Article

Determination of adsorption and kinetic parameters for methyl oleate (biodiesel) esterification reaction catalyzed by Amberlyst 15 resin

Authors:
To read the full-text of this research, you can request a copy directly from the authors.

Abstract

In this work, adsorption equilibrium constants, dispersion coefficients, and kinetic parameters were determined for the reversible esterification reaction of oleic acid with methanol, producing methyl oleate (biodiesel) and water. The reaction was carried out at room temperature in the presence of Amberlyst 15 resin, which acts both as an adsorbent and catalyst in an HPLC column, which served as a packed bed reactor. A quasi-homogenous kinetic model coupled with a linear adsorption isotherm was explored. The elution profiles of the reactant and products were experimentally monitored and then compared with a mathematical model. The adsorption and kinetic parameters were determined by minimizing the error between the experimentally obtained elution curves and the model-predicted values using the genetic algorithm optimization technique. Further experiments were conducted under varying conditions to establish the validity of the obtained model parameters. It was also found that the system is not affected by internal and external mass transfer resistances. The mathematical model predicted the experimental outcome quite accurately. This article is protected by copyright. All rights reserved

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

... Many works can be found in the literature, which report about kinetic models for fatty acid esterification with different heterogeneous catalysts, such as sulfated zirconia [23,24], Relite CFS [25], silica-supported tungstophosphoric acid [26], niobium oxide [12,27], or Amberlyst-46 [28]. As far as the use of Amberlyst-15 is concerned, simplified or more complex kinetic models can be found to describe the esterification of decanoic acid with methanol [16], nonanoic acid with ethanol [29], or oleic acid with methanol [30,31]. Furthermore, a kinetic/equilibrium model was also developed to explain the esterification of an artificially-acidified-soybean oil and a commercial mixture of waste fatty acids with high-acidity, both in the presence of Amberlyst-15 or Relite CFS [32]. ...
... Despite that many heterogeneous kinetic models were proposed in the literature [12,16,25,28,31], the pseudo-homogeneous second-order reversible one is less complex and it requires smaller number of parameters to be estimated [16,25]. Furthermore, it is a ready-to-use simple approach that can be easily implemented in commercial process simulation software [17,19,21,23,27]. ...
Article
Full-text available
Fatty acid esterification with alcohols is a crucial step in biodiesel synthesis. Biodiesel consists of long-chain alkyl esters that derive from the transesterification or hydro-esterification of the triglycerides that are contained in vegetable oils. In the first route, the esterification of the free fatty acids is an important pretreatment of the feed; in the second, it is the main reaction of the industrial process. Knowledge of appropriate kinetic models for the catalytic esterification of fatty acids with alcohols is critical in the design of biodiesel synthesis processes. In this work, the kinetic behavior of the reversible esterification of lauric, myristic, palmitic and stearic acid, which are the most common saturated fatty acids that are contained in triglyceride feedstocks for biodiesel, with methanol at different temperatures (70–150 °C) and molar ratios of the reactants (1:1–1:2–1:5) was investigated in a batch laboratory basket reactor both in the presence and absence of Amberlyst-15 as the catalyst. Results obtained with Amberlyst-15 were fitted through a ready-to-use pseudo-homogeneous reversible model suitable for process design. The kinetic model was compared with that obtained in a previous work with niobium oxide as the catalyst. With respect to the results that were obtained with niobium oxide, the influence of the chain length of the acid on the kinetic behavior was strongly reduced in the presence of Amberlyst-15. This phenomenon was ascribed to a different catalytic mechanism.
... Scheme 2. Esterification reaction of a fatty acid with methanol [92]. ...
