PetroOXY Method Research Articles

Fabrication and characterization of a novel zein/pectin/pumpkin seed oil Pickering emulsion and the effects of myricetin on oxidation stability

In this study, zein/pectin/pumpkin seed oil (PSO) Pickering emulsions (ZPPEs) were fabricated loading with myricetin (MYT), and the quality control methods of oxidation stability were innovatively investigated. The microstructure and particle properties of zein-pectin particles were determined. The zein to pectin ratio of 5:3 and oil phase fraction (φ = 50 %) turned out as the most optimal conditions for the stabilization of myricetin-loaded ZPPEs. The expected oil-in-water emulsion-type structure was confirmed by confocal laser scanning microscopy (CLSM). The internal 3D structure of Pickering emulsions (Lugol's solution improved the water-phase contrast) was imaged by micro-computed tomography (Micro-CT) for the first time. Results showed a sponge like structure of water phase in emulsion with 42 μm as mean droplet size. Light-induced oxidation was evaluated with the PetroOxy method and malondialdehyde (MDA) assays. Encapsuling ZPPEs with MYT could prevent the light induced oxidation, especially, loading of MYT at the core of the emulsion. The analysis of Electronic nose (E-nose) was used to analyze the odor before and after UV-induced oxidation, and showed a good discrimination. This study provided a new approach to prepare ZPPEs with high oxidation stability. Micro-CT, PetroOxy and E-nose could be new methods for characterization and quality assessment of Pickering emulsions.

A renewable lignin-derived bio-oil for boosting the oxidation stability of biodiesel

The valorisation of lignin is being increasingly recognised to improve the economics of pulp and paper making mills. In the present study, an integrated lignin–glycerol valorisation strategy is introduced with an overarching aim for enhancing the process value chains. LignoBoost kraft lignin was subjected to base-catalysed depolymerisation using glycerol as a co-solvent. The generated bio-oil was used as a renewable additive to biodiesel for enhancing its oxygen stability. The influence of three independent parameters including temperature, time and glycerol amount on lignin depolymerisation was investigated. Response surface methodology was applied to design the experiments and to optimise the process for maximising the yield and antioxidant impact of bio-oil. The results showed that glycerol has a positive qualitative and quantitative impact on the produced bio-oil, where an enhancement in the yield (up to 23.8%) and antioxidant activity (up to 99 min induction period) were achieved using the PetroOxy method (EN16091). The addition of 1 wt% bio-oil to biodiesel has led to an improvement in the oxidation stability over a neat sample of up to ∼340%, making it compliant with European standard (EN14214). The proposed process presents a biorefinery paradigm for the integrated utilisation of waste cooking oil, lignin and glycerol.

Assessment of ethanol autoxidation as a drop-in kerosene and surrogates blend with a new modelling approach

Bioethanol has been considered as a more sustainable alternative for fossil fuels, and it has been used as a drop-in fuel mixture. In this paper, the autoxidation properties of real kerosene as well as single, binary and ternary surrogates with the presence of ethanol are investigated for the first time. A simplified python code is proposed to predict the pressure drop of the PetroOXY method that was used for assessing the fuel autoxidation properties. The experimental results show that the addition of an ethanol concentration reduces the induction period of real kerosene while increasing that of surrogate mixtures. Also, the maximum pressure during the PetroOXY test increases with the increase of ethanol concentration. The model is able to predict the induction period of ethanol accurately by employing an automated reaction mechanism generator. A strategy to increase the autoxidation stability of ethanol by adding 1 g/L antioxidant has been evaluated. The efficiency of the antioxidants for ethanol is in the following order: PY > Decalin > DTBP > Tetralin > BHT > MTBP > BHA > TBHQ > PG.

Action of natural antioxidants on the oxidative stability of soy biodiesel during storage

