Search

Hazelnut shell ash was investigated as a new base catalyst for the transesterification of used cooking sunflower oil to biodiesel. To understand its catalytic properties, the prepared ash was characterized by EDX, XRD, TGA/DTA, Hg porosimetry, N2 physisorption, FE-SEM, and basic strength measurements. The effects of the catalyst loading in the range of 1–5% of the oil weight and the methanol-to-oil molar ratio of 6:1–18:1 on the kinetics of the fatty acid methyl esters synthesis were established. Moreover, the leaching and reusability of the catalyst were assessed. The obtained results revealed that hazelnut shell ash was mostly composed of K, Ca, and Mg. The highest ester content (98%) was achieved at the catalyst loading of 5%, the methanol-to-oil molar ratio of 12:1, and the reaction time of 10 min. The contribution of homogeneous catalysis because of the catalyst leaching was confirmed but did not determine the overall reaction rate. The catalyst can be reused after the recalcination at 800 °C for 2 h achieving the high methyl esters content (>96%) in 30 min after three subsequent runs. The overall reaction followed the pseudo-first-order kinetics with respect to triacylglycerols. A linear relationship between the apparent reaction rate constant and the catalyst loading and the methanol-to-oil molar ratio was determined. The determined value of the reaction rate constant was 0.0576 dm6/(min•mol2).

The investigation of reaction kinetics is crucial for practical implications in process equipment design and scaling up. In this study, a kinetic analysis of the methanolysis of a blend of radish and castor oil catalyzed by calcium oxide was carried out. The objectives were to propose a comprehensive model for describing the kinetics of this methanolysis reaction and determine its activation energy. The methanolysis was conducted in a batch reactor under atmospheric pressure with the following reaction conditions: a radish-to-castor oil blend mass ratio of 1:1, a methanol-to-oil molar ratio of 12:1, a catalyst amount of 5% of the oil blend weight, and reaction temperatures of 30 C, 45 C, and 60 C. The model involving the changing reaction mechanism and the triacylglycerol (TAG) mass transfer limitation was first simplified to a pseudo-first order model regarding TAGs and fatty acid methyl esters, which was then used to calculate the apparent reaction rate constant. A good agreement between the calculated and experimental values of the TAG conversion degree was proved by a low mean relative percentage deviation of ±6.1% (based on 66 data), thus validating the applied simple kinetic model. A positive effect of the reaction temperature on the apparent reaction rate constant was observed. Using the Arrhenius equation, the activation energy of methanolysis was determined to be 46.12 kJ/mol. The obtained value of activation energy is much lower than values of activation energy determined for the calcium oxide-catalyzed methanolysis of single oil feedstocks, such as soybean, canola, Jatropha, and waste frying oils. The lower activation energy suggests the potential for enhanced efficiency and feasibility of utilizing this blend as a feedstock for biodiesel production compared to the individual oily feedstocks previously studied.

Possibilities of using waste plum stones in biodiesel production were investigated. The plum kernels were used as a source to obtain oil by the Soxhlet extraction method, while the whole plum stones, the plum stone shells that remained after the crashing, and the plum kernel cake that remained after the oil extraction, were burned off to obtain ashes. The collected ashes were characterized by elemental composition, porosity, and base strength and tested for catalytic activity in transesterification of esterified plum kernel oil. Dominant elements were potassium, calcium, and magnesium at different contents in the three obtained ashes. The most active catalyst was the plum stone shell ash, so the effect of temperature (40, 50, and 60°C) on the reaction rate was investigated. The reaction rate constant increased with the reaction temperature with the activation energy value of 58.8 kJ mol-1. In addition, the plum stone shell ash can be reused as a catalyst after recalcination., U ovom radu istraživana je mogućnost korišćenja otpadnih koštica šljive u proizvodnji biodizela. Jezgra šljive su iskorišćena kao sirovina za dobijanje ulja primenom Soxhlet-ove metode ekstrakcije. Cele koštice, ljuske koštica šljive i pogača dobijena nakon ekstrakcije ulja iz jezgra šljive spaljeni su da bi se dobio pepeo, koji je korišćen kao katalizator. Dobijene tri vrste sakupljenog pepela su najpre okarakterisane u pogledu hemijskog sastava, poroznosti i baznosti, a zatim je testirana katalitička aktivnost u transesterifikaciji esterifikovanog ulja koštica šljive. Dominantni elementi u pepelu, kao što su kalijum, kalcijum i magnezijum, imali su različit sadržaj u sve tri vrste pepela. Najveću katalitičku aktivnost pokazao je pepeo koštica šljive, zbog čega je dalje istraživan uticaj temperature (40, 50 i 60 °C) na brzinu reakcije katalizovane ovim pepelom. Konstanta brzine reakcije povećavala se sa porastom temperature reakcije, a vrednost energije aktivacije je 58,8 kJ mol-1 . Pored toga, pepeo koštica šljive može se ponovo koristiti kao katalizator nakon rekalcinacije.

