Search

Synthesis of biodiesel from various plant oils is realized by the transesterification of triglycerides with methanol or by a reaction usually defined as methanolysis. The usage of low-quality oils, such as waste cooking oil (WCO), is followed by undesirable side reactions as a result of the increased content of free fatty acids (FFA), and water. The presence of FFA in WCO usually requires a pretreatment stage before subjecting it to methanolysis. In the present work, heterogeneously catalyzed methanolysis of WCO with and without pretreatment was investigated. Removal of FFA from WCO was conducted by using only quicklime or with the addition of a small amount of methanol (FFA to methanol = 1:3 molar ratio). The obtained results showed that pretreatment of WCO with quicklime at 30 °C after 1 h reduces the FFA content by 72 %, while the adsorption capacity was determined to be 910 mg g-1. The adsorptive pretreatment, as a simple operation, using low-cost quicklime under mild conditions, had a positive effect on the transesterification rate with CaO∙ZnO as a catalyst, enabling the achievement of over 96 % of biodiesel yield in only 15 min, compared to 1 h without the pretreatment. Furthermore, pretreated WCO allows an increase in repeated catalyst use and overall savings in the necessary amount of catalyst. The present study showed that quicklime is an economic, environmental-friendly, and sustainable material for FFA removal from WCO.

Deep eutectic solvents (DESs) are called 'designer solvents' due to various structural variations and the benefit of tailoring their physicochemical properties. For industrial applications of DESs it is crucial to know their physical and thermodynamic properties such as density, viscosity, and refractive index. These properties were measured for three lecithin (LEC)-based DESs with glycerol (G), triethanolamine (TEOA), and oleic acid (OLA) as functions of temperature. The viscosity was fitted by both Arrhenius-type and Vogel-Tamman-Fulcher equations. The density, viscosity, and refractive index of tested DESs decreased with the increase in temperature. The LEC:G DES exhibited the lowest density at all tested tempe-ratures. This DES was selected as a cosolvent in the ethanolysis of cold-pressed black mustard (Brassica nigra L.) seed oil catalyzed by either calcined or non-calcined CaO. The reaction was carried out in a batch stirred reactor under the following conditions: the temperature of 70 °C, the ethanol-to-oil molar ratio of 12:1, and the amount of DES and CaO of 20 and 10 wt.% (to oil), respectively. The presence of DES accelerated the reaction, while the separation of the final reaction mixture phases was faster.

Ten organic solvents (triethanolamine, diethanolamine, ethylene glycol, methyl ethyl ketone, n-hexane, triethylamine, ethylene glycol dimethyl ether, glycerol, tetrahydrofuran and dioxane) were applied as cosolvents in the CaO-catalyzed ethanolysis of sunflower oil performed in a batch stirred reactor under the following reaction conditions: temperature 70 °C, ethanol-to-oil mole ratio 12:1, initial catalyst concentration 1.374 mol·L-1 and amount of cosolvent 20 % based on the oil amount. The main goals were to assess the effect of the used cosolvents on the synthesis of fatty acid ethyl esters (FAEE) and to select the most efficient one with respect to the final FAEE content, reaction duration and safety profile. In the absence of any cosolvent, the reaction was rather slow, providing a FAEE content of only 89.7±1.7 % after 4 h. Of the tested cosolvents, diethanolamine, triethanolamine and ethylene glycol significantly accelerated the ethanolysis reaction, whereby the last two provided a final FAEE content of 93.1±2.1 and 94.1±1.5 %, respectively, within 0.5 h. However, because of its safety profile, triethanolamine was selected as the best cosolvent for the ethanolysis of sunflower oil catalyzed by calcined CaO.

Triethanolamine was applied as an efficient „green“ cosolvent for biodiesel production by CaO-catalyzed ethanolysis of sunflower oil. The reaction was conducted in a batch stirred reactor and optimized with respect to the reaction temperature (61.6-78.4°C), the ethanol-to-oil molar ratio (7:1-17:1) and the cosolvent loading (3-36 % of the oil weight) by using a rotatable central composite design (RCCD) combined with the response surface methodology (RSM). The optimal reaction conditions were found to be: the ethanol-to-oil molar ratio of 9:1, the reaction temperature of 75°C and the cosolvent loading of 30 % to oil weight, which resulted in the predicted and actual fatty acid ethyl ester (FAEE) contents of 98.8 % and 97.9±1.3 %, respectively, achieved within only 20 min of the reaction. Also, high FAEE contents were obtained with expired sunflower oil, hempseed oil and waste lard. X-ray diffraction analysis (XRD) was used to understand the changes in the CaO phase. The CaO catalyst can be used without any treatment in two consecutive cycles. Due to the calcium leaching into the product, an additional purification stage must be included in the overall process. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. III 45001]

