Eley-Rideal Model Research Articles

Production of triacetin from industrially derived purified glycerol: Experimental proof of concept, kinetic model derivation and validation

This study illustrates the purification of end-of-life crude glycerol from a real biodiesel production process and its conversion into triacetin via esterification with acetic acid. Crude glycerol of 50.9 wt% purity was physicochemically treated to 74.3 wt% reducing the content of ashes (16.1 to 9.8 wt%), matter organic non-glycerol (25.6 to 9.8 wt%) and water (7.4 to 6.1 wt%). For esterification, catalyst screening with commercial ion exchange resins and zeolites showed that Amberlyst 36 attained a triacetin yield of 30.1 % and stability after 5 cycles. An increase of temperature, molar ratio, and catalyst loading positively affected the reaction rates and equilibrium, whereas increasing water content in the feedstock only showed effect on the equilibrium leading to lower triacetin yields. After dismissing mass transfer limitations, a thorough study on the reaction kinetics analysed the effect of temperature (100–130 °C), molar excess of acetic acid (6–12) and catalyst loading (2.5–7.5 wt%) on the concentration profiles. Kinetic models based on Langmuir-Hinshelwood-Hougen-Watson and Eley-Rideal equations were formulated to fit the experimental data, where an Eley-Rideal model accounting only for water adsorption fitted best. Deactivation was also contemplated considering the ash content in the substrate, yet the model does not correlate with a loss of catalytic activity. The activation energies for the forward and backward reactions of the in-series esterification reactions are 38.2 – 45.8 kJ mol–1 and 47.0 – 50.3 kJ mol–1, respectively, and the enthalpy for water adsorption is 28.2 kJ mol–1.

Kinetic modeling of dual-stage oxidative extractive denitrogenation of model fuel

The petroleum fraction of crude oil is laden with notorious nitrogen compounds, whose removal facilitates fuel oil transport and enhances the longevity of hydrodesulfurization catalysts. Petroleum refining operation thus demands the adoption of unconventional techniques, such as coupled oxidative–extractive denitrogenation. Kinetic models can provide insights into the reaction mechanism and the design and performance of reactors. In this work, nine different kinetic models were developed by applying the Langmuir–Hinshelwood and Eley–Rideal approaches to various reaction pathways. The screening of the kinetic models was done based on the values of the rate law parameters and corresponding R 2 and adjusted R 2 values calculated through a multi-parametric, non-linear regression based on the Levenberg–Marquardt algorithm. Out of all the models, the Eley–Rideal model corresponding to the rate expression rs9 was found to be the best fit, reflecting that hydrogen peroxide remained in bulk while pyridine alone was adsorbed on the catalyst. The selection of suitable extractants for the extractive removal of oxidation products was made based on their extraction efficiency and partition coefficients. The ternary liquid–liquid equilibrium (LLE) data for the (acidulated water-pyridine-isooctane) and (acidulated water-pyridine N-oxide-isooctane) systems were plotted, and Othmer–Tobias, Hand, and Bachman correlations explained the consistency of the experimental LLE data.

Thermodynamic and kinetic study on the catalysis of tributyl aconitate by Amberlyst-15 in a cyclic fixed-bed reactor

Abstract Tributyl aconitate is a new type of alternative plasticizer to phthalates. Amberlyst-15 was used to catalyze the esterification of aconitic acid and n-butanol for the preparation of tributyl aconitate in a cyclic fixed-bed reactor. The influence of the reaction conditions on the conversion was investigated. The results showed that the conversion of aconitic acid increased significantly with the rise of temperature and catalyst loading. The reaction conditions were optimized as: temperature: 115 °C; initial mass ratio of AA and n-butanol: 1:4; catalyst loading: 25 %; reaction absolute pressure: 85 kPa; volume flow rate: 30 mL min−1. Thermodynamics and kinetics of the reaction was studied. The non-ideality of the reaction system was rectified using the UNIFAC group contribution method. The kinetic process was simulated using the pseudo-homogeneous (PH) model, Eley-Rideal (E-R) model, and Langmuir-Hinshelwood-Hougen-Watson (LHHW) model. The results revealed that the E-R model exhibited superior suitability in simulating the kinetic process.

