Fatty Acid Methyl Ester Content Research Articles

Synergistic effect of growth conditions and organic carbon sources for improving biomass production and biodiesel quality by the microalga Choricystis minor var. minor

In the search for microalgae species with potential for biodiesel production, Choricystis minor var. minor has been seen as a promising source of biomass due to its high lipid content and the satisfactory characteristics of its fatty acid methyl esters (FAMEs). For this reason, the objective of this study was to investigate the synergistic effect of growth conditions and organic carbon sources on cultivation of this microalga. To do so, experimental cultivations were conducted in photoautotrophic, heterotrophic and mixotrophic metabolisms using glucose, fructose, glycerol or sucrose – in growth conditions that use organic carbon. Thus, growth parameters of the cultures were evaluated and at the end of the cultivations, FAMEs yield and profile were determined by gas chromatography, the efficiency of carbon conversion into biomass was evaluated and a microbial analysis was conducted. Regarding growth conditions, the findings have confirmed that, regardless of the organic carbon source used, the heterotrophic and mixotrophic metabolisms can present advantages over the photoautotrophic one. In addition, biomass production was higher with the use of glucose than with other organic carbon sources, regardless of growth condition (heterotrophic or mixotrophic). Moreover, cultivations with the addition of CO2 have converted carbon into biomass less efficiently. On the other hand, photoautotrophic cultures presented the lowest bacterial load. In comparison to photoautotrophic and mixotrophic, heterotrophic cultures have led to lower FAMEs content and higher yields of unsaturated fatty acids. The most satisfactory FAMEs profile for biodiesel production was obtained with mixotrophic growth using fructose.

Extraction of microalgal oil from Nannochloropsis oceanica by potassium hydroxide-assisted solvent extraction for heterogeneous transesterification

The feasibility of potassium hydroxide for simultaneous removal of chlorophyll during solvent extraction from wet microalgae (200 g/L) was evaluated. Extracted oil was converted to biodiesel by ZSM-5-based heterogeneous catalysts. The total oil (fatty acid-based) content of Nannochlorposis oceanica cultivated in open raceway ponds was 19.5%. The oil recovery yields from dry and wet microalgae using hexane were 44.4 and 11.8%, respectively, whereas using a hexane-methanol mixture were increased to 79.3 and 74.8%, respectively. For the heterogeneous transesterification of microalgal oil extracted by the hexane-methanol mixture from wet microalgae, the fatty acid methyl ester (FAME) contents were 2.3, 48.3, and 4.7% of product recovered after reaction for ZSM-5, Na/ZSM-5, and SO42−/ZSM-5, respectively; by the potassium hydroxide-assisted process, the corresponding FAME contents were increased to 21.9, 86.2, and 86.0%, respectively, due to improvement of the oil properties by the decrease of the chlorophyll content. Through the addition of potassium hydroxide, chlorophyll was effectively removed from oil, and eventually, the biodiesel conversion was sharply increased with heterogeneous Na/ZSM-5 and SO42−/ZSM-5 catalysts.

Primitive techno-economic study of bio-diesel and bio-active compound production from microalgae

BackgroundMicroalgae cells can be identified as a potential source for new and renewable energy. The economic investigation for biodiesel and bio-active compound production from the microalgae community (Bloom), which are collected from the high rate algal pond (HRAP) constructed to treat municipal wastewater at Zenin wastewater treatment plant, Giza, was the main target of study.ResultsThe microscopical examination showed that Scenedesmus obliquus is the dominant species. The total carotenoids were extracted using jojoba oil and determined by high-performance liquid chromatography (HPLC) to reach 81.44 μg/g. The biodiesel production through acid transesterification reaction recorded 70.6% of fatty acid methyl ester content with high cetane number (44) and low acid value. Such results prove that the obtained biodiesel has better ignition quality. The total phenolic and flavonoid compounds have been derived from the remaining biomass to give 5.36 ± 0.03 and 1.50 ± 0.19 mg/g respectively. Finally, total proteins and carbohydrates content in algal cells were recorded 54.3 and 1.5 mg/g successivelyConclusionThe preliminary economic evaluation showed that the production of biodiesel and carotenoids from the microalgae growing in municipal wastewater can be considered, as a techno-economic feasible process.

