| abstract |
The invention relates to a 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 silica-alumina-based non-zeolitic support containing a quantity greater than 5% by weight and less 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 0.01 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 and 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. |