Novi tehnološki postupak prihvaćen 24.02.2020. godine.

Microwave-assisted extraction (MAE) conditions were optimized to improve extract quality of medicinal herb — Hypericum perforatum L. (St. John’s wort) dust. Response surface methodology was applied initially to obtain the highest concentration of total polyphenols in extract solids (MAE-e). St. John’s wort was mixed with 30% ethanol in 50 mL/g solvent to solid ratio, and treated with 170 W microwave power for 40 s to yield an extract with 411.26 ± 6.21 mg GAE/g of polyphenols. This extract contained a significantly higher content of polyphenols (42.50%) and had significantly higher antioxidant activity than the macerate obtained by using European Medicines Agency (EMA) recommended procedure. The advantage of the EMA procedure was the higher yield of extract per gram of plant material. Therefore, another set of MAE conditions was defined to maximize the yield of polyphenols per gram of plant material (MAE-p). The MAE-p extract was produced by using 30% ethanol, 10 mL/g solvent to solid ratio, and 170 W microwave power for 100 s, which was, again, a markedly shorter period than 72 h of maceration. The MAE-p extract had a slightly, but significantly higher yield (5.2%), more polyphenols (8.8%), and improved antioxidant activity compared to the EMA macerate. Antimicrobial activity against several pathogens was stronger for the MAE extracts. The chemical composition of extracts was slightly different and MAE favored extraction of glycosides, in particular, rutin (quercetin-3-O-rutinoside), while the EMA macerate contained quercetin aglycon in the highest concentration. Our study demonstrates that statistically planned experiments allow for significant improvement of the extraction process, which application could facilitate better use of natural resources and deliver more potent extracts than those obtained by currently recommended procedures.

In this doctoral dissertation the synthesis of fatty acid ethyl esters (FAEEs) from triacylglycerols’ derived from the expired sunflower oil was analyzed via chemically-catalyzed ethanolysis reaction. The ethanolysis was performed as a heterogeneous alkaline catalyzed reaction in which the catalyst was CaO (calcined and non-calcined) in the presence of different choline chloride (ChCl)-based deep eutectic solvents, namely ChCl:urea (ChCl:U), ChCl:1,3-dimethylurea (ChCl:DMU), ChCl:thiourea (ChCl:TU), ChCl:propylene glycol (ChCl:PG), ChCl:ethylene glycol (ChCl:EG) and ChCl:glycerol (ChCl:G) in ChCl:hydrogen bond donor molar ratio 1:2. The physical (density, dynamic viscosity, electrical conductivity and refractive index) and the thermodynamic (thermal expansion coefficient, molecular volume, lattice energy and heat capacity) properties of the prepared deep eutectic solvents were determined at atmospheric pressure over the temperature range of 293.15–363.15 K. These prepared deep eutectic solvents and their constituents were individually tested as cosolvents in the ethanolysis of expired sunflower oil catalyzed by either calcined or non-calcined CaO at temperature of 70 °C and ethanol-to-oil molar ratio of 12:1. All tested deep eutectic solvents promoted the ethanolysis by a successful activation of non-calcined CaO, which was attributed to the CaCO3 and Ca(OH)2 dissolution from the surface of the solid catalyst particles. Either with calcined or non-calcined CaO, the polyol-based deep eutectic solvents gave higher FAEEs’ content than the amide-based deep eutectic solvents. ChCl:EG and ChCl:PG were more efficient than ChCl:G even with non-calcined CaO. However, ChCl:G is more suitable since glycerol, as a by-product of the ethanolysis, can be used for preparation of this deep eutectic solvent, so the overall FAEE production costs could be reduced. The phase separation of the reaction mixture was faster in the presence of the deep eutectic solvents. After five reuses, n

Supplementary material for: Marinković, D., Miladinovic, M. R., Avramović, J. M., Krstic, I. B., Stanković, M., Stamenković, O., Jovanović, D. M.,& Veljković, V. B. (2018). Kinetic modeling and optimization of sunflower oil methanolysis catalyzed by spherically-shaped CaO/gamma-Al2O3 catalyst. Energy Conversion and Management, 163, 122-133. https://doi.org/10.1016/j.enconman.2018.02.048

