Eley-Rideal Model Research Articles

Catalytic oxidative dehydrogenation of carveol to carvone over the phthalocyanine complex FePcCl16 immobilized on the mesoporous silica SBA-15

The immobilization of the FePcCl16 complex on the mesoporous silica SBA-15 and its performance in the eco-friendly oxidative dehydrogenation of carveol to carvone in the presence of t-butyl hydroperoxide (TBHP) under mild conditions is reported. The successful covalently anchored of FePcCl16 complex inside the pores of SBA-15, without complex or support damage, was confirmed by XRD, BET, UV–vis, SEM, TEM and Raman analysis. The best results achieved were after 1h of reaction, with 40% carvone selectivity and a carveol conversion around of 75%; carvone selectivity decayed when carveol conversion increased. Several mechanisms and rate equations derived from the kinetic models based on the Power Law, Langmuir-Hinshelwood, and Eley-Rideal model were proposed. Although the Power Law model showed the best mathematical fitting, the Eley-Rideal model seems to explain better the chemical sense of reaction. FePcCl16-NH2-SBA-15 catalyst was stable under the reaction conditions and it can be used up to twice without significant decrease in its catalytic activity.

Preparation of bimodal mesoporous silica containing cerious salt and its application as catalyst for the synthesis of biodiesel by esterification

A kind of bimodal mesoporous silica catalyst modified with ammonium cerous sulfate (ACS/BMMS) was synthesized and applied in the esterification of free fatty acid and alcohol. The characterization results including XRD, N2 adsorption and desorption, FTIR, 29Si-NMR and TEM showed that ACS/BMMS has orderly arranged bimodal mesopores, the small mesopore diameter is about 4.0–6.0 nm and the large mesopore diameter is in the range of 7.0–9.0 nm. The chemical interaction existed between silica group Si (OH)2(OSi)2 and the NH4+, SO42− and Ce-O groups of cerious salt. When the loading is not more than 10%, cerious salt dispersed finely on the supports. Oleic acid and methanol were used as the raw material of probe reaction; ACS/BMMS had significantly better activity than the ACS/SBA-15, ACS/SBA-16, ACS/MCM-41, BMMS and bulk ACS. The optimum loading of ACS is 10%, the optimum reaction conditions are reaction temperature 140 °C, reaction time 2 h, mole ratio of methanol to oleic acid 2.0 and the dosage of catalyst 4.0%, in above situation the conversion of oleic acid is about 94.0%, the reusability of ACS/BMMS is much better than bulk ACS. The kinetic study showed that the esterification of oleic acid and methanol on ACS/BMMS match Eley–Rideal model very well.

Kinetic Studies of Free Fatty Acid Esterification using Cation Exchange Resins as Catalyst

Objective: The aim of this work is to study the kinetics of Free Fatty Acid (FFA) esterification using cation exchange resins with different polymer structure arrangement as catalysts. Methods/Statistical Analysis: In this current work, cation exchange resins (i.e. Sulphonated Hypercrosslinked Exchange Resin (SHER), RCP160M and SK104H) were employed as catalysts in free fatty acid (FFA) esterification of Simulated Used Cooking Oil (SUCO). The kinetic models, pseudohomogenous (PH), Langmuir-Hinshelwood-Hougen-Watson (LHHW) and Eley-Rideal (ER) model were used to correlate the experimental data. The kinetic parameters i.e., the rate constant, adsorption coefficients and activation energy were determined using the non-linear regression analysis in POLYMATH 6.10 program. Findings: The kinetic results revealed that the esterification reaction of SUCO using SHER was successfully fitted with LHHW model, whereas for RCP160M and SK104H the experimental data was well fitted by the ER model (Case II) and ER model (Case I) respectively. The activation energy, Ea was observed to be 48.8, 37.2 and 45.3 kJ mol -1 for SHER, RCP160M and SK104H, which the reaction step were governed by chemical step (Ea> 15 kJ mol -1 ) and there is no mass transfer limitation occurred during the reaction. Application/Improvements: From the findings, the newly synthesized SHER was found to be a promising catalyst in the esterification of FFA.

