Preparation of Al chelate compounds with different carbon chain length andits application for surface modifier of silica

Al chelate compounds with different carbon chain length were synthesized by reactions of aluminum sec-butoxide with beta-ketoesters having different c arbon chain length, such as acetoacetic acid ethyl ester (n = 2), acetoacet ic acid pentyl ester (n = 5), acetoacetic acid octyl eater (n = 8) and acet oacetic acid oleyl eater (n = 18), Silica was modified by aluminum sec-buto xide and these Al chelate compounds (ALK, C2, C5, C8 and C18 respectively). Then the modified silica nias dried at 100 degrees C and heated up to 400 degrees C. We studied the influence of carbon chain length on the hydrophil ic-hydrophobic property of dried silica by measurement of adsorption amount of water vapor. In addition the surface property of heated silica was stud ied by measurement of specific surface area and pore size distribution. It was found that the adsorption amount of water vapor on dried silica decreas ed with increasing the length of carbon chain such as ALK, C2 and C5. Adsor ption amount of water vapor was the same on C5, C8 and C18, Porous Al2O3 wa s prepared from ALK and C2 by drying at 100 degrees C by hydrolysis of alum inum sec-butoxide and Al chelate compounds. Porous Al2O3 was also prepared by thermal decomposition of Al chelate compounds from C5, C8 and C18 by hea ting at 200 degrees C. The mechanism of pore formation changed according to the carbon chain length of Al chelate compounds. The porous Al2O3 prepared from Al chelate compounds had smaller and more uniform pore size than that prepared from aluminum sec-butoxide.