The study on the preparation of γ-Al2O3 support by sol-gel method

• Main Authors: Wang, Chi-Yao, 王繼耀
• Other Authors: T. C. Huang
• Format: Others
• Language: zh-TW
• Published: 1998
• Online Access: http://ndltd.ncl.edu.tw/handle/15193847611715901031

碩士 === 國立成功大學 === 化學工程學系 === 86 === In this study, the sol-gel technique and oil-drop method were used to prepare the microporous alumina support. The influences of sol-gel process variables, such as acid/alkoxide/water molar ratio, on the microstructure of the support were investigated. Furthermore, effects of the microstructure of γ-Al2O3 support on the properties of Pt/γ-Al2O3 catalyst were also studied. From the experimental esults, the crush strength of the Al2O3 support prepared by sol-gelprocess (~35N/mm) is much higher than those commercial ones (~10N/mm). The microstructure of the Al2O3 support was influenced by the preparation variables,i.e. acid/alkoxide/water molar ratio. When the acid/ alkoxide ratio varied from 0.03 to 0.15, the specific surface area of the support was in the range of 225 to 243 m2/g, the pore size was from 51 to 56 *, and the pore volume was from 0.43 to 0.46 cm3/g. When the acid/koxide ratio varied from 1.0 to 1.5, the specific surface area of the support was in the range of 235 to 253 m2/g, the pore size was from 52 to 55 *, and the pore volume was from 0.46 to 0.48 cm3/g. When the alkoxide/ water ratio varied from 1/ 50 to 90, the specific surface area of the support was in the range of 232 to 257 m2/g, the pore size was from 49 to 55 *, and the pore volume was from 0.43 to 0.46 cm3/g.It showed that supports with different microstructure can be obtained by controlling preparation variables of sol-gel process.The Pt-catalyst prepared with H2PtCl6 as the precursor is an egg-shell type. The Pt dispersion and the impregnating depth were influenced by the acid/alkoxide/water molar ratio and metal loading. The maximum depth of impregnation was obtained at loading 2wt% Pt, and the maximum metal dispersion was at 1wt% Pt.I the sol-gel process, with the acid/alkoxide ratio was from 0.07 to 0.15 in the sol-gel process, the profiles of Pt concentration in the support particles showed a U-type. The Pt- impregnating depth was increased with increasing the acid amount, but the Pt-dispersion showed no significant change as the acid amount was varied. Furthermore, it showed that maximum Pt-dispersion can be obtained when the acid/alkoxide ratio was 0.07/1.2.