Experimental investigation on the destruction rates of organic waste with high moisture content by means of self-sustained smoldering combustion

Self-sustained smoldering has been identified as an effective and efficient treatment for waste with high moisture content. To create the necessary conditions for the propagation of a smoldering reaction through the material, the waste is mixed with an inert material, such as sand, to create a porous matrix. This work shows the effect of different experimental parameters (moisture content, fuel concentration and airflow) on the fuel consumption rate during smoldering experiments under robust conditions. Fuel composition was the same for all experiments conducted. The main observation of these experiments is that the consumption rate remains invariant with the original moisture content of the waste, while showing a linear relationship with fuel concentration and airflow. An expression that describes the fuel consumption rate as a function of both parameters is presented. Based on the experimental observations, a kinetic mechanism analogous to the Eley–Rideal model for gas reactions on the surface of a solid is proposed. Finally, an expression that describes the smoldering front propagation velocity as proportional to the airflow and to the inverse of the density of the sand is presented. This expression is verified by 80 smoldering experiments under a wide range of operating conditions and four reactor sizes. The equation can be utilized for every reactor size, moisture content, fuel concentration and airflow rate, so long the smoldering reaction is robust.

A comparative study of LHHW and ER kinetic models for NO oxidation over Co3O4 catalyst

Experimental data for the NO oxidation to NO2 at atmospheric pressure over Co3O4 catalyst were subjected to various kinetic rate models. The power law kinetics, Langmuir-Hinshelwood-Hougen-Watson (LHHW) kinetics, and Eley-Rideal (ER) kinetics were employed to suggest a possible reaction mechanism and a suitable kinetic rate equation. The kinetic rate equation based on the LHHW kinetics with adsorption of NO as the rate-controlling step and the kinetic rate equation based on the ER kinetics with surface reaction as the rate-limiting step were first equivalently found as the best-fit kinetic rate equations. In each case similar activation energies were resulted and that the oxygen adsorption was found inhibiting the rate of the oxidation reaction. However, the final discrimination based on the literature findings suggested the ER model as the best-fit kinetic model with activation energy of 58.3kJ/mol and enthalpy of dissociative adsorption of oxygen as −2.10kJ/mol.

Facile Synthesis of Tributyrin Catalyzed by Versatile Sulfated Iron Oxide: Reaction Pathway and Kinetic Evaluation

Tributyrin, the triglyceride ester, exhibits strong properties as inhibitor of cancer cell growth in both humans and animals, which can increase the shelf life of drug. In this paper, tributyrin was synthesized by esterification reaction of butanoic acid with glycerol catalyzed by a low cost, ecofriendly green catalyst sulfated iron oxide. Effect of varying catalyst loading, stirring speed, and temperature on initial reaction rate was investigated. Reaction kinetics and adsorption and thermodynamic parameters were determined by evaluating the effect of concentration of butanoic acid, glycerol, and water addition on reaction rate. Eley–Rideal model using activity coefficients was employed to account for nonideality of the system to elucidate the experimental data. A maximal acid conversion of 91.8% was obtained at the temperature of 448.15 K. Activation energy was calculated to be 25.348 kJ/mol. The end product of reaction was characterized by means of thin layer chromatography (TLC), Fourier transform inf...

Estimation of kinetic parameters and diffusion coefficients for the transesterification of triolein with methanol on a solid ZnAl2O4 catalyst

The transesterification of vegetable oils by methanol implies a set of three parallel–series reversible reactions. Over a heterogeneous catalyst, reactions are limited by molecular diffusion, resulting in the use of a large excess of methanol to achieve a high conversion. This excess is detrimental to process efficiency because it involves large energy requirement for downstream separation. In order to identify the coupled physico-chemical phenomena and to optimize the process, a pilot unit was developed to perform transesterification of triglycerides with methanol over a solid ZnAl2O4 catalyst in a tubular fixed bed reactor under high pressure and temperature. The effects of different parameters such as particle diameter, temperature, residence time and molar feed ratio of methanol to triglyceride on fatty acid methyl ester (FAME) yield and triglyceride (TG) conversion were studied. A pseudo-homogeneous reactor model has been developed to identify rate laws and kinetic parameters by exploiting the experimental data in stationary regime. A set of kinetic constants was also determined for the given catalyst considering two kinetic models: an Eley–Rideal model with the reaction between TG and methanol as the rate determining step and a classical second order model taking into account thermodynamic equilibrium without adsorption. A heterogeneous model has also been established to determine molecular diffusion coefficients for each species in the mixture, through the use of experimental results in the transient regime. These molecular diffusion coefficients are dependent on the mixture viscosity and temperature. As a result, it was determined that diffusion of triglycerides and the first reaction kinetic rates are limiting the global conversion of the system.

