Flexible method for producing oil bases with a ZSM-48 zeolite

Process for the production of oils and optionally high quality middle distillates from a hydrocarbon feedstock including at least 20% of end volume above 340° C., process that successively comprises the following stages:

• (a) Hydrotreatment carried out at a temperature of 330-450° C., under a pressure of 5-25 MPa, with a volumetric flow rate of 0.1-6 h−1, in the presence of hydrogen in the hydrogen/hydrocarbon volumetric ratio of 100-2000, and in the presence of an amorphous catalyst that comprises at least one metal of group VIII and at least one metal of group VI B,
• (b) Hydrocracking, without intermediate separation of the effluent that is obtained at the end of the hydrotreatment, whereby the hydrocracking is carried out at a temperature of 340-430° C., under a pressure of 5-25 MPa, with a volumetric flow rate of 0.1-5 h−1, in the presence of hydrogen, and in the presence of a catalyst that contains at least one zeolite and that also contains at least one element of group VIII and at least one element of group VI B,
• (c) atmospheric distillation of the effluent that is obtained at the end of the hydrocracking to separate the gases from the liquid, and to recover at least one liquid fraction that contains compounds with a boiling point of higher than 340° C.,
• (d) whereby said fraction is treated directly by catalytic dewaxing at a temperature of 200-500° C., under a total pressure of 1-25 MPa, with an hourly volumetric flow rate of 0.05-50 h−1, with 50-2000 l of hydrogen/l of feedstock, in the presence of a catalyst that also comprises at least one element with a hydro-dehydrogenating function and at least one zeolite that is selected from the group that is formed by zeolites ZSM-48, EU-12, EU-11 and ZBM-30,
• (e) the dewaxed effluent is directly subjected to a hydrofinishing treatment that is carried out at a temperature of 180-400° C., which is lower than the catalytic dewaxing temperature by at least 20° C. and at most 200° C., under a total pressure of 1-25 MPa, with an hourly volumetric flow rate of 0.05-100 h−1, in the presence of 50-2000 liters of hydrogen/liter of feedstock, and in the presence of an amorphous catalyst for the hydrogenation of aromatic compounds, comprising at least one metal that is selected from the group of metals of group VIII and metals of group VI B,
• (f) the effluent that is obtained from the hydrofinishing treatment is subjected to a distillation stage that comprises an atmospheric distillation and a vacuum distillation so as to separate at least one oil fraction at a boiling point of higher than 340° C. and that has a pour point of lower than −10° C., a content by weight of aromatic compounds of less than 2% and a VI of greater than 95, a viscosity at 100° C. of at least 3 cSt (or 3 mm2/s) and so as optionally to separate at least one middle distillate fraction that has a pour point of less than or equal to −20° C., a content of aromatic compounds of at most 2% by weight and a content of polyaromatic compounds of at most 1% by weight.