Estimation of the content of fatty acid methyl esters (FAME) in biodiesel samples from dynamic viscosity measurements

In order for biodiesel to be commercialized as pure biofuel or blending stock for diesel fuels, it must meet a set of requirements defined in standard specifications for a safe and satisfactory engine operation, one of these specifications is the content of fatty acid methyl esters (FAME). Besides, this parameter indicates the performance of the transesterification reaction for biofuel production from vegetable oils. There are several methods to determinate FAME content in biodiesel samples (chromatography, nuclear magnetic resonance spectroscopy and FTIR spectroscopy); however, they take long times and high cost for FAME content determination. From a practical point of view, in industrial biodiesel production is usually necessary to estimate the FAME value quickly. This paper presents correlations experimentally obtained from different oil feedstocks in order to estimate the biodiesel FAME content from the biodiesel dynamic viscosity, a fast determination parameter.     

Glycerol removal from biodiesel using membrane separation technology

Membrane separation technology was used to remove free glycerol from biodiesel in order to meet the ASTM D6751 and EN 14214 standards. Fatty acid methyl esters (FAME) produced from canola oil and methanol were purified using ultra-filtration. The effect of different materials present in the transesterification reaction, such as water, soap, and methanol, on the final free glycerol separation was studied. A modified polyacrylonitrile (PAN) membrane, with 100 kD molecular weight cut-off was used in all runs. Tests were performed at 25 °C and 552 kPa operating pressure. The free glycerol content in the feed, retentate and permeate of the membrane system was analyzed using gas chromatography according to ASTM D6584. Results showed low concentrations of water had a considerable effect in removing glycerol from the FAME even at approx. 0.08 mass%. This is four orders of magnitude less than the amount of water required in a conventional biodiesel purification process using water washing. It is suggested that the mechanism of separation of free glycerol from FAME was due to the removal of an ultrafine dispersed glycerol-rich phase present in the untreated FAME. This was confirmed by the presence of particulates in the untreated FAME. The size of the particles and the free glycerol separation both increased with increasing water content of the FAME. The trends of separation and particle size vs. water content in the FAME phase were very similar and exhibited a sudden increase at 0.08 mass% water in the untreated FAME. This supports the conclusion that water increased the size of the distributed glycerol phase in the untreated FAME leading to its separation by the ultra-filtration membrane. The technology for the removal of free glycerol from biodiesel was found to use 2.0 g of water per L of treated FAME (0.225 mass% water) vs. the current 10 L of water per L of treated FAME.     

Conversion of biomass to fuel: Transesterification of vegetable oil to biodiesel using KF loaded nano-γ-Al2O3 as catalyst

KF-impregnated nanoparticles of γ-Al₂O₃ were calcinated and used as heterogeneous catalysts for the transesterification of vegetable oil with methanol for the synthesis of biodiesel (fatty acid methyl esters, FAME). The ratio of KF to nano-γ-Al₂O₃, calcination temperature, molar ratio of methanol/oil, transesterification reaction temperature and time, and the concentration of the catalyst were used as the parameters of the study. A methyl ester yield of 97.7 ± 2.14% was obtained under the catalyst preparation and transesterification conditions of KF loading of 15 wt%, calcination temperature of 773 K, 8 h of reaction time at 338 K, and using 3 wt% catalysts and molar ratio of methanol/oil of 15:1. This relatively high conversion of vegetable oil to biodiesel is considered to be associated with the achieved relatively high basicity of the catalyst surface (1.68 mmol/g) and the high surface to volume ratio of the nanoparticles of γ-Al₂O₃.     

Development and validation of a two phase CFD model for tubular biodiesel reactors

The use of biodiesel as an alternative to diesel has gained increasing momentum over the past 15 years. To meet this growing demand there is a need to optimise the transesterification reactor at the heart of the biodiesel production system. Assessing the performance of innovative reactors is difficult due to the liquid–liquid reaction mixture that is affected by mass transfer, reaction kinetics and component solubility. This paper presents a Computational Fluid Dynamic model of a tubular reactor developed in ANSYS CFX that can be used to predict the onset of mixing via turbulent flow. In developing the model an analysis of the reaction mixture is provided before the presentation of experimental data, which includes flow visualisation results and temperature dependant viscosity and density data for each phase. The detailed data and model development procedure represents an advancement in the modelling of the two phase transesterification reaction used in biodiesel production.     