Article
Full-text available
Waste cooking oil (WCO) is a promising feedstock for producing biodiesel, which plays a significant role in waste resource reusing and renewable energy production. It is known that cost is the main factor restricting the large-scale production of biodiesel. Therefore, the Life Cycle Cost (LCC) method was used to analyze the economic feasibility of the biodiesel production process from WCO. Our results show that the cost of producing 1 t of WCO biodiesel is 6291.56 RMB, which is 3.49% higher than the price of 0# diesel. The factors influencing WCO biodiesel production cost was further analyzed. Although WCO has a low commercial price, necessary pretreatment is inevitable and creates additional processing cost, since WCO cannot be directly used for transesterification to produce biodiesel. The cost of pretreatment process is relatively high, accounting for 15.60% of the total cost. Special waste management policy should be implemented and waste cooking oil recycling technology should be advanced, in order to make WCO biodiesel more economically competitive. Aspen Plus software was used to simulate the production process of biodiesel from WCO, and the production process was simulated by a two-step method. The practicability of simulation was confirmed by purity of biodiesel reaching 99.6 wt%. In the simulation, processing parameters of methanol rectification tower and biodiesel rectification tower were optimized to provide a reliable benchmark for the industrial biodiesel production from WCO.
... Amberlyst 15 was selected as a strong ion-exchange resin containing sulfonic acid groups, styrene divinylbenzene and ionic H structure. Amberlyst 15 was generally used as a catalyst for different synthesis, such as esterification reaction (Ray and Ray 2016;Chin et al. 2015). It was also used for the removal of various metal ions and organic species from various samples by using adsorption (Hassankiadeh et al. 2015;Mustafa et al. 2011;Naushad et al. 2014). ...
Article
Full-text available
Preconcentration of Cd(II) and Pb(II) was carried out by using column solid phase extraction method. Amberlyst 15 was used as solid phase for these analytes. The optimum extraction conditions such as pH (4), type and volume of eluent (5 mL of 2 mol L⁻¹ HNO3) sample flow rate (1 mL min⁻¹) and sample volume (100 mL for Cd(II) and 750 mL for Pb(II)) were determined. The recoveries were found for Cd(II) and Pb(II) as 104% ± 1% and 102 % ± 2%, respectively. The limit of detections were found as 0.23 µg L⁻¹ for Cd(II) and 0.13 µg L⁻¹ for Pb(II). The effects of foreign ions were also studied. The method was validated by analyzing standard reference material and spiked water samples. Percent relative error and relative standard deviation were below 3% and 4%, respectively.
Article
In order to accurately predict the complex chromatographic behaviors of the components to be separated, the fuzzy Langmuir adsorption equations and the back propagation‐artificial neural network (BP‐ANN) are combined to establish fuzzy Langmuir adsorption models. Herein, the fuzzy Langmuir adsorption equations are deduced based on a series of different traditional adsorption equations such as with or without competition, one or two kinds of adsorbed sites, monomolecular or multimolecular adsorption, etc. The major adsorption parameter Ci (form concentration) is the function of the actual concentration ci, expressed in matrix form constructed by BP‐ANN and is obtained by solving the equilibrium dispersive chromatography model with the inverse method and genetic algorithm. Finally, the fuzzy Langmuir models are applied to study the chromatographic behaviors of m‐cresol and p‐cresol on MIL‐53 (Al) stationary phase. The results show that the models have excellent curve fitting ability, and can be used to determine the adsorption relationship and predict the chromatographic elution curves under complex or unknown adsorption mechanism. Fuzzy Langmuir adsorption models are proposed, which have the dual advantages of mechanism and data‐driven modeling. The calculated elution curves based on the models are almost consistent with the experimental elution curves under "breathing" effect. The proposed method can be used to determine the single‐component and two‐component competitive adsorption equations under complex adsorption mechanism.
