Paraffin separation membranes

High-Performance Olefin-Paraffin Separation Membranes... 

Kang, S.W., Char, K. and Kang, Y.S. 2008a. Novel apphcation of partially positively charged silver nanoparticles for facilitated transport in olefin/paraffin separation membranes. 

So, Sulfolane and Carom, ca 1997, are two current rival processes. Sulfolane has a slight advantage over Carom ia energy consumption, while Carom has 6—8% less capital for the same capacity Sulfolane unit. In 1995, Exxon (37) commercialized the most recent technology for aromatics recovery when it used copolymer hoUow-fiber membrane ia concentration-driven processes, pervaporation and perstraction, for aromatic—paraffin separation. Once the non aromatic paraffins and cycloparaffins are removed, fractionation to separate the C to C aromatics is relatively simple. 

Okamoto, K.,S. Kawamura, M. Yoshino, H. Kita, Y. Hirayama, N. Tanihara, and Y. Kusuki, Olefin/ paraffin separation through carbonized membranes derived from an asymmetric polyimide hollow fiber membrane, Ind. Eng. Chem. Res., 38, 4424,1999. 

The best hope for olefin/paraffin facilitated membrane separations seems to be the solid polymer electrolyte membranes discussed earlier, the results of which are shown in Figures 11.21 and 11.22. If stable membranes with these properties can be produced on an industrial scale, significant applications could develop in treating gases from steam crackers that manufacture ethylene and from polyolefin plants. 

I. Pinnau and L.G. Toy, Solid Polymer Electrolyte Composite Membranes for Olefin/ Paraffin Separation, 7. Membr. Sci. 184, 39 (2001). 

A. Morisato, Z. He, I. Pinnau and T.C. Merkel, Transport Properties of PA12-PTMO/ AgBF4 Solid Polymer Electrolyte Membranes for Olefin/Paraffin Separation, Desalination 145, 347 (2002). 

D.T. Tsou, M.W. Blachman and J.G. Davis, Silver-facilitated Olefin/Paraffin Separation in a Liquid Membrane Contactor System, Ind. Eng. Chem. Res. 33, 3209 (1994). 

In addition to the polymer and facilitated transport membranes, novel materials are being proposed and investigated to achieve membranes with economically attractive properties. Carbon molecular sieve (CMS) membranes prepared by pyrolysis of polyimides displayed much better performance for olefin/paraffin separation than the precursor membranes [39, 46, 47]. Results obtained with CMS membranes indicated properties well beyond the upper-bond trade-off curve, as shown in Figure 7.8. Nonetheless, this class of materials is very expensive to fabricate at the present time. An easy, reliable, and more economical way to form asymmetric CMS hollow fibers needs to be addressed from a practical viewpoint. 

The preceding discussions illustrate that membranes have shown great potential as an alternative for olefin/paraffin separation, yet the performance of current membranes is insufficient for commercial deployment of this technology. Advanced material development is highly desired to improve the membrane properties and reduce cost. Another possible approach involves hybrid membranes with zeolites or CMS incorporated in a continuous polymer phase. More discussion in this regard will be covered later in this chapter. 

Yoshino, M., Nakamura, S., Kita, H., Okamoto, K.-i., Tanihara, N. and Kusuki, Y. (2003) Olefin/paraffin separation performance of asymmetric hollow fiber membrane of 6FDA/BPDA-DDBT copolyimide. Journal of Membrane Science, 212, 13-27. 

Title Dithiolene Functionalized Polymer Membrane for Olefin/Paraffin Separation... 

Chen TJ and Sweet JR, Selective separation of naphthenes from paraffins by membrane extraction, US Patent 5,107,056, 1992. Tompkins CJ, Michaels AS, and Peretti SW, Removal of p-nitrophenol from aqueous solution by membrane-supported solvent extraction, Journal of Membrane Science 1992, 75, 277-292. 

Safarik DJ and Eldridge RB. Olefin/paraffin separation by reactive absorption a review. IndEng Chem Res 1998 37 2571-2581. 61. Matsumoto H, Tanioka A, and Kawauchi S. Effect of fixed charge groups and counter ions on the transport phenomena and paraffin and olefin across anhydrous negatively charged membranes. J Colloid Interface Sci 1998 208 310-318. 

Yang JS and Hsiu GH. Swollen polymeric complex membranes for olefin-paraffin separation. J Membr Sci 1998 138 203-211. Henley E and Santos M. Permeation of vapors through polymers at low temperatures and elevated pressure. AIChEJ 1967 13 1117-1125. 

Bessarabov DG, Theron JP, and Sanderson RD. Novel application of membrane contactors Solubility measurements of 1-hexene in solvents containing silver ions for liquid olefin/paraffin separations. Desalination, 1998 115(3) 279-284. 

Nymeijer K. Gas-liquid membrane contactors for olefin/paraffin separation. PhD Thesis, University of Twente, The Netherlands, ISBN 90-365-1878, 2003. 

Tsou DT, Blachman MW, and Davis JC. Silver-facilitated olefin/paraffin separation in a hquid membrane contactor system. Ind. Eng. Chem. Res. 1994 33 3209-3216. 

Kowah AS, Chen H, and Sirkar KK. Glycerol-based immobilized hquid membranes for olefin-paraffin separation. Ind. Eng. Chem. Res. 2002 41 347-356. 

A number of hydrocarbon separations have been intensely studied and piloted in recent years and commercialization is expected soon. Pervaporation is expected to be one of a number of proven options for sulfur and benzene removal from fuels and olefin/ paraffin separations. These plants will use robust, specially engineered polymer membranes, installed in large-scale tubular modules. 

Table 9-3. Effect of silver concentration on olefin/parafFin separation in AgBp4-PEO membrane at 689.1 kPa feed pressure and 23 °C [40].

Faiz R., Li K. 2012. Polymeric membranes for light olefin/ paraffin separation. Desalination 287 82-97. 

The rest of this Chapter is organized as follows. Section 10.2 outlines a typical olefin/paraffin separation scheme in a conventional ethylene plant, which includes the selected distillation colunms for retrofitting with a membrane unit. Section 10.3 describes the mathematical modeling of the membrane unit and the various assumptions that were made. Section 10.4 presents the procedure of simulating a retrofitted HMD system and the preliminary techno-economic analysis that was carried out. Section 10.5 covers the formulation of MOO problem, which includes selection of objectives, decision variables and constraints in the optimization problems studied. In Section 10.6, results from the optimization of two objectives for various cases are presented and discussed. Finally, conclusions of this study are given in Section 10.7. 

Membrane permeance and selectivity data are based on those of polymeric membranes obtained from Faiz and Li (2012). This is due to a lack of studies on CMS membranes for the separation of olefins/parafifins. The assumption of the use of polymeric membrane data is conservative since CMS membranes have been shown to give better permeance and selectivity than polymeric membranes for olefln/paraffin separation (Xu et al., 2012)... 

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