Influences of Water Content in Feedstock Oil on Burning Characteristics of Fatty Acid Methyl Esters

Strong alkaline-catalyst transesterification with short-chain alcohol is generally used for biodiesel production due to its dominant advantages of shorter reaction time and higher conversion rate over other reactions. The existence of excess water content in the feedstock oil might retard the transesterification rate and in turn deteriorate the fuel characteristics of the fatty acid methyl esters. Hence, optimum water content in the raw oil, aimed towards both lower production cost and superior fuel properties, becomes significant for biodiesel research and industrial practices. Previous studies only concerned the influences of water contents on the yield or conversion rate of fatty acid methyl esters through transesterification of triglycerides. The effects of added water in the reactant mixture on burning characteristics of fatty acid methyl esters are thus first investigated in this study. Raw palm oil was added with preset water content before being transesterified. The experimental results show that the biodiesel produced from the raw palm oil containing a 0.05 wt.% added water content had the highest content of saturated fatty acids and total fatty acid methyl esters (FAME), while that containing 0.11 wt.% water content had the lowest content of total FAME and fatty acids of longer carbon chains than C16 among the biodiesel products. Regarding burning characteristics, palm-oil biodiesel made from raw oil with a 0.05 wt.% added water content among those biodiesels was found to have the highest distillation temperatures, flash point, and ignition point, which implies higher safety extents during handling and storage of the fuel. The added water content 0.05 wt.% in raw oil was considered the optimum to produce palm-oil biodiesel with superior fuel structure of fatty acids and burning characteristics. Higher or lower water content than 0.05 wt.% would cause slower nucleophilic substitution reaction and thus a lower conversion rate from raw oil and deteriorated burning characteristics in turn.

Biofuel production from wet microalgae biomass: Comparison of physicochemical properties and extraction performance

A one-step process that integrates cell disruption with lipid extraction from wet microalgae was proposed by using n-hexane/formic acid. The scanning electron microscopy showed that raw microalgae cells were completely disrupted. The derivative thermogravimetric analysis indicated that formic acid could lead to a fast-thermal decomposition of microalgae residues at the temperatures ranged from 175 to 280 °C. The Fourier transform infrared spectroscopy revealed that the intensities of CO vibrations increased with an increase of the carbonyl compounds. When microalgae were treated with this mixed solvent at an n-hexane/formic acid ratio of 9:2 (v/v) and an addition dosage of 80 mL/g wet microalgae at 80 °C for 2 h, the optimal crude lipid yield was 256.3 mg/g dry weight. A high fatty acid methyl ester (FAME) content of 83.6% was achieved, dominated by palmitic acid, palmitoleic acid, oleic acid, and linoleic acid. Compared with the conventional methods including n-hexane, ethanol, n-hexane/methanol, and chloroform/methanol without pre-treatment, the crude lipid yields increased by 15%–402%. Compared with the chloroform/methanol extraction supplemented by ultrasound, microwave, hydrothermal, and dilute nitric acid pre-treatments, the achieved FAME contents increased by 79%–99%. Additionally, the energy yield from n-hexane/formic acid extraction reached up to 8.55 kJ/g volatile solid.

Recovery of intermittent cycle extended aeration system sludge through conversion into biodiesel by in-situ transesterification

The feasibility of using intermittent cycle extended aeration system (ICEAS) sludge as a lipid feedstock for biodiesel production was investigated. The main effects of in situ transesterification parameters, reaction temperature (30–70 °C), reaction time (4–24 h), catalyst concentration (1–5% v/v), and proportion of methanol to dry sludge (5–25 ml/g) at five-levels as well as their simultaneous interactions were evaluated to develop an empirical model. Optimized conditions were obtained at 60 °C, 4.65% (v/v) H2SO4, 17.84 h reaction time, and 5:1 methanol to dry sludge proportion (ml/g), leading to a maximum of 18.58% (w/w) biodiesel yield with 94.23% fatty acid methyl ester content. This result was higher in comparison with yields derived from conventional activated sludge, membrane bioreactor and anaerobic-anoxic-oxic processes. The ICEAS technology advantages are owned to its different configurations leading to production of one blended sludge, shorter hydraulic retention time and higher chemical oxygen demand to nitrogen ratios. The predominance of fatty acid methyl esters such as palmitic, oleic, palmitoleic, stearic, linoleic and myristic acid methyl ester, in the obtained biodiesel, indicated suitability of ICEAS sludge as feedstock for biodiesel production.