Catalytic destruction of vinyl chloride over an alumina–supported platinum catalyst

In this study, vinyl chloride (VC), the primary material for manufacturing polyvinyl chloride (PVC), is decomposed via catalytic oxidation (C-OX) using Pt/γ-Al2O3 catalyst. The effects of related major factors such as reaction temperature (T) and gas hourly space velocity on the conversion of VC (X) were examined. The values of T for achieving conversions of 50% and 90% are 504 and 580 K with C-OX, respectively, whereas those without Pt/γ-Al2O3 (i.e., thermal oxidation, T-OX) are 900 and 983 K, respectively, thus indicating that C-OX significantly reduces T for effective oxidation of VC to form CO2, HCl, and Cl2 when compared with T-OX. The mineralizations of carbon in VC to form CO2 are 75.5% and 38% for C-OX and T-OX, respectively, at 90% X. The conversions of chlorine atom in 1,2-dichloroenane (DCEA) to Cl in HCl and Cl2 are approximately 42% and 50.8% for C-OX and T-OX, respectively, at 90% X. These results indicate that the Pt/γ-Al2O3 catalyst exhibits remarkable performance for the mineralizations to form CO2 even though a proportion of chlorine atoms are adsorbed on the Pt surface. The Eley–Rideal model can be used to describe the experimental results, thus yielding activation energy and frequency factor values of 49.0 kJ mol−1 and 1.77 × 106 s−1, respectively. The obtained information and kinetic parameters are useful for the rational design and operation of C-OX process for the abatement of VC.

A comparative study on the catalytic performance of different types of zeolites for biodiesel production

Abstract Microporous zeolites (BEA type Beta zeolite and MFI type ZSM-5 zeolite) and micro-mesoporous zeolites (MFI type ZRP-5 zeolite) with various Si/A1 ratios were employed in the esterification of oleic acid with ethanol. The effect of pore size on the internal mass transfer limitation was investigated by Thiele modulus calculation. The results showed that the zeolites with high Si/Al ratios had better catalytic performance, and of these three zeolites at the same Si/A1 ratios, the ZRP-5 zeolite exhibited the lowest internal mass transfer limitations but the worst catalytic performance. Through the comparison of the Eley–Rideal model and the Langmuir–Hinshelwood model, it was indicated that on the surface of hydrophilic ZRP-5 zeolites, the adsorption of the polar ethanol molecules were more favorable than the adsorption of oleic acid molecules, resulting in less coverage of oleic acid molecules on the surface of zeolites and lower conversion rate of esterification. Moreover, the Cassie–Baxter model and the water adsorption capacity test were used to further validate the assumption of kinetic model. The highest conversion rate of 73.6% was achieved when the reaction was catalyzed by high hydrophobic Beta (50) zeolites under optimized conditions of the molar ratio of oleic acid to ethanol of 1:20, catalyst loading of 0.167 meq/g (oleic acid), temperature of 78.0 °C, reaction time of 10.0 h and stirring speed of 600 rpm. The conversion rate of oleic acid remained above 70.0% after five runs and there was no apparent loss of the active component (Al) from the zeolite.

