Production of middle distillates from an effluent originating from fischer-tropsch synthesis comprising a step of reducing the content of oxygenated compounds

A method for producing middle distillates from a feedstock produced by Fischer-Tropsch synthesis and containing oxygenated compounds, said method comprising at least:

• a) hydrotreating said feedstock in the presence of a hydrotreating catalyst at a temperature of 100 to 450° C., at a pressure of 0.2 to 15 MPa, the hydrogen necessary for the reaction of hydrotreating being introduced in hydrotreating at a flow rate such that the hydrogen/feedstock volume ratio is 10 to 3000 normal liters per liter, and at an hourly space velocity of 0.1 to 40 h−1,
• b) hydroisomerizing/hydrocracking of at least a part of a liquid and gaseous effluent originating from a), in the presence of a hydroisomerization/hydrocracking catalyst,
• c) gas/liquid separation of a stream originating from b) into a gaseous fraction comprising predominantly hydrogen, a hydroisomerized/hydrocracked organic liquid fraction and an aqueous fraction,
• d) fractionating of the organic liquid fraction separated in c) to obtain at least a gaseous fraction comprising predominantly light gases (C1-C4), a gasoline fraction comprising naphtha, a middle distillate fraction comprising kerosene and gas oil and a residual fraction,
• e) methanating CO and CO2 carried out in the presence of a methanation catalyst
• on at least a part of said gaseous fraction separated in c) before recycle of hydrogen to the hydrotreating in a),
• and/or on at least a part of the liquid and gaseous effluent originating from the hydrotreating a),
• in which
• if methanation e) is implemented between a) and b), the hydroisomerization/hydrocracking b) is carried out on at least a part of the gaseous and liquid effluent originating from said e),
• and
• hydrogen in a) is obtained at least partly from the gaseous fraction separated in c).