Hydrodeoxygenation of stearic acid to produce diesel–like hydrocarbons: kinetic modeling, parameter estimation and simulation

Abstract

• Different assumptions for the adsorption step were tested to develop a suitable kinetic model for the hydrodeoxygenation of stearic acid. • Reaction rates constants, equilibrium adsorption constants and activation energies were estimated. • The model based on non-dissociate H 2 and single-site adsorption provided the best fitting quality. • The Peng-Robinson equation of state had better performance than the Predictive-Soave-Redlich-Kwong equation to calculate hydrogen solubilities in the reaction mixture. There has been an increasing search for renewable sources to produce alternative biofuels due to the growth in the global energy demand and the environmental impacts caused by fossil fuels. Green diesel obtained via hydrotreatment of vegetable oils and fats is a promising option, mainly due to the possibility of being integrated into an existing refinery. Here, we investigate the kinetics of hydrodeoxygenation of stearic acid as a model compound of triglyceride raw materials over NiMo/Al 2 O 3 catalyst to obtain hydrocarbons in the diesel range. Kinetic models based on different assumptions to the adsorption step, such as Eley–Rideal and Langmuir–Hinshelwood mechanisms, were evaluated through nonlinear regression to parameter estimation using a hybrid algorithm combining Particle Swarm Optimization and Nelder–Mead method. All proposed models fitted well to the experimental data, presenting correlation coefficients higher than 90% for the fatty acid and the final hydrocarbons. However, the surface reaction limited model based on competitive adsorption with non-dissociate H 2 adsorbed showed the best results and was used to simulate the process.