Supported salt melts

Finally, we mention supported molten metal catalysis (SMMC), in which molten metal catalysts are dispersed as nanodroplets or as thin film on the surface of porous supports. Supported salt melts provide a well-defined volume, accessible to few reactant components, with a surface that is dynamically restructuring to give access to metal cations. The supported molten salt forms a thin layer on the top of the support that is stable up to high temperatures (600 °C). Usually, the whole surface is covered, but micro- and small meso-pores are preferentially filled. Such catalysts possess very interesting properties for the oxidative dehydrogenation of light alkanes [138]. 

Recently, there has been considerable interest in developing molten salts that are less air and moisture sensitive. Melts such as l-methyl-3-butylimidazolium hexa-fluorophosphate [211], l-ethyl-3-methylimidazolium trifluoromethanesulfonate [212], and l-ethyl-3-methylimidazolium tetrafluoroborate [213] are reported to be hydro-phobic and stable under environmental conditions. In some cases, metal deposition from these electrolytes has been explored [214]. They possess a wide potential window and sufficient ionic conductivity to be considered for many electrochemical applications. Of course if one wishes to take advantage of their potential air stability, one loses the opportunity to work with the alkali and reactive metals. Further, since these ionic liquids are neutral and lack the adjustable Lewis acidity common to the chloroaluminates, the solubility of transition metal salts into these electrolytes may be limited. On a positive note, these electrolytes are significantly different from the chloroaluminates in that the supporting electrolyte is not intended to be electroactive. 

The synthetic route to metals porphyrazines requires the preparation of porphyrazine core at the beginning. The starting material of porphyrazine was disodium salt of dithiomaleonitrile which was obtained from the reaction of carbondisulfide with sodiumcyanide in two steps. The results of IR spectrum and melting point (290°C) of compound supported the stmcture we aimed. 

Comprehensive reviews describing the preparation, purification, and physical and electrochemical properties of these melts have been published [17-20]. The most popular systems are mixtures of A1C13 with either l-(l-butyl)pyridinium chloride (BupyCl) or 1 -methyl-3-ethylimidazolium chloride (MeEtimCl). These systems are very versatile solvents for electrochemistry because they are stable over a wide temperature range. In many ways they can be considered to be a link between conventional nonaqueous solvent/supporting electrolyte systems and conventional high-temperature molten salts. 

Some salts that melt at low temperatures can disperse spontaneously onto the surface of a suitable support even at room temperature. Worthy of special mention is the behavior of HgCI2 mixed with active carbon. This low-melting-point salt disperses at 30°C onto a support having a very specific surface, namely, active carbon, at a noticeable rate, as is shown in Fig. 9. Hydrated nitrates and chlorides can also disperse spontaneously at ambient or mild temperatures onto the surface of y-Al203, as is evidenced in Fig. 10. 

---