The Influence of Light and Nutrient Starvation on Morphology, Biomass and Lipid Content in Seven Strains of Green Microalgae as a Source of Biodiesel

The development of clean and renewable energy sources is currently one of the most important challenges facing the world. Although research interests in algae-based energy have been increasing in the last decade, only a small percentage of the bewildering diversity exhibited by microalgae has been investigated for biodiesel production. In this work, seven strains of green microalgae belonging to the genera Scenedesmus, Tetradesmus and Desmodesmus were grown in liquid medium with or without a nitrogen (N) source—at two different irradiances (120 ± 20 and 200 ± 20 μmol photons m−2 s−1)—to evaluate biomass production and FAME (fatty acid methyl esters) content for biodiesel production. The strains of Tetradesmus obliquus and Desmodesmus abundans grown in N-deprived medium showed the highest FAME content (22.0% and 34.6%, respectively); lipid profile characterization highlighted the abundance of saturated FAME (as C16:0 and C18:0) that favors better viscosity (flow properties) and applicability of biodiesel at low temperatures. Light microscopy and confocal laser scanning microscopy observations were employed as a fast method to monitor the vital status of cells and lipid droplet accumulation after Nile red staining in different culture conditions.

Constrained iterative learning control of batch transesterification process under uncertainty

Biodiesel are fatty acid methyl esters (FAME), which can be produced by the transesterification reaction of vegetable oils with methanol. A batch transesterification process is often associated with model uncertainties and unmeasured disturbances, which may create a detrimental effect on the batch end FAME yield due to plant-model mismatch. Therefore, batch-to-batch iterative learning control (ILC) is necessary to track the desired reference FAME profile under such process variations. This work demonstrates a constrained quadratic programming problem (QPP) based batch-to-batch ILC framework for optimizing the endpoint FAME concentration by controlling the hot water flow profile passing through the reactor jacket under uncertainty. Parametric uncertainties are modeled separately in two case studies, which involve different batch transesterification models differing in the state variables. Case study 1 considers uncertainty in the apparent activation energy and brings out a comparative study between a QPP based ILC and a heuristics based approach. The comparison is shown based on the tracking performance of the ILC in terms of reduction in the batch end tracking error and total root mean square error of the same. Batch-to-batch ILC is superior as it produces faster convergence of the tracking error by saving 6 batches as compared to the heuristics approach. Case study 2 involves the implementation of constrained QPP based ILC algorithm on a proposed 54-state detailed batch transesterification model of canola oil, where uncertainty is modeled as the change in the input triglyceride composition from the base case. The desired reference FAME concentration profile is tracked in 9 batches for fixed uncertainty whereas it takes 15 batches to achieve the stochastic convergence under stochastic disturbance.

Sugarcane Bagasse Hydrolysate as Organic Carbon Substrate for Mixotrophic Cultivation of Nannochloropsis sp. BR2

In the present study, the mixotrophic growth of the microalga Nannochloropsis sp. BR2 in sugarcane bagasse was analyzed and compared with its photoautotrophic cultivation. Nannochloropsis cultures cultivated mixotrophically in sugarcane bagasse showed significantly higher biomass productivity, fatty acid methyl ester (FAME) and protein contents of 63.28 mg L−1 d−1, 170.51 mg g−1 and 35.2% of dry weight, respectively, compared to the photoautotrophic cultivations with biomass productivity, FAME and protein contents of 51 mg L−1 d−1, 139.21 mg g−1 and 31.6% of dry weight. Whereas, total carotenoid during photoautotrophic cultivation was 5.833 mg g−1 and decreased to 4.542 mg g−1 in mixotrophic cultures. This can be explained by the additional carbon source in the form of sugars that are metabolized to the fatty acid building block acetyl-CoA, while photosynthetic pigments were less needed. Findings of this study demonstrate that acid-pretreated hydrolysate of lignocellulosic waste from sugarcane bagasse can be developed into a potential feedstock for efficient microalgal cultivation.

