Enhanced introduction of extra-framework metal into aluminosilicate zeolites

A process for the preparation of an extra-framework metal-containing aluminosilicate zeolite involves the steps of: (a) forming a reactant mixture A comprising (i) an aqueous slurry of an aluminosilicate zeolite in a H+-form, and (ii) a metal containing compound or free metal, wherein the mixture does not comprise ammonia, ammonium hydroxide or an ammonium salt, and (b) reacting the metal containing compound or free metal with the aluminosilicate zeolite in a H+-form in reactant mixture A and forming a product mixture B, a reaction mixture comprising the extra-framework metal-containing aluminosilicate zeolite. The metal comprises one or more of copper, iron, manganese, nickel and palladium. The step of reacting the metal with the aluminosilicate zeolite in a H+-form is performed in a single exchange. The extra-framework metal-containing aluminosilicate zeolite can then be used directly in forming a washcoat that can be applied to a support.