One of the main problems that the biodiesel industry faces comes from biodiesel's instability when exposed to long storage periods. Its degradation has accelerated by the presence of factors such as oxygen, temperature, metals, humidity, among others. This study adds one more dimension in the field of exploring natural antioxidants to improve the quality of biodiesel, investigating the efficiency of bilberry extracts (BE), oregano (OE) extract, basil extract (BAE), and quercetin (QC) as antioxidants in biodiesel, by non-accelerated methods or analytical methods (water content, acidity value, peroxide value, iodine value, and viscosity) and accelerated methods (Rancimat and PetroOXY) during 180 days of storage. The antioxidant activity evaluated by the capture of the radical ABTS+ [2,2′-azino-bis(3-ethylbenzothiazoline)- 6-sulfonic acid] revealed that among the extracts, the most significant activity was achieved by the oregano extract, followed by the bilberry extract and basil extract. After the storage process, it has observed that the binary samples BBEQC3000 (biodiesel + extract of bilberry + quercetin 3000 ppm), BOEQC3000 (biodiesel + extract of oregano + quercetin 3000 ppm), and BBAEQC3000 (biodiesel + extract of basil + quercetin 3000 ppm) exhibited the least effects of oxidative degradation, both in terms of accelerated and non-accelerated methods. The susceptibility of soy biodiesel to oxidation during storage is well known, and its additivation using natural antioxidants can allow economic gains since natural antioxidants have the advantage of being easy to obtain and relatively low cost, making it a very alternative, viable to delay the oxidative degradation process of biodiesel during storage. The correlation between the Rancimat and PetroOXY techniques during storage revealed that the PetroOXY method could be considered an alternative method to measure the oxidation stability of soybean biodiesel samples and may be used to predict this stability in future standards and standards even though more studies need to be carried out.

Study of pressure and temperature influence on rapeseed biodiesel oxidation kinetics using PetroOXY method

In this manuscript, the kinetics of oxidation of canola oil-based biodiesel were investigated using the PetroOXY method (ASTM D7545) at different pressures (350, 700, and 715kPa). The examined temperature range was 130–145°C, with Ionol BF200 antioxidant concentration varying from 0 to 4000ppm. An apparent activation enthalpy was calculated from the Arrhenius equation, yielding apparent enthalpies that were independent of oxygen pressure, of around 100kJ/mol. Critical antioxidant concentrations for biodiesel destabilization were independent of temperature and increased as pressure was decreased. When compared to the Rancimat method for analysis of biodiesel oxidation, the PetroOXY method was considered a better alternative, requiring analysis times as low as 1/20 of the time spent using the Rancimat method.

Reproducibility of PetroOxy and its correlation with the Rancimat method

The current trend of reducing greenhouse gas emissions and carbon footprint as well as legislation requirements means an increase in the effort to replace fossil fuels by using renewable sources. One of the possibilities is usage of methyl esters (FAME or UCOME) as a bio-component in diesel fuel. Now the maximum FAME content in diesel is 7 vol% (according to the standard EN590 – B7). Increasing the proportion of FAME means a deterioration in oxidation stability. FAME is produced by the transesterification of the triglycerides present in vegetable oils. A major disadvantage of biodiesel (FAME) is ability to be slowly oxidised by air oxygen. Oxidation products may impair fuel properties, quality and engine performance. This is the reason why the oxidation stability of diesel and biodiesel is an important quality parameter. It could be detected using several methods, for example: Rancimat, PetroOxy or thermal techniques. The Rancimat method is intended for biodiesel and for diesel with a minimum 2 vol% content of FAME as mentioned in the standards EN 590 and EN 14214. The disadvantage is the time required for this method (more than 8 h for biodiesel and 20 h for diesel). The PetroOxy is shorter and its results can be converted to Rancimat stability. The set of 75 samples (40 samples of B7 and 35 samples of FAME) was measured using both mentioned methods. Three values of oxidation stability were determined for all of the analysed samples. In the first laboratory, oxidation stability of the samples was measured using both methods. In the second laboratory, oxidation stability was measured using only the PetroOxy. The PetroOxy results from both laboratories were compared with a high correlation value (R2 = 0,954). In the next step, outliers were removed from dataset. Experimental results of the Rancimat method were correlated with recalculated values of PetroOxy method from both laboratories. Correlation equation provided by the manufacturer of PetroOxy was used for recalculation of PetroOxy results to Rancimat results at first. Measured results were then compared with recalculated results. The largest difference in results was found in the B7 samples. Because of these differences the correlation equation between PetroOxy and Rancimat was optimized. Two different equation were made (for each laboratory). The recalculated oxidation stability results were compared with the primary results from Rancimat. The newly correlated values showed a higher degree of agreement with the experimental data than when the results were recalculated using the correlation equation provided by manufacturer. These optimized correlation equation have proven to be more suitable for industrial laboratories.

