Kinetic modeling strategy for an exothermic multiphase reactor system: Application to vegetable oils epoxidation using Prileschajew method

Abstract

Epoxidation of cottonseed oil by peroxyformic acid (PFA) was studied in a semibatch calorimeter. This liquid-liquid reaction system is composed of different exothermic steps. Thus, a kinetic modeling strategy to diminish the number of parameters to estimate was developed by investigating each reaction system: PFA synthesis and decomposition, ringopening and epoxidation. A thermal study was conducted by determining heat capacity of the different organic species, and by analyzing the evolution of global heat-transfer coefficient with the reaction extent. The epoxidation reaction was performed in a semibatch reactor under isoperibolic mode within an initial temperature range of 50-708C, an organic phase of 30-34 wt %, a formic acid molar flow rate of 0.02-0.05 mol/min and an addition time of 25-50 min. The interfacial mass transfer was supposed to be faster than the intrinsic reaction kinetics suppressing the use of mass transfer correlation. Nonlinear regression was used to estimate the kinetic and thermal parameters. The kinetic parameters of epoxidation of the three different fatty acids, namely oleic, linoleic, and its intermediate were estimated. The reaction enthalpy of epoxidation was estimated to 2230 6 3.8 kJ/mol, and the reaction enthalpy of ring-opening was measured to be 290 kJ/mol by Tian-Calvet calorimeter.Kinetic modeling of vegetable oils epoxidation by peroxycarboxylic acids formed in situ in batch and semibatch reactor system has been described by several research groups. This system is complex due to the presence of several consecutive steps. Different approaches have been done such as:Taking into account mass transfer parameters using different correlations or by estimating them, this model is called two-phase kinetic model. Frequently, only carboxylic and peroxycarboxylic acids mass-transfer coefficients were taken into account. [24][25][26] Pseudohomogeneous model by assuming fast mass transfer compared to reaction kinetics, this leads to a simplification of the mass balance equations. [27][28][29][30][31][32] Establishing the mass balance only on the organic phase and assuming steady-state approach on peroxycarboxylic acids formation. 13,[33][34][35][36][37][38][39][40] The advantage of that approach is that graphical method can be used to determine epoxidation rate constants, but one neglects ring-opening reaction. This model is called homogeneous model.Some authors have focused their study only on the ringopening reactions system in batch or semibatch reactor. One can distinguish the two following approaches:Only considering the organic phase and using a pseudofirst-order approach. 41-43 Figure 1. Simplified mechanism of the Prileschajew oxidation of vegetable oils.

Catalytic developments in the epoxidation of vegetable oils and the analysis methods of epoxidized products

“…125 Many studies have focused on controlling the reaction under benign conditions and classied the safety parameters required to avoid the runaway reaction in view of kinetic modeling. [126][127][128][129][130] To diminish the side reactions, many types of research have been carried out to search various catalysts and to optimize reaction parameters such as H 2 O 2 concentrations, acetic acid to ethylenic unsaturation, and solvent systems. In general, an 80% conversion rate for plant oils can be done with epoxidation in the presence of peracid under boosted conditions 131,132 while the epoxidation of fatty acid esters gave much higher yield.…”

Influence of ring‐opening reactions on the kinetics of cottonseed oil epoxidation

“…The percarboxylic acid, produced in situ in the aqueous phase, diffuses to the organic phase to epoxidize the unsaturated groups of the vegetable oils. The epoxidized group is highly reactive and can undergo the ring‐opening side reactions by different nucleophiles . The kinetics of the ring‐opening reaction is dependent on the pH of the reaction mixture.…”

“…For this reaction system, the perhydrolysis reaction, that is, reaction‐producing percarboxylic acid, is catalyzed by an acid. Different catalytic systems and technologies can be used to enhance the rate of epoxidation: homogeneous catalyst, heterogeneous catalyst, enzymatic catalyst, or process intensification …”

“…Several research groups have studied the kinetic model of this reaction system. A literature survey can be found in the article of Zheng et al . Two main approaches are used: pseudohomogeneous and two‐phase model .…”

In‐line monitoring of hydrogen peroxide in two‐phase reactions using raman spectroscopy

“…1 Hydrogen peroxide, when coupled with a catalyst, oxidizes alcohols, olefins, and sulfides 2,3 and is used industrially for the epoxidation of oils. 4,5 The latest generation of propylene oxide and caprolactame processes uses hydrogen peroxide, 6 reducing the amount of salt and halogenated effluents. By replacing other oxidants with hydrogen peroxide, the amount of waste and cost can be reduced and the selectivity and yield can be improved.…”