The MnCO3/Na silicate (Mn/Na/Si mole ratio of 4.65:1:1.65) catalyst in the form of solid particles with diameter of 0.99–1.99 mm was used as a catalyst for transesterification of soybean oil in batch autoclave at different conditions: 388–468 K, methanol-to-oil mole ratio 12:1–30:1, catalyst amount based on the mass of oil 0–12.5 %. The complete triacylglycerols (TAG) conversion and high yield of fatty acid methyl ester (FAME) was obtained after 1 h at 458 K, methanol-to-oil mole ratio 30:1 and 10 % of catalyst. Kinetics of transesterification process was analyzed by three models: the simple first order irreversible reaction rate, as well as two more complex models recently reported in literature. The catalyst reuse in transesterification process was tested and the average values of 99.0 % of TAG conversion and 97.5 % of FAME yield were obtained after 8 consecutive runs. Different techniques were used to characterize fresh and used MnCO3/Na silicate catalyst. The determined amounts of leached Na (

Vegetable oils are mainly esters of fatty acids and glycerol, which can be converted to fatty acid methyl esters (FAME), also known as biodiesel, by the transesterification reaction with methanol. In order to attain environmental benignity, a large attention has been focused in the last decades on utilizing heterogeneous catalysts for biodiesel production instead the homogenously catalyzed transesterification of vegetable oil. The pure CaO or CaO mixed with some other metal oxide due to its low solubility in methanol, FAME and glycerol, low cost and availability is one of the most promising among the proposed heterogeneous catalysts. Solid catalysts which contain CaO usually fulfill a number of important requirements, such as high activity at mild temperature, marginal leaching of Ca cations, long life activity, reusability in transesterification of vegetable oil and easy recovery from the final products of transesterification (FAME and glycerol). This review is focused to the recent application of pure CaO or CaO in complex catalyst structure and their use as heterogeneous base catalysts for biodiesel synthesis and suitability for industrial application. [Projekat Ministarstva nauke Republike Srbije, br. 45001]

The goal of this study was to prepare CaO.ZnO catalyst which contain small amount of K2CO3 and analyze its activity for biodiesel synthesis. Catalyst was prepared using the following procedure: CaO and ZnO (molar ratio of 1:2), water and K2CO3 (in various amounts) were mechanochemically treated and after milling heated at 700 oC in air atmosphere for obtaining mixed CaO•ZnO/xK2CO3 oxides (x = 0, 1, 2 and 4; mole of K2CO3 per 10 mole of CaO). All the samples were characterized by X-ray diffraction (XRD), inductively coupled plasma (ICP), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), infrared spectroscopy (FTIR), scanning electron microscopy/energy-dispersive spectroscopy (SEM/EDS), particle size laser diffraction (PSLD) distribution, solubility measurement of Ca, Zn and K ions in methanol as well as by determination of their alkalinity (Hammett indicator method). Prepared CaO•ZnO/xK2CO3 composite powders were tested as catalysts for methanolysis of sunflower oil at 70ºC using molar ratio of sunflower oil to methanol of 1:10 and with 2 mas% of catalyst based on oil weight. The presence of K2CO3 in prepared samples was found to increase the activity of catalyst, and that such effect is caused by homogeneous-heterogeneous catalysis of biodiesel synthesis. [Projekat Ministarstva nauke Republike Srbije, br. 45001]

The kinetics of heterogeneous methanolysis of sunflower oil was studied at 60°C using mechanochemically synthesized CaO∙ZnO as catalyst. Influence of agitation speed, catalyst amount and methanol to oil molar ratio on the rate of reaction was analyzed. The rate of the process depends on the two resistances - mass transfer of triglycerides to the catalyst surface and chemical reaction on the catalyst surface, which are defined as the values of the overall triglyceride volumetric mass transfer coefficient, kmt,TG, and the effective pseudo first-order reaction rate constant, k, respectively. These kinetic parameters actually determine the value of the apparent reaction rate constant, kapp, whose change with time is defined with the change of triglyceride (TG) conversion. The kinetic model was proposed and the model parameters determined. [Projekat Ministarstva nauke Republike Srbije, br. 45001]

Mechanochemical treatment of Serbian kaolin clay was carried out in a planetary ball mill using two different milling media, hardened steel or zirconia vials and balls. The samples obtained with various milling times were characterized by the particle size laser diffraction (PSLD), X-ray diffraction (XRD), differential scanning calorimetry/thermogravimetry (DTA/TGA) and Fourier-transform infrared (FTIR) analyses. Mechanochemical treatment induced amorphization of the kaolinite phase accompanied by dehydroxylation. It was found that for the given milling parameters, amorphization mainly took place in the milling period up to 15 min, and was completed after about 30 min of milling for both milling media used. The pozzolanic activities were determined by the Chapelle method. Milling in the hardened steel milling medium had no significant influence on pozzolanic activity, even though there was accumulated iron contamination. For both milling media, pozzolanic activity of 0.79 was obtained for the samples milled for 15 min and it remained almost unchanged with prolonged milling. The determined pozzolanic activity values are close to these of commercial metakaolinite or metakaolinite obtained by the calcination of the same clay, therefore, indicating possibility for obtaining high reactive pozzolana by mechanochemical treatment of Serbian kaoline clay. [Projekat Ministarstva nauke Republike Srbije, br. TR 36017 and 45001]

