Solvent usage in the pharmaceutical sector accounts for as much as 90 % of the overall mass during manufacturing processes. Consequently, solvent consumption poses significant costs and environmental burdens. Continuous processing, in particular continuous‐flow reactors, have great potential for the sustainable production of pharmaceuticals but subsequent downstream processing remains challenging. Separation processes for concentrating and purifying chemicals can account for as much as 80 % of the total manufacturing costs. In this work, a nanofiltration unit was coupled to a continuous‐flow rector for in situ solvent and reagent recycling. The nanofiltration unit is straightforward to implement and simple to control during continuous operation. The hybrid process operated continuously over six weeks, recycling about 90 % of the solvent and reagent. Consequently, the E‐factor and the carbon footprint were reduced by 91 % and 19 %, respectively. Moreover, the nanofiltration unit led to a solution of the product eleven times more concentrated than the reaction mixture and increased the purity from 52.4 % to 91.5 %. The boundaries for process conditions were investigated to facilitate implementation of the methodology by the pharmaceutical sector.
In the last decades, the rapid advancement of solvent-resistant membranes and catalysis led to the development of more efficient and sustainable materials and processes. The present article critically assesses membrane-assisted catalysis in organic media, which is a multidisciplinary field combining materials science, reaction engineering, organic chemistry, and membrane science and technology. The membranes act either as catalysts directly accelerating the rate of the reaction or as selective barriers for separating homogeneous catalysts from the reaction mixture. The discussions are grouped based on the catalyst type, and introductory tables given for each group allow direct comparison of the literature with regards to reaction type, solvent(s) employed, type of membrane, catalyst rejection, highest conversion and volumetric productivity. Major achievements, limitations and inconsistencies in the field are presented along with future research directions and requirements.
This paper reports a novel method for the preparation of chiral stationary phases (CSPs) using an acridino-18-crown-6 ether selector as a model compound. Chiral stationary phase (R,R)-CSP- 2A: was obtained by in situ continuously recirculating the solution of carboxyl-substituted acridino-18-crown-6 ether (R,R)- 4: , dicyclohexylcarbodiimide and 3-(triethoxysilyl)propylamine through a high-performance liquid chromatography (HPLC) column containing blank silica gel in elevated pressure and temperature. The enantiomer separating ability of chiral stationary phase (R,R)-CSP- 2A: was investigated by HPLC using mixtures of enantiomers of 1-(1-naphthyl)ethylamine hydrogen perchlorate, 1-(2-naphthyl)ethylamine, 1-(4-bromophenyl)ethylamine and 1-(4-nitrophenyl)ethylamine hydrogen chloride. The best results were found for the separation of the mixtures of enantiomers of Br-PEA.
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