Tributyl Citrate Production via Reactive Distillation—Conceptual Design and Pilot-Scale Validation

Abstract

This work describes the conceptual design and a pilot-scale validation of a reactive distillation column for tributyl citrate (TBC) production by esterification of citric acid (CA) with n-butanol (BuOH). The conceptual design was carried out using novel reactive residue curve maps for mixtures of six components. Subsequently, a computational sensitivity analysis based on validated kinetic and phase equilibrium models enabled identifying critical design and operating variables to assess during experiments. Further pilot-scale experiments were performed according to a Box–Behnken design. The highest productivity at the pilot scale was obtained for a reflux ratio of 0.17, a CA/BuOH mole ratio of 1:13, and a feed flow of the reactive mixture of 4.9 kg/h. These conditions resulted in a CA conversion above 98.8%, a TBC yield of 52%, and a productivity of 24.4 kg/h/m3. It was verified that the process can successfully operate with azeotropic BuOH as feedstock and a prereactor, improving selectivity toward TBC.

Water‐Doped Brønsted Acidic Protic Ionic Liquids for Enhanced Tributyl Citrate Synthesis in a Two‐Phase Esterification System

“…Compared to other ILs (entry 4–5, 11–20) the protic ILs studied herein enable conducting the process in a similar two‐phase reaction system, facilitating easy isolation of the product from the post‐reaction mixture. Nevertheless, the proposed method in the presence of inexpensive protic ILs offers the synthesis of TBC at the lowest temperature and shortest reaction time with improved yields (>99 %), and high selectivity of up to 99 %, resulting from negligible yield of dibutyl or monobutyl citrates, resulting from the optimization of the reaction conditions (reactions of indirect esterification to mono‐ and diesters are relatively very fast [46,52,53,68,69] …”

“…Nevertheless, the proposed method in the presence of inexpensive protic ILs offers the synthesis of TBC at the lowest temperature and shortest reaction time with improved yields (> 99 %), and high selectivity of up to 99 %, resulting from negligible yield of dibutyl or monobutyl citrates, resulting from the optimization of the reaction conditions (reactions of indirect esterification to mono-and diesters are relatively very fast. [46,52,53,68,69]…”

“…[46,51] Other promising method for TBC production involves reactive distillation. [46,52,53] Consequently, there is an interest in the exploration of alternative catalysts that possess exceptional activity, selectivity, and stability, while simultaneously addressing the challenges arising from the utilization of conventional acids.…”

“…Especially, neutralization of the homogenous catalysts is needed [46,51] . Other promising method for TBC production involves reactive distillation [46,52,53] …”