The Experts below are selected from a list of 312 Experts worldwide ranked by ideXlab platform
Saim Ozkar - One of the best experts on this subject based on the ideXlab platform.
-
Transition metal nanoparticle catalysts in releasing hydrogen from the Methanolysis of ammonia borane
International Journal of Hydrogen Energy, 2020Co-Authors: Saim OzkarAbstract:Abstract Ammonia borane (H3N·BH3, AB) is one of the promising hydrogen storage materials due to high hydrogen storage capacity (19.6% wt), high stability in solid state as well as in solution and nontoxicity. The Methanolysis of AB is an alternative way of releasing H2 due to many advantages over the hydrolysis such as having high stability against self releasing hydrogen gas. Here we review the reports on using various noble or non-noble metal(0) catalysts for H2 release from the Methanolysis of AB. Ni(0), Pd(0), and Ru(0) nanoparticles (NPs), stabilized as colloidal dispersion in methanol, are highly active and long lived catalysts in the Methanolysis of AB. The catalytic activity, lifetime and reusability of transition metal(0) NPs show significant improvement when supported on the surface of solid materials. The supported cobalt, nickel, copper, palladium, and ruthenium based catalysts are quite active in H2 release from the Methanolysis of AB. Rh(0) NPs are highly active catalysts in releasing H2 from the Methanolysis of AB when confined within the void spaces of zeolite or supported on oxide nanopowders such as nanosilica, nanohydroxyapatite, nanoalumina or nanoceria. The oxide supported Rh(0) NPs can provide high activity with turnover frequency values as high as 218 min−1 and long lifetime with total turnover values up to 26,000 in generation of H2 from the Methanolysis of AB at 25 °C. When deposited on carbon the bimetallic AgPd alloy nanoparticles have the highest activity in releasing H2 through the Methanolysis of AB.
-
rhodium 0 nanoparticles supported on nanosilica highly active and long lived catalyst in hydrogen generation from the Methanolysis of ammonia borane
Applied Catalysis B-environmental, 2016Co-Authors: Derya Ozhava, Saim OzkarAbstract:Abstract Nanosilica stabilized rhodium(0) nanoparticles (Rh(0)/nanoSiO 2 ), in situ formed from the reduction of rhodium(II) octanoate impregnated on the surface of nanosilica, are active catalyst in hydrogen generation from the Methanolysis of ammonia borane at room temperature. Monitoring the hydrogen evolution enables us to follow the kinetics of nanoparticles formation. The resulting sigmoidal kinetic curves are analyzed by using the 2-step mechanism of the slow, continuous nucleation and autocatalytic surface growth. By using the temperature dependent kinetic data, we could calculate the activation energy for the nucleation and autocatalytic surface growth of rhodium(0) nanoparticles as well as for the catalytic Methanolysis of ammonia borane. Rh(0)/nanoSiO 2 could be isolated and characterized by a combination of advanced analytical techniques including XRD, TEM, EDX, XPS, and N 2 adsorption–desorption. The results reveal that rhodium(0) nanoparticles are highly dispersed on nanosilica surface and have tunable particle size depending on the initial metal concentration. An increase in the mean particle size of rhodium(0) nanoparticles is observed when the initial metal concentration increases. Rh(0)/nanoSiO 2 are highly active and long lived catalyst in hydrogen generation from the Methanolysis providing an exceptional initial turnover frequency of TOF = 168 min −1 (504 min −1 corrected for the surface atoms) at 25.0 ± 0.5 °C, which is the highest value ever reported for rhodium catalysts. An inverse dependence of TOF on the initial rhodium concentration is observed and ascribed to the increasing size of rhodium(0) nanoparticles. Carbon disulfide poisoning and filtration experiments unequivocally demonstrate that rhodium(0) nanoparticles are the true heterogeneous catalyst in hydrogen generation from the Methanolysis of ammonia borane.
