Nanofiltration solvent-resistant

In contrast to the use in aqueous media, the first applications studied in nonaqueous media were not very successful. Membranes showed important performance loss, due to chemical 

The largest industrial SRNF plant is installed in the petrochemical industry (Bhore et al., 1999). Wax is a monoester of fatty acids that severely modifies the properties of lube oil and must therefore be removed (Hart et al., 1995). The traditional process of dewaxing involved the cooling of a hydrocarbon mixture in solvent or solvent mixtures (methyl ethyl keton, acetone) to temperatures typically ranging from —5 to — 18°C. In this chilling section, waxy components coagulated and were precipitated or filtered the solvent in the filtrate was removed by evaporation and reused in the process (Cuperus and Ebert, 2002). 

A typical application of SRNF is found in the vegetable oil industry. It is estimated that more than 2 million tons of extraction solvent is used in the United States alone. Starting from seed from plants as soybean or sunflower, oil is obtained by solvent extraction, eventually in combination with mechanical extraction. Hexane is by far the most common extraction solvent. Currently, evaporation is used to recover these solvents and reuse them in the process, which requires a considerable amount of energy, approximately 530 kJ/kg oil. In addition, the elevated temperatures hold a risk on thermal damage, and explosive vapors may create safety problems (Raman et al., 1996). These Umitations can be partially overcome by membrane technology. 

Oil-micelle mixtures are formed during hexane extraction and consist of triglycerides (oils), phospholipids, and solvent. Due to its polarity, phospholipids form very loose conglomerates that can be filtered off by membranes. The process results in a filtrate with clear oil and hexane and a phospholipid fraction that can be worked up more easily. Although hexane has to be removed by stripping, potential savings are found in the reduction of chemicals and improved quality of oil. Raman et al. (1996) reported that a mixture containing 20% of oil could be concentrated to 45% with a commercial SRNF membrane. 

A large number of fine chemicals or pharmaceutically active ingredients are synthesized with complex reaction paths. It often occurs that different steps require different solvents as reaction medium. In such cases, a solvent exchange must take place. A traditional procedure to transport relatively large, nonvolatile components to another solvent is a put-and-take distillation, in which the original solvent is stepwise boiled out and replaced by similar volumes of the second solvent. The technique is only effective if the first solvent has a much lower boiling temperature than the second solvent, for example, the replacement of methanol by toluene. Azeotropic mixtures may cause additional problems. 

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TABLE 4.2. Commercially available solvent resistant nanofiltration membranes... 

J.T. Scarpello, D. Nair, L.M. Freitas dos Santos, L.S. White and A.G. Livingston, The Separation of Homogenous Organometallic Catalysts using Solvent Resistant Nanofiltration, J. Membr. Sci. 203, 71 (2002). 

Solvent resistant nanofiltration membranes are a much more recent evolution. Historically, the membranes developed by Membrane Products Kyriat Weizmann (Israel) - now Koch - (MPF 44, MPF 50, MPF 60) were the first nanofiltration membranes intended for application in organic solvents, although other membranes (e.g., PES and PA membranes) also have a limited solvent stability. The Koch membranes are based on PDMS, similarly to pervaporation membranes, although the level of crosslinking is quite different. 

Table 3.2 Commercial solvent-resistant nanofiltration membranes with characteristics as specified by the manufacturers.

For relatively porous nanofiltration membranes, simple pore flow models based on convective flow will be adapted to incorporate the influence of the parameters mentioned above. The Hagen-Poiseuille model and the Jonsson and Boesen model, which are commonly used for aqueous systems permeating through porous media, such as microfiltration and ultrafiltration membranes, take no interaction parameters into account, and the viscosity as the only solvent parameter. It is expected that these equations will be insufficient to describe the performance of solvent resistant nanofiltration membranes. Machado et al. [62] developed a resistance-in-series model based on convective transport of the solvent for the permeation of pure solvents and solvent mixtures ... 

A new approach is the application of chemometrics (and neural networks) in modeling [73]. This should allow identification of the parameters of influence in solvent-resistant nanofiltration, which may help in further development of equations. Development of a more systematic model for description and prediction of solute transport in nonaqueous nanofiltration, which is applicable on a wide range of membranes, solvents and solutes, is the next step to be taken. The Maxwell-Stefan approach [74] is one of the most direct methods to attain this. 

Solvent-resistant nanofiltration and pervaporation are undoubtedly the membrane processes needed for a totally new approach in the chemical process industry, the pharmaceutical industry and similar industrial activities. This is generally referred to as process intensification and should allow energy savings, safer production, improved cost efficiency, and allow new separations to be carried out. 

Problems to be solved are related to membrane stability (of polymeric membranes, but also the development of hydrophobic ceramic nanofiltration membranes and pervaporation membranes resistant to extreme conditions), to a lack of fundamental knowledge on transport mechanisms and models, and to the need for simulation tools to be able to predict the performance of solvent-resistant nanofiltration and pervaporation in a process environment. This will require an investment in basic and applied research, but will generate a breakthrough in important societal issues such as energy consumption, global warming and the development of a sustainable chemical industry. 

