Process for the preparation of middle distillates and lube bases starting from synthetic hydrocarbon feedstocks

A process for the contemporaneous preparation of middle distillates and lubricating bases starting from a feedstock comprising a mix of prevalently paraffinic hydrocarbons obtained by means of a synthesis process from hydrogen and carbon monoxide, consisting of at least 30% of a high-boiling fraction with a distillation temperature higher than 360° C., comprising:

• (i) at least one hydrocracking step, wherein said hydrocarbon mix is reacted with hydrogen at a temperature of between 200 and 450° C. and a pressure of between 0.5 and 15 MPa, in the presence of a catalyst, for a time sufficient for converting at least 40% of said high-boiling fraction, into a fraction of hydrocarbons which can be distilled at temperatures lower than 360° C.;
• (ii) at least one distillation step of the product of step (i) for separating at least a fraction of middle distillate and at least one high-boiling residue suitable for producing a lubricating base with an initial boiling point equal to or higher than 340° C., wherein said hydrocracking step (i) is effected in the presence of a supported catalyst comprising:
• (A) a support of an acidic nature consisting of a catalytically active porous solid, including silicon, aluminum, phosphorus and oxygen bonded to one another in such a way as to form a mixed amorphous solid forming a single phase, characterized by an Si/Al atomic ratio of between 15 and 250, a P/Al ratio of at least 0.1, but lower than 5, a total pore volume ranging from 0.5 to 2.0 ml/g, an average pore diameter ranging from 3 nm to 40 nm, and a specific surface area ranging from 200 to 1000 m2/g;
• (B) at least one metal with a hydro-dehydrogenating activity selected from groups 6 to 10 of the periodic table of elements, dispersed on said support (A) in an amount of between 0.05 and 5% by weight with respect to the total weight of the catalyst.