Patent ID: 8709234

Claim:
A process for producing middle distillates from a paraffinic feed produced by Fischer-Tropsch synthesis unit, comprising the following steps in succession: a) separating at least one gaseous C4− fraction, termed the light fraction, with an end boiling point of less than 20° C., from an effluent derived from the Fischer-Tropsch synthesis unit to obtain a single C5+ liquid fraction, termed the heavy fraction, with an initial boiling point in the range of 20° C. to 40° C.; b) hydrogenating the unsaturated olefinic type compounds of at least a portion of said heavy liquid fraction C5+, in the presence of hydrogen and a hydrogenation catalyst at a temperature in the range of 100° C. to 180° C., at a total pressure in the range of 0.5 to 6 MPa, at an hourly space velocity in the range of 1 to 10 h −1 , and at a hydrogen flow rate corresponding to a hydrogen/hydrocarbons volume ratio in the range of 5 to 80 Nl/l/h to obtain a liquid hydrogenated effluent; c) hydroisomerizing/hydrocracking the entire liquid hydrogenated effluent from step b) with no prior separation step in the presence of hydrogen and a hydroisomerization/hydrocracking catalyst; d) distilling resultant hydrocracked/hydroisomerized effluent from step (c) and wherein said hydroisomerization/hydrocracking catalyst comprises up to 3% by weight of at least one hydro-dehydrogenating element selected from noble metals from group VIII and a support comprising at least one silica-alumina, said silica-alumina having the following characteristics: a weight content of silica SiO 2 in the range of 5% to 95%; a Na content of less than 300 ppm by weight; a total pore volume in the range of 0.45 to 1.2 ml/g, measured by mercury porosimetry; said silica-alumina having a porosity as follows: i) the volume of mesopores with a diameter in the range of 40 Å to 150 Å and with a mean diameter in the range of 80 to 140 Å represents 20-80% of the total pore volume measured by mercury porosimetry; ii) the volume of macropores with a diameter of more than 500 Å, represents 20% to 80% of the total pore volume, by mercury porosimetry; a specific surface area in the range of 100 to 550 m 2 /g.