Patent ID: 7704378

Claim:
Process for preparing middle distillates from a paraffinic feedstock produced by Fischer-Tropsch synthesis, using a hydrocracking/hydroisomerization catalyst which comprises: at least one hydro-dehydrogenating element chosen from the group formed by the noble elements of Group VIII of the periodic table. a non-zeolitic silica-alumina-based support containing a quantity greater than 5% by weight and lower than or equal to 95% by weight of silica (SiO 2 ). an average pore diameter, measured by mercury porosimetry, comprised between 20 and 140 Å, a total pore volume, measured by mercury porosimetry, comprised between 0.1 ml/g and 0.6 ml/g, a total pore volume, measured by nitrogen porosimetry comprised between 0.1 ml/g and 0.6 ml/g, a BET specific surface comprised between 100 and 550 m 2 /g, a pore volume measured by mercury porosimetry, comprised in the pores with a diameter larger than 140 Å, smaller than 0.1 ml/g, a pore volume, measured by mercury porosimetry, comprised in the pores with a diameter larger than 160 Å, smaller than 0.1 ml/g, a pore volume, measured by mercury porosimetry, comprised in the pores with a diameter larger than 200 Å, smaller than 0.1 ml/g, a pore volume, measured by mercury porosimetry, comprised in the pores with a diameter larger than 500 Å, smaller than 0.01 ml/g, an X-ray diffraction diagram which contains at least the main lines characteristic of at least one of the transition aluminas comprised in the group made up of the alpha, rho, chi, eta, gamma, kappa, theta and delta aluminas, wherein the non-zeolitic based support was obtained from a process compromising starting from a mixture of a partially soluble alumina compound in an acid medium with a totally soluble silica compound or with a totally soluble combination to alumina and hydrated silica, the resultant mixture is concentrated to form a moldable mixture, the resultant moldable mixture is molded and the resultant molded article is subjected to a hydrothermal or thermal treatment.