Described is a process for the treatment of a gas stream containing nitrogen oxides. The process comprises the steps of: (1) providing a gas stream containing one or more nitrogen oxides; (2) contacting the gas stream provided in step (1) with a transition metal containing zeolitic material having a BEA-type framework structure for reacting one or more of the nitrogen oxides; wherein the zeolitic material is obtainable from an organotemplate-free synthetic process. Also described is an apparatus for the treatment of a gas stream comprising containing nitrogen oxides.