Fatty Acid Methyl Esters from the Herbal Industry Wastes as a Potential Feedstock for Biodiesel Production

Due to thegrowing awareness of fossil fuel depletion and environmental issues, biodiesel alternative fuel is currently of substantial interest. This research assessed herbal industry wastes as a potential resource for biodiesel production for the first time. Fatty acid methyl esters (FAMEs), obtained in the transesterification reaction, were extracted from the herbal samples by ultrasound-assisted extraction and identified withgas chromatography-mass spectrometry in the selected ion monitoring mode. The presence of at least 20 (e.g., in chamomile and chicory) FAMEs, up to 31 in nettle and senna, was reported. The unsaturated FAMEs were found in higher amounts than saturated. Linoleic acidwas the major polyunsaturated FAME in herbal wastes, while palmitic acid was the major saturated FAME. The highest content of FAMEs was identified in rye bran, Figure tea, and chicory. According to the cetane number prediction, BS EN 14214:2012+A2:2019, and hierarchical clustering on principal components (HCPC)wastes from, e.g., nettle, sage, and senna, are the most suitable in biodiesel production with fuel properties acceptable by the EuropeanStandards.Principal component analysis and HCPC allowed to classify and groupsimilar plants according to their FAMEs content; however, additional studies of herbal biofuel properties are needed.

Biodiesel production by interesterification of rapeseed oil with methyl formate in presence of potassium alkoxides

An alternative method for the biodiesel or fatty acid alkyl ester (FAAE) synthesis has been proposed—rapeseed oil interesterification with methyl formate. Reaction with methyl formate proceeds at a relatively low temperature (28 °C) instead of 55–65 °C necessary for triglyceride reactions with methanol and other monoesters. Similarly to transesterification with methanol, the product of the reaction with methyl formate consists of two layers. The main product the fatty acid methyl ester (FAME) is located in the top layer, but the process by-product formins forms the bottom layer. In this work, solutions of potassium alkoxides (methoxide, ethoxide, isopropoxide, tert-butoxide) in appropriate alcohols as homogeneous catalysts were used, adhering to the catalyst to oil molar ratio (COMR) 0.1 and methyl formate to oil molar ratio (MFOMR) 18. The FAAE content in the biodiesel layer in presence of all catalysts was 77–81 wt.%, which is lower than the level required by the EN14214 but significantly higher than the FAME content in reactions with methyl acetate under the same conditions. Fuel properties such as flash point, carbon residue, density, viscosity, and cold flow properties were investigated. For samples with MFOMR equal to or higher than 36 FAAE exceed 93% and the main characteristics of samples correspond to the EN14214 limits even without product purification.

Added-value molecules recovery and biofuels production from spent coffee grounds

Spent Coffee Grounds worldwide production is estimated at around 6 M tons only at industrial level. The abundance and the heterogeneity of this substrate make it an ideal substrate for a biorefinery approach based on the “cascade biorefinery hierarchy”. Currently, the major part of spent coffee grounds is sent to incineration and landfill disposal, options which should be avoided. Instead, they could be valorised through biofuels production. All the operational parameters leading to the highest biogas (350-400LCH4/kgTVS), bioethanol (3–4%v/v) and biodiesel (over 90% of Fatty Acid Methyl Esters concentration) yields from spent coffee grounds have been discussed in this review paper. They are rich in an oil phase containing different added-value molecules (tocopherols, cafestol, kahweol along with linoleic and palmitic acids), which can be extracted and used as additives for food, cosmetic and pharmaceutical applications. Solid/liquid extraction techniques of coffee oil from spent coffee grounds such as the most common Soxhlet technique and the more innovative fluids in supercritical conditions have been discussed, with coffee oil recovery of around 5–15%w/w and 15–20%w/w, respectively. The most recent applications of the extracted coffee oil have been also presented: the added-value molecules recovery and purification after micro/ultra and nano filtrations processes and the polyhydroxyalkanoates (0.84 g/g) and biosurfactants (3.5 g/L) production. Considering the whole information, an integrated biorefinery scheme, along with the respective mass balances were proposed. The novelty of this paper lies in the integration of the state-of-the-art data, in a biorefinery concept that would allow the production of both biofuels and value-added products.

