High Pressure Reactive Distillation Simulation for the Esterification of Pyrolysis Bio-oil.

Reactive distillation (RD), which has tremendous advantages over traditional reaction and separation unit operations including handling of unfavorable chemical and phase interactions, enhancing conversion and selectivity, circumventing azeotropic mixtures and reducing capital and energy costs, has been utilized for the reactive separation of various equilibrium controlled chemical systems. Aspen simulation for RD of pyrolysis bio-oil esterification with n-butanol is carried out using UNIQUAC property method in RADFRAC module by minimizing Gibbs free energy at 10 bar. The binary and ternary interaction between the components were studied for n-butanol/acetic acid esterification system to determine the azeotropes and the homogeneous region of mixtures, before carrying out RD operation. The conversions for the esterification reactions were found to be 75-95% for various simulated bio-oils, and water was completely separated from the ester products which should increase the fuel quality. Higher water percentage in bio-oil feed was found to reduce ester separation and stoichiometric acid:alcohol mole flow rate was determined to be optimum. The reaction of phenol with fatty acids was incorporated and phenol was found to react with formic acid entirely, which increases the reaction conversion to 94%. All the distillation column parameters such as condenser and reboiler heat duty, number of stages, reflux ratio, feed stages location and inlet conditions were optimized for a complex mixture of fatty acids and phenol to develop a cost minimized RD unit. This study can serve as a simulation platform to design RD unit for pyrolysis bio-oil upgradation without any intermediate cooling unit between pyrolysis and upgradation units.