NO-CO reaction over Pt/gamma-Al2O3 catalysts prepared by microemulsion method

A new method for preparing metal-supported catalysts using microemulsion wa s applied to the platinum-alumina catalysts employed for the NO-CO reaction , and the effects of time of platinum particle preparation on the reaction were investigated. Two catalysts were prepared in different time intervals of 0 min and 10 min, and the size of the platinum particle sizes of these c atalysts after calcination in air was measured using XRD. In the case of 0 min preparation time, the platinum particle size was smaller than 3 nm afte r calcination at 400 degrees C, but it became 12 nm after calcination at 70 0 degrees C. On the other hand, in the case of 10 min, it was about 10 nm a t 400 degrees C and 12 nm at 700 degrees C. In the NO-CO reaction over thes e two catalysts, the NO conversions at low temperatures were almost the sam e, but the NO conversion and NO selectivity above 340 degrees C were differ ent over these catalysts. The catalyst prepared in 0 min showed low NO conv ersion and low NO selectivity, but that prepared in 10 min showed high NO c onversion and high N-2 selectivity. With the catalyst prepared in 0 min, th e platinum particles became anisotropic in shape, and their crystal surface s, which have high NO dissociation activity decreased, however, with that p repared in 10 min, the platinum particles and their crystal surface activit y did not drastically change because the platinum particles were partially embedded in gamma-alumina formed by ME Method.