Improving biodiesel made from cottonseed and soyabean oil with partial hydrogenation

Biodiesel limitations such as poor cold-flow properties and oxidation stability limit its usage in diesel engines. Partial hydrogenation is reported to be one of the ways to improve these limitations. Partial hydrogenation of biodiesel made from cottonseed and soyabean oil was studied. Before and after hydrogenation, the fatty acid methyl ester contents of cottonseed and soyabean biodiesel were detected with gas chromatography–mass spectrometry. It was revealed that methyl linolenic and methyl linoleic decreased while methyl stearic and methyl oleic increased after the partial hydrogenation for both soyabean and cottonseed biodiesel. Methyl oleic increased by 127 and 237% for soyabean and cottonseed biodiesel, respectively. A thermogravimetric test was also conducted on the fuel samples to observe the volatilisation of the fuels. There was an increase in fuel properties such as cetane number and kinematic viscosity, while iodine value decreased after partial hydrogenation. In addition, there was no significant change in oxygen content, low-heat value and density for both soyabean and cottonseed biodiesel. In summary, partial hydrogenation is a good method of upgrading biodiesel fuel properties such as cold-flow properties and oxidation stability.

Surfactant-assisted in situ transesterification of wet Rhodotorula glutinis biomass

In situ transesterification of oleaginous microbes with short chain alcohol has been developed as a renewable process for the production of biodiesel. Dry biomass is often a requisite for the process to avoid the adverse effect of water on the productivity. As a consequence, large amount of energy consumption is required for prior biomass drying. In this study, the wet biomass of Rhodotorula glutinis, an oleaginous yeast, was used directly in in situ transesterification without biomass drying. The reaction conditions were optimized for the production of fatty acid methyl esters (FAME) and the effects of adding different surfactants were also studied. The highest FAME yield of 110% was achieved with a methanol loading of 1:100at 90°C for 8h as catalyzed by 0.36MH2SO4, and the FAME content was 97%, which meets the 96.5% specified in both European biodiesel standards and Taiwanese biodiesel standards. The addition of 50mM 3-(N,N-dimethylmyristylammonio)propanesulfonate (3-DMAPS, a zwitterionic surfactant) improved the FAME yield from 69% to 83%, which was obtained with a low methanol loading of 1:10at 90°C for 10h. Hence, the production of FAME with wet biomass under optimized reaction conditions was as effective as that with the dry form. This clearly indicates that using wet R.glutinis as the feedstock is feasible for the production of biodiesel by in situ transesterification.

Determination of the Uptake of Ibuprofen, Ketoprofen, and Diclofenac by Tomatoes, Radishes, and Lettuce by Gas Chromatography–Mass Spectrometry (GC–MS)

The present study aimed to assess the uptake of the common nonsteroidal anti-inflammatories ibuprofen, ketoprofen and diclofenac by lettuce, radishes, and tomatoes. The influence of multiple routes of exposures (soil, water, vapor) of the pharmaceuticals were invstigated. The impact of accumulated pharmaceuticals active ingredients on the vegetable quality as the carbohydrate, amino acid, volatile organic aroma, and fatty acid methyl ester content were also investigated. The determination of the pharmaceutical active ingredients and vegetable quality compounds was performed by gas chromatography. For all of the vegetables, the diclofenac bioconcentration factor was the highest, as the concentration was between 31 and 118 ng·g−1. Ibuprofen was easily accumulated in radishes and lettuce, with levels between 6 and 58 and 11 and 73 ng·g−1, respectively. Higher concentrations of the pharmaceutical active ingredients were determined when the soil was artificially contaminated. The average values of bioconcentration factors considering studied pharmaceuticals active ingredients were in the following order: diclofenac > ibuprofen > ketoprofen. Considering the impact upon the vegetable carbohydrate content, a decreasing tendency in percentage values was observed for the carbohydrate concentration in radishes and tomatoes treated by pharmaceuticals through contaminated soil and water. Similarly, the volatile organic aroma compounds decreased from 7% to 36% compared with the controls when the vegetables were cultivated in contaminated conditions.