Experimental analysis of lipid extraction and biodiesel production from wastewater sludge

The most promising renewable alternative fuel, biodiesel, is produced from various lipid sources. Primary and secondary sludge of municipal wastewater treatment facilities are potential sources of lipids. In this study, factorial experimental analyses were used to study the influence of different variables on the lipid extraction and biodiesel production from dried municipal primary and secondary sludge (Adelaide Pollution Control Plant, London, ON, Canada). The empirical models were developed for each factorial analysis. The temperature turned out to be the most significant variable for lipid extraction by using methanol and hexane as solvents. Extraction using methanol resulted in a maximum of 14.46 (wt/wt) % and 10.04 (wt/wt) % lipid (on the basis of dry sludge), from the primary and secondary sludge sources respectively. A maximum of 11.16 (wt/wt) % and 3.04 wt/wt% lipid (on the basis of dry sludge) were extracted from the primary and secondary sludge sources, respectively, using hexane as a solvent. The FAME (fatty acid methyl ester) yield of the H₂SO₄ catalyzed esterification–transesterification of the hexane and methanol extracted lipids were 41.25 (wt/wt) % and 38.94(wt/wt) % (on the basis of lipid) for the primary sludge, and 26.89 (wt/wt) % and 30.28 (wt/wt) % (on the basis of lipid) for the secondary sludge. The use of natural zeolite as a dehydrating agent was increased the biodiesel yield by approximately 18 (wt/wt) % (on the basis of lipid). The effect of temperature and time was also investigated for biodiesel production from the lipid of wastewater sludge. The yield and quality of the FAME were determined by gas chromatography.     

Transesterification of vegetable oil to biodiesel fuel using alkaline catalyst

Biodiesel is gaining more and more importance as an attractive fuel due to the depleting fossil fuel resources. Chemically biodiesel is monoalkyl esters of long chain fatty acids derived from renewable feed stock like vegetable oils and animal fats. It is produced by transesterification in which, oil or fat is reacted with a monohydric alcohol in presence of a catalyst to give the corresponding monoalkyl esters. This article reports experimental data on the production of fatty acid methyl esters from vegetable oils, soybean and cottonseed oils using sodium hydroxide as alkaline catalyst. The variables affecting the yield and characteristics of the biodiesel produced from these vegetable oils were studied. The variables investigated were reaction time (1-3 h), catalyst concentration (0.5-1.5 w/wt%), and oil-to-methanol molar ratio (1:3-1:9). From the obtained results, the best yield percentage was obtained using a methanol/oil molar ratio of 6:1, sodium hydroxide as catalyst (1%) and 60 ± 1 °C temperature for 1 h. The yield of the fatty acid methyl ester (FAME) was determined according to HPLC. The composition of the FAME was determined according to gas chromatography. The biodiesel samples were physicochemically characterized. From the results it was clear that the produced biodiesel fuel was within the recommended standards of biodiesel fuel.     

Technologies for production of biodiesel focusing on green catalytic techniques: A review

Biodiesel production is undergoing rapid technological reforms in industries and academia. This has become more obvious and relevant since the recent increase in the petroleum prices and the growing awareness relating to the environmental consequences of the fuel overdependency. In this paper, various technological methods to produce biodiesel being used in industries and academia are reviewed. Catalytic transesterification, the most common method in the production of biofuel, is emphasized in the review. The two most common types of catalysts; homogeneous liquids and heterogeneous solids, are discussed at length in the paper. Two types of processes; batch and continuous processes, are also presented. Although batch production of biodiesel is favored over continuous process in many laboratory and larger scale efforts, the latter is expected to gain wider acceptance in the near future, considering its added advantages associated with higher production capacity and lower operating costs to ensure long term supply of biodiesel.     