Production of esters with numerous applications: Kinetics of Dowex 50W catalyzed transesterification of methyl acetate with three‐ and four‐carbon structured alcohols

AbstractIn this investigation, a strongly acidic exchange resin was used for the transesterification of methyl acetate with n‐propanol, n‐butanol, and iso‐butanol. Kinetic and equilibrium experiments for the three systems were conducted using a temperature‐controlled batch reactor setup. The effects of the following operating parameters on the transesterification were explored: reaction temperature, catalyst loading, and methyl acetate‐to‐alcohol molar ratio. The conversion of the limiting reactant in the reaction mixture increased with increasing reaction temperature, catalyst loading, and varying reactant proportions from 1:1 to other ratios. It was found that excess methyl acetate would result in higher limiting reactant conversion than using excess alcohol with the same initial molar proportionality between the excess and the limiting reactants. It was found that an increase in the chain length of the alcohol and/or branching suppressed the conversion of the reactants owing to steric hindrance. To mathematically correlate the data, several kinetic models were tested, and the Eley–Rideal model was selected. Accordingly, a reaction mechanism was proposed.

Mn/Ce@HKUST-1 for Efficient Removal of Gaseous Thallium: Insights from Kinetic and Experimental Studies.

Gaseous thallium (Tl) pollution events, primarily caused by non-ferrous mineral refineries and fossil fuel combustion, have increased over the past few decades. To prevent gaseous Tl distribution from flue gas, MnO2/CeO2@HKUST-1 (MCH) was synthesized and found to achieve a gaseous Tl(I) removal level of up to 90% at 423 K, a weight hourly space velocity (WHSV) of 2000 h-1/mL with an Mn dose of 10%, maintained over 10 h. The best Mn/Ce ratio was found to be 9:1. To further investigate surface kinetic behavior, four commonly used kinetic models were applied, including the Eley-Rideal (ER) model, Langmuir-Hinshelwood (LH) model, Mars-van Krevelen (MVK) model, and pseudo-first-order (PFO) model. While the ER and LH models had the slightest deviation, the MVK model was the most reliable. The CatMAP software was also used to match the simulation deviation. This work demonstrated the Tl removal mechanism and provided insights into the accuracy of kinetic models on minor-radius heavy metal. Thus, this research may help promote the design of reactors, heavy metal removal rates, and flue gas purification technology selection.

Ammonia free catalytic reduction of nitric oxide on Ni-embedded graphene nanostructure: A density functional theory investigation

In this study, the catalytic reduction reaction of NO (directly) without the presence of ammonia (NH3) was studied on the Ni-embedded graphene (Ni@GN) layer using periodic Density Functional Theory (DFT) calculations. Ni-embedded graphene surface can be synthesized experimentally and it is predicted that it will cost much less than single crystal surfaces due to the economic usage of the transition metal atoms. First of all, by optimizing the geometric structure of the Ni@GN layer, crucial geometric features and electron density differences (EDD) were obtained. Based on the different adsorption configurations of NO molecule, the reduction reaction was investigated by Langmuir-Hinshelwood (L-H) and Eley-Rideal (E-R) based mechanisms. Finally, N2O degradation was analyzed in detail. It is shown that the Eley-Rideal model is a more dominant mechanism on the Ni@GN surface than the other model. In addition, all proposed reaction pathways for NO reduction are exothermic. This information can be used for the research and development of graphene-based materials for NO reduction; paves the way for finding new Ni-based catalysts based on active single transition metal atom embedded on different kind of defects.

