Kinetics of asphaltene thermal cracking and catalytic hydrocracking

Abstract

A pentane-insoluble asphaltene was processed by thermal cracking and catalytic hydrocracking over NiMo/γ-Al2O3 in a microbatch reactor at 430°C. Kinetic analysis shows that the first-order kinetics fits the data of conversion in reaction times ≤30min approximately, but deviates from the data of times over 30min significantly; whereas the second-order kinetics fits the data of the reaction times up to 60min adequately, to give the apparent rate constants of 1.704×10−2 and 9.360×10−2wt frac−1min−1 for the two cracking processes. Furthermore, a three-lump kinetic model is proposed to include parallel reactions of asphaltenes to produce liquid oil (k1) and gas+coke (k3), and consecutive reaction from liquid to gas+coke (k2). The evaluated value of k1 is 1.697×10−2 and 9.355×10−2wt frac−1min−1, k2 is 3.605×10−2 and 6.347×10−3min−1 , and k3 is 6.934×10−5 and 4.803×10−5wt frac−1min−1 for asphaltenes thermal cracking and catalytic hydrocracking, respectively. Selectivity analysis shows that the catalytic hydrocracking process promotes liquid production and inhibits coke formation effectively.