Process for the conversion of feedstocks resulting from renewable sources for producing gas oil fuel bases with a low sulphur content and with an improved cetane number

A process for the treatment of petroleum feedstocks, at least 80% by weight of which boils above 340° C. and which comprise at least 0.05% by weight of sulphur, in order to produce at least one gas oil cut with a sulphur content of at most 50 ppm by weight, the said process comprising the following stages:

• a) mild hydrocracking in a fixed bed of at least one catalyst at a temperature of between 300 and 500° C., a pressure of between 2 MPa and 10 MPa and an hourly space velocity of between 0.1 h−1 and 10 h−1 and in the presence of 100 to 5000 Nm3 of hydrogen/m3 of feedstock, providing a net conversion to products boiling below 360° C. being between 10 and 50% by weight,
• b) separation, from the effluent resulting from stage a), of a gas comprising hydrogen, of the hydrogen sulphide formed in stage a), of at least one distillate cut including a gas oil fraction and of a fraction which is heavier than gas oil,
• c) hydrotreating, by contact with at least one catalyst, of at least a portion of said distillate cut obtained in stage b) including the gas oil fraction, as a mixture with a feedstock resulting from a crude or refined renewable source, at a temperature of between 180 and 320° C., a pressure of between 2 and 10 MPa and an hourly space velocity of between 0.1 and 10 h−1 and in the presence of 200 to 5000 Nm3 of hydrogen/m3 of feedstock,
• d) separation of the hydrogen, of the gases and of at least of said one gas oil cut.