Influence of binary, ternary and quaternary mixtures on oxidative stability and study of kinetics and thermodynamic parameters of the degradation process of soybean biodiesel

Currently, studies show that plant extracts may exert antioxidant action and have aroused great interest because they have the property of preventing or minimizing the oxidative stress caused by free radicals. This study concerning to the binary, ternary and quaternary mixtures of plant extracts and the natural antioxidant quercetin with soybean biodiesel in concentrations ranging from (500 to 3000 ppm), using the acceletated oxidation techniques (Rancimat and PetroOXY), where the temperatures varied from 90 °C to 140 °C. The stabilizing factor was studied and indicated the existence of an antioxidant effect and not an antagonistic effect. Among the extracts the highest quantitative levels of flavonoids and total carotenoids were obtained in the following decreasing sequence: oregano extract (OE) > basil extract (BAE) > bilberry extract (BE), while for antioxidant activity front the DPPH radical the decreasing sequence was: oregano extract (OE) > bilberry extract (BE) > basil extract (BAE). The activation energies of the antioxidant mixtures were obtained by the Arrhenius equation and followed the ascending order: OEQC (62.69 kJ/mol) < BOBE (65.01 kJ /mol) < BAEQC (77.15 kJ/mol) < BEQC (77.73 kJ/mol) < BOBEQC (81.73 kJ /mol) by the technique Rancimat and BEQC (40.90 kJ/mol) < OEQC (41.82 kJ/mol) < BAEQC (42.32 kJ/mol) < BOBEQC (44.48 kJ/mol) < BOBE (45.31 kJ/mol) by the technique PetroOXY. The thermodynamic parameters ΔH* and ΔS*, were obtained by the Eyring equation and the ΔG* by the fundamental equation of thermodynamics, being evident, by the results shown, the existence of an endothermic and non-spontaneous process. The shelf life of antioxidant mixtures with biodiesel followed the descending order: BAEQC > BEQC > OEQC > BOBEQC > BOBE and OEQC > BAEQC > BEQC > BOBEQC > BOBE in the Rancimat and PetroOXY method, respectively. Therefore, the use of mixtures of these natural antioxidants was very promising and of fundamental importance in the control of the oxidative process of soybean biodiesel.

Oxidative Stability of Acylated and Hydrogenated Ricinoleates Using Synthetic and Natural Antioxidants

As increasing environmental policies constrains are imposed, the demand for biodegradable products also increases. Although vegetable oils present some properties that favor its use for formulation of a bio-based lubricant, its poor resistance to oxidation hinders its application as such. In this study, the thermo-oxidative stability of bio-based products was compared to petroleum-based lubricants and vegetable oils through the PetroOXY method. Chemical modifications in the ricinoleic acids were carried out using long-chain alcohols in esterification reactions. Acetates were obtained from ricinoleates with and without hydrogenation steps. Additionally, commercial antioxidants and phenolic compounds (saturated and unsaturated cardanol) obtained from cashew nut shell liquid were added to the synthesized samples with higher induction times. The results show that the chemically modified bio-based products exhibited improved oxidative stability (up to 6 times) and depressed pour point (−42°C) when compared to pure castor oil. Overall, the addition of antioxidants increased from 6 to 20 times the oxidative stability of the bio-based products. Propyl gallate and saturated cardanol showed higher efficiency for retarding the oxidative process of bio-based samples than the commercial antioxidants.

Accelerated oxidation of fresh and stored biodiesel samples obtained from castor and soybean oils using the petrooxy method

In this study the accelerated oxidation of biodiesel obtained by transesterification of castor and soybean oil was evaluated for fresh samples and compared with the same samples after ca. one year of storage under controlled conditions. The oxidation kinetics of the samples was accelerated using the PetroOXY method at temperatures of 100, 120 and 140 °C and initial oxygen pressure of 700 kPa. Total acid number (TAN) of the samples at increasing accelerated oxidation times (up to 60 min) was used to follow the kinetics behavior for both castor and soybean biodiesel. A steep increase in total acid number of soybean biodiesel oxidized at 140 °C (reaching values up to 100 mg KOH/g) was observed. For biodiesel samples from castor oil, values of less than 20 mg KOH/g were reached under the same conditions. For castor biodiesel, kinematic viscosity and specific gravity were also evaluated with increasing accelerated oxidation times. Our results indicate that the oxidative stability after one year of storage for soybean biodiesel was more affected than for castor oil biodiesel.

