Metal aluminophosphate molecular sieves

The crystal structures of several metal aluminophosphate molecular sieves, in Innovation Zeolite Mater. Sci. (eds P.J. Grobet, W.J. Mortier, E.F. Vansant, and G. Schulz Eklofi), Stud. Surf. Sci. Gatal., vol. 37, Elsevier, Amsterdam, pp. 269-279. 

Synthesis and Characterization of Metal Aluminophosphate Molecular Sieves... 

The difficulty of incorporating metal ions into the molecular sieve lattice results from the fact that actually two requirements have to be fulfilled, i.e., (i) the metal cation must have approximately the size of the atom it replaces (Si, A1 or P) and (ii) it must be able to coordinate in a tetrahedral position in the firamework. Fiuthermore, to function as a successful redox catalyst, a change in the valency and/or the coordination of the oxidant must be realized via reversible change of the coordination of the metal cation. Only a limited number of cations have been reported to be incorporated in the fiamework of zeolite and metal-aluminophosphate molecular sieves. These cations include Co, V, Mn, Cr. Ti [158,159] and a short compilation of the structures available (isomorphously substituted molecular sieves) is compiled in Table 1. Generally, it seems that aluminophosphate lattices are more easily adaptable for isomorphous substitution, but that the resulting materials have a lower stability than the corresponding zeolite frameworks [160]. 

Metal aluminophosphate molecular sieves (MeAPO-s) and metal silicoaluminophosphates (MeAPSO-s) are ALPO4-S and SAPO-s which contain divalent Co, Fe, Mg, Mn, or Zn, or trivalent Fe. ELAPO-s and ELAPSO-s contain Li, Be, B, Ga, Ge, As, or Ti. 

J.M. Bennett and B.K. Marcus, The Crystal Structures of Several Metal Aluminophosphate Molecular Sieves. Stud. Surf. Set Catal., 1988, 37, 269-279. 

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