Irregularly shaped non-spherical supported catalyst, and a process for hydroconversion heavy oil fractions

A process for preparing a catalyst comprising an alumina-based support, at least one catalytic metal or compound of a catalytic metal from group VIB and/or VIII, the pore structure of which is composed of a plurality of juxtaposed agglomerates and each formed by a plurality of acicular platelets, the platelets of each agglomerate generally being oriented radially with respect to the others and with respect to the centre of the agglomerate, said support having an irregular and non-spherical shape and being mainly in the form of fragments, said process including the following successive steps:

• a) granulation starting from an active alumina powder having a low crystallinity and/or amorphous structure, to obtain agglomerates in the form of beads;
• b) maturing said beads in a moist atmosphere between 60° C. and 100° C. then drying said beads;
• c) sieving resultant dried beads to recover a fraction of said beads;
• d) crushing said fraction of beads to modify the shape of at least 50% by weight of the beads the remainder being spherical agglomerates;
• e) calcining at least a portion of said crushed fraction at a temperature in the range of 250° C. to 900° C.;
• f) impregnating resultant calcined crushed fraction with acid and conducting an autoclaving treatment at a temperature in the range of 80° C. to 250° C.;
• g) drying resultant acidified and autoclaved fraction, then calcining the resultant dried and autoclaved fraction of step (f) at a temperature in the range of 500° C. to 1100° C. to obtain said support, and
• h) impregnating said support with at least one solution of said at least one catalytic metal or compound of said catalytic metal from group VIB and/or VIII, and the resultant catalyst has a higher mechanical resistance to attrition than a comparable catalyst wherein the crushing step is conducted after the autoclaving treatment.