Kinetic modeling and optimization of sunflower oil methanolysis catalyzed by spherically-shaped CaO/gamma-Al2O3 particles were conducted in batch stirred and packed-bed tubular reactors at 60 degrees C. The proposed three-parameter kinetic model describing the overall reaction with a variable mechanism was successfully applied to both batch and continuous reactions. The process optimization was done using the response surface methodology combined with a central composite design. The obtained optimal catalyst concentration, methanol-to-oil molar ratio and reaction time for the batch reaction were 0.55% (CaO to the oil), 9:1 and 5.22 h, respectively. In the continuous process, the catalyst was highly active stable and slightly leachable during 30 h. The deactivation of the catalyst was due to massive deposition of the organic molecules from the reaction mixture, which sheltered the catalytically active sites on the catalyst surface.

Waste lard from piglet roasting and quicklime (basically CaO) as a priceless fatty feedstock and a cheap solid catalyst, respectively were tested for the biodiesel production by methanolysis in a batch stirred reactor at moderate reaction temperatures (40-60 degrees C) for the kinetic study. For comparison, unheated and heated pork lards, as well as pure CaO, were also included in this study. The mass transfer limitation was observed in the initial period of all methanolysis reactions. The kinetic model combining the changing-and first-order reaction rate laws with respect to triacylglycerols and fatty acid methyl esters (FAMEs), respectively was verified for all three lardy feedstocks and both catalysts. The catalytic activity of quicklime was the same as that of pure CaO. The activation energy was demonstrated to be independent of the feedstock and the catalyst (59.1 +/- 0.6 kJ/mol) but the waste lard reacted faster than the unheated and heated pork lards. At the methanol-to-lard molar ratio of 6:1, the catalyst amount of 5% (based on the lard weight) and the reaction temperature of 60 degrees C, a high FAME concentration in the final ester products (97.5%) within 60 min were achieved with the waste lard and quicklime in two consecutive batches. The same kinetic model was applicable in a continuous packed-bed tubular reactor filled with quicklime bits (2.0-3.15 mm) at the methanol-to-waste lard molar ratio of 6:1, the reaction temperature of 60 degrees C and the residence time of 1 h. Under these conditions, the biodiesel yield was 97.6%, while the FAME concentration in the biodiesel product was 96.5%.

The present paper is an overview of the recent progress in the development of various CaO-based catalysts suitable for biodiesel production. The mechanism, kinetics and optimization of transesterification reaction over these catalysts are first considered. Then, the practical application of CaO-based catalysts is discussed with a special stress on leaching and reusability of these catalysts. Also, various continuous reactor systems currently in use for biodiesel production are appraised. In addition to it, purification of crude biodiesel and the ecological aspects of using CaO-based catalysts are considered. Finally, the potentials of CaO-based catalysts for heterogeneous catalysis for biodiesel production are emphasized to assess the future perspectives of their use. This review might help in selecting suitable CaO-based catalysts and the optimum reaction conditions for biodiesel production.

The kinetic model originally developed for quicklime-catalyzed methanolysis of sunflower oil was tested for another three calcium-based catalysts, namely, neat CaO, Ca(OH)2, and CaO·ZnO. This model includes the changing reaction mechanism and the triacylglycerol (TAG) mass transfer. The applicability and generalization capability of this model for heterogeneous methanolysis reaction catalyzed by calcium-based catalysts was evaluated. As indicated by the high coefficient of determination and the relatively small mean relative percentage deviation, the model was a reliable predictor of the time variation of TAG conversion degree in the sunflower oil methanolysis over all four calcium-based catalysts within the ranges of the reaction conditions applied. This model is recommended in general for describing the kinetics of sunflower oil methanolysis over calcium-based catalysts.The kinetic model originally developed for quicklime-catalyzed methanolysis of sunflower oil was tested for another three calcium-based catalysts, namely, neat CaO, Ca(OH)2, and CaO·ZnO. This model includes the changing reaction mechanism and the triacylglycerol (TAG) mass transfer. The applicability and generalization capability of this model for heterogeneous methanolysis reaction catalyzed by calcium-based catalysts was evaluated. As indicated by the high coefficient of determination and the relatively small mean relative percentage deviation, the model was a reliable predictor of the time variation of TAG conversion degree in the sunflower oil methanolysis over all four calcium-based catalysts within the ranges of the reaction conditions applied. This model is recommended in general for describing the kinetics of sunflower oil methanolysis over calcium-based catalysts.

