Palladium-based membranes selective

As mentioned earlier, two compatible reactions may be coupled or conjugated properly by a shared membrane through which the species (as a product on one side of the membrane and a reactant on the other) common to both reactions selectively passes. Summarized in Table 8.5 are some documented studies of reaction coupling using dense palladium-based membranes with the alloying component ranging from nickel, ruthenium, rhodium to silver. 

Depending on the type of catalyst adopted, the operating temperatures can vary between 600 K (low-temperature shift catalyst) and 700 K (high-temperature shift catalyst). Because of the relatively high temperatures employed, studies reported in the literature usually refer to the use of inorganic membrane reactors [13-16]. In particular, because palladium and its alloys are extremely selective to hydrogen, many reports discuss work on palladium-based membrane reactors. 

Progress in the field of palladium-based membrane has been driven by their capacity to produce a pure hydrogen stream, owing to infinite hydrogen perm-selectivity with respect to all other gases. On the other hand, some drawbacks limit their commercialization, mainly ... 

Palladium-based dense metallic membranes have been known to be completely selective for hydrogen permeation and are used in commercially available small-scale hydrogen purification units (e.g., Johnson Matthey, 2007 REB Research, 2007 Power + Energy, 2007 ATI Wah Chang, 2007). These hydrogen purification units typically use palladium-alloy... 

Recently, attempts have been made to reduce the cost of palladium metal membranes by preparing composite membranes. In these membranes a thin selective palladium layer is deposited onto a microporous ceramic, polymer or base metal layer [19-21], The palladium layer is applied by electrolysis coating, vacuum sputtering or chemical vapor deposition. This work is still at the bench scale. 

In Table 2.7, the comparison between the CO eonversion values obtained in different palladium-based MRs and the equilibrium ones is reported, demonstrating the capacity of palladium-based MRs to overcome the thermodynamie limits and to obtain high CO conversion. Chapter 7 reports a detailed assessment of selective membrane application for WGS process. 

Palladium-based Selective Membranes for Hydrogen Production... 

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