Experimental study and kinetic model analysis on photothermal catalysis of formaldehyde by manganese and cerium based catalytic materials

ABSTRACT Modern people spend more and more time in cars in their daily lives, and the pollution of formaldehyde in the car may directly affect people’s health. Thermal catalytic oxidation technology by solar light is a potential way to purify formaldehyde in cars. MnOx-CeO2 was prepared by the modified co-precipitation method as the main catalyst, and the basic characteristic (SEM, N2 adsorption, H2-TPR, UV-visible absorbance) were also analyzed in detail. The experimental study was set up to simulate the solar photothermal catalysis of formaldehyde in-car environment. The results showed that the higher the temperature in the experimental box (56.7 ± 0.2°C, 62.6 ± 0.2°C, 68.2 ± 0.2°C), the better the formaldehyde degradation by catalytic effect (formaldehyde degradation percentage: 76.2, 78.3, 82.1). With increase of the initial formaldehyde concentration (200 , 500 , 1000 ), the catalytic effect first increased and then decreased (formaldehyde degradation percentage: 63, 78.3, 70.6). The catalytic effect risen gradually with the increase of load ratio (10, 20, and 40), and the formaldehyde degradation percentages were 62.8, 78.3, and 81.1, respectively. According to the expressions of the Eley-Rideal (ER) model, the Langmuir-Hinshelwood (LH) model, and the Mars-Van Krevelen (MVK) model, the experimental results were fitted and verified, and it was found that the ER model had a high degree of fit. It is more suitable to explain the catalytic mechanism of formaldehyde by MnOx-CeO2 catalyst in the experimental cabin, where formaldehyde is in the adsorption state and oxygen is in the gas phase. Implications: Judging from the current research status, vehicles have become an indispensable mode of travel for people, and the air quality in the vehicle is not optimistic. Most vehicles generally have the phenomenon of excessive formaldehyde. The characteristic of formaldehyde in the car is the continuous release, especially in the hot summer, the temperature inside the car rises sharply under the sun radiation. At this time, the formaldehyde concentration exceeds the standard by 4 to 5 times, which can cause great damage to the health of the passengers. In order to improve the air quality in the car, it is necessary to adopt the correct purification technology to degrade formaldehyde. The problem brought by this situation is how to effectively use solar radiation and high temperature in the car to degrade formaldehyde in the car. Therefore, this study uses the thermal catalytic oxidation technology to catalyze the degradation of formaldehyde in the high temperature environment of the car in summer. The selected catalyst is MnOx-CeO2, mainly because manganese oxide (MnOx) itself is the most effective catalyst for volatile organic compounds (TCO) among transition metal oxides, and CeO2 has excellent oxygen storage and release capacity and Oxidation activity, which helps to improve the activity of MnOx. Finally, the effects of temperature, initial concentration of formaldehyde and catalyst loading on the experiment were explored, and the kinetic model of thermal catalytic oxidation of formaldehyde with MnOx-CeO2 catalyst was analyzed to provide technical support for the future application of this research in practice.

Novel CoMn2O4 as a highly efficient catalyst for the oxidation of o-, m-, p-xylene: Preparation and kinetic study

In this research, a novel CoMn2O4 catalyst was prepared for the removal of o-xylene, m-xylene, and p-xylene. The catalyst showed better activity than that of MnO2 and Co3O4. The better activity of CoMn2O4 was attributed to the abundant concentration of Co2+, Mn3+, and lattice oxygen. Kinetic studies were carried out for the catalytic oxidation of three xylenes over the CoMn2O4 catalyst based on the Power-Low model, the Mars-van Krevelen model, the Eley-Rideal model, and the Langmuir-Hinshelwood model. All the three reactions could be most accurately described by the Mars-van Krevelen model, which suggested that the isomers of xylene had very little effect on the mechanism of xylene oxidation over the CoMn2O4 catalyst. The activation energies of the oxidation processes of o-xylene, m-xylene, and p-xylene were 94.64 kJ/mol, 78.46 kJ/mol, and 57.13 kJ/mol, respectively. The proposed mechanism based on the Mars-van Krevelen model suggested that xylene molecules reacted with the Co3+ and Mn4+/Mn3+ on the CoMn2O4 catalyst and participated in the cycle of adsorption, redox, and desorption.

