Recovery and reuse of ionic liquids and palladium catalyst for Suzuki reactions using organic solvent nanofiltration

Abstract

The separation, post-reaction, of ionic liquids and catalysts from reaction products is an unresolved challenge in the application of ionic liquids to organometallic catalysis. This paper addresses this challenge using organic solvent nanofiltration technology. Suzuki reactions were carried out in a homogeneous solution, comprising 50 : 50 wt% ethyl acetate and ionic liquid. The post reaction mixture was diluted further with ethyl acetate and then separated by nanofiltration into a permeate fraction and a retained (retentate) fraction. The product was recovered in the nanofiltration permeate, while the ionic liquid and palladium catalyst were retained by the membrane and recycled into subsequent consecutive reactions. Thus, the organic solvent nanofiltration was able to separate the Suzuki reaction product from both catalyst and ionic liquid. Three ionic liquids were tested: cocosalkyl pentaethoxi methyl ammonium methosulfate (ECOENG 2 500), tetrabutylammonium bromide (TBAB) and trihexyl(tetradecyl)phosphonium chloride (CyPhos 1 101). All the ionic liquids screened showed positive effects on the catalytic stability, significantly reducing the formation of palladium black and providing high reaction yields over consecutive recycles. The best performance was observed for the CyPhos 1 101 system. Additional investigations employing this ionic liquid showed that the reaction-recycle process can be successfully performed at lower catalyst-substrate ratios, leading to higher catalyst turnover numbers.

Membranes for Organic Solvent Nanofiltration Based on Preassembled Nanoparticles

“…OSN is a technique for economic and efficient separation of molecules in the range of 200-1,000 g.mol -1 which are dissolved in organic solvents. It has been successfully applied in a variety of chemical processes such as catalyst recovery, solvent recycling, chiral separations and ionic liquid separation [3][4][5] . The most widely studied and commercialized OSN membranes are asymmetric polymeric membranes prepared by the phase inversion technique.…”

Ionic Liquids Recycling for Reuse

“…The purity of the recovered AmimCl was above 99%, confirmed by 1H NMR spectroscopy [Cao et al, 2007]. However, for the future industrial applications on a large scale, other methods suggested for removal of water may prove to be more practical [Wong et al, 2006;Swatloski et al, 2003]. These alternative methods include nanofiltration, reverse osmosis, pervaporation, and salting out of the IL.…”

“…However, while solvent extraction is suitable for separation of apolar products, its use in separation of polar products is more problematic. For the latter case, a moderately polar extracting organic solvent is required, but since ILs tend to have significant partition coefficients into polar solvents, or are completely miscible with them, this can result in loss of IL to the product stream [Wong et al, 2006]. Fig.…”

“…Based on the fact that the IL AmimCl can be effectively recycled after each acetylation, Swatloski et al (2003) provides a technically feasible and environmentally acceptable method to prepare acetone-soluble cellulose diacetates in one step using relatively cheap cornhusk as cellulose resource. The separation, post-reaction, of ILs and catalysts from reaction products is a challenge in the application of ILs to organometallic catalysis [Wong et al, 2006]. Suzuki reaction is a key step in the synthesis of active pharmaceutical ingredients.…”

Ionic liquids: a versatile medium for palladium-catalyzed reactions

“…53 Organic solvent nanofiltration have been used to separate the product from both catalyst and ILs in some cases. 120 All the ILs screened showed positive effects on the catalytic stability, significantly reducing the formation of palladium black and providing high reaction yields over consecutive recycles.…”