Article
The objective of this study is the investigation of solubility, critical states and liquid-liquid equilibrium of the quaternary system oleic acid – methanol – methyl oleate – water and its ternary and binary subsystems at 303.15 K and atmospheric pressure. A brief review of the literature on the studied system is presented. The compositions for binodal curves and for surface of solubility were determined using cloud-point technique. Tie-lines of liquid–liquid equilibrium were obtained using NMR spectroscopy. Experimental results were represented by diagrams in concentration simplices including 3D phase diagram in composition tetrahedron. A comparative analysis with the available literature data has been carried out. Correlation and prediction of experimental LLE data was performed using NRTL and UNIFAC models, respectively. Results of modeling was found to has a satisfactory agreement with the experimental data.
Article
Close boiling points pose great challenges to the separation of the isomers m-cresol and p-cresol. Metal-organic frameworks (MOFs) material with uniform pore structure, high specific surface area and good chemical stability is a potential adsorbent. In this study, m-cresol and p-cresol were separated by a chromatographic process with aluminum terephthalate metal-organic framework (MIL-53(Al)) as stationary phase and acetonitrile as mobile phase. In view of the unique "breathing" effect of MOFs materials, according to the kinetic process and thermodynamic equilibrium of adsorption and desorption, the hybrid adsorption isotherm equations were established, which can reflect the "breathing" effect by combining the Langmuir adsorption process of narrow pore and the multi-stage adsorption process of large pore. The parameters of adsorption isotherm were determined by inverse method and genetic algorithm, and the adaptability of the equilibrium dispersive chromatography model based on this adsorption isotherm to the single-component adsorption process and two-component competitive adsorption process was proved under different injection concentration, injection time and flow velocity conditions. The separation process of m-cresol and p-cresol was optimized by the chromatographic model and genetic algorithm. Under the optimized conditions, the separated m-cresol and p-cresol were obtained with the purity values of 96.26% and 93.23%, and the recovery values of 96.93% and 96.59%, respectively.
Article
An integrated process of catalytic hydrolysis and membrane separation was developed for fatty acids (FAs) production from lard oil. Both sulphonated cation exchange resin (SCER) and 0.98 g/g H2SO4 as catalysts were used to produce fatty acids (FAs) from lard oil by three-step hydrolysis, respectively. Simultaneously, polyethersulphone (PES) ultrafiltration membrane was employed to separate glycerol and water from the products. The hydrophilicity and morphology of the pristine and used PES membranes were characterized by contact angle measurement and field-emission scanning electronic microscopy, respectively. The final optimal yields of FAs obtained by SCER and H2SO4 catalysis at 100 °C and atmospheric pressure were 85.6% at 16.0 h of operation and 94.5% at 18.0 h of operation, respectively. Furthermore, the yield of FAs obtained from an integrated process of SCER-catalyzed hydrolysis and membrane separation achieved up to 99.9% at 10.0 h, 90 °C, and operating pressure of 100 kPa. This article is protected by copyright. All rights reserved
Article
Reaction distillation was first used for the process of acrylic acid synthesis through transesterification of methyl acrylate with acetic acid using a strongly acidic cationic exchange resin catalyst (NKC-9). Pseudo-homogeneous (P-H) and Langmuir-Hinshelwood (L-H) heterogeneous kinetic models were presented and fitted with the experimental data obtained from the batch reaction. The key factors of the heterogeneous kinetic model were the four components' adsorption equilibrium constants on the catalyst surface, and they were determined by adsorption experiments. The activity coefficients were calculated using the NRTL method. The catalyst stability was evaluated in a fixed-bed reactor. Catalyst activity showed no obvious decrease after 1000 h of running. A reactive distillation column for acrylic acid synthesis was proposed and designed with process simulation.
Article
Full-text available
The esterification of free fatty acids (FFA) found in vegetable oils with CH3OH using a solid catalyst is a promising method to convert FFA into valuable fatty acid methyl ester (FAME, biodiesel) and obtain a FFA-free oil that can be further transesterified using alkali bases. The present work aimed at determining active and durable solid catalysts for the esterification of palmitic acid (PA, C16H32O2) dissolved in commercial sunflower oil with methanol. Contrary to the case of experiments realized at high dilution in solvents or in pure FFA medium, in which methanol is fully soluble, a lack of full miscibility occurred in the present case. Both a stirred batch reactor and, for the first time to our knowledge, a recirculating system using a fixed bed-reactor were used to investigate this system.
