Upgrading hydrocarbon pyrolysis products

A pyrolysis tar hydroprocessing process comprising:

• (a) providing a first mixture comprising ≧10.0 wt % hydrocarbon;
• (b) pyrolysing the first mixture to produce a second mixture comprising ≧1.0 wt % of C2 unsaturates;
• (c) separating a tar stream from the second mixture, wherein the tar stream includes ≧90 wt % of the second mixture's molecules having an atmospheric boiling point of ≧290° C.;
• (d) providing a primer fluid, the primer fluid comprising (i) aromatic and non-aromatic ring compounds, (ii) vinyl aromatics, and having an ASTM D86 10% distillation point ≧60.0° C. and a 90% distillation point ≦350.0° C.;
• (d1) hydroprocessing the primer fluid to produce a hydroprocessed primer fluid by contacting the primer fluid with at least one hydroprocessing catalyst under catalytic hydroprocessing conditions in the presence of molecular hydrogen;
• (e) hydroprocessing the tar stream by contacting the tar stream with at least one hydroprocessing catalyst under catalytic hydroprocessing conditions in the presence of molecular hydrogen and in the presence of the hydroprocessed primer fluid to convert at least a portion of the tar stream to a hydroprocessed product;
• and
• (f) separating from the hydroprocessed product a mid-cut comprising from 20 to 70 wt % of the hydroprocessed product and having an ASTM D86 10% distillation point ≧60.0° C. and a 90% distillation point ≦350.0° C.;
• and
• (g) recycling at least a portion of the mid-cut and substituting the recycled mid-cut for at least a portion of the hydroprocessed primer fluid utilized in hydroprocessing the tar stream.