Long-term evaluation of NiMo/alumina-carbon black composite catalysts in hydroconversion of Mexican 538 °C+ vacuum residue

Alumina with (8-18 wt.%) carbon black composite (AMAC) supports was prepared as bimodal extrudates, containing 11-20% of total pore volume as macropores (i.e. >1000 Å). These supports, in spite of containing carbon black and macropores, showed good side crushing strength (0.67-1.19 kg/mm) after pyrolysis in 6% O2/N2. AMAC-catalysts were obtained after impregnating these alumina-carbon black supports with Ni and Mo, to obtain 3.5 wt.% NiO and 15 wt.% MoO3. These catalysts were evaluated for about 700 h in the hydroconversion of a Mexican vacuum residue (538 °C+) at 415 °C, 200 kg/cm2, H2/HC = 6000 ft3/barrel in a pilot plant equipped with a Robinson-Mahoney reactor. In comparison with a commercial bimodal alumina-based catalyst (ComCat), AMAC catalysts showed much fewer sediments and less Conradson carbon formation. Initial HDS in AMAC containing macropores can be as high as 92%, while that in a ComCat is 86%. On average, yields of naphtha and kerosene were 2.6 and 1.34 times higher with AMAC catalysts than those with ComCat, while diesel yields were similar.