Catalysts intercalation compounds

Unfortunately, it is difficult to ascertain the identity of the actual catalytic species, and it is not clear whether catalysis by a true intercalation compound has been established. For instance, a frequent method for ammonia and Fischer-Tropsch catalyst generation is the following ... 

X-Ray studies confirm that platinum crystallites exist on carbon supports at least down to a metal content of about 0.03% (2). On the other hand, it has been claimed that nickel crystallites do not exist in nickel/carbon catalysts (50). This requires verification, but it does draw attention to the fact that carbon is not inert toward many metals which can form carbides or intercalation compounds with graphite. In general, it is only with the noble group VIII metals that one can feel reasonably confident that a substantial amount of the metal will be retained on the carbon surface in its elemental form. Judging from Moss s (35) electron micrographs of a reduced 5% platinum charcoal catalyst, the platinum crystallites appear to be at least as finely dispersed on charcoal as on silica or alumina, or possibly more so, but both platinum and palladium (51) supported on carbon appear to be very sensitive to sintering. 

Combined with appropriate amorphous carbon precursors graphite intercalation compounds could be used in one-stage process of production of carbon-carbon composites, which could possess attractive properties for such applications as supercapacitors elements, sorbents as well as catalyst supports and materials for energy- and gas-storage systems. 

Potassium mclal reacts with gniphiie to form an intercalation compound approximating CuK. Will this material act as an acidic or basic catalyst "... 

Due to their high charge density [44,47], a high degree of anion exchange (80-100%) can be readily achieved [48], Like the ZrPs, they are also thermally stable. The intercalation compounds of LDH are found to have potential importance as catalysts, ion exchangers, ceramic precursors, antacid drugs, and as hosts for anionic dyes and metal complexes [49],... 

Potassium carbonate is a well-known catalyst for the steam gasification of carbonaceous materials. We discuss the use of in situ high temperature X-ray diffraction to demonstrate that intercalation compound-like structures are not involved as stable intermediates. 

Graphite intercalate compounds are among the best known carbonaceous catalysts, and there is good evidence that electron transfer is important in these systems. The systems were reviewed by Boersma in 1974 and attention will be focused on a few important papers before and after then. 

Graphite intercalate compounds have been known for some but their possibilities as catalysts have been explored comparatively recently. Their catalytic activities obviously depend on the nature of the intercalated material, and a range of graphite intercalates has been identified (see Table 3),... 

Metal chloride intercalate compounds such as graphite-FeQa, ZnCl2, BeCl2, ZrCU, NbCls, and TaCls are all Friedel-Crafts catalysts, and their action has been well described. The mechanism of formation of graphite acceptor compounds of this type is of interest in that electrons are removed from graphite to form negative ions the neutral molecules formed at the same time diffuse into the lattice. 

It is obvious that graphite intercalation compounds can be catalysts of some significance, in which the graphite forms part of the catalyst rather than acting just as a support. The obvious problem is the stability of the intercalates, both with respect to texture and to chemical stability. The interest in the catalysts, particularly in the Far East, is reflected in two recent reviews regrettably the author has not been able to obtain a translation of these. 

Synchrotron radiation is widely used for EXAFS. Rao and Gopalakrishnan [2] have reviewed the results obtained in studies of amorphous materials, catalysts, fast ionic conductors and intercalation compounds. 

Polypyridine complexes of transition metals such as Ru, Fe, Os, Rh and Cr have been under active investigation [1]. Various layered materials such as clay minerals, metal phosphates and transition metal oxides have been known as host materials for intercalation compounds. On this basis, intercalation compounds have been studied as catalysts [2],... 

---