• Energy Research

The kinetics of the sunflower oil methanolysis process was studied at lower temperatures (10-30 degrees 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 kinetics of Ca(OH)(2)-catalyzed methanolysis of sunflower oil was studied at a moderate temperature (60 degrees 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.

Biodiesel, an alternative to fossil fuels, consists of alkyl, usually methyl, esters of fatty acids (FAME). Conventionally, it is mostly obtained by homogeneous base catalyzed methanolysis of edible oils. Despite the significant advantages, the main drawbacks of this process are the high requirements in terms of the quality of the raw materials and environmentally unfavorable processes of catalyst separation and products purification. For these reasons, the researches of biodiesel synthesis are aimed at developing new processes that are economically and environmentally acceptable. In this paper processes of FAME synthesis, their advantages, disadvantages and opportunities for improving are analyzed, in order to develop processes suitable for industrial applications. The main aim was to present an overview of the researches in developing biodiesel synthesis providing a high FAME yield, which are environmentally-friendly and economically acceptable. Heterogeneously catalyzed process has most often studied, aiming at developing catalytic active, stable and cheap catalysts as well as at process improvement. The developments of enzyme and noncatalytic processes are mainly aimed at reducing production costs and increasing the FAME yield under mild reaction conditions, respectively. Generally, the perspectives of biodiesel synthesis include the use of continuous processes and suitable reactor systems.

A heterogeneous reaction process using propylene glycol (PEG), ethyl acetate and diethyl ether as cosolvents for the transesterification of sunflower oil with ethanol in the presence of calcium oxide as a catalyst has been developed. Significant results were obtained with propylene glycol as a cosolvent. Under determined reaction conditions (CaO concentration, based on the oil weight 1.3736 mol∙dm-3; temperature 70°C; and ethanol-to-oil molar ratio 12:1), the conversion of sunflower oil to fatty acid ethyl esters (FAEE) exceeded 98% after 120 min, which was 2 times faster than transesterification of sunflower oil without a cosolvent. After initially enhanced ethanolysis, after 180 min ethyl acetate and diethyl ether negatively influenced the reaction rate and the FAEE yield.

The kinetics of the sunflower oil ethanolysis process using NaOH as a catalyst was studied at different reaction conditions. The reaction system was considered as a pseudo-homogeneous one with no mass transfer limitations. It was also assumed that the chemical reaction rate controlled the overall process kinetics. A simple kinetic model consisting of the irreversible second-order reaction followed by the reversible second-order reaction close to the completion of the ethanolysis reaction was used for the simulation of the triglyceride conversion and the fatty acid ethyl ester formation. The proposed kinetics model fitted the experimental data well.

Abstract In the present work, the sodium hydroxide-catalyzed synthesis of fatty acid ethyl esters (FAEE) from sunflower oil and ethanol was optimized using a 33 full factorial design of experiments with two replications and the response surface methodology (RSM). The effects of temperature, ethanol-to-oil molar ratio and catalyst loading on the FAEE were studied. The ANOVA results shows that at the 95% confidence level all three factors and the 2-way interactions of reaction temperature with ethanol-to-oil molar ratio and catalyst loading significantly affect the FAEE formation. A second-order polynomial equation is developed to relate the FAEE purity and the operational variables (temperature, ethanol-to-oil molar ratio and catalyst loading). The fitted model shows a good agreement between predicted and actual FAEE purities (R2 = 0.937; mean relative percentage deviation ±1%), demonstrating the validity of the regression analysis in the process optimization. The optimal process conditions were: ethanol-to-oil molar ratio of 12:1, reaction temperature of 75 °C and catalysts loading of 1.25%. The RSM is proved to be suitable method for optimizing the operating conditions in order to maximize the FAEE purity.

Abstract Biodiesel has been studied in last few decades because of limited energy resources and a huge increase of the energy demand. The basic feedstocks for the production of biodiesel are vegetable oils and animal fats that contain primarily triacylglycerols while the main reaction is transesterification. This reaction is most frequently conducted at commercial scale in the presence of the homogeneous alkali catalyst. Previous studies on biodiesel were mainly focused on its production and fuel properties, while its environmental management is rarely considered. The present work is a review of the previous studies on treating wastewaters generated by the biodiesel production processes involving alkali-catalyzed transesterification. The attention is focused on physical, chemical, physico-chemical, electrochemical, biological and integrated treatment processes of biodiesel wastewaters. Both advantages and disadvantages of different biodiesel wastewater treatment processes are discussed. Since different input biodiesel wastewaters are employed in different studies, it is difficult to compare different treatments with respect to their contaminant removal efficiencies. Proper acidification and chemical coagulation/flocculation or electrocoagulation remove grease and oil successfully but they are unsuccessful in removing COD. The combinations of acidification, coagulation and the electrochemical treatment improve the removal efficiencies of COD and BOD. Advanced oxidation technologies appear not to be effective in removing the contaminants from raw biodiesel wastewaters. The performance of biological processes is improved by the pretreatment of biodiesel wastewater with acidification, chemical coagulation, electrocoagulation or photo-Fenton. When selecting a treatment process, it should be evaluated with respect to its treatment efficiency and operational requirements. The right choice is probably an integration treatment involving acidification, coagulation/flocculation or electrocoagulation and a biological process. The reuse of the pretreated wastewater is also an interesting alternative.

In this paper, extraction of resinoid from the aerial parts of white lady's bedstraw (Galium mollugo L.) using an aqueous ethanol solution (50% by volume) was studied at different temperatures in the absence and the presence of ultrasound. This study indicated that ultrasound-assisted extraction was effective for extracting the resinoid and gave better resinoid yields at lower extraction temperature and in much shorter time than the maceration. A phenomenological model was developed for modeling the kinetics of the extraction process. The model successfully describes the two-step extraction consisting of washing followed by diffusion of extractable substances and shows that ultrasound influences only the first step. The extraction process was optimized using response surface methodology (RMS) and artificial neural network (ANN) models. For the former modeling, the second-order polynomial equation was applied, while the second one was performed by an ANN-GA combination. The high coefficient of determination and the low MRPD between the ANN prediction and the corresponding experimental data proved that modeling the extraction process in the absence and the presence of ultrasound using ANN was more accurate than RSM modeling. The optimum extraction temperature was determined to be 80 and 40 °C, respectively for the maceration and the ultrasound-assisted extraction, ensuring the highest resinoid yield of 22.0 g/100g in 4h and 25.1g/100g in 30 min, which agreed with the yields obtained experimentally for the same time (21.7 and 25.3g/100g, respectively).

Processes of bioethanol production currently applied all over the world are reviewed in this paper. Attention is focused on potentially cheap biomass sources, as well as the most important operating factors controlling the progress and result of saccharification and fermentation reactions and affecting the yield of fermentable sugars and ethanol, respectively, such as: the type and concentration of acid, the type of enzyme, the type of working microorganism, operating temperature, duration time and pH. The hydrolysis conditions, namely duration time, temperature and sulfuric acid concentration, were combined in a single parameter, known as the "combined severity" (CS), in order to estimate the efficiency of bioethanol production from biomass. When the CS increases, the yield of fermentable sugars also increases. The decrease in the yield of monosaccharides coincides with the maximum concentrations of by-products, such as furfural and 5-hydroxymethylfurfural, which are well-known as yeast inhibitors. The highest ethanol yields has been obtained using the yeast Saccharomyces cerevisiae. With low oil prices and political reluctance to implement carbon taxes, fuel-ethanol production will remain uncompetitive unless some other form of cost reduction can be made, such as feedstock preparation costs.