Article
Full-text available
Methyl tert-butyl ether (MTBE), a high-octane blending agent for motor gasoline, is produced by reacting directly tert-butyl alcohol (TBA) with methanol using Amberlyst 15 ion-exchange resin, which acts as both catalyst and adsorbent. Experiments were carried out in a fixed-bed reactor in the temperature range 318–328 K using rectangular pulse input and measuring the elution profiles of TBA, MTBE, and H2O. A mathematical model based on a quasi-homogeneous kinetics was developed, which assumes the reaction in the polymer phase to be homogeneous. The kinetic parameters, as well as the adsorption equilibrium constants of water, TBA, and MTBE in methanol together with their dependence on temperature, were determined by tuning the simulation results to fit the experimental data using a state-of-the-art optimization technique, the genetic algorithm. The model was further validated using the tuned adsorption and rate parameters to predict other experimental results. The kinetics reported in the present study were obtained under conditions free of both external and internal mass transfer resistance. The enthalpy and entropy of adsorption obtained from Arrhenius plots were found to be consistent with thermodynamics.
Article
Full-text available
Biodiesel is a biodegradable and renewable fuel, emerging as a viable alternative to petroleum diesel. Conventional biodiesel processes still suffer from problems associated with the use of homogeneous catalysts and the limitations imposed by the chemical reaction equilibrium, thus leading to severe economic and environmental penalties. This work provides a detailed review – illustrated with relevant examples – of novel reactive separation technologies used in biodiesel production: reactive distillation/absorption/extraction, and membrane reactors. Reactive separation offers new and exciting opportunities for manufacturing the fatty acid alkyl esters involved in the industrial production of biodiesel and specialty chemicals. The integration of reaction and separation into one operating unit overcomes equilibrium limitations and provides major benefits such as low capital investment and operating costs. These reactive separation processes can be further enhanced by heat-integration and powered by heterogeneous catalysts, to eliminate all conventional catalyst related operations, using efficiently the raw materials and the reaction volume, while offering higher conversion and selectivity, as well as significant energy savings compared with conventional biodiesel processes. Remarkable, in spite of the high degree of integration, such integrated reactive-separation processes are still very well controllable as illustrated by the included examples.
Article
Full-text available
Multiobjective optimization involves the simultaneous optimization of more than one objective function. This is quite commonly encountered in Chemical Engineering. A considerable amount of research has been reported in this area over the last twenty years. This is reviewed in the present paper. The general background of this area is presented at the beginning, followed by a description of how the results can be described in terms of Pareto sets. We then present the several methods available for generating these optimal solutions. Applications of optimization in Chemical Engineering wherein multiple objectives are encountered, as well as special adaptations of the basic algorithms required to solve these problems, are then discussed. Some comments are also made on possible directions that future research may take in this area.
Article
Full-text available
The advantages of biodiesel as an alterna- tive fuel and the problems involved in its manufactur- ing are outlined. The pros and cons of making biodie- sel via fatty acid esterification using solid acid cata- lysts are examined. The main problem is finding a suitable catalyst that is active, selective, and stable un- der the process conditions. Various solid acids (zeo- lites, ion-exchange resins, and mixed metal oxides) are screened as catalysts in the esterification of do- decanoic acid with 2-ethylhexanol, 1-propanol, and methanol at 130 - 1808C. The most promising candi- date is found to be sulphated zirconia. The catalyst=s stability towards thermal decomposition and leaching is tested and the effects of the surface composition and structure on the catalytic activity are discussed.