-
rhodium 0 nanoparticles supported on hydroxyapatite nanospheres and further stabilized by dihydrogen phosphate ion a highly active catalyst in hydrogen generation from the Methanolysis of ammonia borane
International Journal of Hydrogen Energy, 2015Co-Authors: Derya Ozhava, Saim OzkarAbstract:Abstract Rhodium(0) nanoparticles, supported on nanosized hydroxyapatite (Rh(0)/nanoHAP), were prepared by ion exchange of Rh +3 ions with Ca +2 ions of hydroxyapatite, followed by reduction of the resulting Rh +3 /nanoHAP precatalyst during the catalytic Methanolysis of ammonia borane (AB) in the presence of tetrabutylammonium dihydrogen phosphate (TBAP) at room temperature. Rh(0)/nanoHAP were characterized by a combination of advance analytical techniques including ICP-OES, XRD, TEM, EDX, XPS, ATR–IR and N 2 adsorption–desorption. Rh(0)/nanoHAP with an average particle size of 4.7 ± 0.8 nm were found to be highly active catalyst in hydrogen generation from the Methanolysis of AB liberating 3.0 equivalent H 2 per mole of AB. They provide 26,000 turnovers in hydrogen generation from the Methanolysis of AB over 23 h before deactivation and an initial TOF value of 147 min −1 which is the highest TOF value ever reported for the Methanolysis of AB using rhodium catalyst at 25.0 ± 0.5 °C. Carbon disulfide poisoning experiment demonstrates that Rh(0)/nanoHAP catalyzed Methanolysis of AB is a heterogeneous catalysis. This study also covers the detailed kinetics of the Methanolysis of AB catalyzed by Rh(0)/nanoHAP depending on stabilizer concentration, catalyst concentration and temperature. The apparent activation energy of the catalytic reaction was calculated from the evaluation of temperature dependent kinetic data: E a app = 56 ± 2 kJ/mol.
-
pvp stabilized nickel 0 nanoparticles as catalyst in hydrogen generation from the Methanolysis of hydrazine borane or ammonia borane
Applied Catalysis B-environmental, 2015Co-Authors: Derya Ozhava, Nihan Zulay Kilicaslan, Saim OzkarAbstract:Abstract Herein we report the results of a detailed study on the in-situ generation of poly(N-vinyl-2-pyrrolidone) (PVP) stabilized nickel(0) nanoparticles and their catalytic activity in Methanolysis of hydrazine borane and ammonia borane. PVP-stabilized nickel(0) nanoparticles with an average particle size of 3.0 ± 0.7 nm were in-situ generated from the reduction of nickel(II) 2-ethylhexanoate during the Methanolysis of hydrazine borane in the presence of PVP at room temperature. Polymer stabilized nickel(0) nanoparticles could be isolated from the solution by centrifugation and characterized by UV–vis spectroscopy, XPS, TEM, and SAED. PVP-stabilized nickel(0) nanoparticles are highly active and long lived catalyst in hydrogen generation from the Methanolysis of hydrazine borane and ammonia borane at ambient temperature. The results of kinetic study reveal that the Methanolysis is first order with respect to catalyst concentration and zero order regarding to substrate concentration in both cases. PVP-stabilized nickel(0) nanoparticles provide 14,500 turnovers in hydrogen generation from the Methanolysis of hydrazine borane and 5300 turnovers from the Methanolysis of ammonia borane. They also provide an initial turnover frequency of 35.6 and 12.1 min−1 for the catalytic Methanolysis of hydrazine borane and ammonia borane, respectively.
-
zeolite confined rhodium 0 nanoclusters as highly active reusable and long lived catalyst in the Methanolysis of ammonia borane
Applied Catalysis B-environmental, 2010Co-Authors: Salim Caliskan, Mehmet Zahmakiran, Saim OzkarAbstract:Abstract Addressed herein is the preparation, characterization and the catalytic use of zeolite confined rhodium(0) nanoclusters in the Methanolysis of ammonia-borane. Rhodium(0) nanoclusters could be generated in zeolite-Y by a two-step procedure: (i) incorporation of rhodium(III) cations into the zeolite-Y by ion-exchange and (ii) reduction of rhodium(III) ions within the zeolite cages by sodium borohydride in aqueous solution, followed by filtration and dehydration by heating to 550 °C under 10 −4 Torr. Zeolite confined rhodium(0) nanoclusters are stable enough to be isolated as solid materials and characterized by ICP-OES, XRD, SEM, EDX, HR-TEM, XPS and N 2 adsorption–desorption technique. The zeolite confined rhodium(0) nanoclusters are isolable, bottleable, redispersible and reusable as an active catalyst in the Methanolysis of ammonia-borane even at low temperatures. They provide exceptional catalytic activity with an average value of TOF = 380 h −1 and unprecedented lifetime with 74,300 turnovers in the Methanolysis of ammonia-borane at 25 ± 0.1 °C. The work reported here also includes the full experimental details of the collection of a wealth of previously unavailable kinetic data to determine the rate law, and activation parameters ( E a , Δ H ≠ and Δ S ≠ ) for the catalytic Methanolysis of ammonia-borane.
