less solvent (theoretical analysis suggests up to 96 % reduction is possible). 9 different membranes, both commercial (GMT, Novamem, SolSep) and in-house fabricated, are screened and tested on a separation challenge associated with the synthesis of macrocycles -amongst the membrane materials are polyimide (PI), polybenzimidazole (PBI) and, polyetheretherketone (PEEK).3

Porous Polymer Membranes by Hard Templating – A Review

“…This is typically closely linked to the water use and/or waste water production of a process. [175,176] Phase inversion processes are polluting water that has to be recovered after use. Hard templating methods often use less solvents and water as phase inversion.…”

Synthesis of Three New Bifunctional Glucose-Thiourea Organocatalysts and Their Application in Asymmetric <i>Michael</i> Addition

“…Nowadays more and more attention is paid to protect our environment, so catalyst recovery can be a useful tool for reach this goal. Our recent article [19] presents a preliminary study of the potential of the so-called organic solvent nanofiltration (OSN) [20][21][22] in the purification and recovery of pyridino-and piperidino-crown ether based organocatalysts. According to these results, the sustainable technology of OSN has been proposed for catalyst 11 and solvent recovery based on which we will shortly report a new process for our organocatalysts in asymmetric Michael additions.…”

Synthesis and determination of pKa values of new enantiopure pyridino- and piperidino-18-crown-6 ethers

“…The residue was purified by column chromatography on silica gel using MeOH-acetonitrile 1:10 mixture as an eluent to yield (R,S,S,S)-7 (173.9 mg, 57%) as a white crystal or (R,S,S,S)-8 (146.0 mg, 48%) as a colourless oil. Physical and spectroscopic data of the products are the following: (1R,4S,14S,17S)-(-)-4,14-Dimethyl-6,9,12-trioxa-3,15,21-triazabicyclo (1R,4S,14S,17S)-(-)-4,14-Diisobutyl-6,9,12-trioxa-3,15,21-triazabicyclo -Dibutylpyridine-2,6-dicarboxamide (20). To pyridinedicarboxylic acid 17 (10.0 g, 59.8 mmol) was added first a catalytic amount of DMF (two drops) followed by thionyl chloride (43.4 mL, 71.1 g, 598 mmol), and the resulting mixture was stirred at reflux temperature under Ar for 2 h. The volatile components were evaporated and the traces of SOCl 2 were removed by repeated distillation of toluene from the mixture.…”

“…19 Schaepertoens et al recently proposed a three-stage membrane cascade for the purification of dibenzo-18-crown-6 ether and in situ solvent recycle. 20 This article presents a preliminary study of the potential of OSN in the purification and recovery of pyridino-and piperidino-crown ether based catalysts.…”