• Energy Research

Crude biodiesel was proven as a cosolvent in the methanolysis of sunflower oil catalyzed by calcined CaO. This reaction was modeled and optimized statistically in terms of reaction temperature (33.2–66.8 °C), methanol-to-oil molar ratio (3.5:1–8.5:1) and catalyst concentration (0.219–1.065 mol/L). The cosolvent loading was 10 wt% (based on oil weight). The optimum reaction conditions were found to be: the methanol-to-oil molar ratio of 7.1:1, the catalyst concentration of 0.74 mol/L and the reaction temperature 52 °C, ensuring the best esters content of 99.8%, for the reaction time of 1.5 h, which is close to the reported experimental value of 98.9%. Also, the used catalyst was recycled with no additional treatment in the further four consecutive cycles under the following reaction conditions: methanol-to-oil molar ratio 6:1, the concentration of catalyst 0.642 mol/L (only in the first run), the reaction temperature 50 °C, cosolvent-crude biodiesel loading 10 wt% to oil weight. The second recycling reaction provided the highest FAME content of 97.7% after 5 h. This is the peer-reviewed version of the article: Todorović, Zoran B., Dragan Z. Troter, Dušica R. Đokić-Stojanović, Ana V. Veličković, Jelena M. Avramović, Olivera S. Stamenković, Ljiljana M. Veselinović, and Vlada B. Veljković. 2019. “Optimization of CaO-Catalyzed Sunflower Oil Methanolysis with Crude Biodiesel as a Cosolvent.” Fuel 237 (February): 903–10. [https://doi.org/10.1016/j.fuel.2018.10.056]. Supplementary material: [https://hdl.handle.net/21.15107/rcub_dais_4071] Published version: [https://hdl.handle.net/21.15107/rcub_dais_4070]

For commercial application, the ester product of alkali-catalyzed transesterification of vegetable oil or animal fats should be refined after glycerol separation by settling to fulfill the biodiesel standard specifications. This crude biodiesel, after neutralization and methanol removal, should be further cleaned by either one of the following methods: wet washing, dry washing, membrane extraction or using ion liquids. This paper presents a review on the traditional (wet and dry washing) and novel (membrane separation technology and usage of ion liquids) methods of crude biodiesel purification. It also provides a comparison of crude biodiesel purification methods. Each method has its advantages and disadvantages, which should be carefully analyzed when choosing the proper one for refining crude biodiesel.

Abstract The production of fatty acid methyl esters (FAME) from crude tobacco seed oil (TSO) having high free fatty acids (FFA) was investigated. Due to its high FFA, the TSO was processed in two steps: the acid-catalyzed esterification (ACE) followed by the base-catalyzed methanolysis (BCM). The first step reduced the FFA level to less than 2% in 25 min for the molar ratio of 18:1. The second step converted the product of the first step into FAME and glycerol. The maximum yield of FAME was about 91% in about 30 min. The tobacco biodiesel obtained had the fuel properties within the limits prescribed by the latest American (ASTM D 6751-02) and European (DIN EN 14214) standards, except a somewhat higher acid value than that prescribed by the latter standard (

Abstract Kinetic modeling and optimization of sunflower oil methanolysis catalyzed by spherically-shaped CaO/γ-Al2O3 particles were conducted in batch stirred and packed-bed tubular reactors at 60 °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.

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).

Abstract The ultrasound-assisted sunflower oil methanolysis using KOH as a catalyst was studied at different reaction conditions. A full factorial experiment 3 3 with replication was performed. The effects of three reaction variables, methanol-to-oil molar ratio, catalyst loading and the reaction temperature on fatty acid methyl ester yield were evaluated by the analysis of variance and the multiple regression. At the 95% confidence level all three factors and the interaction of the reaction temperature and methanol-to-oil molar ratio were effective on fatty acid methyl ester formation, the most important factor being the catalyst loading. The relationship between the factors and their interactions was modeled by the second-order polynomial equation.

Abstract Developing technologies for the production of alternative fuels from biorenewable resources is a field of interest for many researchers. Adequate substitute to diesel fuel is biodiesel that is synthesized through the transesterification of vegetable oils or animal fats and fulfilled the international standards. Ionic liquids (ILs) and deep eutectic solvents (DESs) have gained tremendous attention for their use in biodiesel production because of environmental benefits and process improvements. The present work overviews the use of ILs and DESs in the reaction and purification steps of biodiesel production processes where they are used as catalysts, cosolvents and extracting solvent. In addition, the possibilities of recycling and reusing of ILs and DESs are pointed out. Moreover, optimization and kinetic studies of biodiesel synthesis in the presence of ILs or DESs are discussed. The use of novel technologies combined with ILs or and DESs are also considered. Therefore, the present paper highlights the promising uses of ILs and DESs in biodiesel production in the future.

Abstract Loading CaO onto spherically-shaped γ-Al 2 O 3 support was applied for the preparation of a cost-effective and environmentally-friendly heterogeneous catalyst for biodiesel production. Physico-chemical, textural and morphological characterization was performed using optical emission spectroscopy (ICP OES), Hg-porosimetry, N 2 physisorption, scanning electron microscopy (FESEM), X-ray diffraction (XRPD), Fourier transform infrared spectroscopy (ATR FTIR) and Hammett indicators. The effects of catalyst preparation conditions (different precursor salts and calcination temperatures) on the catalyst activity, and the reaction conditions (methanol-to-oil molar ratio and catalyst loading) on the reaction rate and esters yield were studied. In addition, catalyst stability was investigated. The most active catalyst was derived from the nitrate precursor after calcination at 475 °C (inert atmosphere). Under mild reaction conditions (60 °C, 5 h, 900 rpm, methanol-to-oil molar ratio of 12:1 and catalyst loading (CaO wt% to the oil) of 0.5%), the equilibrium ester content of 94.3% was obtained in the methanolysis of sunflower oil in a batch reactor. The catalyst remained sufficiently active in two consecutive cycles without any pretreatment. Mechanical erosion caused by stirring and massive deposition of organic molecules from the reaction mixture caused the decrease of catalytic activity while CaO leaching was negligible.