R. Takahashi et al., Silica-alumina catalyst with bimodal pore structure prepared by phase separation in sol-gel process, J CATALYSIS, 200(1), 2001, pp. 197-202
An amorphous silica-alumina catalyst with distinct bimodal pore structure w
as prepared by sol-gel reactions of tetraethoxysilane (TEOS) and aluminum n
itrate in the presence of poly(ethylene oxide) (PEO). It contains macropore
s effective for rapid molecular transportation and mesopores providing a la
rge specific surface area of similar to 600 m(2) g(-1). The pore size distr
ibution of the macropores is sharp and its average diameter varies from 0.3
to 5 mum by altering the starting compositions such as water/TEOS and PEO/
TEOS weight ratios. The macropores are formed when transitional morphologie
s of spinodal decomposition are fixed by sol-gel transition of inorganic co
mponents, and their size is controlled by altering the timing of the onset
of spinodal decomposition and gelation. A change in the starting compositio
n would affect this timing. In addition to macropores, silica-alumina has a
large number of Bronsted acid sites, and shows excellent catalytic activit
y in the cracking of cumene. PEO would have the effect of increasing the un
iformity of Al atoms in the silica network, which would be a cause of the f
ormation of Bronsted acid sites. (C) 2001 Academic Press.