New insights on the effects of SO2 on NO oxidation from flue gas with H2O2 vapor over Fe2O3/SiO2

The positive effects of SO2 on NO oxidation with H2O2 vapor over a Fe2O3/SiO2 catalyst were investigated. In well-designed experiments, the pretreatment of S-contained gaseous species and NO oxidation were carried out. The results indicated that the sulfate species from the oxidation of SO2 could significantly promote NO oxidation. In the radical scavenger and ESR tests, the H2O2 decomposition over SO2-pretreated Fe2O3/SiO2 produced •OH and •SO4-. The •OH was dominant for NO oxidation. The XPS tests verified the Fe(III) reduction and the surface SO42- species formation on Fe2O3/SiO2. According to the kinetic studies, the NO adsorbed Eley-Rideal model gave the best fit, indicating that the adsorbed NO over SO2-pretreated Fe2O3/SiO2 was oxidized by H2O2. The systematic research revealed that the generation of •OH from H2O2 decomposition over adsorbed H2SO4 was faster than that over Fe2O3/SiO2.

Kinetics of glycerol dehydration-hydrogenation reaction in the vapor phase in a fixed bed down flow tubular reactor over a bi-functional Cu-Zn/MgO catalyst

Kinetic models were developed for the vapor phase hydrogenolysis of glycerol in a fixed bed down flow tubular reactor over a highly stable bi-functional Cu-Zn/MgO catalyst. The kinetic experiments were conducted at atmospheric pressure, at different temperatures (200–220 °C), and contact time (W/FGo) (101.5–609 kgcat. h kmol−1), respectively. The Langmuir-Hinshelwood-Hougen-Watson (LHHW) and Eley-Rideal (ER) type kinetic models were tried considering a two-step glycerol dehydration-hydrogenation process. The model equations were solved in MATLAB by using the ode23 function and the kinetic parameters were optimized by using the genetic algorithm optimization technique. The activation energy for the dehydration and hydrogenation steps was found to be 57.73 ± 10 kJ/mol and 156.71 ± 10 kJ/mol from LHHW kinetic model and 82.6 ± 8.3 kJ/mol and 146.2 ± 3.9 kJ/mol from ER kinetic model, respectively. Results demonstrated that both the models were fitted very well with the experimental data generated. However, the parity plots of the simulated and experimental partial pressure of glycerol, acetol, and 1,2-PD suggested that ER model was more appropriate as compared to the LHHW model.

Preparation of Ti Material Supported SBA-15 Functionalized with Sulfonic Acid Environmental Friendly Catalyst: Application for Esterification Process

Kinetics of catalytic esterification between propionic acid and n-butanol has been studied in a batch reactor by using a Ti-supported SBA-15 catalyst with sulfonic acid. The synthesized catalyst is used to test the efficacy of catalyst for esterification reaction. The SBA-15 acidity is tied to incorporation of Ti and -SO3H groups through and the use of Si/Ti with Si/S molar ratios. The results are mesoporous materials with a typical hexagonal structure of the Ti SBA-15 and wide areas and high pore diameters that are operated with sulfonic groups. The addition of SBA to Ti leads mainly to catalytic materials with Bronsted and Lewis acid sites. Ti SBA-15 is the most effective catalyst for sulfonic acid, with the highest consents of Lewis acid sites and deactivation resistance and low hydrophilicity. The effect of temperature, catalyst amount, and molar ratio on reaction kinetics has been studied. The conversion of propionic acid is found to be 91% at 115°C at a 2 : 1 ratio of n-butanol to propionic acid molars with 2% of sulfonic acid supported Ti SBA-15. The Eley-Rideal kinetic model is used to fit the experimental data. The activation energy and kinetic factor are found to be 29.63 kJ mol–1 and k o 0.549 L2 g-1 mol-1, respectively.

