Molecular Sieve Membranes for Gas Separation

Department of Chemical Engineering, Norwegian University of Science and Technology, N-7491 Trondheim, Norway 

Gas-separation Problems Combined with Membrane Reactors 

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A new area of polymer science termed nano-macromolecular chemistry [Eirich, 1993] also has relevance to future polymer blend technology and application. Langmuir-Blodget techniques allow for the formation of films of one molecule thickness. Utilizing polymerizable molecules for these films, a polymer molecule or network can yield a film with the thickness of several nanometers. Alternating layers comprised of different polymers could be prepared to yield specific optical or electrical properties. Polymerization of calix-arenes to yield molecular sieving membranes for gas separation has been discussed by Conner et al. [1993]. 

Wang L-J and Chau-Nan Hong F. Carbon-based molecular sieve membranes for gas separation by inductively-coupled-plasma chemical vapor deposition. Micropor. Mesopor. Mat. 2005 77 167-174. 

Wang, L.-J., and Hong, F. C.-N. (2005a). Effects of surface treatments and annealing on carbon-based molecular sieve membranes for gas separation. Appl. Surf. Sci. 240, 161-174. 

Tseng, H.H., Kumar, I.A., Weng, T.H., Lu, C.Y., Wey, M.Y., 2009, Preparation and characterization of carbon molecular sieve membranes for gas separation-the effect of incorporated multi-wall carbon nanotubes. Desalination 240 40-45. 

Liu, P.K.T., Carbon Molecular Sieve Membrane as Reactor/Separator for Water-Gas-Shift Reaction, Proceedings of2007 U.S. DOE Hydrogen Annual Merit Review Meeting, Arlington, VA, May 2007. 

The concept of caibon membrane for gas separation can be found in the early nineteen seventies. Barrer et al. compressed non-porous graphite caibon into a plug, called caibon membrane [8]. Bird and Trimm used poly(fuifuiyl alcohol) (PFA) to prepare unsupported and supported caibon molecular sieve membranes. During carbonization, they encountered shrinkage problems, which lead to cracking and deformation of the membrane. Hence, they failed to obtain a continuous membrane [9]. 

Jones CW, Koros WJ (1994) Carbon molecular sieve gas separation membranes I-preparation and characterization based on polyimide precursors. Carbon 32 (8) 1419-1425 Liang C, Sha G, Guo S (1999) Carbon membrane for gas separation derived from coal tar pitch. Carbon 37 (8) 1391-1397... 

Lee LL, Tsai DS (2001) Synthesis and permeation properties of silicon-carbon-based inorganic membrane for gas separation. Ind Eng Chem Res 40 (2) 612-616 Sedigh MG, Xu L, Tsotsis TT, Sahimi M (1999) Transport and morphological characteristics of polyetherimide-based carbon molecular sieve membranes. Ind Eng Chem Res 38 (9) 3367-3380... 

Successful spinning of mixed-matrix hollow-fiber membranes for gas separation has so far been only demonstrated in apatentby Ekineret al. ° A major hurdle to the commercial implementation of mixed-matrix membranes has been the lack of reproducibility in forming successful mixed-matrix membranes. Challenges with poor polymer- sieve interaction, variability in molecular sieve transport, surface characteristics, and effects of contaminants on molecular sieve performance have been identified in dense mixed-matrix... 

Rao, PS, Wey, MY, Tseng, HH, Kumar, lA and Weng, TH (2008), A comparison of carbon nanotube molecular sieve membrane with polymer carbon molecular sieve membranes for the gas separation apphcation , MicroporoMS Mesoporous Mafer, 113,499-510... 

Some small-pore zeolite and molecular sieve membranes, such as zeolite T (0.41 nm pore diameter), DDR (0.36 x 0.44nm) and SAPO-34 (0.38nm), have been prepared recenhy [15-21]. These membranes possess pores that are similar in size to CH4 but larger than CO2 and have high CO2/CH4 selechvihes due to a molecular sieving mechanism. For example, a DDR-type zeolite membrane shows much higher CO2 permeability and CO2/CH4 selechvity compared to polymer membranes [15-17]. SAPO-34 molecular sieve membranes show improved selechvity for separation of certain gas mixtures, including mixtures of CO2 and CH4 [18-21]. 

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