Molecular absorption spectrophotometric method for the determination of phosphorus in biodiesel

A molecular absorption method is proposed for the determination of phosphorus in biodiesel. The samples are mineralized using an ashing procedure at 550 °C followed by dissolution of the residue. The analytical procedure is based on the formation of a blue molybdenum complex. 1-amino-2-naphthol-4-sulfonic acid is used as reducing agent. The method was applied to biodiesel samples prepared from soy, canola and sunflower oils and from bovine fat. The limit of detection is 0.57 mg P kg⁻¹ and the limit of quantification is 1.7 mg P kg⁻¹. The observed mean relative standard deviation is about 5%. The simplicity of the procedure added to its precision, accuracy and low cost suggest that it is an excellent option for the determination of phosphorus in biodiesel.     

Investigation of terminalia (Terminalia belerica Robx.) seed oil as prospective biodiesel source for North-East India

Terminalia (Terminalia belerica Robx.) is available in the northeastern region of India. The fruit of terminalia has some medicinal value and its kernel contains 43% oil. The prospect of terminalia oil for biodiesel production is investigated with reference to some relevant properties. The fatty acid profile of oil extracted from terminalia is found comparable with similar seed oils attempted for biodiesel production in this region. Terminalia oil contains 32.8% palmitic acid, 31.3% oleic acid, and 28.8% linoleic acid. The calorific value and kinematic viscosity of terminalia oil are 37.50 MJ/kg and 25.60 cSt, respectively. The calorific value and cetane number of terminalia FAME are within the acceptable limit of the EN 14214 standard. However, the flash point of terminalia FAME (90 °C) is relatively lower than the minimum required standard. Overall, the properties of biodiesel obtained from terminalia seed conform to the existing biodiesel standard. In addition to assisting the national biodiesel mission, the extension and regeneration of forest areas through terminalia planting would help us to curb the seemingly irreversible trend of de-forestation in the northeast region of India.     

生物柴油特性及作为混合燃料添加剂的研究

论述了生物柴油优越的理化特性,可作为柴油的替代燃料,并讨论了生物柴油作为乙醇（甲醇）与柴油或汽油混合燃料的添加剂情况.通过溶解度测定及三相图实验数据表明生物柴油作为乙醇与柴油添加剂,促溶效果较好;对于生物柴油-汽油-乙醇体系来讲,三者可以任意比例混合,可改善汽油的燃烧性能;对于生物柴油-柴油-甲醇体系,效果不理想.     

Electroanalytical determination of TBHQ, a synthetic antioxidant, in soybean biodiesel samples

This paper reports an electroanalytical method developed for tert-butylhydroquinone (TBHQ) determination in biodiesel in the presence of surfactant Triton X-100 (T-100). T-100 was shown to improve the electroanalytical signal and its use was decisive for direct analysis of TBHQ in biodiesel, only requiring previous dilution of biodiesel samples in methanol. Several parameters were studied and optimized for the development of this methodology. Under optimal conditions, oxidation peak current was proportional to TBHQ concentration in the range of 1.05-10.10 × 10⁻⁶ mol L⁻¹, with limits of detection and quantification of 3.43 × 10⁻⁸ mol L⁻¹ and 1.14 × 10⁻⁷ mol L⁻¹, respectively, by square wave voltammetry (SWV). The results achieved with the proposed method were satisfactory, relative to those obtained using high-performance liquid chromatography (HPLC).     

A critical look at the microalgae biodiesel

The quantitative production of microalgae oil is often overestimated. The cost of the salts invested in the production of 1 kg algal diesel approximates the actual price of 1 kg mineral diesel. Total sum of electrical energy expenses for production of biodiesel from microalgae is several‐fold higher than the energy income from combustion of the same quantity. The biological value of cultivated microalgae as food is much higher than as fuel. An opinion is shared that money ought to be invested in microalgal biomass production as a food additive, forage, and pharmaceuticals. The aim is to prevent making too hasty steps and investments in microalgal biodiesel.     

Theoretical study of the transesterification of triglycerides to biodiesel fuel

The transesterification of various triglycerides was considered in terms of the activation energy obtained from quantum computational chemistry. According to these values, the effect upon the reactivity of the structure of the triglyceride is not particularly large. Moreover, the transesterification reaction is completed via a transition state, in which ring formation consisting of the carbon of the carboxyl and alkoxy groups appears, even if a long-chain alcohol is used as a reactant. Finally, an ideal reaction pathway, in which the ester bond at the center of the triglyceride is transesterified before peripheral ester bonds, was shown by an activation energy analysis and electrostatic potential (ESP) distribution.     

