Comparative study of the oxidative and thermal stability of vegetable oils to be used as lubricant bases

Politi, José Roberto dos Santos; Matos, Paulo Roberto Rodrigues de; Sales, Maria J. A.

doi:10.1007/s10973-012-2529-6

Cited by 26 publications

(11 citation statements)

References 15 publications

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“…5 . For each of the four raw lipid samples, mass loss could be roughly divided into three stages [ 50 , 51 ]: ~ 50% of the mass loss occurred during the first stage with a derivative thermogravimetry peak and corresponding DTA exothermic peak at 350 °C. This transition is due to the formation of alkyl radicals and their reaction with oxygen.…”

Section: Resultsmentioning

confidence: 99%

Effective lipid extraction from undewatered microalgae liquid using subcritical dimethyl ether

Wang

Oshita

Takaoka

2021

Biotechnol Biofuels

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Background Recent studies of lipid extraction from microalgae have focused primarily on dewatered or dried samples, and the processes are simple with high lipid yield. Yet, the dewatering with drying step is energy intensive, which makes the energy input during the lipid production more than energy output from obtained lipid. Thus, exploring an extraction technique for just a thickened sample without the dewatering, drying and auxiliary operation (such as cell disruption) is very significant. Whereas lipid extraction from the thickened microalgae is complicated by the high water content involved, and traditional solvent, hence, cannot work well. Dimethyl ether (DME), a green solvent, featuring a high affinity for both water and organic compounds with an ability to penetrate the cell walls has the potential to achieve this goal. Results This study investigated an energy-saving method for lipid extraction using DME as the solvent with an entrainer solution (ethanol and acetone) for flocculation-thickened microalgae. Extraction efficiency was evaluated in terms of extraction time, DME dosage, entrainer dosage, and ethanol:acetone ratio. Optimal extraction occurred after 30 min using 4.2 mL DME per 1 mL microalgae, with an entrainer dosage of 8% at 1:2 ethanol:acetone. Raw lipid yields and its lipid component (represented by fatty acid methyl ester) contents were compared against those of common extraction methods (Bligh and Dryer, and Soxhlet). Thermal gravimetry/differential thermal analysis, Fourier-transform infrared spectroscopy, and C/H/N elemental analyses were used to examine differences in lipids extracted using each of the evaluated methods. Considering influence of trace metals on biodiesel utilization, inductively coupled plasma mass spectrometry and inductively coupled plasma atomic emission spectroscopy analyses were used to quantify trace metals in the extracted raw lipids, which revealed relatively high concentrations of Mg, Na, K, and Fe. Conclusions Our DME-based method recovered 26.4% of total raw lipids and 54.4% of total fatty acid methyl esters at first extraction with remnants being recovered by a 2nd extraction. In additional, the DME-based approach was more economical than other methods, because it enabled simultaneous dewatering with lipid extraction and no cell disruption was required. The trace metals of raw lipids indicated a purification demand in subsequent refining process.

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Section: Resultsmentioning

confidence: 99%

Effective lipid extraction from undewatered microalgae liquid using subcritical dimethyl ether

Wang

Oshita

Takaoka

2021

Biotechnol Biofuels

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“…4. The peaks at 3,007 cm − 1 were consistent with ole nic C-H stretching in unsaturated fats [45]. The peaks at 2,953 cm − 1 were assigned to C-H stretches in -CH 3 .…”

Section: Ftir Tg/dta and Elemental Compositionmentioning

confidence: 77%

A Novel Method for Extraction of Lipids From Liquid Microalgae Without Dewatering

