Dynamic modeling and simulation of three-phase reactors for hydrocracking of vegetable oils

Abstract

A dynamic, plug-flow, one-dimensional, and heterogeneous mathematical model for a trickle-bed reactor is described and used to simulate the catalytic hydrocracking of non-edible vegetable oil with countercurrent operation mode. The reactor model considers the hydrocracking reaction of triglycerides towards renewable fuels, which is present in the hydrotreatment process of vegetable oils. The dynamic model was first validated using experimental data reported in the literature, which were obtained in an isothermal micro-scale reactor with cocurrent downflow during hydrocracking of Jatropha oil over a commercial CoMo catalyst. Then, the three-phase reactor model was applied to predict the dynamic behavior of an industrial hydrocracking reactor in order to gain some insight into the transient behavior of the liquid molar concentration, partial pressure, and temperature profiles, which were obtained and discussed as a function of time and axial position of the catalytic bed. The simulations obtained with the proposed dynamic model showed good agreement with the experimental data and trends previously reported for the operation variables profiles at steady-state and relevant findings at industrial scale were obtained. One of the main challenges to produce biofuels by vegetable oils hydroprocessing is to control the high-temperature gradients along the catalyst bed because of the high reaction heat released; therefore, the development of dynamic trickle-bed reactor models, as shown in this work, can be used as a tool to predict the operational behavior of the unit under different reaction conditions and layouts to found the best scheme to control the effects by high-temperature rise.