Vlada B Veljkovic - One of the best experts on this subject based on the ideXlab platform.
-
a kinetic study of quicklime catalyzed sunflower oil Methanolysis
Chemical Engineering Research & Design, 2014Co-Authors: Marija R Miladinovic, Olivera S Stamenkovic, Jugoslav Krstic, Marija B Tasic, Vlada B VeljkovicAbstract:Abstract The quicklime-catalyzed sunflower oil Methanolysis was studied at mild reaction conditions. Quicklime (calcined at 550 °C for 4 h) in amounts of 1.0, 2.5, 5.0 and 10.0% (based on the oil weight) and different molar ratios of methanol-to-oil (6:1, 12:1 and 18:1) were employed to investigate their influence on the methyl esters content and the kinetics of the Methanolysis reaction. The optimal methanol-to-oil molar ratio and quicklime amount for achieving the highest fatty acid methyl esters content were established to be 12:1 and 5% (based on the oil weight), respectively. The sigmoidal kinetics of quicklime-catalyzed Methanolysis reaction was described by a model which included the changing mechanism of the reaction and the triacylglycerols mass transfer limitation. The kinetic parameters were determined and correlated with the process variables. A good agreement between the kinetic model and the experimental data for all applied reaction conditions was observed.
-
optimization of ultrasound assisted base catalyzed Methanolysis of sunflower oil using response surface and artifical neural network methodologies
Chemical Engineering Journal, 2013Co-Authors: Katarina M Rajkovic, Olivera S Stamenkovic, Jelena M Avramovic, Petar S Milic, Vlada B VeljkovicAbstract:Abstract The sunflower oil transesterification, catalyzed by KOH in the presence of ultrasound, was optimized by combining a 3 4 full factorial design of experiments with either a back-propagation artificial neural network (ANN) with the topology 4–10–1 or the response surface methodology (RSM). Four input factors, methanol/oil molar ratio, reaction temperature, catalyst loading and time and one output response, FAME yield, were included into the optimization study. The main goals were to test how accurately these two combinations predict and simulate the FAME yield achieved by the base-catalyzed Methanolysis of sunflower oil under ultrasonication. Another aim was to compare the performances of the developed two models as a tool assisting decision making during the investigated Methanolysis process. The ANN is shown to be a powerful tool for modeling and optimizing FAME production. Its predictions of FAME yield are very good all through the Methanolysis process studied in wide ranges of the process factors. This is proved by a low value (±3.4%) of the mean MRPD between the experimental and simulated values of FAME yield, suggesting that they are almost the same. The ANN predictions were much better than those (±24.2%) obtained by the second-order polynomial equation from the RSM. The generalization ability of the developed ANN model for the base-catalyzed Methanolysis optimization was well documented for different feedstocks and operational variables in the presence and absence of the ultrasound. The maximum FAME yield of 89.9% predicted by the ANN model could be achieved in 60 min at the reaction temperature of 30 °C, the initial methanol/oil molar ratio of 7.5:1 and the catalyst loading of 0.7%.
