A process for preparing a zeolitic material comprising a metal M, having framework type AEI, and having a framework structure which comprises a tetravalent element Y, a trivalent element X, and oxygen, said process comprising (i) providing a zeolitic material comprising the metal M, having a framework type other than AEI, and having a framework structure comprising the trivalent element X, and oxygen; (ii) preparing a synthesis mixture comprising the zeolitic material provided in (i), water, a source of the tetravalent element Y, and an AEI framework structure directing agent; (iii) subjecting the synthesis mixture prepared in (ii) to hydrothermal synthesis conditions comprising heating the synthesis mixture to a temperature in the range of from 100 to 200° C. and keeping the synthesis mixture at a temperature in this range under autogenous pressure, obtaining the zeolitic material having framework type AEI; wherein Y is one or more of Si, Ge, Sn, Ti, Zr; wherein X is one or more of Al, B, Ga, In; wherein M is a transition metal of groups 7 to 12 of the periodic table of elements.