Catalytic hydrocracking of a Mexican heavy oil on a MoS2/al2o3catalyst: II. Study of the transformation of isolated aromatics fraction obtained from SARA analysis

Catalytic hydrocracking of isolated aromatics fraction from a heavy crude oil was studied on a slurry batch reactor at isothermal conditions using 8.27 MPa H-2 pressure, different temperatures (380 degrees C, 390 degrees C, and 400 degrees C), different reaction times (1.0 h, 2.5 h, and 4.0 h) and employing a sulfided Mo/gamma-Al2O3 catalyst. The ASTM D2007 method had been applied to a Mexican heavy oil to obtain the aromatics fraction. Feedstock and products (gas and liquid) were analyzed by GC-MSD and GC-FID. Additionally, the liquid phase was analyzed by the ASTM D7169 method. A kinetic model was proposed to establish the effect of the processing the heavy cuts (gasoil, atmospheric residue, and vacuum residue) to light distillate cuts production (gas, naphtha and, kerosene). It was determined that the feedstock is composed of aromatics (mono, di, tri, or tetra-cycle) with alkyl tails, oxygenated aromatics, nitrogen aromatics, and sulfur aromatics. The catalytic hydrocracking products were saturate compounds and lower molecular weight aromatics; no coke was detected. The produced gas was composed by saturated compounds. The fitted kinetic parameters and the chromatographic analyses indicate that aromatics in feedstock were transformed following primary reactions in series. The main producers of naphtha were aromatics in kerosene and atmospheric residue, the reactions were dealkylation or hydrogenation; this after the opening of aromatic rings in the high molecular aromatics. The gas producers were substituted aromatics in the kerosene cut that is kept at the liquid phase during reaction, also, at high temperatures the hydrotreatment reactions of aromatic compounds in gasoil produces gas.