Abstract
An integrated reaction-separation process based on only solvents is presented, and thus without the need for related technical equipment (reactor-separator). Both product purification and reactant recovery are achieved automatically for an asymmetric aldol reaction employing a biphasic solvent system as compartmentalizing soft matter. Firstly, COSMO-RS based simulation is introduced as a theoretical guidance in the solvent selection for the reactant 3-chlorobenzaldehyde and non-solvent selection for the R-aldol product, (R)-4-(3-chlorophenyl)-4-hydroxybutan-2-one. This encompasses solubility as core critical parameter, as well as chemo-physical properties and environmental profiling. Such criteria-cascaded screening could effectively reduce a 7665 solvents-database into 1 candidate solvent, which is dodecane, before experimental process assessment. Secondly, this screening’s top candidate was validated as the best reaction solvent by first a solubility test and then by a batch reaction, in which a conversion of 69% was achieved. As desired, the mono-phase reaction yielded spontaneously the product layer and the separate dodecane phase as the second layer, which indeed allowed facile separation of the product from the residual reactant. In a third step, a segmented flow process was developed giving a highest product yield of 63% and a total conversion 92% respectively after a 2 h residence time.
Highlights
Process intensification is defined as a game changer in both equipment design and processing for chemistry, breaking with former methodologies [1]
For the aldol reaction considered, solvents with a ketonemoiety and other compounds such as aldehydes, alcohols, ammonia, which may interfere with the reactants, were eliminated
As some of the solvents in the database are solids at room temperature which need to be molten for purpose, the melting point (M.P.) was considered
Summary
Process intensification is defined as a game changer in both equipment design and processing for chemistry, breaking with former methodologies [1]. The integration of reaction and distillation into one system, is a key example [2]. A plethora of single chemical reactions has been performed with flow chemistry [8], and several benefits are reported [9]. Even several flow chemical reactions in series have been performed, i.e. multi-step reactions in continuous-flow [8,10]. Impressive end-to-end processing of medicines from raw material in one run have been reported, which has even been connected with compounding/formulating equipment to deliver pills in a continuous fashion [11,12]. A high number of reactor and separator equipment and huge controlling tasks, i.e. high system complexity, is needed, which generally affects costs, reliability, and productivity; there is still a lack of scale-up flow separators [11,12]
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