Metal mobility under hydrothermal

Since the first synthesis of mesoporous materials MCM-41 at Mobile Coporation,1 most work carried out in this area has focused on the preparation, characterization and applications of silica-based compounds. Recently, the synthesis of metal oxide-based mesostructured materials has attracted research attention due to their catalytic, electric, magnetic and optical properties.2 5 Although metal sulfides have found widespread applications as semiconductors, electro-optical materials and catalysts, to just name a few, only a few attempts have been reported on the synthesis of metal sulfide-based mesostructured materials. Thus far, mesostructured tin sulfides have proven to be most synthetically accessible in aqueous solution at ambient temperatures.6-7 Physical property studies showed that such materials may have potential to be used as semiconducting liquid crystals in electro-optical displays and chemical sensing applications. In addition, mesostructured thiogermanates8-10 and zinc sulfide with textured mesoporosity after surfactant removal11 have been prepared under hydrothermal conditions. 

The efficiency of the above catalysts for NO reduction depends definitely on the kind of metals and their loadings onto supports, the type of reductants and the feed gas composition employed as well as on the kinds of supports and structure of the parent zeolite and its historical nature during preparation. In particular, the effect of the presence of H2O and SO2 in the exhaust gas from mobile sources is well documented on the maintenance of time-on-stream deNOx activity of SCR catalysts, and their resistance to these co-existing gases is an essential parameter determining successful applications to engine sources. The durability of the documented catalysts under hydrothermal conditions should also be considered to verify if those were applicable to controlling vehicle NOx... 

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