Hydrogen sulfide membrane-., permeable

Ion-selective electrodes can also become sensors (qv) for gases such as carbon dioxide (qv), ammonia (qv), and hydrogen sulfide by isolating the gas in buffered solutions protected from the sample atmosphere by gas-permeable membranes. Typically, pH glass electrodes are used, but electrodes selective to carbonate or sulfide may be more selective. 

Robinson AV. 1982. Effect of in vitro exposure to hydrogen sulfide on rabbit alveolar macrophages cultured on gas-permeable membranes. Environ Res 27 491-500. 

Effect of temperature on permeability of hydrogen sulfide in a 10% H2S/CH4 gaseous mixture through various polyphosphazene membranes... 

McKinley studied the effects of poisoning by H2S on membrane materials of pure palladium, and alloys of palladium with silver, nickel, copper and gold [74]. Only the Pd-Au alloys showed reasonable resistance to poisoning by hydrogen sulfide according to McKinley [74]. An alloy of 60 wt% Pd and 40 wt% Au retained 80% of its initial (unpoisoned) permeability upon exposure to 4 ppm H2S and retained 40% of its permeability during exposure to 20 ppm H2S at 623 K (350 °C). In contrast, pure palladium was poisoned to 30% of its initial, unpoisoned value after 6 days exposure to only 4 ppm H2S. An alloy of 73 wt% Pd and 27 wt% Ag was completely poisoned within hours after exposure to only 4 ppm... 

Klmura et al. (J 2) reported progress toward applying facilitated transport membranes to industrial scale separations. They measured carbon dioxide and hydrogen sulfide permeabilities at industrially significant operating conditions (6.90 x io kPa COj, 363 03 K). Under these conditions, the authors determined that carbon dioxide transport is influenced by both diffusion and reaction rates. 

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 ... 

Molecular sieves and membranes have been undergoing development for the removal of hydrogen sulfide and CO2 from gas streams, especially when the amount of the acid gas(es) is low (Benson, 1981 Chiu, 1990 Winnick, 1991 Mokhatab et al., 2006 Speight, 2007, 2008). The most appropriate use of the sieves and the membranes would be the use of the sieve to selectively remove hydrogen sulfide, without removing much of the CO2, and/or the use of membranes permeable to hydrogen sulfide but not to CO2. 

Hydrogen sulfide is present within natural gas and biogas, as well as being found in sufficient quantities in syngas to warrant removal [32,33]. The permeability of H2S through a range of polymeric membranes and their selectivity to CO2 is shown in Figure 11.3. 

Figure 11,4 CO2 permeability in PDMS under mixed gas conditions with (grey) and without (black) 500 ppm or H2S present. Reprinted with permission from Journai of Membrane Science, The effect of hydrogen sulfide, carbon monoxide and water on the performance of a PDMS membrane in carbon dioxide/nitrogen separation by Colin Scholes, Sandra Kentish and Ceoff Stevens, 350, 1-2, 189-199, Copyright (2010) Elsevier Ltd...

Another kind of membrane material is represented by a group of nanoporous, hydrogen-selective carbon molecular sieve membranes, which exhibit excellent permeation characteristics and hydrogen permeabilities competitive with metallic membranes (Harale et al., 2007). Furthermore, they are unaffected by CO or hydrogen sulfide (H2S) contamination. Nevertheless, their hydrothermal stability is not guaranteed at r > 623 K. 

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