For the four Pt/$\gamma$-$Al_2O_3$ catalysts prepared by the incipient wetness technique, the effects of each sintering factor were investigated by the $H_2$ chemisorption method, with varying sintering temperature, sintering time, and sintering atmosphere.
Platinum contents were 0.5, 1.0, 3.0, and 5.6 wt.% and sintering temperatures were selected as 500, 550, 600, 650, and 700℃, and sintering times were 1,4, and 16 hours, and finally $O_2$, $H_2$, and $N_2$ gas were used as sintering atmospheres.
When the activity of catalyst was analyzed in terms of platinum dispersion, the decreasing order of relative dispersion with regard to the change of platinum content was 1.0＞0.5＞3.0＞5.6 wt.% platinum catalyst.
The sintering phenomena were very sensitive to the temperature change in the range of 500-600℃, and the redispersion was observed for the catalysts with low platinum contents treated for 1 hours.
The power law fitting was not applicable to the change of sintering time, and the isothermal steady state dispersion was observed. The decay of platinum dispersion was significant at initial sintering time and its type was monotonic decrease.
When sintering atmospheres were varied, the decreasing order of platinum dispersion was $O_2$＞H_2＞$N_2$ and except for 1.0 wt.% platinum catalyst, the activity of catalysts sintered under $H_2$ atmosphere was the best.
Incipient wetness technique 에 의해 만들어진 네 가지의 Pt/$\gamma-Al_2O_3$ 촉매에 대하여 소결온도, 소결시간, 소결기체를 변화시켜 가면서 각 소결인자들이 소결에 미치는 영향을 수소흡착 방법을 이용하여 조사하였다.
백금함량은 0.5, 1.0, 3.0, 5.6, wt.% 로 하였고 소결온도는 500℃ 에서 700℃ 까지 50℃ 씩 변화시켰으며, 소결시간은 1시간, 4시간, 16시간으로 하였고 소결기체로는 산소, 수소, 질소를 사용하였다.
촉매의 활성도를 백금의 분산정도로 나타내었는데, 금속함량에 따라 1.0 ＞ 0.5 ＞ 3.0 ＞ 5.6 wt.% 백금촉매순으로 상대분산도가 감소하였다.
소결현상은 500 - 600℃ 사이에서 매우 민감한 변화를 보였으며 산소기체하에서 1시간동안 소결된 촉매의 경우에는 재분산현상이 일어났다.
Power - law fitting 에 의해 소결현상을 해석하는 것은 불가능했고 시간의 경과에 따라 등온정상상태 분산 현상이 나타났고 초기시간동안에 분산도의 감소가 심하였으며 감소형태는 단조감소였다.
소결기체를 변화시켰을 때 분산도가 감소하는 순서는 O_2 ＞ H_2 ＞ N_2였으며 1.0 wt.% 백금촉매를 제외하고는 수소하에서 소결된 촉매의 활성도가 가장 좋았다.
