Applications of Organic Solvent Nanofiltration

The use of film theory to describe solution mass transfer phenomena in pressure-driven membrane processes has a proven track record for aqueous systems. Under the flow conditions encountered in nanofiltration, the simplified film theory description of mass transfer has an accuracy close to solutions obtained by computational fluid dynamics (CFD) modeling (Zydney, 1997). The film theory, for component i, gives, for the total volumetric flux [see Peeva et al. (2004) for details]  

Concentration polarization can be coupled with a model for membrane transport [e.g., the solution diffusion model of Eq. (16.4)] (Nakao et al., 1986 Van der Berg and Smolders, 1989), to describe membrane transport in a mass transfer limited system. 

Combined solution-diffusion film theory models have been presented already in several publications on aqueous systems however, either 100% rejection of the solute is assumed or detailed experimental flux and rejection results are required in order to find parameters by nonlinear parameter estimation (Murthy and Gupta, 1997). Consequently, it is difficult to apply these models for predictive purposes. Peeva et al. (2004) presented the first consideration of concentration polarization in OSN. They coupled the solution-diffusion membrane transport model, Eq. (16.4), with film theory to describe flux and rejection of toluene/ docosane and tolune/TOABr binary mixtures. This approach was able to integrate concentration polarization and nonideal solution behavior into OSN design models and predict fluxes over a wide range of solvent mixtures from a limited data set of the pure solvent fluxes. The only parameters to be estimated, other than physical properties, are the mass transfer coefficients, which may be measured, and the permeabUilies, which may 

Applications have been proposed for a variety of industries including fine chemical and pharmaceutical synthesis, food and beverage, and refining. 

The separation of reaction products from catalysts is a recurrent problem in homogeneous catalysis. The major drawback of the common separation techniques applied in homogeneous catalysis is the extensive (and usually destmctive) postreaction workup required. OSN membranes, being selective between high MW catalysts ( 450 Da) and reaction products, are able to perform this separation. Nair et al. (2002) presented a membrane-based (STARMEM 122) process for the separation of a phase transfer catalyst (PTC) and a Heck reaction transition metal catalyst from the reaction media. For the PTC catalyst the process was so efficient that rejections superior to 99% were observed for both pre- and postreaction mixtures and no reaction rate decline was observed for two consecutive catalyst recycles. 

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Han, S., Wong, H., and Livingston, A. (2005) Application of organic solvent nanofiltration to separation of ionic liquids and products from ionic liquid mediated reactions. Trans. Inst. Chem. Eng., 83 (A3), 309-316. 

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