Article
Biodiesel is an alternative fuel for diesel engines consisting of the alkyl monoesters of fatty acids from vegetable oils or animal fats. Most of the biodiesel that is currently made uses soybean oil, methanol, and an alkaline catalyst. The high value of soybean oil as a food product makes production of a cost-effective fuel very challenging. However, there are large amounts of low-cost oils and fats such as restaurant waste and animal fats that could be converted to biodiesel. The problem with processing these low cost oils and fats is that they often contain large amounts of free fatty acids (FFA) that cannot be converted to biodiesel using an alkaline catalyst. In this study, a technique is described to reduce the free fatty acids content of these feedstocks using an acid-catalyzed pretreatment to esterify the free fatty acids before transesterifying the triglycerides with an alkaline catalyst to complete the reaction. Initial process development was performed with synthetic mixtures containing 20% and 40% free fatty acids, prepared using palmitic acid. Process parameters such as the molar ratio of alcohol, type of alcohol, acid catalyst amount, reaction time, and free fatty acids level were investigated to determine the best strategy for converting the free fatty acids to usable esters. The work showed that the acid level of the high free fatty acids feedstocks could be reduced to less than 1% with a 2-step pretreatment reaction. The reaction mixture was allowed to settle between steps so that the water-containing alcohol phase could be removed. The 2-step pretreatment reaction was demonstrated with actual feedstocks, including yellow grease with 12% free fatty acids and brown grease with 33% free fatty acids. After reducing the acid levels of these feedstocks to less than 1%, the transesterification reaction was completed with an alkaline catalyst to produce fuel-grade biodiesel.
Article
The simulated countercurrent moving bed chromatographic reactor (SCMCR) is a device for carrying out chemical reaction and separation simultaneously in a fixed bed. It mimics the behavior of a countercurrent moving bed, in which a stream of solids flows countercurrent to an inert fluid and past a stationary reactant inlet, by periodically changing feed locations sequentially along a fixed bed. True countercurrent motion is thus replaced by a periodic motion, while overcoming the problems of solids handling and attrition inherent in moving bed operations, as well as avoiding the flow channeling that would be attendant with scaleup to large column diameters. The present investigations seek to determine to what extent the moving bed reactor advantages of high product purity and favorable equilibrium shifts are retained in SCMCR operations. Two configurations of the SCMCR, a single fixed bed having a series of inlets and outlets along its length, and a series of columns with an inlet or outlet between each, are considered. Model calculations predict that both configurations give high purity product streams and nearly unit conversions of the equilibrium limited reaction.
Article
In this paper, the adsorption equilibrium constants, dispersion coefficients, and kinetic parameters were obtained for the liquid phase reversible reaction of methanol with acetic acid catalyzed by Amberlyst 15. The adsorption and kinetic parameters are determined corresponding to two different mobile phases, methanol and water. Such parameters are required for three different applications of the model reaction: namely, synthesis of methyl acetate, removal of dilute acetic acid from wastewater, and hydrolysis of methyl acetate. Experiments were conducted in a packed bed reactor in the temperature range 313–323 K using a rectangular pulse input. A mathematical model for a quasi-homogeneous kinetics was developed. The adsorption and kinetic parameters together with their dependence on temperature were determined by tuning the simulation results to fit the experimentally measured breakthrough curves of acetic acid, water (or methanol) and methyl acetate using a state-of-the-art optimization technique, the genetic algorithm. The mathematical model was further validated using the tuned parameters to predict experimental results at different feed concentrations and flow rates. The kinetics reported in this study was obtained under conditions free of both external and internal mass transfer resistance. The computed parameters were found to predict experimental elution profiles for both batch and plug flow reactors reasonably well.
