Abstract: Micro-mesoporous gel consisting of a silica matrix possibly wherein one or more metal oxides selected from transition metals or metals belonging to groups IIIA, IVA and VA are uniformly dispersed, characterized by a monomodal porosity distribution.

Abstract: An amorphous, micro/mesoporous silica-alumina gel with controlled pore size, having a surface area of at least 500 m.sup.2 /g and with a molar ratio of SiO.sub.2 :Al.sub.2 O.sub.3 of at least 30:1, is prepared by hydrolysing and causing a tetra-alkyl ammonium hydroxide, an aluminum trialkoxide, and a tetra-alkyl orthosilicate to gelate, by operating at a temperature equal to, or higher than, the boiling temperature, under atmospheric pressure, of any alcohols which are developed as a by-product from said hydrolysis reaction, without said alcohols being removed, or being substantially removed, from the reaction media; and the so produced gel being dried and fired. So obtained gel is an active catalyst in hydrocarbon conversion reactions, in particular in light olefin isomerization and oligomerization processes, e.g., in propylene oligomerization processes to yield useful liquid hydrocarbons for gasoline and jet fuel formulation.