Wang

Oshita

Takaoka

2020

Preprint

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Background: Recent studies of lipid extraction from microalgae have focused primarily on dewatered or dried samples, and the processes are simple with high lipid yield. Yet, the dewatering with drying step is energy-intensive, which makes the energy output from the extracted lipid is less than the energy needed to produce it. Thus, exploring an extraction technique for just a thickened sample without the dewatering, drying and auxiliary operation (such as cell disruption) is very significant. Whereas lipid extraction from the thickened microalgae is complicated by the high-water content involved, and traditional solvent hence cannot work well. Dimethyl ether (DME), a green solvent, featuring a high affinity for both water and organic compounds with an ability to penetrate the cell walls, has the potential to achieve this goal. Results: This study investigated an energy-saving method for lipid extraction using DME as the solvent with an entrainer solution (ethanol and acetone) for flocculation thickened microalgae. Extraction efficiency was evaluated in terms of extraction time, DME dosage, entrainer dosage, and ethanol:acetone ratio. Optimal extraction occurred after 30 minutes using 4.2 mL DME per 1 mL microalgae, with an entrainer dosage of 8% at 1:2 ethanol:acetone. Raw lipid yields and fatty acid methyl ester contents were compared against those of common extraction methods (Bligh & Dryer and Soxhlet). Thermal gravimetry/differential thermal analysis, Fourier-transform infrared spectroscopy, and C/H/N elemental analyses were used to examine differences in lipids extracted using each of the evaluated methods. Considering influence of trace metals on biodiesel utilization, inductively coupled plasma mass spectrometry and inductively coupled plasma atomic emission spectroscopy analyses were used to quantify trace metals in the extracted raw lipids, which revealed relatively high concentrations of Mg, Na, K, and Fe.Conclusions: Our DME-based method recovered 26.4% of total raw lipids and 54.4% of total fatty acid methyl esters at first extraction with remnants being recovered by a 2nd extraction. In additional, the DME-based approach was more economical than other methods, because it enabled simultaneous dewatering with lipid extraction and no cell disruption was required. The trace metals of raw lipids indicated a purification demand in subsequent refining process.

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“…It is a fact that the thermal and oxidative stability of vegetable oils are inversely proportional to the amount of unsaturations of a vegetable oil because these reactions occur in the π bonds of the molecules. 56 However, the increase in temperature also increases the kinetic energy of the system and, consequently, favors the processes of oxidation and weakening of the double bonds and thus increases the packaging effect of the unsaturated chains and decreases the excess volume of mixtures. It was possible to perceive this event in the profiles of vegetable oils with hexane when evaluating Figure 2a−c, in which, for soybean oil, the temperature change showed small distances in the volumetric profile, while for canola and sunflower oil, the distances were greater.…”

Section: Resultsmentioning

confidence: 99%

Measurement and Prediction of Properties for Mixtures of Vegetable Oils + Hexane at Different Temperatures

Costa

Pereira

2019

J. Chem. Eng. Data

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The present study aimed to evaluate the effect of temperature, composition, and type of vegetable oil on the properties of mixture hexane + vegetable oil. Experimental data of densities for mixtures of vegetable oils (canola, soybean, and sunflower) with hexane were measured at temperatures between 293.15 and 323.15 K in order to evaluate the excess volume profiles of each system. Predictive and adjusted equations were used to compare the results and evaluate models. The thermodynamic properties of the mixture (excess Gibbs free energy, entropy, and enthalpy ( G ex, S ex, and H ex, respectively)) were determined and evaluated. All volume profiles presented a negative behavior, and the increase in this effect was observed when the temperature was increased; also, it was noted that the most unsaturated vegetable oils suffered a greater influence of temperature on their volumetric profiles. Prediction models showed good agreement with the experimental data of the literature. The G ex profiles presented a negative behavior in all cases, while the S ex and H ex profiles were positive. In general, large differences were not observed between the profiles of G ex, S ex, and H ex for the studied mixtures of hexane and vegetable oils.

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Comparative study of the oxidative and thermal stability of vegetable oils to be used as lubricant bases

Cited by 26 publications

References 15 publications

Effective lipid extraction from undewatered microalgae liquid using subcritical dimethyl ether

Effective lipid extraction from undewatered microalgae liquid using subcritical dimethyl ether

A Novel Method for Extraction of Lipids From Liquid Microalgae Without Dewatering

Measurement and Prediction of Properties for Mixtures of Vegetable Oils + Hexane at Different Temperatures

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