Tributyl citrate production via reactive distillation: Model reconciliation, optimization, scale up and sustainability indicators

Abstract

• Reconciliation of a reactive distillation (RD) model for tributyl citrate (TBC) production. • A RD Industrial process for TBC production is designed and optimized. • Homogeneous and heterogenous catalysts are assessed. • Comparison with current industrial technology is presented. • Economic and sustainability indicators are presented. This work describes a model reconciliation of a reactive distillation (RD) process for the production of tributyl citrate based upon pilot scale experimental data. Steady state modeling of the process was constructed using previously validated thermodynamics and reaction kinetics that included catalytic and self-catalytic contributions. The set of pilot scale experimental data included input–output flow rates, and composition and temperature profiles of 18 runs under continuous operation. In order to reconcile the RD model, heat losses, catalyst effectiveness, Murphree efficiencies, and reactive and non-reactive liquid holdup were adjusted to fit the measured data. After reconciliation, the obtained model was in good agreement with pilot scale results, with average mass fractions and temperatures deviations < 2%. Once reconciled, the RD model was used to design and optimize the performance of a 5000 ton/yr industrial scale facility. The optimization procedure included decision, design and operating variables of continuous or discrete nature. The best configurations involved a single RD column for the heterogeneous catalyst, or a pre-reactor-RD column scheme for the homogeneously catalyzed process. Reflux ratios ranged from 0.01 to 0.5 and pre-reactor residence times were around 1 h. The optimized configuration for heterogeneous catalyzed process exhibited up to 30% energy savings with respect to the homogeneous case. The unitary TBC production costs were calculated to be 1.66 and 1.69 USD/kg for the heterogeneous and homogeneous case respectively. Finally, the optimized configurations were compared using sustainability indicators.