Article
The characteristics of ion-exchange resins provide the basis for many processes of practical interest involving both sorption separations and catalytic reactions. The optimal design and operation of these processes require a proper understanding of the equilibrium behavior of multicomponent liquid mixtures in contact with cross-linked polymeric resins, in terms of both the amount and composition of the sorbed mixture. For this, a model which describes the equilibrium between a polymer phase, described through the extended Flory−Huggins theory, and a liquid phase, which does not contain the polymer, has been developed. This has then been coupled with a kinetic model describing the catalytic reaction inside the resin particles. The model has been validated through an appropriate experimental analysis involving both equilibrium partitioning and reactive experiments, for the case of a highly cross-linked sulfonated resin in the presence of various mixtures of the components involved in the esterification of ethanol with acetic acid. The results indicate the ability of the resin not only to catalyze the esterification reaction but also to shift the corresponding equilibrium conversion, due to its swelling capability. This approach is believed to apply to a wide class of reactions catalyzed by polymeric resins, and it is suitable for the optimal design of the corresponding processes.
Article
The objective of this work was to establish fixed bed sorption enhanced reactors (SER) and simulated moving bed reactors (SMBR) for the production of high purity biodiesel (fatty acid methyl ester, FAME) using esterification reactions between fatty acids (FA) in used oils and methanol. This study has demonstrated that these processes have tremendous potential in terms of overcoming the low conversion and separation difficulties that are faced in conventional biodiesel production processes. Additionally, the SMBR process operating conditions can be optimized to produce FAME at a desired purity in a continuous mode. The novelty of this work lays in the development of generic and comprehensive dynamic simulation and systematic parametric analysis frameworks. These were used to deduce the following operating conditions for achieving more than 90% conversion of FA and 80% purity of FAME, from an SMBR process: switching time of 900 s, length of 0.25 m, and feed, raffinate, and eluent flow rate ratios of 0.41, 0.49, and 0.75, for a given velocity of 2.4 × 10−4 m/s in the reaction zone.
Article
In the present work, the kinetics of oleic acid esterification with methanol has been studied by using an acid ion-exchange polymeric resin (Relite CFS) as the heterogeneous catalyst. The kinetics of the reaction has been studied by performing batch runs at different temperatures and in the presence of a certain amount of triglyceride for simulating an oil with a high content of free fatty acids, which is of great potential interest as a raw material in the biodiesel production process. The experimental data have been interpreted with a second-order, pseudo-homogeneous kinetic model, and a good agreement between the experimental data and the model has been obtained.
Article
Biodiesel is synthesized via the transesterification of lipid feedstocks with low molecular weight alcohols. Currently, alkaline bases are used to catalyze the reaction. These catalysts require anhydrous conditions and feedstocks with low levels of free fatty acids (FFAs). Inexpensive feedstocks containing high levels of FFAs cannot be directly used with the base catalysts currently employed. Strong liquid acid catalysts are less sensitive to FFAs and can simultaneously conduct esterification and transesterification. However, they are slower and necessitate higher reaction temperatures. Nonetheless, acid-catalyzed processes could produce biodiesel from low-cost feedstocks, lowering production costs. Better yet, if solid acid catalysts could replace liquid acids, the corrosion and environmental problems associated with them could be avoided and product purification protocols reduced, significantly simplifying biodiesel production and reducing cost. This article reviews some of the research related to biodiesel production using acid catalysts, including solid acids.
Article
Previous experimental data on mass transfer between particles and fluid in fixed and fluidized beds are reanalyzed and correlating equations are developed for the various situations.
Article
Diagnostic tests for detecting heat and mass-transfer effects in experimental catalytic reactors are reviewed and updated. New perturbation criteria are presented for intraparticle, interphase, and interparticle transport in both single- and mixed-phase flow in fixed beds. Emphasis is placed on the proper choice of reactor parameters to minimize deviations from isothermal plug-flow performance.