Study of the kinetic and thermodynamic parameters of the oxidative degradation process of biodiesel by the action of antioxidants using the Rancimat and PetroOXY methods

The addition of antioxidants to biodiesel, as well as the elimination of conditions favoring the initiation of the oxidation reaction, can inhibit or retard the oxidative process. In this work, we present a comparative study of the antioxidant activity of extracts of bilberry (BE), oregano (EO), and basil (BAE), quercetin (QC) and pyrogallol (PY) in biodiesel derived from soybean oil. The oxidation stability of the samples was studied using the Rancimat and PetroOXY methods under 90, 100, 110, 120, 130 and 140 °C. Among the extracts, the highest total phenolic contents were found in the oregano extract, followed by the basil and bilberry extracts. The apparent activation energy for the consumption of the antioxidants was determined by the Arrhenius equation. The substrates were ranked in the descending order of PY (81.39 kJ mol−1) > QC (77.73 kJ/mol) > BE (63.85 kJ/mol) > BAE (62.02 kJ/mol) > OE (52.04 kJ/mol) for the Rancimat method and PY (79.64 kJ/mol) > QC (68.92 kJ/mol) > BE (45.31 kJ/mol) > OE (44.48 kJ/mol) > BAE (41.98 kJ/mol) for the PetroOXY method. Parameters such as enthalpy, entropy, and Gibbs free energy indicated a non-spontaneous endothermic process, as expected for antioxidant samples. The shelf-life of the samples was predicted as: PY > QC > BE > BAE > OE and PY > QC > OE > BE > BAE for Rancimat and PetroOXY methods, respectively. Considering the sensibility and the analysis time, both methods meet the necessary requirements for the stability evaluation of biodiesel samples.

Oxidation stability of biodiesel fuel produced from Jatropha Curcas L using Rancimat and PetroOXY method

ABSTRACT In the present work, the oxidation stabilities of oil biodiesel fuel from Jatropha curcas L were investigated by using both Rancimat and PetroOXY test method. Three types of conventional antioxidants, i.e. butylated hydroxytoluene, 6,6-di-tert-butyl-2,2-methylenedi-p-cresol, and commercialized amine, were employed and the oxidation stability effects of those additives were examined. Oxidation stability was influenced differently depending on the type of antioxidants and their concentrations. The obtained experimental data from Rancimat and PetroOXY test methods resulting in a linear correlation at various mixtures shows the potential use of PetroOXY test method for future analytical oxidation stability test. In this research, the changes in the chemical properties of fuel sample, such as: peroxide value, acid value, composition, and kinematic viscosity, obtained from the experimental work were thoroughly discussed.

Rancimat and PetroOxy oxidation stability measurements of rapeseed oil methyl ester stabilized with hydrazides and antioxidants

Fossil fuels are still one of the world’s major sources of energy. Because of their reduced availability in the future, however, renewable resources like biodiesel provide an attractive substitute to meet the growing demand for energy supply. Significant problems associated with the use of biodiesel are low its oxidation stability and a higher NOx emission tendency. It was shown by Bär et al. (2017) [1] that 2,4,6-tris-isopropylbenzoic acid hydrazide and benzoic hydrazide can act as antioxidants in distilled biodiesel. Simultaneously, hydrazides showed the potential to lower NOx emissions [2]. In this context, 14 additional hydrazides and four phenolic antioxidants were tested for their antioxidant properties by using the Rancimat method (DIN EN 15751) and PetroOxy method (DIN EN 16091). All hydrazides were employed at a concentration of 7.26 mmol/kg, which corresponds to approximately 1000 ppm of benzoic hydrazide. It is shown that all hydrazides increase the oxidation stability. The Rancimat tests verified that m-anisic hydrazide was most effective and extended the induction period by 16.0 h, whereas isonicotinic hydrazide showed a maximum induction period extension of 24.47 min in the PetroOxy tests. Differences in measurement principles, temperatures and oxygen partial pressures of both methods might explain the varying result. However, the phenolic antioxidant 2,2′-methylenebis(6-tert-butyl-4-methyl-phenol) increased the induction period from 3.7 h for neat RME to a maximum of 21.2 h in the Rancimat test and from 16.18 min to a maximum of 71.91 min in the PetroOxy test.

Evaluation of the oxidation stability of biodiesel stabilized with antioxidants using the PetroOXY method

In this paper, the PetroOXY method has been mainly used to determine the oxidation stability of biodiesel stabilized with five synthetic antioxidants. The differences in the antioxidant activity of these phenolic compounds could be clearly distinguished with this method. Pyrogallol (PY) and propyl gallate (PG) prove more efficient in inhibiting biodiesel oxidative degradation than butylated hydroxyanisol (BHA) and butylated hydroxytoluene (BHT). BHT and BHA act more efficiently in the PetroOXY test than in the Rancimat method with regard to stabilization factor. Tert-butylhydroquinone (TBHQ) displays the weakest antioxidant activity in PetroOXY, inconsistent with the best stabilizing effects shown in the Rancimat method. The influence of reaction temperature on the induction period is very pronounced. From the plots of logarithm of induction period against temperature, the storage life of biodiesel at ambient temperature can be predicted with the extrapolation method, and the temperature sensitivity of these antioxidants can also be obtained. Changes in the mechanism of the oxidation process with the introduction of antioxidants may give variations in the temperature dependence.

