Nitric oxide reduction catalyzed by amorphous copper-zirconium and copper titanium alloys

Amorphous alloys have been regarded as interesting from the catalytic point of view because they lack of long range ordering. Moreover, the surface of amorphous alloys is rich in low-coordination sites and defects which play an important role in catalysis. Amorphous Cu-Zr and Cu-Ti ribbons were produced by melt spinning methods. The surface of amorphous materials was prepared, before catalytic tests, by immersion in HF solutions or by H2 flow reduction. A selective dissolution of first transition metals was exhibited by HF surface pre-treatment. A porous and Cu-rich surface was obtained. In the reduction of NOx with propylene in presence of O2, amorphous ribbons exhibited an initial high activity that decreased until the steady-state was reached. This behaviour can be explained with the oxidation of copper active sites by the oxygen contained in the reaction stream. Cu-Zr alloys showed higher catalytic activity than Cu-Ti alloys. Moreover, the HF treatment increased the activity of the materials, and the HF treated alloys were more active than the H2 treated alloys.