A Study on the Effects of Metal on the Acidity of MeAPO/MeAPSO

Microporous crystalline metal aluminophosphates (MeAPOs) and metalsilicoaluminophosphates (MeAPSOs) having appropriate acidic propertiesand porous structure have been considered as the novel and usefulcatalysts in petrochemical industries. In present work, a theoretical studyhas been carried out on parameters affecting the acidity of MeAPOs andMeAPSOs by the extensive review of the literature. Metal incorporationmanner, bond length and angle of T-O-T, substitution mechanism, andstructural effects were found to be the effective parameters on acidicproperties of these molecular sieves. Among the methods of metalincorporation, the isomorphous substitution was known as the mostsuccessful way of modifying the acid sites. The coordination needs, theorder of material addition in synthesis procedure, pH, and Me/P+Al valuesin the synthesis gel, charge of the template used and metal ionic radiusare the most effective factors on isomorphous substitution. It revealed thatMetal ions of Ti, V, Mn, Co, and Zn show the most isomorphousincorporation by the formation of tetrahedral coordination in the lattice.

Keywords:

Metal Silicoaluminophosphate , Acidity , Isomorphous substitution , Transition metals , Structure