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A commercial debut for a process to make mesoporous silica.
Next month, Taiyo Kagaku Co. (Yokkaichi, Japan;
edlinks.che.com/7370-563) will start up a 20-m.t/yr plant -
said to be the world's first - for the production of mesoporous silica. Taiyo
Kagaku developed the new production process based on technology first
introduced by Toyota Central R&D Laboratories, Inc. (Aichi, Japan; CE, April 2004, p. 17).
The commercial grade mesoporous silica, tradenamed
TMPS, is composed of honeycomb-shaped pores with adjustable sizes between 1.5
and 7.0 nm, and a surface area over 1,000 m2/gm - properties that
make the material suitable for a number of applications. For example, TMPS
silica impregnated with platinum catalyzes the conversion of carbon monoxide
to carbon dioxide easily at 20-50° C, which could be important for removing
traces of CO from H2 in fuelcell applications. TMPS can also serve
as a carrier for chlorophyll (for artificial photosynthesis), enzymes (for
protein reactions) and other catalysts (for organic synthesis).
TMPS is manufactured by dispersing sodium
silicate into water with a surfactant such as an alkyl trimethyl ammonium. The
solution is heated to 40-100°C and the pH is adjusted to greater than 10,
whereby the sodium ions are replaced with the surfactant to form a silicate
organic complex. The pH of the solution is then reduced below 10 by adding
acid, causing the silano groups on the silicate layers to undergo
dehydrocondensation and form a three-dimensional structure of crosslinked
polysilicate and surfactant complex, which has a honeycomb structure with a
surfactant-micelle core and polysilicate walls. This complex is then calcined
in air at 700-1,000°C to remove the micelle cores, to form the targeted pores.
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