-
the production of biodiesel from vegetable oils by ethanolysis current state and perspectives
Fuel, 2011Co-Authors: Olivera S Stamenkovic, Ana V Velickovic, Vlada B VeljkovicAbstract:At present, the homogeneous base-catalyzed Methanolysis reaction of vegetable oils is a most often used process for the industrial biodiesel production. The toxicity of methanol, the risk of the methanol vapor explosion and the possibility of the ethanol production from biorenewable resources have contributed to the development of a vegetable oil ethanolysis process for the biodiesel production. In the reaction of vegetable oils and ethanol in the presence of a catalyst, completely agricultural fuels consisted of fatty acid ethyl esters (FAEE) are obtained having physico-chemical properties similar to those of the appropriate methyl esters and diesel fuel. The ethanolysis reaction of various oily feedstocks has been widely studied to optimize the reaction conditions and to develop new catalytic systems and processes based on chemical and biological catalysts, as well as the development of non-catalytic processes. Most researches investigate the application of homogeneous base catalysts. This paper studies the review of vegetable oil ethanolysis investigations for the biodiesel production done so far. The goals of the paper are to present the development of FAEE synthesis by catalytic and non-catalytic processes, their advantages and disadvantages, the influence of some operating and reaction conditions on the process rate and ethyl esters yield, the kinetics models describing the ethanolysis process rate, the process optimization and the possibilities for improving the FAEE synthesis process.
-
The production of biodiesel from vegetable oils by ethanolysis: Current state and perspectives
Fuel, 2011Co-Authors: Olivera S. Stamenković, Ana V. Veličković, Vlada B VeljkovicAbstract:At present, the homogeneous base-catalyzed Methanolysis reaction of vegetable oils is a most often used process for the industrial biodiesel production. The toxicity of methanol, the risk of the methanol vapor explosion and the possibility of the ethanol production from biorenewable resources have contributed to the development of a vegetable oil ethanolysis process for the biodiesel production. In the reaction of vegetable oils and ethanol in the presence of a catalyst, completely agricultural fuels consisted of fatty acid ethyl esters (FAEE) are obtained having physico-chemical properties similar to those of the appropriate methyl esters and diesel fuel. The ethanolysis reaction of various oily feedstocks has been widely studied to optimize the reaction conditions and to develop new catalytic systems and processes based on chemical and biological catalysts, as well as the development of non-catalytic processes. Most researches investigate the application of homogeneous base catalysts. This paper studies the review of vegetable oil ethanolysis investigations for the biodiesel production done so far. The goals of the paper are to present the development of FAEE synthesis by catalytic and non-catalytic processes, their advantages and disadvantages, the influence of some operating and reaction conditions on the process rate and ethyl esters yield, the kinetics models describing the ethanolysis process rate, the process optimization and the possibilities for improving the FAEE synthesis process. © 2011 Elsevier Ltd. All rights reserved.
-
modeling the kinetics of calcium hydroxide catalyzed Methanolysis of sunflower oil
Bioresource Technology, 2010Co-Authors: Olivera S Stamenkovic, Vlada B Veljkovic, Miodrag L Lazic, Zoran B Todorovic, Ivana B Bankovicilic, Dejan SkalaAbstract:Abstract The kinetics of Ca(OH) 2 -catalyzed Methanolysis of sunflower oil was studied at a moderate temperature (60 °C), a methanol-to-oil molar ratio (6:1) and different catalyst amounts (from 1% to 10% based on oil weight). The Methanolysis process was shown to involve the initial triglyceride (TG) mass transfer controlled region, followed by the chemical reaction controlled region in the latter period. The TG mass transfer limitation was caused by the low available active specific catalyst surface due to the high adsorbed methanol concentration. Both the TG mass transfer and chemical reaction rates increased with increasing the catalyst amount.
Olivera S Stamenkovic - One of the best experts on this subject based on the ideXlab platform.
-
a kinetic study of quicklime catalyzed sunflower oil Methanolysis
Chemical Engineering Research & Design, 2014Co-Authors: Marija R Miladinovic, Olivera S Stamenkovic, Jugoslav Krstic, Marija B Tasic, Vlada B VeljkovicAbstract:Abstract The quicklime-catalyzed sunflower oil Methanolysis was studied at mild reaction conditions. Quicklime (calcined at 550 °C for 4 h) in amounts of 1.0, 2.5, 5.0 and 10.0% (based on the oil weight) and different molar ratios of methanol-to-oil (6:1, 12:1 and 18:1) were employed to investigate their influence on the methyl esters content and the kinetics of the Methanolysis reaction. The optimal methanol-to-oil molar ratio and quicklime amount for achieving the highest fatty acid methyl esters content were established to be 12:1 and 5% (based on the oil weight), respectively. The sigmoidal kinetics of quicklime-catalyzed Methanolysis reaction was described by a model which included the changing mechanism of the reaction and the triacylglycerols mass transfer limitation. The kinetic parameters were determined and correlated with the process variables. A good agreement between the kinetic model and the experimental data for all applied reaction conditions was observed.
