Kinetics and Selectivity of Asphaltene Thermal Cracking, Thermal Hydrocracking, and Catalytic Hydrocracking

摘要

A pentane-insoluble asphaltene was processed by thermal cracking, thermal hydrocracking, and catalytic hydrocracking in a microbatch reactor at 430° C. The experimental data of asphaltene conversion fit second-order kinetics adequately to give the apparent rate constants of 1.704 x 10~(-2), 2.435 x 10~(-2), and9.360x 10~(-2) wt frac~(-1) min~(-1) for the above three cracking processes, respectively. A three-lump kinetic model is proposed and solved to obtain rate constants of parallel reactions of asphaltenes to produce liquid oil (k_1) and gas + coke (k_1) and a consecutive reaction from liquid to gas + coke (k_2). The value of k_1 is 1.697 x 10~(-2), 2.430 x 10~(-2), and 9.355 x 10~(-2) wtfrac~(-1) min~(-1); k_2 is 3.605 x 10~(-2), 2.426 x 10~(-2), and 6.347 x 10~(-3) min~(-1); and k_3 is 6.934 x 10~(-5), 5.416 x 10~(-5), and 4.803 x 10~(-5) wt frac~(-1) min~(-1) for asphaltenes thermal cracking, thermal hydrocracking, and catalytic hydrocracking, respectively. Analysis of selectivity shows that the catalytic hydrocracking process provides the highest liquid production, and the coking process provides the highest coke formation, as expected. An induction period of coke formation was found to increase from thermal cracking to thermal hydrocracking to catalytic hydrocracking process.