Increasing lattice metal content of porous inorganic crystalline compositions

A method for enhancing the catalytic activity of a porous inorganic crystalline composition comprising 98 mole percent or more SiO.sub.2 and 2 mole percent or less oxides of at least one initial lattice metal selected from those of Groups IIIB, IVB, VB, VIB, VIIB, VIII, IIIA, IVA and VA of the Periodic Table of the Elements and having an anhydrous anionic framework molar composition expressed by the formula

• (1-x)SiO.sub.2 :(x)MO.sub.n/2
• wherein x is less than or equal to 0.02, M is said initial lattice metal and n is the valance of M, said crystalline composition having a total cation exchange capacity of less than about 0.7 meq/gram, which comprises the steps of
• calcining said crystalline composition at a temperature of from about 200.degree. C. to about 600.degree. C.,
• contacting said calcined crystalline composition at a temperature of from about 100.degree. C. to about 850.degree. C. with a volatile compound comprising at least one metal to be tetrahedrally coordinated in the framework of said crystalline composition for a time sufficient to increase the total amount of tetrahedrally coordinated lattice metal in the framework of said crystalline composition whereby said total amount is greater than the amount of said initial lattice metal prior to said contacting, said volatile compound comprising said metal having a radius ratio of less than 0.6 and a size and shape which permits said volatile compound to enter the pores of said crystalline composition at the contacting temperature, and
• converting said volatile compound contacted crystalline composition to the hydrogen or hydronium form.