Meso porous silica from acid-treated kaolinite

【Background】

Mesoporous silica has uniform porous texture in sizes (2-10 nm range) and arrangements ( hexagonal, lamella, and framework.) Fig.1 shows the schematic drawing of the liquid-cystal templating mechanism. Hexagonal arrays of cylindrical micelles are formed in the solution, and silicates species occupy the spaces between the cylinders. The targeted mesoporous structures are, thus, obtained by burning out of organic templates. Mesoporous silica has found great utility as catalysts and adsorbents because of the regular arrays of uniform pore channels. Larger surface area is desired for enhancing of the reactions.

【Purpose and Preparation method】

The unique point of our work is using kaolinite as the starting material for preparation of mesoporous silica. Kaolinite (Al₂Si₂O₅(OH)₄) is widely used as a coating agent for paper. Microporous silica which has smaller pores than mesopores was prepared by calcining and selective acid leaching of kaolinite. Mesoporous silica was synthesized by hydrothermal treatment of the microporous silica as a silicate source by the process shown in Fig.1.

【Results】

The maximum specific surface area of the obtained mesoporous silica was about 1500 m²/g. This value was larger tnan those of the reported mesoporous silicas prepared from silicasources gels, and the highest in the world.

【References】

1. Nikkei Business Daily, June 27, 2005
   
   
2. "Synthesis of high surface area Al-containing mesoporous silica from calcined and acid leached kaolinites as the precursors"
   C. D. Madhusoodana, Y. Kameshima, A. Nakajima, K. Okada, T. Kogure and Kenneth. J. D. MacKenzie Journal of Colloid and Interface Science, 297 (2006) 724
   Fig.１　Synthesis mechanism of mesoporous silica