졸 합성시 숙성이 γAl₂O₃ 입자의 표면특성에 미치는 영향

Effects of Surface Characterization of γAl₂O₃ Particles by Aging in the Sol Preparation

${\gamma}-AlO$(OH) 졸 입자 뿐만 아니라 소성처리된 ${\gamma}-Al_2O_3$ 입자의 표면특성을 ${\gamma}-AlO$(OH) 졸 제조시 숙성단계에 의하여 조절하였다. 연구결과, ${\gamma}-AlO$(OH) 졸 입자의 등전점은 숙성 증가에 따라 pH 9.25에서 pH 8.70까지 감소하였으며 ${\gamma}-Al_2O_3$ 입자의 경우는 pH 9.90에서 pH 8.86까지 감소하였다. 숙성에 따른 ${\gamma}-Al_2O_3$ 입자의 산, 염기 특성을 고찰한 결과, ${\gamma}-Al_2O_3$ 입자의 산량은 숙성시간의 증가에 따라 0.1367 mmol/g에서 0.0783 mmol/g까지 감소하였으며, Hammett 산성도함수 $H_o$는 4.8 이상의 산세기를 보였다. 한편 ${\gamma}-Al_2O_3$ 입자의 염기량은 숙성시간의 증가에 따라 0.4399 mmol/g에서 0.3074 mmol/g 까지 감소하였다. 따라서 졸-겔법에 의한 ${\gamma}-Al_2O_3$ 제조시 숙성공정이 산, 염기점의 양을 포함한 표면특성을 조절할 수 있는 중요 공정변수임을 제시하였다.

The surface characteristics of calcined ${\gamma}-Al_2O_3$ particles as well as ${\gamma}-AlO$(OH) sol particles were controlled by aging in the boehmite sol preparation. As a result of the study, the IEPs of ${\gamma}-AlO$(OH) particles were decreased from pH 9.25 to pH 8.70 and those of the calcined ${\gamma}-Al_2O_3$ particles were decreased from pH 9.90 to pH 8.86 by the increase of the aging times. As a result of the acidic and basic characterization of the calcined ${\gamma}-Al_2O_3$ particles by the aging, the amount of acid sites was decreased from 0.1367 mmol/g to 0.0783 mmol/g by the increase of the aging times and Hammett acidity, $H_o$ was showed the acidic strength of 4.8 or above. On the other hand, the amount of basic sites was decreased from 0.4399 mmol/g to 0.3074 mmol/g by the increase of the aging times. Based on these results, we proposed the fact that the aging step in the sol-gel process was an important step to control the surface characterization of ${\gamma}-Al_2O_3$ particles including acidity and basicity.