The quicklime-catalyzed sunflower oil methanolysis was studied at mild reaction conditions. Quicklime (calcined at 550 degrees C for 4h) 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.

The synthesis of fatty acid methyl esters (FAME) from sunflower oil by the quicklime-catalyzed methanolysis reaction was investigated. The catalyst was obtained by calcination of quicklime which was characterized as a mesoporous material with higher basicity and specific area than uncalcinated quicklime. In order to investigate the influence of the methanol-to-oil molar ratio and the catalyst amount on the reaction rate and the FAME yield, sunflower oil methanolysis catalyzed by quicklime was performed in a batch reactor under moderate reaction conditions (reaction temperature 60°C and atmospheric pressure), at different molar ratios of methanol to oil (6:1 – 18:1) and catalyst amounts (1- 10 % based on the oil weight). The variations of the FAME concentration during the reaction were sigmoidal. The FAME formation rate in the initial period of the reaction was slow due to the mass transfer limitation in the three-phase system (methanol-oil-quicklime), followed by the period of the faster FAME formation rate which became slower as the reaction approached the completion. The overall reaction rate depended on the catalyst amount and increased with increasing the catalyst amount due to the increase of the number of catalyst particles and, consequently, the number of active sites on the catalyst surface. Further, the influence of the methanol-to-oil molar ratio on the FAME yield depended on the catalyst amount. At lower catalyst amounts, the FAME yield was slightly higher at higher initial amounts of methanol because the excess of methanol shifted the reaction equilibrium towards the FAME formation. However, the equilibrium was achieved at almost the same time for all methanolto- oil molar ratios. On the other hand, at higher catalyst amounts the molar ratio of methanol to oil had no effect on the reaction rate and the FAME yield. The continuous process for the FAME synthesis was developed and the experiments were conducted in two types of reactors. In order to estimate

The aim of this study was to research the seasonal changes of antioxidant enzyme activity and total antioxidant capacity in leaves of Astragalus onobrychis L. subsp. chlorocarpus (Griseb.) S. Kozuharov et D.K. Pavlova. Leaves of A. onobrychis were collected during the different stages of growth and analyzed for antioxidant enzyme activity: superoxide dismutase, catalase, guaiacol peroxidase, glutathione peroxidase. Quantities of malonyldialdehyde, superoxide radicals, and hydroxyl radicals were measured as well as the content of soluble proteins. Furthermore, total antioxidant capacity was determined by the inhibition of chemiluminescence activity of blood phagocytes by leaf extracts. Stages of vegetation significantly affected the accumulation of superoxide radicals, but there were no significant differences in hydroxyl radical quantity and lipid peroxidation levels during vegetation. Soluble proteins vary greatly between different stages of growth. Seasonal changes were found to have an effect on enzymatic activities. During the spring season, guaiacol peroxidase showed the highest levels. Catalase and glutathione peroxidase increased their activities in summer, while, during the autumn season, superoxide dismutase showed maximum activity. On the basis of chemiluminescence assay, it can be concluded that leaf extract of A. onobrychis possesses a significant antioxidant capacity thus protecting plants during environmental stress.

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., Homogena bazno katalizovana metanoliza je najčešće primenjivan postupak dobijanja biodizela u industrijskim uslovima. Visoki zahtevi u pogledu kvaliteta uljnih sirovina i ekološki problemi otpadnih voda doprineli su razvoju novih postupaka sinteze biodizela. Među njima značajno mesto zauzima heterogena bazno katalizovana metanoliza ulja, koja je u poslednjoj deceniji intenzivno proučavana sa aspekta razvoja novih katalitičkih sistema, optimizacije reakcionih uslova metanolize i mogućnosti reciklovanja katalizatora. Ispitivanja ovakvih sistema čine osnovu za razvoj kontinualnih postupaka heterogene bazno katalizovane metanolize, na kojima će se u bliskoj budućnosti bazirati industrijska proizvodnja biodizela. U ovom radu analizirana su dosadašnja ispitivanja postupaka dobijanja biodizela heterogenom bazno katalizovanom metanolizom. Cilj rada je da se ukaže na primenu različitih baznih jedinjenja kao katalizatora, načine njihove pripreme, nanošenja na nosače i recikliranja, kao i na mogućnosti unapređenja postojećih i razvoja novih procesa dobijanja biodizela baznom katalizom.