The effect of binary antioxidant proportions on antioxidant synergy and oxidation stability of Jatropha and Karanja biodiesels

Oxidation has been measured a major problem for biodiesel commercialization. Auto-oxidation takes place when exposed to air, heat, light and metallic contaminants which affects adversely the fuel characteristics of biodiesel. Addition of synthetic antioxidants generally improves the oxidation stability of biodiesel; however the use of large concentration of additives makes the process uneconomical. This study investigates the effectiveness of individual as well as binary antioxidants to improve the oxidation stability of Jatropha and Karanja biodiesels. Antioxidant synergy was investigated using 500, 600 and 700 ppm of antioxidant combinations namly Pyrogallol:Propyl gallate (PY:PrG), Pyrogallol:tert-butyl hydroquinone (PY:TBHQ) and Pyrogallol:Butylated hydroxyanisole (PY:BHA) at weight ratios of 9:1, 3:1, 2:1, 1:1, 1:2, 1:3 and 1:9, respectively. It was observed that higher blends of binary mixture produced negative synergy, however the best antioxidant synergy showed by the binary systems of PY:PrG, and PY:TBHQ, when the additives are mixed at 1:3 weight ratios; whereas binary mixture of PY:BHA resulted in complete antagonism. However, the effectiveness of the binary system on oxidation stability was found in order of 1:3/3:1 > 1:2/2:1 > 1:1 > 1:9/9:1. The efficacy of antioxidant combinations was evaluated by using pressurized PetroOXY method. Further the dependency of oxidation stability and antioxidant synergy on the fatty acid composition of biodiesel was also observed.

Influence of Phenols on the Oxidation Stability of Home Heating Oils/FAME Blends

The formation of deposits in fossil and biogenic home heating oils as well as in their blends is well-known. As a result, sediments can plug filters and nozzles in heating systems and thus cause operability problems. Different kinds of compounds are presumed to be involved in these processes. It is well-known that phenols play an important part but, on the other hand, phenols are also known to act as antioxidants that delay the oxidation of fuel compounds, and thus the formation of reactive products. To study the antioxidant effect of different phenols, model fuels (biogenic, fossil and a 10% v/v blend) were doped with several representatives of this class of compounds. The samples were artificially aged using the PetroOXY (DIN EN 16091) method. The induction time was recorded and gave information on the impact of the tested substance on the model fuel. Infrared spectrometry was used to investigate the oxidation products. Furthermore, the phenols of a commercial heating oil were extracted and then the oil...

Oxidation stability of biodiesel fuels and blends using the Rancimat and PetroOXY methods. Effect of 4-allyl-2,6-dimethoxyphenol and catechol as biodiesel additives on oxidation stability.

In the present work, several fatty acid methyl esters (FAME) have been synthesized from various fatty acid feedstocks: used frying olive oil, pork fat, soybean, rapeseed, sunflower, and coconut. The oxidation stabilities of the biodiesel samples and of several blends have been measured simultaneously by both the Rancimat method, accepted by EN14112 standard, and the PetroOXY method, prEN16091 standard, with the aim of finding a correlation between both methodologies. Other biodiesel properties such as composition, cold filter plugging point (CFPP), flash point (FP), and kinematic viscosity have also been analyzed using standard methods in order to further characterize the biodiesel produced. In addition, the effect on the biodiesel properties of using 4-allyl-2,6-dimethoxyphenol and catechol as additives in biodiesel blends with rapeseed and with soybean has also been analyzed. The use of both antioxidants results in a considerable improvement in the oxidation stability of both types of biodiesel, especially using catechol. Adding catechol loads as low as 0.05% (m/m) in blends with soybean biodiesel and as low as 0.10% (m/m) in blends with rapeseed biodiesel is sufficient for the oxidation stabilities to comply with the restrictions established by the European EN14214 standard. An empirical linear equation is proposed to correlate the oxidation stability by the two methods, PetroOXY and Rancimat. It has been found that the presence of either catechol or 4-allyl-2,6-dimethoxyphenol as additives affects the correlation observed.

