Mesoporous alumina gel and process for its preparation

Mesoporous material comprising an γ alumina throughout which optionally one or more oxides selected from silica, boron oxide, phosphorous oxide, the oxide of a metal of group VIII and/or VIB having general formula MOx, are uniformly dispersed, with the following molar ratios between said oxides and the alumina:

• SiO2/Al2O3=0-3.0
• B2O3/Al2O3=0-4.0
• P2O5/Al2O3=0-0.2
• MOx/Al2O3=0-0.2.
• wherein the material has a surface area of between 260 and 700 m2/g, a pore volume of between 0.2 and 1.0 cm3/g, a monomodal pore size distribution of between 20 and 70 Å, and substantially all pore diameters of between 20 and 70 Å,
• wherein an X-ray diffraction spectrum from powders of the mesoporous material exposed to CuKα radiation has in the high angular region a pattern typical or indicative of γ alumina, wherein at angular values of not more than 2θ=5°, there are (1) no coherent scattering phenomena or (2) there is an enlarged diffraction line or there is weak or diffuse scattering, and,
• wherein said material is prepared by a process comprising:
• (a) preparing a solution, in an alcohol having the formula R″OH, wherein R″ is a linear or branched C1-C5 group, of an aluminum alkoxide having the formula Al(OR)3, wherein R is a linear or branched C1-C5 alkyl group, and optionally of a source of one or more elements selected from silicon, boron, phosphorous, and/or a compound soluble in an alcohol environment of a metal of a group VIII;
• (b) subjecting the alcohol solution prepared in step (a) to hydrolysis and gelification, at a temperature of between 20 and 80° C., with a water solution containing a hydroxide of tetralkylammonium having the formula R′4N—OH, wherein R′ is a linear or branched C2-C7 alkyl group, and optionally a compound of a metal of group VIB soluble in a basic environment, the quantity of the constituents of the mixture thus obtained being such as to respect the following molar ratios:
• H2O/Al2O3 = 15-100 R″OH/Al2O3 = 5-50 R′4N—OH/Al2O3 = 0.3-5 SiO2/Al2O3 = 0-3.0 B2O3/Al2O3 = 0-4.0 P2O5/Al2O3 = 0-0.2 MOX/Al2O3 = 0-0.2
• (c) subjecting the gel obtained in step (b) to drying and calcination.