Effect of Hydrolytic Temperature on Pore Structure of Alkoxide-derived Aluminas

Alkoxide 법으로 합성한 알루미나의 동공구조에 미치는 가수분해 온도의 영향

  • 조정미 (성신여자대학교 화학과) ;
  • 정필조 (한국화학연구소 무기화학부)
  • Published : 1988.03.01

Abstract

Pore structures of Alkoxide-derived aluminas are investigated by BET Nitrogen Sorption method. Aluminas are derived from hydrolysis of aluminum isopropoxide at 3$^{\circ}$and 8$0^{\circ}C$ with stoichiometric quantities of water in use. The resulting hydrolysates are then subjected to thermal treatment for a fixed period of time from 200$^{\circ}$to 50$0^{\circ}C$ in gradual fashions. The hydrolysates obtained at 3$^{\circ}C$ increase their pore volumes with increasing heat treatment, exhibiting their pore-size distributio as twinpeaked. In contrast, the reverse is true to the hydrolysates obtained at 8$0^{\circ}C$, showing their pore size distribution as single-peaked. This suggests that the pore shapes of the former shall be slit-shaped, whilst whose as the latter shall be of a ink-bottle shape. All the evidence indicates that the hydrolytic temperatures play an important role not only in determining the pore shapes of the alumina samples, but in controlling the liberation of structural water in the alumina layers. It is also, surmized that the subsequent heat treatment may at best affect the mode of pore size distribution for the resulting alumina product(s).

Alkoxide 법으로 합성한 알루미나의 동공 구조를 BET 법으로 구한 흡 탈착 등온선의 hysteresis loop와 동공 분포로부터 고찰하였다. 알루미나는 aluminum isopropoxide를 화학량의 물로 가수분해하여 제조하였고, 가수분해 온도는 3$^{\circ}C$와 8$0^{\circ}C$에서 수행하였다. 이어 20$0^{\circ}C$부터 50$0^{\circ}C$까지 단계적으로 승온시키며 일정시간 열처리하였다. 3$^{\circ}C$ 가수분해 시료의 동공부피는 열처리 온도에 비례하여 증가하였으며, 동공크기는 쌍입분포(twin peaked pore size distribution)형으로 나타났다. 그러나 8$0^{\circ}C$ 가수분해 시료는 열처리에 의하여 동공부피가 감소하고, 동공크기는 단입분포(single peaked pore size distribution)로 나타났다. 이러한 관찰 결과로부터 전자의 동공형태는 slit형, 후자는 ink-bottle형을 하고 있는 것으로 추정되었다. 이와 같이 가수분해 온도는 동공 형태를 결정하는 중요한 인자일 뿐만 아니라, 층상 알루미나의 구조수 일탈 거동을 결정하는데 중요하다. 열처리 효과는 단지 최종 제품의 동공 분포를 결정하는데 영향을 주고 있는 것으로 해석되었다.

Keywords

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