Optimization of <Emphasis Type="Italic">Brassica carinata</Emphasis> oil methanolysis for biodiesel production

Synthesis of FAME from Brassica carinata oil to produce biodiesel was accomplished using potassium hydroxide as the catalyst. A factorial design of experiments and a central composite design were used. The variables chosen were: type of Brassica carinata oil, initial catalyst concentration, and temperature; and the responses were FAME purity and yield. The type of B. carinata oil included high-erucic B. carinata (HEBC) and lowerucic B. carinata (LEBC) varieties. The results show that the type of B. carinata oil does not affect the purity and yield of FAME. However, HEBC oil is more suitable for biodiesel production because its iodine value is lower and within the European Union specifications. The initial catalyst concentration is the most important factor, having a positive influence on FAME purity but a negative effect on FAME yield. The temperature has a significant positive effect on FAME purity and a significant negative influence on FAME yield. Second-order models were obtained to predict FAME purity and yield as a function of catalyst concentration and temperature for HEBC oil methanolysis. The best conditions for this process are 25°C, and 1.2–1.5 wt% for the catalyst concentration.     

Transesterification of soybean frying oil to biodiesel using heterogeneous catalysts

In the present work, the transesterification reaction of soybean frying oil with methanol, in the presence of different heterogeneous catalysts (Mg MCM-41, Mg-Al Hydrotalcite, and K⁺ impregnated zirconia), using low frequency ultrasonication (24 KHz) and mechanical stirring (600 rpm) for the production of biodiesel fuel was studied. Selection of catalysts was based on a combination of porosity and surface basicity. Their characterization was carried out using X-ray diffraction, Nitrogen adsorption-desorption porosimetry and scanning electron microscopy (SEM) with energy dispersive spectra (EDS). The activities of the catalysts were related to their basic strength. Mg-Al hydrotalcite showed particularly the highest activity (conversion 97%). It is important to mention that the catalyst activity of ZrO₂ in the transesterification reaction increased as the catalyst was enriched with more potassium cations becoming more basic. Use of ultrasonication significantly accelerated the transesterification reaction compared to the use of mechanical stirring (5 h versus 24 h).     

New porphyrins tailored as biodiesel fluorescent markers

This work reports the synthesis, characterization, and evaluation of new porphyrins tailored to become biodiesel fluorescent markers. The compounds were obtained by the synthetic modification of the commercially available porphyrin 5,10,15,20-meso-tetrakis(pentafluorophenyl)porphyrin (TPPF₂₀) using ethanol and hexadecan-1-ol (cetylic alcohol) as nucleophilic reagents.The stability of the marked biodiesel fuel solutions was investigated every 15 days for a total period of 3 months, and under different storage temperature and light exposure condition, simulating the conventional stock conditions. The influence of the different substituents of the porphyrins on the fluorescence properties of the biodiesel fuel markers was also assessed.The resulting porphyrins were highly soluble in biodiesel fuel and displayed strong fluorescence characterized by two strong emission bands. The fluorescent markers did not affect the biodiesel physical properties and were stable in storage conditions for at least 3 months at a concentration of 4 ppm.The best storage condition was found to be absence of light and 6 °C; the limit of detection by photoluminescence technique had magnitude of 10⁻¹³ mol L⁻¹.The synthesized porphyrins were characterized by nuclear magnetic resonance (¹H-NMR and ¹⁹F-NMR), mass spectrometry (HRMS), ultraviolet visible absorption spectroscopy, and photoluminescence spectroscopy.     

