Design of membrane cascades according to the method of McCabe-Thiele: An organic solvent nanofiltration case study for olefin hydroformylation in toluene

Abstract

International audienceThe method of McCabe-Thiele is widely used for the design of distillation columns. At a given pressure, this graphical method is only based on 3 equations: (i) the partitioning curve linking the liquid and gas phases for a given component at a given plate thanks to a unique set of thermodynamic data and (ii) two operating lines, each one describing the liquid/gas equilibrium of two consecutive plates either in the enrichment section or in the stripping one. In this paper, the method has been adapted to the membrane separation processes aiming at the easy selection of a first set of appropriate designs of cascades that fulfill given separation targets, especially in the case of a binary mixture of components having both intermediate rejections and very different concentrations. Membrane cascades involving several recyclings of the permeate and retentate streams are proposed according to a similar but more sophisticated methodology than for distillation, since for a selected membrane and for given hydrodynamic conditions (pressure, velocity, temperature), several proposals can be made for each equation mentioned above. In short, a set of operating lines is generated varying with the volume reduction ratio (VRR) either for the permeate or the retentate retreatment sections. The method is applied to the OSN separation of a final synthesis medium of a homogeneous catalyzed reaction, namely olefin hydroformylation achieved in toluene. This example is a typical one dealing with the more general case of a product to be extracted in the permeate and a catalytic system to be recovered in the retentate for further recycling in the synthesis reactor aiming at a greener production process. The initial concentration ratio of the two components to separate in OSN is 1/1000 and both compounds have intermediate rejections of 30% and 88%. Thanks to this method, the design of several membrane cascades is proposed and discussed according to different goals of separation (target product purity or recovery, enrichment of component to be recycled, energy consumption, etc.). © 2017 Elsevier B.V

Coupling Rhodium‐Catalyzed Hydroformylation of 10‐Undecenitrile with Organic Solvent Nanofiltration: Toluene Solution versus Solvent‐Free Processes

“…Changing 10‐undecenitrile for mixtures of the reaction products and by‐products would have a little impact on flux, as evidenced from experience . To overcome the lack of sufficient amount of all components, preventing from an experimental determination, we have intensively studied the Biphephos/Aldehyde separation on a theoretical point of view . Assuming constant rejection of 88 % for Biphephos and 30 % for the aldehyde, or taking into account rejection variations with the concentration, resulted in similar results in the 1–10 VRR range.…”

“… Overall recoveries of the Biphephos ligand in the retentate and the target Aldehyde in the permeate at different VRR based on OSN performances with the Biphephos system in toluene and Pervap 4060 membrane at 10 bar adapted from simulation …”

“…[54] To overcome the lack of sufficient amount of all components, preventing from an experimental determination, we have intensively studied the Biphephos/Aldehyde separation on a theoretical point of view. [44][45][46]53] Assuming constant rejection of 88 % for Biphephos and 30 % for the aldehyde, or taking into account rejection variations with the concentration, resulted in similar results in the 1-10 VRR range. Figure 7 depicts the overall simulated recoveries of Biphephos in the retentate and the aldehyde in the permeate vs. VRR.…”

“…One has to keep in mind that, generally, this is more an efficient enrichment step than a very fine purification process such as chromatography. An increase in performances can be envisioned by complexifying the OSN scheme with a membrane cascade (see Discussion) . Moreover, the membrane ability to separate the target product(s) from the unreacted substrate(s) and other by‐products have to be evaluated.…”

“…An increase in performances can be envisioned by complexifying the OSN scheme with a membrane cascade (see Discussion). [44][45][46][47][48][49][50][51] Moreover, the membrane ability to separate the target product(s) from the unreacted substrate(s) and other by-products have to be evaluated. Once the ligand has been selected, coupling reaction and OSN for the recycling of the catalytic system has been performed and compared in toluene and in bulk.…”