Novel alumina-on-alumina composite supports

An alumina-based catalyst support having the following characteristics:

• a specific surface area measured by nitrogen adsorption isotherm, of less than 90 m2/g
• a total pore volume measured by mercury intrusion of at least 0.3 cm3/gram.
• an at least bimodal distribution of porosity making it possible to distinguish a main porosity characterized in that at least 80% of the total pore volume corresponds to pores larger than 15 nm and a secondary porosity characterized by the fact that at least 3% of the total pore volume corresponds to pores smaller than 12 nm.
• an ordered relationship between the main porosity and the secondary porosity defined by the fact that any element in the main porosity is connected either to the outside of the support particle, or to at least one element in the secondary porosity, this expression to be taken in a non-exclusive sense.
• crystallographic phases determined by X-ray diffraction corresponding to the alpha or theta or kappa or delta or gamma aluminas.