-
optimization of ultrasound assisted base catalyzed Methanolysis of sunflower oil using response surface and artifical neural network methodologies
Chemical Engineering Journal, 2013Co-Authors: Katarina M Rajkovic, Olivera S Stamenkovic, Jelena M Avramovic, Petar S Milic, Vlada B VeljkovicAbstract:Abstract The sunflower oil transesterification, catalyzed by KOH in the presence of ultrasound, was optimized by combining a 3 4 full factorial design of experiments with either a back-propagation artificial neural network (ANN) with the topology 4–10–1 or the response surface methodology (RSM). Four input factors, methanol/oil molar ratio, reaction temperature, catalyst loading and time and one output response, FAME yield, were included into the optimization study. The main goals were to test how accurately these two combinations predict and simulate the FAME yield achieved by the base-catalyzed Methanolysis of sunflower oil under ultrasonication. Another aim was to compare the performances of the developed two models as a tool assisting decision making during the investigated Methanolysis process. The ANN is shown to be a powerful tool for modeling and optimizing FAME production. Its predictions of FAME yield are very good all through the Methanolysis process studied in wide ranges of the process factors. This is proved by a low value (±3.4%) of the mean MRPD between the experimental and simulated values of FAME yield, suggesting that they are almost the same. The ANN predictions were much better than those (±24.2%) obtained by the second-order polynomial equation from the RSM. The generalization ability of the developed ANN model for the base-catalyzed Methanolysis optimization was well documented for different feedstocks and operational variables in the presence and absence of the ultrasound. The maximum FAME yield of 89.9% predicted by the ANN model could be achieved in 60 min at the reaction temperature of 30 °C, the initial methanol/oil molar ratio of 7.5:1 and the catalyst loading of 0.7%.
-
the production of biodiesel from vegetable oils by ethanolysis current state and perspectives
Fuel, 2011Co-Authors: Olivera S Stamenkovic, Ana V Velickovic, Vlada B VeljkovicAbstract:At present, the homogeneous base-catalyzed Methanolysis reaction of vegetable oils is a most often used process for the industrial biodiesel production. The toxicity of methanol, the risk of the methanol vapor explosion and the possibility of the ethanol production from biorenewable resources have contributed to the development of a vegetable oil ethanolysis process for the biodiesel production. In the reaction of vegetable oils and ethanol in the presence of a catalyst, completely agricultural fuels consisted of fatty acid ethyl esters (FAEE) are obtained having physico-chemical properties similar to those of the appropriate methyl esters and diesel fuel. The ethanolysis reaction of various oily feedstocks has been widely studied to optimize the reaction conditions and to develop new catalytic systems and processes based on chemical and biological catalysts, as well as the development of non-catalytic processes. Most researches investigate the application of homogeneous base catalysts. This paper studies the review of vegetable oil ethanolysis investigations for the biodiesel production done so far. The goals of the paper are to present the development of FAEE synthesis by catalytic and non-catalytic processes, their advantages and disadvantages, the influence of some operating and reaction conditions on the process rate and ethyl esters yield, the kinetics models describing the ethanolysis process rate, the process optimization and the possibilities for improving the FAEE synthesis process.
-
modeling the kinetics of calcium hydroxide catalyzed Methanolysis of sunflower oil
Bioresource Technology, 2010Co-Authors: Olivera S Stamenkovic, Vlada B Veljkovic, Miodrag L Lazic, Zoran B Todorovic, Ivana B Bankovicilic, Dejan SkalaAbstract:Abstract The kinetics of Ca(OH) 2 -catalyzed Methanolysis of sunflower oil was studied at a moderate temperature (60 °C), a methanol-to-oil molar ratio (6:1) and different catalyst amounts (from 1% to 10% based on oil weight). The Methanolysis process was shown to involve the initial triglyceride (TG) mass transfer controlled region, followed by the chemical reaction controlled region in the latter period. The TG mass transfer limitation was caused by the low available active specific catalyst surface due to the high adsorbed methanol concentration. Both the TG mass transfer and chemical reaction rates increased with increasing the catalyst amount.