Article
The simulated countercurrent moving bed chromatographic reactor (SCMCR) is a device for carrying out chemical reaction and separation simultaneously in a fixed bed. This is a novel reactor type in which separation takes place at the site of chemical reaction to improve product purities and conversions beyond those prescribed by thermodynamic equilibrium. The simulated countercurrent system mimics the behavior of a countercurrent moving bed by periodically changing feed and product locations sequentially along a fixed bed. The present investigations endeavor to determine to what extent the moving bed reactor advantages of high product purity and favorable equilibrium shifts are retained in SCMCR operations. An equilibrium stage model of the SCMCR consisting of a single fixed bed having series of inlets and outlets along its length is considered. The mass balance equations are discretized to give an equilibrium plate model. Predictions of the concentration profiles in the column(s) are obtained for the 1,3,5-trimethylbenzene hydrogenation reaction at 463 K. It is shown that reaction and separation can be achieved simultaneously and that the yield of the reversible reaction can be improved greatly. Under appropriate operating conditions, the model calculations predict high-purity product streams and nearly complete conversion of a reaction which would otherwise be limited by equilibrium to 62%.
Article
Biodiesel, a renewable fuel of vegetal origin, has been an object of a rapidly growing interest, in the latest years, both as a pure fuel and as blending component to reduce exhaust pollutants of traditional diesel fuel. Biodiesel is conventionally produced through a well-established technology that involves the use of alkaline catalysts and is, therefore, not compatible with the presence of free fatty acids (FFAs) in the feedstock due to the formation of soaps. Also the presence of FFA in small amounts is detrimental, because, formed soaps strongly affect the successive glycerol separation giving place to a long settling time. Normally, highly refined vegetable oils are used as raw materials for biodiesel production. A preliminary stage of acidity reduction is necessary, when the starting material is characterized by a high free acidity (higher than 0.5% by weight). This pre-treatment can be pursued, as example, by means of an esterification reaction of the FFAs with methanol, catalyzed by sulphonic ionic exchange resins. In the present work, a batch reactor has been used for the study of the above-mentioned reaction and different acid ionic exchange resins have been tested as heterogeneous catalysts. Two kinds of substrates have been submitted for esterification with methanol: a model mixture of soybean oil artificially acidified with oleic acid and a commercial high-acidity mixture of waste fatty acids (oleins). A detailed kinetic model has been developed and tested in which the following key phenomena, characterizing the system, have been introduced: (i) the physical phase equilibrium (partitioning equilibrium) of the components between the resin-absorbed phase and the external liquid phase; (ii) the ionic exchange equilibria; (iii) an Eley–Rideal surface reaction mechanism. The developed kinetic model was able to correctly interpret all the experimental data collected, both as a function of the temperature and of the catalyst concentration.
Article
The kinetics of the esterification of free fatty acids (FFA) in sunflower oil with methanol in the presence of sulphuric acid at concentrations of 5 and 10 wt% relative to free acids as catalyst and methanol/oleic acid mole ratios from 10:1 to 80:1 was studied. The experimental results were found to fit a first-order kinetic law for the forward reaction and a second-order one for the reverse reaction.The influence of temperature on the kinetic constants was determined by fitting the results to the Arrhenius equation. The energy of activation for the forward reaction decreased with increasing catalyst concentration from 50 745 to 44 559 J/mol.Based on the experimental results, a methanol/oleic acid mole ratio of 60:1, a catalyst (sulphuric acid) concentration of 5 wt% and a temperature of 60 °C provided a final acid value for the oil lower than 1 mg KOH/g oil within 120 min. This is a widely endorsed limit for efficient separation of glycerin and biodiesel during production of the latter.
Article
The production of fatty acid methyl esters, to be used as a diesel substitute (biodiesel), has been studied. The reaction of refined sunflower oil and methanol was carried out over different types (acid and basic, homogeneous and heterogeneous) of catalysts. The catalyst that led to largest conversions was sodium hydroxide. No methyl esters were detected when zirconium-based catalysts and an immobilized lipase were used. The process of biodiesel production was optimized by application of the factorial design and response surface methodology. Temperature and catalyst concentration were found to have a positive influence on conversion, concentration effect being larger than temperature effect. A second-order model was obtained to predict conversions as a function of temperature and catalyst concentration. Optimum conditions for the production of methyl esters were found to be mild temperatures (20–50°C) and large catalyst concentrations (1.3%).