Monolithic Stirrer Reactors for the Sustainable Production of Dihydroxybenzenes over 3D Printed Fe/γ-Al2O3 Monoliths: Kinetic Modeling and CFD Simulation

The aim of this work is to evaluate the performance of the stirring 3D Fe/Al2O3 monolithic reactor in batch operation applied to the liquid-phase hydroxylation of phenol by hydrogen peroxide (H2O2). An experimental and numerical investigation was carried out at the following operating conditions: CPHENOL,0 = 0.33 M, CH2O2,0 = 0.33 M, T = 75–95 °C, P = 1 atm, ω = 200–500 rpm and WCAT ~ 1.1 g. The kinetic model described the consumption of the H2O2 by a zero-order power-law equation, while the phenol hydroxylation and catechol and hydroquinone production by Eley–Rideal model; the rate determining step was the reaction between the adsorbed H2O2, phenol in solution with two active sites involved. The 3D CFD model, coupling the conservation of mass, momentum and species together with the reaction kinetic equations, was experimentally validated. It demonstrated a laminar flow characterized by the presence of an annular zone located inside and surrounding the monoliths (u = 40–80 mm s−1) and a central vortex with very low velocities (u = 3.5–8 mm s−1). The simulation study showed the increasing phenol selectivity to dihydroxybenzenes by the reaction temperature, while the initial H2O2 concentration mainly affects the phenol conversion.

Kinetic modeling of conversion of glycerol to 1,2-propanediol over bifunctional LDH catalyst

The performance of a highly efficient Cu0.45Zn0.15Mg5.4Al2O9 catalyst was investigated using a high-pressure autoclave reactor by adjusting several reaction conditions. The involvement of intermediates (Hydroxyacetone, Propylene glycol, Ethylene glycol) was explored to better understand the reaction pathways. The hydrogenolysis reaction was shown to be a multistep process, including the dehydration of glycerine to hydroxyacetone and then the hydrogenation of hydroxyacetone to 1,2-PDO. Finally, several kinetic models were established, and experimental outcomes were fitted to these models. The reaction kinetic parameters were calculated in MATLAB using ode45 and ode23s combined with optimization strategies to solve the resultant ordinary differential equations. The modified Power law model and the Eley-Rideal (E-R) models adequately correlated the experimental outcomes for two step hydrogenolysis reaction, according to the findings. The modified power law model revealed a pseudo-first order reaction in case of glycerol, and the energy of activation was calculated as 52.6 ​kJ/mol.

Kinetic studies for DRM over high-performance Ni–W/Al2O3–MgO catalyst

The reaction kinetics of DRM over high-performance Ni–W/Al2O3–MgO bimetallic catalyst is investigated in a fixed bed reactor. The variation of reaction rate is examined within the CH4 and CO2 partial pressure from 0.2 to 0.6 atm and the temperature range of 600oC–800 °C. It is found that the rate of reaction for DRM is more sensitive to CH4 partial pressure compared to CO2 partial pressures. At a constant partial pressure of CO2 and increasing the CH4 partial pressure, the increase in the reaction rate is more than reverse conditions. The activation energies of consumption of CH4 and CO2 were found to be 45.9 and 31.9 kJ/mol, respectively, showing a higher energy barrier for CH4 activation than CO2. Four typical kinetic models then fitted the experimental results obtained, i.e., Power Law, Langmuir- Hinshelwood and Eley-Rideal model I and II. The Langmuir-Hinshelwood model showed the best fitting between experimental and estimated reaction rates.