-
kinetics of sunflower oil Methanolysis at low temperatures
Bioresource Technology, 2008Co-Authors: Olivera S Stamenkovic, Vlada B Veljkovic, Miodrag L Lazic, Zoran B Todorovic, Dejan SkalaAbstract:Abstract The kinetics of the sunflower oil Methanolysis process was studied at lower temperatures (10–30 °C). The sigmoidal kinetics of the process was explained by the mass transfer controlled region in the initial heterogenous regime, followed by the chemical reaction controlled region in the pseudo-homogenous regime. A simple kinetic model, which did not require complex computation of the kinetic constants, was used for simulation of the TG conversion and the FAME formation in the latter regime: the fast irreversible second-order reaction was followed by the slow reversible second-order reaction close to the completion of the Methanolysis reaction. The mass transfer was related to the drop size of the dispersed (methanol) phase, which reduced rapidly with the progress of the Methanolysis reaction. This was attributed to the formation of the emulsifying agents stabilizing the emulsion of methanol drops into the oil.
Yihsu Ju - One of the best experts on this subject based on the ideXlab platform.
-
a two step acid catalyzed process for the production of biodiesel from rice bran oil
Bioresource Technology, 2005Co-Authors: Siti Zullaikah, Shaik Ramjan Vali, Yihsu JuAbstract:Abstract A study was undertaken to examine the effect of temperature, moisture and storage time on the accumulation of free fatty acid in the rice bran. Rice bran stored at room temperature showed that most triacylglyceride was hydrolyzed and free fatty acid (FFA) content was raised up to 76% in six months. A two-step acid-catalyzed Methanolysis process was employed for the efficient conversion of rice bran oil into fatty acid methyl ester (FAME). The first step was carried out at 60 °C. Depending on the initial FFA content of oil, 55–90% FAME content in the reaction product was obtained. More than 98% FFA and less than 35% of TG were reacted in 2 h. The organic phase of the first step reaction product was used as the substrate for a second acid-catalyzed Methanolysis at 100 °C. By this two-step Methanolysis reaction, more than 98% FAME in the product can be obtained in less than 8 h. Distillation of reaction product gave 99.8% FAME (biodiesel) with recovery of more than 96%. The residue contains enriched nutraceuticals such as γ-oryzanol (16–18%), mixture of phytosterol, tocol and steryl ester (19–21%).
-
lipase catalyzed production of biodiesel from rice bran oil
Journal of Chemical Technology & Biotechnology, 2005Co-Authors: Siti Zullaikah, Shaik Ramjan Vali, Yihsu JuAbstract:Biodiesel has attracted considerable attention as an alternative fuel during the past decades. The main hurdle to the commercialization of biodiesel is the cost of the raw material. Use of an inexpensive raw material such as rice bran oil is an attractive option to lower the cost of biodiesel. Two commercially available immobilized lipases, Novozym 435 and IM 60, were employed as catalyst for the reaction of rice bran oil and methanol. Novozym 435 was found to be more effective in catalyzing the Methanolysis of rice bran oil. Methanolysis of refined rice bran oil and fatty acids (derived from rice bran oil) catalyzed by Novozym 435 (5% based on oil weight) can reach a conversion of over 98% in 6 h and 1 h, respectively. Methanolysis of rice bran oil with a free fatty acid content higher than 18% resulted in lower conversions (<68%). A two-step lipase-catalyzed Methanolysis of rice bran oil was developed for the efficient conversion of both free fatty acid and acylglycerides into fatty acid methyl ester. More than 98% conversion can be obtained in 4–6 h depending on the relative proportion of free fatty acid and acylglycerides in the rice bran oil. Inactivation of lipase by phospholipids and other minor components was observed during the Methanolysis of crude rice bran oil. Simultaneous dewaxing/degumming proved to be efficient in removing phospholipids and other minor components that inhibit lipase activity from crude rice bran oil. Copyright © 2005 Society of Chemical Industry
Dejan Skala - One of the best experts on this subject based on the ideXlab platform.