Use of natural antioxidants in soybean biodiesel

The antioxidant activity of curcumin and β-carotene was studied as a method to control the oxidative process of methyl soybean biodiesel during a 180-day storage period. Initially, the antioxidant activity of curcumin and β-carotene against radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) was tested. Curcumin reduced the concentration of DPPH by 90% whereas β-carotene reduced it by 15%. The antioxidant activity was determined through both the Rancimat and Petro-OXY methods. Results obtained from the two methods were consistent. They showed that curcumin increased the induction period of biodiesel by 83%, indicating the potential use of this antioxidant on an industrial scale. However, the study showed that β-carotene acts as a pro-oxidant, reducing the induction period of biodiesel when subjected to the Rancimat and Petro-OXY tests.

Antioxidant Stability in Vegetable Oils Monitored by the ASTM D7545 Method

AbstractThe PetroOXY method was used to evaluate the kinetics of oxidation of two edible vegetable oils, extracted from moringa and passion fruit. This method, which uses pure oxygen at 700 kPa is effective and fast and our experiments were carried out at temperatures 110–140 °C with BHA antioxidant additive concentration ranging from 0 to 500 ppm. Moringa and passion fruit oils followed first‐order kinetics although, in the case of passion fruit oil, mathematical approximations in the first‐order kinetic expression resulted in a final equation that could also be interpreted as deriving from zero‐order kinetics. The higher stability of moringa oil was characterized by an activation enthalpy ca. 50 % higher than the one related to passion fruit oil.

Comparative study of biodiesel oxidation stability using Rancimat, PetroOXY, and low P-DSC

Oxidation stability of biodiesel is one of the most important factors used to evaluate its quality, allowing its commercialization and ensuring its shelf life. In this context, several accelerated methods have been used to measure oxidative stability to predict the maximum storage time at which biodiesel can be submitted without compromising its quality. In the present study, the oxidation stability of two commercial biodiesel and of their blends with two antioxidants was evaluated using the standard methods described in the EN 14214 norm (Rancimat Method) and in ASTM D7545 (PetroOXY method), as well as by low pressurized differential scanning calorimetry (low P-DSC). Both biodiesel were obtained from soybean oil, produced by methylic and ethylic route. The antioxidants, which were used in different concentrations, have the following active components: bisphenol and phenol. The three assessed methodologies can be used to determine the effect of the commercial antioxidants on the oxidative stability of the studied biodiesel. As each method is based on the measurement of different parameters to obtain the respective oxidation induction time, their results cannot be compared directly. But when the results are expressed in terms of the percentage change of the respective oxidation induction times, there is a higher correlation between those obtained by Rancimat and PetroOXY methods than when compared with the results obtained by low P-DSC. Because of their characteristics, the bisphenolic antioxidant is more effective than the phenolic one and, at a same antioxidant concentration, the oxidation stability of the ethylic biodiesel is higher than that of the methylic one. Considering analysis time and sensitivity, the low P-DSC method is the one that better attends both parameters among the applied methods.

Efficient Antioxidant Formulations for Use in Biodiesel

Biodiesel has a lipid origin; thus, antioxidants commonly used in oils and fats have been adopted for the improvement of the oxidative stability of biodiesel. However, these antioxidants have not shown the same efficiency when they are applied to biodiesel. This fact points out the need to investigate additives that warrant the oxidative stability of biodiesel, especially during long storage periods. In this paper, antioxidant formulations were developed for application in biodiesel, from blends including the synthetic antioxidants butylated hydroxytoluene (BHT), tert-butylhydroquinone (TBHQ), the chelating agent citric acid, and organic rosemary extracts. The antioxidants were applied at different concentrations and combinations and were evaluated by the Rancimat method, EN 14112, and by the pressurized PetroOXY method. The results showed that for ethanol soybean biodiesel, the antioxidant compositions formed by TBHQ (2000 mg kg–1) and citric acid (500 mg kg–1) and by the chloroform rosemary extract (2000 mg kg–1) and citric acid (500 mg kg–1) were the most effective in delaying the oxidative process, in a manner independent of the evaluation method. For the methanol cottonseed oil biodiesel, the best result was obtained using the combination of 1500 mg of TBHQ with 1500 mg of ethanol rosemary extract. However, the formulations using low concentrations of rosemary ethanol extract and citric acid induction periods of >6 h were obtained, reaching the limit specified by European Standard EN 14214.