Analysis of the kinetics of surface reactions on a zinc oxide nanosheet-based carbon monoxide sensor using an Eley–Rideal model

Herein, we experimentally test a mathematical model of the reactions on the surface of a zinc oxide nanosheet-based carbon monoxide sensor. The carbon monoxide is assumed to react with surface oxygen via an Eley–Rideal mechanism, considering only the direct reaction between the two species. We demonstrate that the measured resistance responses of the system are well described by the model, facilitating further analysis of the physical rate constants in the system. By initially considering the system in the absence of any reducing gas, it is shown that various reaction parameters may be precisely estimated. For instance, fitting the model to response curves obtained at different temperatures shows the activation energy of the reaction between oxygen ions and carbon monoxide to be 54±9kJmol−1, whereas the recovery curves yield an estimate of 42±7kJmol−1. Similarly, the energy barrier for the formation of oxygen ions is found to equal 72±9kJmol−1 from the sensor response and 63±10kJmol−1 from the recovery. These estimates are in agreement with values quoted elsewhere in the literature, corroborating the validity of the model. In the absence of surface ions, the energy difference between the Fermi level and the conduction band minimum at the surface is estimated as 590±90meV.

One-pot oxydehydration of glycerol to value-added compounds over metal-doped SiW/HZSM-5 catalysts: Effect of metal type and loading

A one-pot oxydehydration of glycerol to value-added compounds was carried out over metal-doped SiW/HZSM-5 catalyst at low temperature (90°C) and ambient pressure. Effects of metal types (Co, Ce, Ni and V) and loadings (0–8wt.%) on catalyst properties and catalytic activity were explored. Doping different types of metal and loading on the surface of SiW/HZSM-5 catalyst affected surface chemistry and textural chemistry as well as the catalytic activity for glycerol conversion and product yield distribution. The V at 6% loading most effectively enhanced the activity of SiW/HZSM-5 for a one-pot oxydehydration of glycerol to value-added compounds. The presence of V6-SiW/HZSM-5 catalyst can enhance the glycerol conversion up to 99.67% with the yields of glycolic acid, formic acid, acetic acid, acrolein, acrylic acid, and propionic acid of 19.45%, 12.03%, 23.62%, 0.25%, 36.23% and 7.06%, respectively with less than 1.5% of glycerol converting to some undesired products. The kinetic studies of a one-pot oxydehydration of glycerol over this catalyst (V6-SiW/HZSM-5) showed the rate of glycerol conversion depended upon the glycerol concentration according to the pseudo-first order kinetic rate and about the zero order with respect to the H2O2 concentration. The Eley–Rideal model, assuming the reaction between a non-dissociative adsorption of H2O2 and glycerol molecule provided the best fit with the experimental results.

Kinetic studies of the esterification of pure and dilute acrylic acid with 2-ethyl hexanol catalysed by Amberlyst 15

The untreated waste water containing acrylic acid (AA) could have detrimental effect to the environment due to its high value of chemical oxygen demand. Reactive distillation column (RDC) could be a promising treatment method to recover AA from the waste water. In the present work, activity and kinetic studies of the esterification of AA and 2-ethyl hexanol (2EH) were carried out in a batch system to examine the practicability of this method. Ion exchange resin, Amberlyst 15 was employed as a catalyst. The effect of various parameters that affecting conversion and yield such as agitation speed, catalyst particle size, temperature, catalyst loading and initial reactant molar ratio were studied. The effect of the initial water content was studied using both the batch systems with total reflux (TR) and dean stark for continuously water removal (CWR). The increase of equilibrium conversion with the temperature indicated the endothermicity of the reaction. Temperature was the most significant parameter that affected the conversion and yield. The highest yield of 70% was obtained at the temperature of 388K, initial reactant molar ratio of AA to 2EH of 1:3 and catalyst loading of 10wt%. The pseudo-homogeneous (PH), Eley–Rideal (ER) and Langmuir–Hinshelwood–Hougen–Watson (LHHW) kinetic models were used to interpret the kinetic data. The best fit kinetic model for the main esterification reaction was the non-ideal ER model while the side reaction, AA polymerisation was best interpreted by PH model. The kinetic data for the esterification of dilute AA was well described by the inclusion of the correction factor to the kinetic model for the esterification.

