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HWAHAK KONGHAK,
Vol.20, No.6, 433-444, 1982
Vol.20, No.6, 433-444, 1982
Alcohol과 Silane 으로 처리한 Silica의 표면특성
Surface Characteristics of Silica Treated with Alcohols and Silanes
Silica의 표면을 alcohol과 silane으로 처리하여 소수성 silica로 만들었으며, 소수성 silica의 표면을 IR spectra, 수분 및 propane에 대한 흡착, 표면적의 측정 및 DTA 등으로 연구하였다.
Alcohol로 처리된 silica를 IR spectra로 검토한 결과 3,750 cm-1의 silanol group에 의한 peak가 감소함에 따라 2,985∼2,860 cm-1의 alkyl group에 의한 peak는 증가하였다. 그리고 silica를 silane으로 처리한 경우에도 유사한 결과를 나타내었으며 200∼250 ℃의 반응온도에서 반응이 최고로 잘 일어난다.
처리된 silica의 수분흡착량은 미처리된 silica에 비하여 현저히 감소하였으며, 표면에 직환된 methyl group이 방대할수록 수분흡착량이 감소하였다. Propane 기체에 대한 흡착량은 monomethyisilane으로 처리된 silica가 가장 많았으며, dimethylsilane이나 trimethylsilane으로 처리된 silica는 표면에 직환된 방대한 alkyl group으로 인하여 propane의 흡착을 방해하였다. 그리고 propane에 대한 흡착열은 monomethylsilane으로 처리된 silica의 경우에는 8.2 kcal/mole 값을 나타내었으나 그외의 물질로 처리된 silica는 4∼5 kcal/mole의 값을 나타내었다.
처리된 silica의 표면적은 직환된 alkyl group이 silica의 micro pore를 덮어싸고 기공내의 산소의 흡착을 방해하므로 174∼200 m2/g으로 감소되었다. 또한 DTA 곡선을 검토한 결과 처리된 silica는 미처리된 silica에 비하여 수분의 탈착에 의한 흡열 peak가 현저하게 감소되었다.
Alcohol로 처리된 silica를 IR spectra로 검토한 결과 3,750 cm-1의 silanol group에 의한 peak가 감소함에 따라 2,985∼2,860 cm-1의 alkyl group에 의한 peak는 증가하였다. 그리고 silica를 silane으로 처리한 경우에도 유사한 결과를 나타내었으며 200∼250 ℃의 반응온도에서 반응이 최고로 잘 일어난다.
처리된 silica의 수분흡착량은 미처리된 silica에 비하여 현저히 감소하였으며, 표면에 직환된 methyl group이 방대할수록 수분흡착량이 감소하였다. Propane 기체에 대한 흡착량은 monomethyisilane으로 처리된 silica가 가장 많았으며, dimethylsilane이나 trimethylsilane으로 처리된 silica는 표면에 직환된 방대한 alkyl group으로 인하여 propane의 흡착을 방해하였다. 그리고 propane에 대한 흡착열은 monomethylsilane으로 처리된 silica의 경우에는 8.2 kcal/mole 값을 나타내었으나 그외의 물질로 처리된 silica는 4∼5 kcal/mole의 값을 나타내었다.
처리된 silica의 표면적은 직환된 alkyl group이 silica의 micro pore를 덮어싸고 기공내의 산소의 흡착을 방해하므로 174∼200 m2/g으로 감소되었다. 또한 DTA 곡선을 검토한 결과 처리된 silica는 미처리된 silica에 비하여 수분의 탈착에 의한 흡열 peak가 현저하게 감소되었다.
The surface hydroxyl groups of silica have been modified by the treatment of chlorosilanes and alcohols. And the hydrophobic properties of the silica have been studied by IR spectra, propane and water adsorption, surface area, and DTA.
Alcohol modified silica exhibited OH absorption band shift from 3,750 cm-1 to lower frequency along with the increment of alkyl absorption bands at 2,985∼2,860 cm-1. Similar results were observed with silane treatment, showing most optimum treatment temperature at 200∼250 ℃. The adsorption tendency of treated silica toward water were significantly less than untreated silica in the decreasing order of monomethylsilane>dimethylsilane>trimethylsilane.
Adsorption properties of propane gas to the methyl-hydrogen silane treated silica proved to be the best adsorbent to the gas with active hydrogen adsorption site. Others, however, hardly proved themselves to be better adsorbent than untreated silica except ethyl alcohol treated silica. These results are attributed to the hindrance of bulky groups such as dimethyl or trimethyl. The heat of adsorption for propane gas on the monomethylsilane treated silica was 8.2 Kcal/mole, while the other silicas treated by the others was 4-5 Kcal/mole.
The surface area of treated silica decreased to 174∼200 m2/g because of the alkyl groups covering the micro pore of silica and hindering the adsorption of oxygen into the interior of pore volume.
In the DTA curves of the trimethylsilane and ethyl alcohol treated silica, it was found that the peak intensity due to the desorption of water remarkablely decreased and the endothermic peaks due to the decomposition of surface substituted groups appeared at 480 ℃, 530 ℃, and 630 ℃.
Alcohol modified silica exhibited OH absorption band shift from 3,750 cm-1 to lower frequency along with the increment of alkyl absorption bands at 2,985∼2,860 cm-1. Similar results were observed with silane treatment, showing most optimum treatment temperature at 200∼250 ℃. The adsorption tendency of treated silica toward water were significantly less than untreated silica in the decreasing order of monomethylsilane>dimethylsilane>trimethylsilane.
Adsorption properties of propane gas to the methyl-hydrogen silane treated silica proved to be the best adsorbent to the gas with active hydrogen adsorption site. Others, however, hardly proved themselves to be better adsorbent than untreated silica except ethyl alcohol treated silica. These results are attributed to the hindrance of bulky groups such as dimethyl or trimethyl. The heat of adsorption for propane gas on the monomethylsilane treated silica was 8.2 Kcal/mole, while the other silicas treated by the others was 4-5 Kcal/mole.
The surface area of treated silica decreased to 174∼200 m2/g because of the alkyl groups covering the micro pore of silica and hindering the adsorption of oxygen into the interior of pore volume.
In the DTA curves of the trimethylsilane and ethyl alcohol treated silica, it was found that the peak intensity due to the desorption of water remarkablely decreased and the endothermic peaks due to the decomposition of surface substituted groups appeared at 480 ℃, 530 ℃, and 630 ℃.
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