Process for the preparation of micro-mesoporous gel

A process for the preparation of a micro-mesoporous gel consisting of a silica matrix in which optionally one or more oxides of metals selected from the group consisting of transition metals and metals belonging to Groups IIA, IVA and VA, is uniformly dispersed, said gel exhibiting a monomodal distribution of porosity and the presence of a single broad diffraction line, or a widespread scattering at angular values not greater than 2θ=5°, with CuKα radiation and with the absence of other scattering phenomena coherent for greater angular values, consisting essentially of:

• (a) subjecting to hydrolysis and gelification a tetraalkylorthosilicate, optionally in an alcohol solution, with an aqueous solution of a hydroxide of alkyltrimethylammonium having formula (I):
• R(CH3)3N—OH (I)
• wherein R represents a linear alkyl group selected from n-butyl, n-pentyl, n-hexyl and n-heptyl and, optionally one or more soluble or hydrolyzable compounds of one or more metals selected from the group consisting of transition metals and metals belonging to Groups IIIA, IVA and VA;
• the quantity of the constituents of the above solution meeting the molar ratios:
• H2O/SiO2=5-40;
• R—OH/SiO2=0-10
• R(CH3)3N—OH/SiO2=0.05-0.4
• metal oxides/SiO2=0-0.02
• whereas the ratio H2O/R(CH3)3N—OH varies in relation to the number of carbon atoms in the R alkyl chain according to the values shown in Table 2 below:
• TABLE 2 R H2O/R(CH3)3N—OH n-butyl ≦35 n-pentyl <70 n-hexyl <102 n-heptyl ≦136
• at a temperature of between 20° C. and 80° C.;
• and
• (b) subjecting the gel or solid obtained in step (a) to drying and calcination.