ENTRAINED-BED HYDROCONVERSION OF A HEAVY HYDROCARBON FEEDSTOCK, COMPRISING MIXING SAID FEEDSTOCK WITH A CATALYST PRECURSOR CONTAINING AN ORGANIC ADDITIVE

The present invention relates to a slurry hydroconversion process of a heavy oil feedstock (101) comprising: (a) preparing a conditioned feedstock (103) by mixing said feedstock with a catalyst precursor formulation (104) so that a colloidal or molecular catalyst is formed when it reacts with sulfur, said catalyst precursor formulation (104) comprising a catalyst precursor composition (105) comprising Mo, an organic additive (102) comprising a carboxylic acid function and/or an ester function and/or an acid anhydride function, and a molar ratio organic additive (102)/Mo from formulation (4) ranging between 0.1:1 and 20:1; (b) heating said conditioned feedstock; (c) introducing the heated conditioned feedstock (106) into at least one slurry bed reactor and operating said reactor in the presence of hydrogen and at hydroconversion conditions to produce an upgraded material (107), the colloidal or molecular catalyst being formed during step (b) and/or (c).