K. Okada et al., PREPARATION OF MICROPOROUS SILICA FROM METAKAOLINITE BY SELECTIVE LEACHING METHOD, MICROPOROUS AND MESOPOROUS MATERIALS, 21(4-6), 1998, pp. 289-296
Microporous silica was prepared by selective leaching of metakaolinite
, derived from the 1:1 layered clay mineral kaolinite (2SiO(2)Al(2)O(3
)2H(2)O) by firing at 600 degrees C for 24 h. Treatment with 20 mass%
H2SO4 solution at 90 degrees C for 0.5-5 h with stirling. led to a dec
rease in the Al2O3 content and an increase in the specific surface are
a (S-A) with increasing leaching time. The adsorption-desorption isoth
erms of N-2 measured at 77 K show a type I curve, the average pore siz
e, calculated by t-plot method, being about 0.6 nm and the maximum S-A
, about 340 m(2)g(-1). The Si-29 MAS NMR spectrum of the 2 h leached s
ample showed peaks at -101 and -110 ppm, which can be assigned to the
layer structure unit (Q(3)) and the SiO4, tetrahedral framework struct
ure unit (Q(4)), respectively. It is suggested that the SiO4, tetrahed
ral structure of the microporous silica basically maintains the origin
al kaolinite and is different from the general framework structure of
silica gel. (C) 1998 Elsevier Science B.V. All rights reserved.