Microwave-assisted heterogeneous esterification of dibutyl maleate: Optimization using response surface methodology

Microwave-assisted synthesis of dibutyl maleate was carried out with heterogeneous catalyst, Amberlyst-15. Effect of process parameters such as mole ratio, reaction temperature, catalyst loading, and molecular sieves on the conversion was reported using Response Surface Methodology (RSM). Reaction conversion of 62.6% was achieved at optimum parameters of 1:3 acid to alcohol mole ratio, 5.5% (w/w) catalyst loading, 70°C temperature, and 6% (w/w) molecular sieves for reaction time of 60 min. The optimum parameters based on RSM were 1:3.14 acid to alcohol mole ratio, catalyst loading 5.35% (w/w), 77.19°C, and 64.77% predicted conversion. Pseudo- Homogeneous (PH), Eley Rideal (ER), and Langmuir Hinshelwood Hougen Watson (LHHW) models were used to fit experimental kinetic data. Studies revealed that the Eley-Rideal model suited the experimental data. The activation energy of the esterification reaction was calculated as 10.17 kJ/mol. Gibbs free activation energy (ΔG‡), enthalpy of activation (ΔH‡), and entropy of activation (ΔS‡) were evaluated.

Selective Discrimination of VOCs Applying Gas Sensing Kinetic Analysis over a Metal Oxide-Based Chemiresistive Gas Sensor

Semiconducting metal oxide-based gas sensors have inadequate selectivity as they are responsive toward a variety of gases. Here, we report the implementation of gas sensing kinetic analysis of the sensor to identify the tested volatile organic compounds (VOCs) (2-propanol, formaldehyde, methanol, and toluene) precisely. A single chemiresistive sensor was employed having tin oxide-based hollow spheres as the sensing material, which were obtained by chemical synthesis. The gas sensing measurements were conducted in a dynamic manner where the sensor displayed excellent response with high sensitivity. Eley-Rideal model was adopted to obtain the kinetic properties of the gas sensing phenomenon through theoretical fitting of response transient curves and their corresponding kinetic parameters. The calculated characteristic kinetic properties were further examined to discriminate among different VOCs. The approach of using gas sensing kinetic analysis for multiple gas discrimination is an attractive solution to mitigate the problem of cross-sensitivity for resistive gas sensors.

Conversion of methane to methanol on C-doped boron nitride: A DFT study

Computational modeling of the methane-to-methanol catalytic conversion reaction on the carbon-boron nitride nanosheet (C-BNN) was reported with the density functional theory. The charge density on C-BNN was displayed with the electron density difference map and investigated with the Bader charge analysis. The reaction mechanism was constituted according to the Eley Rideal model. CH4 → CH3OH conversion reaction were analyzed through the interaction of CH4 with O or O2 on the surface. The calculated energy barrier of the CH4 + O* → CH3OH and CH4 + O2 → CH3OH + O on C-BNN is 0.97 eV and 0.20 eV respectively. Our calculation results showed that the C-BNN surface was a highly active catalyst for the conversion reaction of methane to methanol. This information can provide different strategies for new catalyst researches with low cost and high catalytic activity.

An assessment on kinetic modeling of esterification reaction from oleic acid and methyl acetate over USY zeolite

In this work, commercial USY Zeolite was employed in oleic acid with methyl acetate esterification. Kinetic studies of esterification were carried out at methyl acetate to the oleic acid molar ratio of 10:1, with 5 wt% and 10 wt% of catalyst content and at 453, 473, 493 and 513 K. The Pseudo-homogeneous (PH) and Heterogeneous kinetic models, according to the Eley-Rideal (ER) and the Langmuir-Hinshelwood (LH) mechanisms, were investigated to correlate experimental data. The Thiele modulus analysis confirmed that the effect of the pore sizes on the internal mass transfer limitations could be neglected, and the study of the internal and external mass transfer limitations showed that the chemical reaction is the rate-controlling step. The coefficient of determination (R 2 ), the Akaike's information criterion (AIC), the relative Akaike weight (λ i ), and Spearman's rank correlation coefficient ( ρ i , j ) were utilized to evaluate the kinetic model's adequacy. The PH model provided the best results according to Akaike's information criterion (AIC) and relative Akaike weight (λ i ). Spearman's rank correlation coefficient ( ρ i , j ) showed that some parameters of ER and LH models presented high correlation and confidence intervals in their parameters, not satisfactorily representing the observed kinetic data. The thermodynamic study through PH model shows that oleic acid with methyl acetate esterification is an endothermic (ΔH = 59.83 kJ mol −1 ) and endergonic (ΔG = 118.66–126.45 kJ mol −1 ) reaction. The activation energy ( E a ) was 41.77 kJ mol −1 , and the negative value of entropy variation (ΔS = −129.8 J mol −1 K −1 ) might be associated with its associative mechanism. The decrease of catalyzed activation energy compared to the uncatalyzed reaction indicates that the USY zeolite was active to the esterification of oleic acid with methyl acetate. • USY zeolite was active in the esterification reaction with methyl acetate. • Three kinetic models were assessed and fitted well to experimental data. • Effect of pore sizes on the internal mass transfer limitations could be neglected. • Statistical criterion discriminated overparametrized models and unreliable parameters. • Pseudo-Homogeneous model was the most suitable.

