Phosphorus substitution, SAPO molecular sieves

Metal aluminophosphates (MeAPO) contain framework metal (Me), aluminum, and phosphorus. When the metal is divalent (e.g., Zn +, Co +, and Mg +) and substitutes for aluminum, a negatively charged framework results, with H+, for example, serving to compensate the charge. Many aluminophosphate molecular sieves have been synthesized. SAPO-11 and MeAPO-11 have interesting catalytic properties. Their structures have onedimensional 10-ring channels. The 10-ring pore aperture is elliptical with dimensions 0.39 x 0.63 nm. Table 1 is a summary of the characteristics of the molecular sieves which have been used for the skeletal isomerization of n-butenes. 

Silicoaluminophosphates (SAPO s) constitute a novel class of crystalline microporous molecular sieves, containing silicon, aluminum and phosphorus 1-3. SAPO-37 is isostructural to faujasite, and has large pores and an anionic framework 2-4. The negative charge arises from the presence of Si species, partially substituting P in a neutral... 

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