| 摘要 |
There is provided a composite oxide represented by the formula iR2O.jAl2O3.kTiO2.mSiO2.nH2O wherein R denotes an alkali metal, i is 0.3 to 1, k is 0 to 0.9, j+k=1, m is 7 to 70 and n is 0.2 to 0.4, said composite oxide being amorphous, and its cumulative specific pore volume of pores having a pore radius of 104 A or less being 2.0 to 3.0 cc/g. This composite oxide can be produced by a process which comprises a first reaction step of adding an acid aqueous solution capable of forming a silicate by reaction with an alkali silicate to 7 to 10% by weight, calculated as silica, of an alkali silicate aqueous solution in the presence of a salt at 10 DEG to 45 DEG C. such that a neutralization ratio becomes 20 to 40%, and a second reaction step of heating the reaction solution obtained in the above reaction at a temperature of 90 DEG C. to a boiling point of the reaction solution and adding thereto an acid aqueous solution capable of forming a silicate by reaction with an alkali silicate such that pH of the reaction solution becomes 3 to 5.
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