Kinetic study for styrene carbonate synthesis via CO2 cycloaddition to styrene oxide using silica-supported pyrrolidinopyridinium iodide catalyst

Reaction kinetics for heterogeneous catalysis of styrene carbonate (SC) synthesis via CO2 cycloaddition to styrene oxide (SO) using silica-supported pyrrolidinopyridinium iodide (SiO2-PPI) catalyst has been investigated. The results obtained from the mixing study and theoretical analysis based on Thiele modulus (< 0.4) and effectiveness factor (∼1.0) revealed no external and internal mass transfer limitations. The experimental results were compared with pseudo-homogeneous (PH) and Langmuir-Hinshelwood (LH), Eley-Rideal (ER) heterogeneous kinetic model. The experimental data was found to be the best fit with the ER model among the three kinetic models. Moreover, the Arrhenius and Eyring equations were used to determining the activation energy (i.e. 64.9 kJ mol–1) and thermodynamic activation parameters such as enthalpy of activation (ΔH‡= 60.6 kJ mol–1), the entropy of activation (ΔS‡ = –148.3 J mol–1 K–1) and Gibb’s free energy (ΔG‡ = 115.9 kJ mol–1 at 373 K). The SiO2-PPI heterogeneous catalyst exhibited excellent reusability: up to five cycles without any substantial decrease in activity and selectivity towards SC formation.

Reaction kinetics for the heterogeneously resin-catalyzed and homogeneously self-catalyzed esterification of thioglycolic acid with 2-ethyl-1-hexanol

• Esterification of thioglycolic acid (TGA) with 2-ethyl-1-hexanol (EHL) was studied. • Heterogeneous and homogeneous reaction kinetics were determined. • The adsorption of water on resin catalyst improved the conversion of TGA. • Heterogeneous kinetics were well described by the PH, ER and LHHW models. • Homogeneous kinetics were described by an improved homogeneous model. Producing 2-ethyl-1-hexyl thioglycolate (ETE) via esterification reaction with thioglycolic acid (TGA) aqueous solution as raw material by reactive-separation coupling technology is a promising process intensification method. To choose suitable reactive-separation coupling strategy, the kinetic studies of the esterification of TGA with 2-ethyl-1-hexanol (EHL) were carried out in a batch system. The commercial ion exchange resin was employed as an eco-friendly catalyst. The effects of temperature, catalyst concentration and molar ratio were determined. It was interesting to observe that the equilibrium conversion of TGA increased with the increase of catalyst mass fraction due to the adsorption of product water onto resin surface. The activity-based pseudo-homogeneous (PH), Eley-Rideal (ER) and Langmuir-Hinshelwood-Hougen-Watson (LHHW) models were used to fit the kinetics data of the resin-catalyzed reaction. The models of ER and LHHW performed better than the PH model. The kinetics of the TGA-self-catalyzed reaction was also determined. An activity-based homogeneous kinetics model could well describe this self-catalyzed reaction. These results would be meaningful to the selection and design of an appropriate reaction-separation strategy for the production of ETE, to realize the process intensification.