H2-permeable membranes

The miniature PHSS design was based on the original design of the macro PHSS [41], The 2 mm diameter PHSS utilized a cylindrical polished-tip platinum anode that was electrically insulated along the side from a platinum cathode that was coiled around the core (Fig. 8.3). The core was housed in a 2mm outside diameter stainless steel cylindrical sleeve that served as an electrical shield and to which a 25 om thick H2S-permeable membrane was fixed to cover the tip. The reservoir between the sleeve and core... 

FIGURE 8.3 Diagram of the miniature PHSS and respirometer system. The respirometer chamber (left) is equipped with three sensors, the PHSS and PNOS in the chamber stopper and the POS diagonal to the chamber bottom, and has a minimum volume of 2 ml. Tissue is held on a support just above the stir bar for adequate perfusion. The miniature PHSS (right) is approximately 5 mm long and 2 mm outside diameter. The anode is polished at the tip, the cathode is coiled around the insulated anode, the H2S-permeable membrane is cemented to the stainless steel sleeve, and the 30 pL electrolyte volume covers both anode and cathode (after [41]). 

A possible scheme of membrane assisted H2S decomposition is based on Claus process to generate heat for the thermal decomposition and on a lower temperature decomposition step equipped with H2 permeable membrane. In this way unconverted hydrogen sulfide, recycled to the Claus reactor, produces the required reaction heat according to the following reaction ... 

Because the PHSS electrochemical components are separated from sample solution by the H2S-permeable polymer membrane which is essentially inert with respect to... 

FIGURE 18.17 A membrane cell for electrolytic production of CI2 and NaOH. Chloride ion is oxidized to CI2 gas at the anode, and water is converted to H2 gas and OH-ions at the cathode. Sodium ions move from the anode compartment to the cathode compartment through a cation-permeable membrane. Reactants (brine and water) enter the cell, and products (CI2 gas, H2 gas, aqueous NaOH, and depleted brine) leave through appropriately placed pipes. 

A= Semi-permeable membrane allowing only the passage of H2 gas... 

The oxygen anions created are selectively transferred through the oxygen-permeable membrane to the anode, where they experience a similar half-cell reaction with a gaseous fuel, either H2, syngas (CO + Hj), or a hydrocarbon, to produce H20 and C02. For example, if the fuel is CH4, the oxidation reaction in the anode is given by... 

There are three ongoing material research areas that are important for the eventual success of the S-1 cycle. First and foremost is the development of construction materials that can handle the corrosive environment for the lifetime of the process equipment, especially heat exchangers, boilers, and reactors. The other two areas involve gas-permeable membranes and catalyst development. Identifying suitable membranes and reaction catalysts can improve the efficiency of the overall cycle and make H2 production more economical. Effort is currently ongoing in all three disciplines to find the optimal material solutions. 

FIGURE 27.11 (See color insert following page S88.) H2 permeability as a function of temperature and RH. Upper limit (solid line) defined by crossover losses (assuming no contribution from O2 crossover), lower Umit (dotted Une) defined by electrode ionomer film-transport requirements, and data are for wet and dry Nafion 1100 EW-based membranes. (Reproduced from Gasteiger, H.A. and Mathias, M. F., in Proceedings of the Symposium on Proton Conducting Membrane Fuel Cells III, 2003. The Electrochemical Society of America. With permission from The Electrochemical Society, Inc.)... 

Permeability results for the 1000 pm thick 100, 80, 60 and 53wt% Pd membranes as a function of inverse absolute temperature in the presence of the flowing 1000 ppm H2S test gas are presented in Figures 2-5. The neat H2 permeability values for the same 1000 pm thick alloys are also included in the figures for comparison. The H2 permeability of 1000 pm thick Pd is shown in each figure for reference. 

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