Kinetic Modeling of Transesterification of Triacetin Using Synthesized Ion Exchange Resin (SIERs)

Strong anion exchange resins with QN+OH-, have the potential to be developed and employed as heterogeneous catalyst for transesterification, as they are chemically stable to leaching of the functional group. Nine different SIERs (SIER1-9) with QN + OH were prepared by suspension polymerization of vinylbenzyl chloridedivinylbenzene (VBC-DVB) copolymers in the presence of n-heptane (pore-forming agent). The amine group was successfully grafted into the polymeric resin beads through functionalization with trimethylamine. These SIERs are then used as a catalyst for the transesterification of triacetin with methanol. A set of differential equations that represents the Langmuir-Hinshelwood-HougenWatson (LHHW) and Eley-Rideal (ER) models for the transesterification reaction were developed. These kinetic models of LHHW and ER were fitted to the experimental data. Overall, the synthesized ion exchange resin-catalyzed reaction were welldescribed by the Eley-Rideal model compared to LHHW models, with sum of square error (SSE) of 0.742 and 0.996, respectively.

Determination of methanolysis rate constants for low and high fatty acid oils using heterogeneous surface reaction kinetic models

Catalytic methanolysis of soybean oil with Amberlyst A26-OH basic ion-exchange resin was studied in the presence and absence of free fatty acids. Catalytic methanolysis of soybean oil is a key step in the biodiesel production process. The use of the heterogeneous Amberlyst A26-OH basic resin to catalyze this conversion is of interest due to the resin’s ability to be recovered, regenerated, and reused. This current research modeled methanolysis on the surface of the heterogeneous catalyst using both the Eley–Rideal and Langmuir–Hinshelwood–Hougen–Watson reaction kinetic models. For all experiments, soybean oil (with and without 5 % oleic acid incorporated) was reacted with methanol at a molar ratio of 1:10 soybean oil to methanol in the presence of Amberlyst A26-OH (added at 20 % by weight of oil). The reaction was carried out over multiple investigations in a batch reactor where the reactants were mixed at 550 rpm and held at 50 °C and atmospheric pressure. The resulting data demonstrated that the Eley–Rideal reaction mechanism offered the best description of the surface interactions occurring on the resin. Based upon Eley–Rideal model fitting, the mean (± standard deviation) methanolysis rate constant (the rate at which methanol was consumed during the reaction) was determined to be 7.48 × 10−4 (±4.05 × 10−5) h−1 with free fatty acid absent and 1.94 (± 1.25 × 10−1) h−1 with free fatty acid present.

Synthesis of Methyl Butyrate Using Heterogeneous Catalyst: Kinetic Studies

This paper illustrates a kinetic investigation of esterification reaction involving butyric acid and methanol over amberlyst-15 catalyst. The catalytic reactions were performed in an isothermal well stirred batch reactor using excess of alcohol to prevent the reverse reaction. The experimental parameters studied were reaction temperature, molar ratios of reactants, catalyst loading, stirring speed, initial water present and quantity of molecular sieves added. The optimum reaction conditions for the ester synthesis were found at temperature 343 K, alcohol to acid ratio 3, stirrer speed 300 rpm, catalyst loading of 6.5 % (w/w basis) and molecular sieves 8.5 %. Addition of water to reactor contents has negative effect as expected. Conversion increased with temperature and catalyst loading whereas it decreased as the molar ratio of alcohol to acid increased beyond 3. Molecular sieves added adsorb water formed in the reaction hence favoring reaction in forward direction. Kinetic data was tested for pseudo-homogeneous model, Langmuir–Hinshelwood model and Eley–Rideal model. Studies show that dual site LHHW with reactants and products adsorbing on catalyst surface is most suited for the experimental data.

A kinetic study on the structural and functional roles of lanthana in iron-based high temperature water–gas shift catalysts

The structural and functional roles of varying amounts of lanthana in co-precipitated high temperature Fe2O3/Cr2O3/CuO water–gas shift catalysts were studied at 1 atm and 350–425 °C temperature range.Addition of 0.5 wt% of lanthana enhanced the reducibility of the catalyst, increased its surface area and its WGS activity from 24 to 31 mmol CO/(gcat min), and reduced the deactivation rate at 400 °C from 23% to 11% relative to a similar catalyst with no lanthana. XRD results suggested that 0.5 wt% of lanthana stabilized the iron–chromium cubic spinel structure most efficiently under the operating conditions; however, further additions appeared to disrupt the spinel structure and degrade the performance of the catalysts.The power-law and Langmuir–Hinshelwood models provided much better fits to the rate data than either the redox or the Eley–Rideal models, suggesting that the reaction tends to follow an adsorptive mechanism. The CO adsorption equilibrium constant was largest for the catalyst with 0.5 wt% lanthana, indicating that the addition of lanthana might facilitate CO adsorption. Water inhibited the reaction as it strongly adsorbed on the catalyst surface.

