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Preparation of New Molecular Sieve Material by Selective Leaching Method

选择性浸出法制备新型分子筛材料

基本信息

批准号：
07455263
负责人：
OKADA Kiyoshi
金额：
$ 3.14万
依托单位：
Tokyo Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07455263/
关键词：
Selective leaching Porous materials gamma-alumina Uniform pore size Water vapor sorption カオリン鉱物

项目摘要

Mesoporous gamma-alumina was prepared by a new synthetic method, i.e. calcining kaolin minerals at around 1000ﾟC to form fine microtexture with dispersing very fine gamma-alumina grains in amorphous silica matrix and selectively leaching amorphous silica properly using KOH solution to evolve uniform mesopores within the pseudomorph particles of the starting materials. Pore structure with very sharp pore size distribution at several nm in size was obtained by this selective leaching method when it was synthesized using kaolinite from Georgia, U.S.A.as the starting material, calcining at 1000ﾟC and selective leaching at 90ﾟC for 1h by 4M KOH solution. The porous gamma-alumina had characteristic properties to show more uniform pore size and larger pore volume than those of various gamma-alumina reported so far. Therefore, the water vapor adsorption-desorption isotherms of the gamma-alumina at room temperature showed very steep increase of adsorption at around relative humidity (RH) of 80% by capillary condensation and reached maximum adsorption of ca.600ml (STP) /g at RH of 90%. On the other hand, desorption of condensed water from mesopores in the gamma-alumina occurred suddenly at RH of 70%. Since the very quick adsorption and desorption of water vapor in the gamma-alumina was understood due to capillary condensation and evaporation owing to the uniform mesopores, mesoporous gamma-alumina with molecular sieve properties was considered to be prepared by the present selective leaching method.

采用一种新的合成方法，即在1000ﾟC左右焙烧高岭土矿物形成细微结构，并在无定形二氧化硅基质中分散超细的伽马氧化铝颗粒，然后用KOH溶液选择性地浸出无定形二氧化硅，在原料的伪晶型颗粒内形成均匀的介孔。以美国佐治亚州高岭土为原料，在1000ﾟC下焙烧，在90ﾟ℃下用4M KOH溶液选择性浸出1h，可得到孔径分布在数nm处的孔结构。与已报道的各种类型的γ-Al_2O_3相比，该多孔γ-Al_2O_3具有更均匀的孔径和更大的孔体积。因此，室温下γ-Al_2O_3的水蒸气吸附-脱附等温线表明，在相对湿度(RH)为80%左右，毛细管冷凝使吸附急剧增加，在相对湿度(RH)为90%时，最大吸附量约为600ml(STP)/g。另一方面，在相对湿度为70%时，γ-Al_2O_3中孔中的凝聚水突然发生脱附。由于均匀的介孔结构使得水蒸气在γ-Al_2O_3中的快速吸附和脱附是由于毛细管冷凝和蒸发所致，因此我们认为用这种选择性浸出的方法可以制备出具有分子筛性质的介孔γ-Al_2O_3。