Powder mixtures of α-Bi2O3 containing 2, 5 and 10 mole % of TiO2, ZrO2 or HfO2 were homogenized, heated at 820ºC for 24 h and quenched in air. X-ray powder diffraction technique was used to characterize the prepared samples. In all cases metastable Bi2O3 polymorphs, γ-Bi2O3 or β-Bi2O3, are found as single or major phases. Addition of Ti4+ ions stabilizes γ-Bi2O3 polymorph, while either Zr4+ or Hf4+ ions stabilize β-Bi2O3 polymorph. In the samples with 2 and 5 mole % of TiO2 the presence of even two γ-Bi2O3 phases (Bi12TiO20 compound and a very low Ti-doped γ-Bi2O3) was established. Similarly, in the sample with 2 mole % of HfO2 two β-Bi2O3 phases were found. Phase composition of prepared samples, values of unit cell parameters and the appearance of two polymorphs with identical crystal structure but different unit cell parameters are discussed and compared with known data.

Nano-sized titanium monoxide (TiO) powder was prepared by mechanochemical synthesis. A mixture of commercial Ti and TiO2 (rutile) powders with the molar ratio of 1:1 was milled in a planetary ball mill for 5, 10, 20, 30 and 60 min under argon atmosphere. The final single-phase titanium monoxide sample was characterized by X-ray diffraction (XRD), magnetic measurements using a superconducting quantum interference device magnetometer (SQUID) and thermogravimetric analysis (TGA). The temperature dependency of the magnetic susceptibility is characterized by significant contribution of Pauli paramagnetism due to conduction electrons.

Nanosized perovskite YTiO3 with the mean crystallite size of 18 nm was synthesized for the first time by mechanochemical treatment. The mechanochemical solid state reaction between commercial Y2O3 powder and mechanochemically synthesized TiO powder in molar ratio 0.5:1 was completed for 3 h in a high-energy planetary ball mill in argon atmosphere. The heating in vacuum at 1150 °C for 12 h transforms nanosized YTiO3 to a well-crystallized single-phase perovskite YTiO3. Both samples were characterized by X-ray diffraction (XRD) and thermogravimetric (TGA/DTA) analyses, as well as superconducting quantum interference device magnetometer (SQUID) measurements.

A powder mixture of α-Bi2O3 and HfO2, in the molar ratio 2:3, was mechanochemically treated in a planetary ball mill under air, using zirconium oxide vials and balls as the milling medium. After 50 h of milling, the mechanochemical reaction led to the formation of a nanocrystalline δ-Bi2O3 phase (fluorite-type solid solution Bi0.78Hf0.59Zr0.63O3.61), with a crystallite size of 20 nm. The mechanochemical reaction started at a very beginning of milling accompanied by an accumulation of ZrO2 arising from the milling tools. The samples prepared after various milling times were characterized by X-ray powder diffraction and DSC analysis. The electrical properties of the as-milled and pressed Bi0.78Hf0.59Zr0.63O3.61 powder were studied using impedance spectroscopy in the temperature range from 100 to 700°C under air. The electrical conductivity was determined to be 9.43×10-6 and 0.080 S cm-1 for the temperatures of 300 and 700°C, respectively.

Mechanochemistry represents an alternative route in synthesis of nanomaterials. Mechanochemical routes are attractive because of their simplicity, flexibility, and ability to prepare materials by solid state reactions at room temperature. The aim of this work is the mechanochemical synthesis of nanostructured titanium oxides of different composition starting from mixtures of Ti and TiO2, TiO and TiO2 or Ti2O3 and TiO2. Emphasis is on the Magneli phases Ti4O7 and Ti5O9 because their mixture is commercially known as EBONEX material. The materials prepared were characterized by XRPD, TG/DTA analysis, SEM and optical microscopy. Titanium monoxide and several Magneli oxides, Ti4O7, Ti5O9 and Ti6O11, are successfully prepared. The results are very interesting because the EBONEX materials were prepared at lower than usual temperature, which would decrease the effective cost of production.

One of the distinguishing features of mechanochemical treatment is crystallite size reduction. The crystallite size of the powder subjected to milling decreases to some minimal value characteristic for the given material. Two processes occur concurrently during milling: reduction of the crystallite size and grain growth, whereby the steady-state crystallite size is attained when the rates of these processes are in equilibrium. This study deals with the kinetics of crystallite size evolution by milling. Published experimental data were analyzed using three kinetic models: dr / dt=-k1r2 + k2r-1; dr / dt=-k1r3 + k2r and dr / dt=-nktn-1(r - rs), where r and rs are the crystallite radius and steady-state crystallite radius respectively, t time, k1 and k2 the rate constants of crystallite reduction and grain growth, respectively, k the rate constant and n the Avrami exponent. The applied kinetic relations describe the crystallite size dependence on milling time in a satisfactory manner.

Copyright of Chemical Industry / Hemijska Industrija is the property of Association of Chemical Engineers and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)