Hydrogen, separation using supported

An essential element of the Hysep technology is the use of thin film palladium composite membranes to enable low cost and reliable hydrogen separation. The supported palladium layer in the Hysep module has a thickness as low as 3-9 pm, a substantial improvement over current commercial available palladium membranes, which are based on self supporting metal foils with a thickness of 20-100 pm. 

Ionic liquids have already been demonstrated to be effective membrane materials for gas separation when supported within a porous polymer support. However, supported ionic liquid membranes offer another versatile approach by which to perform two-phase catalysis. This technology combines some of the advantages of the ionic liquid as a catalyst solvent with the ruggedness of the ionic liquid-polymer gels. Transition metal complexes based on palladium or rhodium have been incorporated into gas-permeable polymer gels composed of [BMIM][PFg] and poly(vinyli-dene fluoride)-hexafluoropropylene copolymer and have been used to investigate the hydrogenation of propene [21]. 

An integrated proof-of-concept (POC) size fluidized-bed methane reformer with embedded palladium membrane modules for simultaneous hydrogen separation is being developed for demonstration (Tamhankar et al., 2007). The membrane modules will use two 6 in. X 11 in. Pd-alloy membrane foils, 25-pm thick, supported on a porous support. The developmental fluidized-bed reactor will house a total of five (5) membrane modules with a total membrane area of about 0.43 m2 and is scheduled for demonstration by September 2007. 

Lin, Y.M. and M.H. Rei, Separation of hydrogen from the gas mixture out of a catalytic reformer by using supported palladium membrane, Sep. Purif. Technol., 25,87-95,2001a. 

Theoretical infinite selectivity can be achieved for hydrogen separation by Pd or Pd-alloy membranes [40]. The reaction is carried out at high temperature, about above 1000 K, because of the equihbrium of the endothermic reactions involved in the process. Many studies demonstrate that Pd-based membranes with ideally infinite selectivity for H2 can be used to increase the equihbrium conversion of methane steam to H2 removal [36, 40]. The driving force in this process is the partial pressure difference. The high cost, hmited hfetime, and low permeabihty are relevant hmits of Pd and Pd-ahoy membrane. To overcome these drawbacks, the studies have been carried out for the preparation of supported metaUic membranes in which a thin metallic layer is supported on a thicker sublayer [73]. 

Uemiya S, Kato W, Uyama A, et al.. Separation of hydrogen from gas mixtures using supported platinum-group metal membranes, Sep. Purif Technol. 2001 22—23 309-317. 

Myers C, Pennline H, Luebke D, llconichb J, Dixon JK, Maginn EJ, Brennecke JF (2008) High temperature separation of carbon dioxide/hydrogen mixtures using facilitated supported ionic liquid membranes. J Membr Sci 322 28-31... 

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