X-Ray study of metallic particle sintering in Pt-NaY zeolite catalysts

From the behaviour of the small and wide angle X-ray intensities scattered from 2.98% Pt-NaY catalyst samples, after the latter have undergone differe nt calcination procedures, it is shown that the calcination performed for 4 h at the temperature of 250 degrees C yields very disperse metal particles because the ammonia is completely eliminated without decomposing into nitr ogen and hydrogen. Calcining at 300 degrees C, ammonia is eliminated in 10 min through its partial decomposition, which is responsible for metal parti cle sintering which, moreover, is fully accomplished for a calcination dura tion of 45 min.