Non-catalytic biodiesel process with adsorption-based refining

Different feedstocks of varying acidity ranks and water contents were subjected to a series of discontinuous steps that simulated a biodiesel production process. The three steps comprised: (i) the non-catalytic transesterification with supercritical methanol at 280 °C; (ii) the distillation of the unreacted methanol, water and volatile products; and (iii) the adsorption of the impurities with adequate adsorbents. Refined soy oil, chicken oil and waste cooking oil were subjected to the same simple procedure. The process produced biodiesel complying with the water, acid, glycerides and methyl esters content specifications of the EN 14214 standard.Biodiesel production by the reaction of oils in supercritical methanol at 280 °C and methanol-to-oil molar ratios of 15 and 20 produced amounts of glycerol as small as 0.02%. This simplified the subsequent refining of the biodiesel and is considered an advantage over the classic alkali-catalyzed process (that produces 10% of glycerol by-product) because washing steps can be spared.The contents of methyl esters, water and free fatty acids showed a volcano pattern when plotted as a function of the reaction time. In the case of the free fatty acids this was attributed to the initial reaction of water and triglycerides to form acids and glycerol that increased the acidity of the product mixture. At longer reaction times these acids were likely transformed into methyl esters or were decarboxylated to hydrocarbons and CO₂. Water formation was attributed to glycerol decomposition and esterification of free fatty acids.The design of a simple process for biodiesel production using a single reaction step with negligible glycerol production and an adsorption-based refining step was thus studied. A possible scheme integrating reaction, methanol recycling, biodiesel purification and heat recovery was discussed. Advantages and disadvantages of process units were analyzed on terms of operating cost and simplicity.     

Life cycle analysis of biodiesel production

Biodiesel has attracted considerable attention as a renewable, biodegradable, and nontoxic fuel and can contribute to solving the energy problems, significantly reducing the emission of gases which cause global warming.The first stage of this work was to simulate different alternative processes for producing biodiesel. The method used for the production of biodiesel is the transesterification of vegetable oils with an alcohol in the presence of a catalyst. The raw materials used were palm oils and waste cooking oil.The second stage was a life cycle analysis for all alternatives under study, followed by an economic analysis for the alternatives that present minor impacts and which are more promising from an economic point of view. Finally, we proceeded to compare the different alternatives from both the point of view of life cycle and economic analysis.The feasibility of all processes was proven and the biodiesel obtained had good specifications.From the standpoint of life cycle analysis, the best alternative was the process of alkaline catalysis with acid pre-treatment for waste cooking oil.The economic analysis was done to the previous mentioned process and to the process that uses raw virgin oils, methanol, and sodium hydroxide. This process has lower investment costs but the process of alkaline catalysis with acid pre-treatment, whose main raw material is waste oil, is much more profitable and has less environmental impacts.     

Predicting the temperature dependent viscosity of biodiesel fuels

The purpose of this work was to develop a method for predicting temperature dependent viscosities of biodiesel based on fatty acid ester composition. The Grunberg-Nissan equation combined with a group contribution method was used as the mixing rule to calculate viscosities of mixtures of fatty acid esters. Prediction errors at 25 °C were less than 2.5% for 22 mixtures of fatty acid ethyl esters. Compared with experimentally measured viscosities at 20-100 °C, predicted viscosities of soybean oil and yellow grease methyl esters were within 3%. For coconut, palm and canola oil methyl esters, maximum errors were underestimations at approximately 7%.     

In situ bismuth-film electrode for square-wave anodic stripping voltammetric determination of tin in biodiesel

A bismuth-film electrode (BiFE) was applied in square-wave anodic stripping voltammetry (SWASV) in order to determine Sn (IV) in biodiesel samples. In situ simultaneous deposition of tin and bismuth at −1.2 V for 90 s was carried out in a supporting electrolyte containing 0.1 mol L⁻¹ acetate buffer (pH 4.5) and 1.73 mmol L⁻¹ caffeic acid as the complexing agent. A single well-defined anodic stripping peak was observed at −0.58 V for the oxidation of Sn to Sn (II), which was used as the analytical signal. The calibration curve was obtained in the concentration range of 0.17–7.83 μmol L⁻¹ with the detection limit being 0.14 μmol L⁻¹ (r = 0.9990). Repeatability and reproducibility for the measurement of the current peak were characterized by relative standard deviations of 3.6% and 4.1%, respectively, for a 5.0 μmol L⁻¹ Sn (IV) solution (n = 10). The method was validated by comparing the results obtained with those provided by application of the atomic absorption spectroscopy technique.