Investigation of reaction parameters, kinetics and mechanism of oleic acid esterification with methanol by using Amberlyst 46 as a catalyst

In this study, the effect of reaction parameters such as molar ratio of methanol to oleic acid, catalyst amount, reaction temperature and reaction time was investigated for esterification of oleic acid with methanol in the presence of Amberlyst 46. The conversion of 98.6% was obtained when the reaction was performed at 3:1 molar ratio of methanol to oleic acid, reaction temperature of 100°C, catalyst amount of 15% and 2h reaction time. The conversions with reused catalyst varied in the range of 96.8% to 98.3%. After the catalyst was reused for ten times under the same reaction conditions negligible catalytic activity loss (<2%) was observed. The pseudo-homogeneous and Eley–Rideal models were used to correlate experimental data. The results support the validity of Eley–Rideal mechanism where the surface reaction was assumed as the rate limiting step.

Kinetics of 1-hexanol etherification on Amberlyst 70

The kinetics of the liquid-phase etherification of 1-hexanol to di-n-ethyl ether and water on the ion-exchange resin Amberlyst 70 in the temperature range 423–463 K is studied. The strong inhibition effect of water is considered following two approaches. First, a model stemming from a Langmuir–Hinshelwood–Hougen–Watson (LHHW) mechanism was used, wherein the inhibitor effect of water was explained by the competitive adsorption of water and hexanol. Secondly, a modified Eley–Rideal (ER) model that includes an inhibition factor, in which a Freundlich-like function is used to explain the inhibitor effect of water by blocking the access of hexanol to the active centers. Both models fitted data quite well, although the best fitting results were obtained with the modified ER model. The activation energy was 125 ± 3 kJ/mol for the LHHW model and 121 ± 3 kJ/mol for the modified ER one.

Impregnation of 12-tungstophosphoric acid on tonsil: An effective catalyst for esterification of formic acid with n-butyl alcohol and kinetic modeling

Esterification of formic acid with n-butanol was catalyzed by dodecatungstophosphoric acid, H3PW12O40 (DTP) impregnated on tonsil earth. A series of catalysts containing 10%, 20% and 30% of DTP on tonsil earth were synthesized. The samples were characterized by FT-IR, XRD, BET and TG. The 20% DTP loaded on tonsil showed the highest catalytic activity among the samples prepared in this study. Therefore the kinetics of esterification of formic acid with butanol has been studied in the presence of 20% DTP/T. The kinetic behavior of the reaction has been found to follow the Eley–Rideal model.

Kinetic Study of Acetic Acid Esterification with Methanol Catalyzed by Gel and Macroporous Resins

The liquid-phase acetic acid esterification kinetics with methanol to methyl acetate and water catalyzed by gel (Lewatit K1221) and macroporous (Lewatit K2629) ion exchange resins have been investigated and compared with literature reported data acquired on Amberlyst 15. The effects of the resin swelling, the initial molar methanol to acetic acid ratio (1:1 – 10:1) and the temperature (303 – 333 K) on the reaction kinetics were investigated. The gel type resin exhibits a remarkably higher catalytic activity compared to the macroporous resins, despite its similar number of sulfonic acid groups. This can be attributed to the differences in active site accessibility during reaction and, hence, in resin swelling, especially when it is in contact with polar components, such as water and methanol. The differences in catalytic behavior between the considered resins have been assessed using an exchange based Eley-Rideal model in which it is assumed that (1) all the active sites are occupied, (2) the acid undergoes a proton exchange with the protonated methanol and (3) the reaction occurs according to an Eley-Rideal mechanism with the surface reaction between protonated acetic acid and methanol from the bulk as ratedetermining step. This model, which implicitly accounts for resin swelling, could describe the observed differences between the various resins. The activation energy was determined at 47 kJ mol−1, irrespective of the resin used.