-
Heterogeneous base-catalyzed Methanolysis of vegetable oils: state of art.
Hemijska Industrija, 2020Co-Authors: Marija R. Miladinović, Olivera S. Stamenković, Vlada B. Veljković, Ivana Lukić, Dejan SkalaAbstract:Today, homogeneous base-catalyzed Methanolysis is the most frequently used method for industrial biodiesel production. High requirements for the quality of the feedstocks and the problems related to the huge amount of wastewaters have led to the development of novel biodiesel production technologies. Among them, the most important is heterogeneous base-catalyzed Methanolysis, which has been intensively investigated over the last decade in order to develop new catalytic systems, optimize the reaction conditions and to recycle catalysts. These studies are a basis for continuous development of biodiesel production on an industrial scale in the near future. The presented work summarize up-to-date studies on biodiesel production by heterogeneous base-catalyzed Methanolysis. The main goals were to point out the application of different base compounds as catalysts, the methods of catalyst preparation, impregnation on carriers and recycling as well as the possibilities to improve existing base-catalyzed biodiesel production processes and to develop novel ones.
-
modeling the kinetics of calcium hydroxide catalyzed Methanolysis of sunflower oil
Bioresource Technology, 2010Co-Authors: Olivera S Stamenkovic, Vlada B Veljkovic, Miodrag L Lazic, Zoran B Todorovic, Ivana B Bankovicilic, Dejan SkalaAbstract:Abstract The kinetics of Ca(OH) 2 -catalyzed Methanolysis of sunflower oil was studied at a moderate temperature (60 °C), a methanol-to-oil molar ratio (6:1) and different catalyst amounts (from 1% to 10% based on oil weight). The Methanolysis process was shown to involve the initial triglyceride (TG) mass transfer controlled region, followed by the chemical reaction controlled region in the latter period. The TG mass transfer limitation was caused by the low available active specific catalyst surface due to the high adsorbed methanol concentration. Both the TG mass transfer and chemical reaction rates increased with increasing the catalyst amount.
-
kinetics of sunflower oil Methanolysis at low temperatures
Bioresource Technology, 2008Co-Authors: Olivera S Stamenkovic, Vlada B Veljkovic, Miodrag L Lazic, Zoran B Todorovic, Dejan SkalaAbstract:Abstract The kinetics of the sunflower oil Methanolysis process was studied at lower temperatures (10–30 °C). The sigmoidal kinetics of the process was explained by the mass transfer controlled region in the initial heterogenous regime, followed by the chemical reaction controlled region in the pseudo-homogenous regime. A simple kinetic model, which did not require complex computation of the kinetic constants, was used for simulation of the TG conversion and the FAME formation in the latter regime: the fast irreversible second-order reaction was followed by the slow reversible second-order reaction close to the completion of the Methanolysis reaction. The mass transfer was related to the drop size of the dispersed (methanol) phase, which reduced rapidly with the progress of the Methanolysis reaction. This was attributed to the formation of the emulsifying agents stabilizing the emulsion of methanol drops into the oil.
-
the effect of agitation intensity on alkali catalyzed Methanolysis of sunflower oil
Bioresource Technology, 2007Co-Authors: Olivera S Stamenkovic, Vlada B Veljkovic, Miodrag L Lazic, Zoran B Todorovic, Dejan SkalaAbstract:Abstract The sunflower oil Methanolysis was studied in a stirred reactor at different agitation speeds. The measurements of drop size, drop size distribution and the conversion degree demonstrate the effects of the agitation speed in both non-reaction (methanol/sunflower oil) and reaction (methanol/KOH/sunflower oil) systems. Drop size distributions were found to become narrower and shift to smaller sizes with increasing agitation speed as well as with the progress of the Methanolysis reaction at a constant agitation speed. During the Methanolysis reaction, the Sauter-mean drop diameter stays constant in the initial slow reaction region, rapidly decreases during the fast reaction period and finally reaches the equilibrium level. Due to the fact that the interfacial area increases, one can conclude that the rate of reaction occurring at the interface will also be enhanced progressively. The “autocatalytic” behavior of the Methanolysis reaction is explained by this “self-enhancement” of the interfacial area, due to intensive drop breakage process.