Modeling the Hydrocracking Kinetics of Atmospheric Residue in Hydrotreating Processes by the Continuous Lumping Approach

The primary objective of this work is to study the hydrocracking associated with the hydrotreatment of atmospheric residue (AR) feedstock and develop a kinetic model describing the undergoing cracking reactions. Experimental data were obtained for three types of conventional hydrotreating catalysts [hydrodesulfurization (HDS), hydrodemetalization (HDM), and hydrodenitrogenation (HDN)] at three space velocities and three operating temperatures. The developed kinetic cracking model is based on the continuous lumping approach, which assumes a continuous concentration and reactivity of the reacting mixtures. Species concentrations were represented as an integro-differential equation with only five modeling parameters. The developed continuous lumping models predicted the concentration profile of the complete true boiling point (TBP) range with reasonably high accuracy. Analysis of experimental results indicated that upgrading of residual fractions is achieved through both catalytic and thermal conversion, where the extent of each depends upon the catalyst type and operating conditions. The yield of the distillate fraction was found to be the highest for the HDN catalyst followed by HDS and HDM catalysts.