Bioactive plant oxylipins-based lipidomics in eighty worldwide commercial dark chocolates: Effect of cocoa and fatty acid composition on their dietary burden

Phytoprostanes (PhytoPs) and phytofurans (PhytoFs) are plant oxylipins (isoprostane-prostaglandin-like compounds) formed by the free radical-catalyzed oxidation of α-linolenic acid (ALA, C18:3, n-3). These oxylipins have been previously described in an array of plant-based foods with similar concentrations as phenolics in some fruits and vegetables, but their occurrence in dark chocolate has not been addressed so far, neither their content nor the influence of cocoa percent and fatty acid composition on the generation of PhytoPs and PhytoFs, to establish new assays in order to boost the dietary burden of these new bioactive compounds, provided by natural plant-based foods intake. In this regard, 80 dark chocolate samples with cocoa (Theobroma cacao L.) content of up to 100% were assessed on their PhytoP and PhytoF profile. These target analytes were isolated using a dispersive liquid–liquid extraction followed by a solid-phase clean-up of the extracts, and quantified using a UHPLC coupled to a triple quadrupole-MS/MS detection system. The content of PhytoPs and PhytoFs in the array of chocolates analyzed oscillated from 2.45 to 1192.43 ng/g fw and from 144.57 to 840.19 ng/g fw, respectively. The profile of these metabolites was studied in conjunction with the fatty acid methyl esters (FAMEs) content and the percentage of cocoa; however, no relationship between PhytoPs and PhytoFs and FAMEs content nor the cocoa percentage was observed. The assessment of dark chocolates on the content of PhytoPs and PhytoFs is of great importance as there is increasing scientific evidence on their immunomodulatory and inflammatory activity, as well as their role as preventive agents against oxidative stress that could confer this food an additional interest to consumers.

Investigation of Growth, Lipid Productivity, and Fatty Acid Profiles in Marine Bloom-Forming Dinoflagellates as Potential Feedstock for Biodiesel

Microalgae-based biodiesel is increasingly recognized as an alternative to crop-based biodiesel. In this study, 10 local strains of dinoflagellates collected from Hong Kong waters, including a monoculture and field sample of Scrippsiella sp. isolated from an algal bloom, were evaluated against the performance of green alga Tetraselmis suecica. The specific growth rate, biomass production, lipid productivity, and fatty acid profile were investigated. The total lipid content of isolated strains ranged from 16.2% to 32.2% of the total dry biomass, whereas palmitic acid (C16:0) and docosahexaenoic acid (DHA, C22:6n3) were dominant in the fatty acid profile. Scrippsiella sp. has a high lipid productivity (47.3 mg/L/day) and fatty acid methyl esters (FAME) content (55.2–73 mg/g dry weight (dw)), which were comparable to that in green alga T. suecica. Further, monoculture and field sampled blooming Scrippsiella sp. showed no significant difference in most parameters, suggesting the possibility of harvesting a natural algal bloom population as a mitigation strategy to harmful algal bloom and to use as biodiesel feedstock. Overall, dinoflagellate species showed a slower growth rate (0.04–0.57 day−1) than most compared species (0.07–1.34 day−1), likely due to a large genome size and low chlorophyll to carbon ratio. Notably, most investigated dinoflagellates were not ideal for mass biodiesel production due to the low growth rate and lipid productivity. However, a high level of polyunsaturated fatty acids (PUFA) in dinoflagellates are prospective for further studies in other biotechnological applications. Though effectively harvesting algal blooming biomass can be complex, it can be further explored as a strategy for algal bloom mitigation and potentially creating values at the advantage of natural bloom when applying harvested biomass for biodiesel and bioactive compounds extraction.