P. T. Witte, S. Roy Chowdhury, J. E. ten Elshof, D. Sloboda-Rozner, R. Neumann, P. L. Alsters, Highly efficient recycling of a sandwich" type polyoxometalate oxidation catalyst using solvent resistant nanofiltration, Chem. Commun. (2005) 1206. 

In catalytic Pd(0) reactions, this phosphonium salt was treated with a Pd(ll) source, base, and substrates to form an active catalyst for Sonogashira, Suzuki, and Heck coupling chemistry (Eq. 42, Eq. 43, Eq. 44). The reactions used 0.5 mol% of the Pd catalyst, >99.9% of which was recovered based on Pd analysis of the filtrate of a nanofiltration using UV-visible and total reflection X-ray fluorescence analysis. The spectroscopic analyses reportedly could detect as little as 0.05% of the 0.01 mmol of starting Pd catalyst in the leachate. The membrane used in this chemistry was a solvent-resistant nanofiltration membrane consisting of a porous poly(acrylonitrile) layer and a dense surface layer of poly(dimethylsiloxane). This membrane worked through nine cycles in the... 

Catalyst separation from reaction mixtures has been efficiently carried out by using solvent-resistant nanofiltration membranes [75]. Following an alternative approach to solving this problem a quaternary ammonium salt has been immobilized on a soluble poly(ethylene glycol) polymer support. The supported catalyst thus obtained, soluble in solvents commonly used in PTC such as dichloromethane and acetonitrile, was used in a series of standard reactions under PTC conditions with comparable results to those obtained with traditional PTC catalysts [76]. Moreover, it compares favorably to other quaternary salts immobilized on insoluble polystyrene supports [77]. The catalyst can be easily recovered by precipitation with ethereal solvent and filtration and shows no appreciable loss of activity when recycled three times. 

Kosaraju, P. B. and Sirkar, K. K. 2008.InterfaciaUy polymerized thin film composite membranes on microporous polypropylene supports for solvent-resistant nanofiltration. Journal of Membrane Science 321 155-161. 

Darvishmanesh S, Buekenhoudt A, Degr vea J, and Van der Bruggen B. General model for prediction of solvent permeation throngh organic and inorganic solvent resistant nanofiltration membranes. 7. Membr. Sci. 2009 334 43-49. 

Vandezande, R, Geversb, L. E. M., and Vankelecom, I. F. J. (2008) Solvent resistant nanofiltration separating on a molecular level. Chemical Society Reviews 37, 365-405. 

D. Bhanushali and D. Bhattacharyya, Advances in Solvent-Resistant Nanofiltration Membranes - Experimental Observations and Applications, Ann. N.Y. Acad. Sci., 984 (2003) 159-177. 

Luthra, X. Yang, L.M. Freitas dos Santos, L. S. White, A.G. Livingston, Phase-transfer catalyst separation and reuse by solvent resistant nanofiltration membranes, Chem. Commun. (2000) 1468-1469. 

L.S. White, Transport properties of a polyimide solvent resistant nanofiltration membrane, J. Memhr. Sci. 205 (2002) 191-202. 

D. Bhanushali, S. Kloos, D. Battar-CHARYYA, Solute transport in solvent-resistant nanofiltration membranes for non-aqueous systems experimental results and the role of solute-solvent coupling, /. Memhr. Sci. 208 (2002) 343-359. 

L. S. White, "Transport Properties of a Polyimide Solvent-resistant Nanofiltration Membrane , J. Memb. Sci. 205, 191 (2002). 

Aerts, S., Vanhulsel, A., Buekenhoudt, A., Weyten, H., Kuypers, S., Che, H., Bryjak, M., Gevers, L.E.M., Vankelecom, I.F.J. and Jacobs, P.A. 2006. Plasma-treated PDMS-membranes in solvent resistant nanofiltration Characterization and study of transport mechanism. 

Li, X., Basko, M., Prez, F.D. and Vankelecom, F.J. 2008a. Multifunctional membranes for solvent resistant nanofiltration and pervaporation application based on segmented polymer networks. 16539-16545. 

Basu, S. Maes, M. Cano-Odena, A. Alaerts, L. De Vos, D.E. Vankelecom, I. F. J. Solvent resistant nanofiltration (SRNF) membranes based on metal-organic frameworks. J. Membrane /., 2009, 344,190-198. 

R. Ding, H. Zhang, Y. Li, J. Wang, B. Shi, H. Mao, J. Dang, J. Liu, Graphene oxide-embedded nanocomposite membrane for solvent resistant nanofiltration with enhanced rejection ability. Chemical Engineering Science 138 (2015) 227-238. 

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