The calcined SBA-15 was impregnated with aqueous solution
of sucrose containing sulfuric acid, similarly to the synthesis of
CMK-18 except for the different amounts of sucrose and H2SO4.
Briefly, 1 g of SBA-15 was added to a solution obtained by
dissolving 1.25 g of sucrose and 0.14 g of H2SO4 in 5 g of H2O.
The mixture was placed in a drying oven for 6 h at 373 K, and
subsequently the oven temperature was increased to 433 K and
maintained there for 6 h. The sample turned dark brown or black
during the treatment in the oven. The silica sample, containing
partially polymerized and carbonized sucrose at the present step,
was treated again at 373 and 433 K using the same drying oven
after the addition of 0.8 g of sucrose, 0.09 g of H2SO4 and 5 g of
H2O. The carbonization was completed by pyrolysis with heating
to typically 1173 K under vacuum. The carbon-silica composite
obtained after pyrolysis was washed with 1 M NaOH solution
(50 vol % ethanol-50 vol % H2O) twice at 373 K or 5 wt %
hydrofluoric acid at room temperature, to remove the silica
template. The template-free carbon product thus obtained was
filtered, washed with ethanol, and dried at 393 K. The energydispersive
X-ray and thermogravimetric analyses showed that the
silica content in the product was normally less than 5 wt % after
the first washing with the NaOH solution. The second washing
gave only trace amounts of silica, indicating that the treatment
with NaOH or HF removed almost all of the silica.