Direct Kinetic Measurements and Master Equation Modelling of the Unimolecular Decomposition of Resonantly-Stabilized CH2CHCHC(O)OCH3 Radical and an Upper Limit Determination for CH2CHCHC(O)OCH3 + O2 Reaction

Abstract Methyl-Crotonate (MC, (E)-methylbut-2-enoate, CH3CHCHC(O)OCH3) is a potential component of surrogate fuels that aim to emulate the combustion of fatty acid methyl ester (FAME) biodiesels with significant unsaturated FAME content. MC has three allylic hydrogens that can be readily abstracted under autoignition and combustion conditions to form a resonantly-stabilized CH2CHCHC(O)OCH3 radical. In this study we have utilized photoionization mass spectrometry to investigate the O2 addition kinetics and thermal unimolecular decomposition of CH2CHCHC(O)OCH3 radical. First we determined an upper limit for the bimolecular rate coefficient of CH2CHCHC(O)OCH3 + O2 reaction at 600 K (k ≤ 7.5 × 10−17 cm3 molecule−1 s−1). Such a small rate coefficient suggest this reaction is unlikely to be important under combustion conditions and subsequent efforts were directed towards measuring thermal unimolecular decomposition kinetics of CH2CHCHC(O)OCH3 radical. These measurements were performed between 750 and 869 K temperatures at low pressures (<9 Torr) using both helium and nitrogen bath gases. The potential energy surface of the unimolecular decomposition reaction was probed at density functional (MN15/cc-pVTZ) level of theory and the electronic energies of the stationary points obtained were then refined using the DLPNO-CCSD(T) method with the cc-pVTZ and cc-pVQZ basis sets. Master equation simulations were subsequently carried out using MESMER code along the kinetically important reaction pathway. The master equation model was first optimized by fitting the zero-point energy corrected reaction barriers and the collisional energy transfer parameters Δ E down , ref $\Delta{E_{{\text{down}},\;{\text{ref}}}}$ and n to the measured rate coefficients data and then utilize the constrained model to extrapolate the decomposition kinetics to higher pressures and temperatures. Both the experimental results and the MESMER simulations show that the current experiments for the thermal unimolecular decomposition of CH2CHCHC(O)OCH3 radical are in the fall-off region. The experiments did not provide definite evidence about the primary decomposition products.

Discrimination between vegetable oil and animal fat by a metabolomics approach using gas chromatography-mass spectrometry combined with chemometrics.

Adulteration of olive oil with the other cheap oils and fats plays an important role in economics and has nutritional benefits. In this work, metabolite profiling was performed using gas chromatography-mass spectrometry to identify and quantify animal fat (lard) adulteration in vegetable oil (olive oil). Principal component analysis could correctly identify and clustering olive oil, sunflower oil, sesame oil, lard, and adulterated samples through the changes in their fatty acid methyl esters (FAMEs) profile. A targeted metabolomics method was then optimized and validated through construction of calibration curves of known FAMSs in olive oil and lard. The method was presented high linearity (R2 > 0.96) and good intra and inter day accuracy and precision (79-101 and 86-102% and 2-7 and 3-7, respectively) for determination of FAMEs. Afterwards the absolute concentration and relative percentage of FAMEs were successfully determined in 12 commercial olive oils and 3 lards samples. Methyl myristate, methyl palmitate, methyl oleate, and methyl stearate were selected as discriminant markers to identify and quantify lard adulteration even at a low level of lard (5%w/w), with errors less than 2% in the comparison of the absolute or relative concentrations of FAMEs using several statistical methods. The proposed methodology allowed us to quantify the FAMEs simultaneously and also could predict small amount of lard in the adulterated olive oil samples.

Analysis of the Content of Fatty Acid Methyl Esters in Biodiesel by Fourier‐Transform Infrared Spectroscopy: Method and Comparison with Gas Chromatography

AbstractThe increasing importance of sustainability in energy production has led to a global commitment to the use of fuels derived from renewable biological sources, such as biodiesel produced from plant crops or biomass residues, that do not compete with human food for their production. For a biofuel to be considered biodiesel, it must satisfy the specifications described in the UNE 14214, with the UNE‐EN 14103 referring to the determination of fatty acid methyl ester content. This standard applies gas chromatography as an analytical technique. Gas chromatography is a widely used technique in the analysis of methyl ester although it has a number of drawbacks such as: long analysis times, a high consumption of high‐quality gases and internal standards, does not allow the analysis of different compounds with the same column, etc. From an industrial production point of view, is necessary to know the fatty acid methyl ester content in biodiesel samples quickly. This paper studies the development of an analytical method using Fourier transform infrared spectroscopy (FTIR) as alternative to gas chromatography (GC), since it is a simple, rapid, and precise analytical technique to quantify fatty acid methyl ester content in biofuel samples.