Abstract
Membrane separation processes tender a capable option for energy-demanding separation processes. Nanofiltration (NF) and reverse osmosis (RO) membranes are among the most explored, with a latent use in the chemical industry. In this study, four commercial membranes (NF90, NF270, BW30, and XLE) were investigated for their applicability based on the key structural performance characteristics in the recycling of Pd-based catalysts from Heck coupling post-reaction mixture. Pure water and organic solvent permeabilities, uncharged solute permeability, swelling, and catalyst rejection studies of the membranes were conducted as well as the morphological characterization using Fourier transform infrared, field emission gun scanning electron microscopy, and atomic force microscopy. Characterization results showed trends consistent with the manufactures’ specifications. Pure water and organic solvent fluxes generally followed the trend NF270 > NF90 > BW30 > XLE, with the solvent choice playing a major role in the separation process. Pd(PPh3)2Cl2 was well rejected by almost all membranes in 2-propanol; however, XLE rejects Pd(OAc)2 better at high pressure in acetonitrile. Our study, therefore, revealed that the separation and reuse of the two catalysts by NF90 at 10 bar resulted in 97% and 49% product yields with 52% and 10% catalyst retention for Pd(OAc)2 while Pd(PPh3)2Cl2. gave 87% and 6% yields with 58% and 36% catalyst retention in the first and second cycles, respectively. Considering, the influence of membrane–solute interactions in Pd-catalyst rejection, a careful selection of the polymeric membrane and solvent, a satisfactory separation, and recovery can be achieved.
Highlights
Separation technology has evolved during the 20th century, driven primarily by advances in the petroleum industry
The results show that BW30 and XLE are similar in terms of pore sizes; Nghiem and Coleman [36] proposed the absence of pores in BW30
The main goal of applying membrane process in the potential separation and recovery of palladium-based catalyst systems from reaction mixtures was achieved through a series of structured activities which include a review of literature, characterization of the membrane, catalyst retention, and recycling
Summary
Separation technology has evolved during the 20th century, driven primarily by advances in the petroleum industry. Numerous technologies such as distillation, extraction, and adsorption have been universally used [1]. A promising field, in pressure-driven processes, is organic solvent nanofiltration (OSN) [3]. Lab-scale and commercial-scale applications of OSN membranes have been reported [4,5]. In the advance and application of the membrane process, characterization of modelling and optimization are essential steps [6,7]. A consistent and reliable method of measuring the separation performance of membranes is essential and allows end-users to make an informed selection [8].
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