Article
Continuous esterification of free fatty acids (FFA) from acidified oil with methanol was carried out with NKC-9 cation-exchange resin in a fixed bed reactor with an internal diameter of 25 mm and a height of 450 mm to produce biodiesel. The results showed that the FFA conversion increased with increases in methanol/oil mass ratio, reaction temperature and catalyst bed height, whereas decreased with increases in initial water content in feedstock and feed flow rate. The FFA conversion kept over 98.0% during 500 h of continuous esterification processes under 2.8:1 methanol to oleic acid mass ratio, 44.0 cm catalyst bed height, 0.62 ml/min feed flow rate and 65°C reaction temperature, showing a much high conversion and operational stability. Furthermore, the loss of sulfonic acid groups from NKC-9 resin into the production was not found during continuous esterification. In sum, NKC-9 resin shows the potential commercial applications to esterification of FFA.
Article
Esterification of oleic acid was performed in a three-phase fixed-bed reactor with a cation exchange resin catalyst (Amberlyst-15) at high temperature, which was varied from 80 to 120 °C. The fatty acid methyl ester (FAME) yields in the fixed-bed reactor were increased with increases in the reaction temperature, methanol flow rate and bed height. Moreover, the FAME yields were higher than those obtained using a batch reactor due to an equilibrium shift toward the product that resulted from continuous evaporation of the produced water. In addition, there was no catalyst deactivation during the esterification of oleic acid. However, addition of sunflower oil to the oleic acid reduced the FAME yield obtained from simultaneous esterification and transesterification. The FAME yield was 97.5% at a reaction temperature of 100 °C in the fixed-bed with a height of 5 cm when the methanol and oleic acid feed rates were 8.6 and 9.0 mL/h, respectively.
Article
In the last few years, biodiesel has emerged as one of the most potential renewable energy to replace current petrol-derived diesel. It is a renewable, biodegradable and non-toxic fuel which can be easily produced through transesterification reaction. However, current commercial usage of refined vegetable oils for biodiesel production is impractical and uneconomical due to high feedstock cost and priority as food resources. Low-grade oil, typically waste cooking oil can be a better alternative; however, the high free fatty acids (FFA) content in waste cooking oil has become the main drawback for this potential feedstock. Therefore, this review paper is aimed to give an overview on the current status of biodiesel production and the potential of waste cooking oil as an alternative feedstock. Advantages and limitations of using homogeneous, heterogeneous and enzymatic transesterification on oil with high FFA (mostly waste cooking oil) are discussed in detail. It was found that using heterogeneous acid catalyst and enzyme are the best option to produce biodiesel from oil with high FFA as compared to the current commercial homogeneous base-catalyzed process. However, these heterogeneous acid and enzyme catalyze system still suffers from serious mass transfer limitation problems and therefore are not favorable for industrial application. Nevertheless, towards the end of this review paper, a few latest technological developments that have the potential to overcome the mass transfer limitation problem such as oscillatory flow reactor (OFR), ultrasonication, microwave reactor and co-solvent are reviewed. With proper research focus and development, waste cooking oil can indeed become the next ideal feedstock for biodiesel.
Article
The transesterification reactions of triolein with ethanol using various ion-exchange resin catalysts were conducted to produce ethyl oleate as a biodiesel. The anion-exchange resins exhibited much higher catalytic activities than the cation-exchange resin. The anion-exchange resin with a lower cross-linking density and a smaller particle size gave a high reaction rate as well as a high conversion. By combining the three-step regeneration method, the resin could be repeatedly used for the batch transesterification without any loss in the catalytic activity. A continuous transesterification reaction was carried out using an expanded bed reactor packed with the most active resin. The reactor system permitted the continuous production of ethyl oleate with a high conversion.