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The method of acid number determination in used aviation lubricating oil by fourier transform infrared (FTIR) spectrometry was studied. Infrared spectra was pretreated by S-G smoothing and the first derivative, and the respective wave number of 19 point and 17 point were selected respectively. After analyzing the spectral absorption of acid radical and comparing the spectra of new oil and used ones, wave number ranges of 3 597~3 202 cm-1, 2 600~2 250 cm-1 and 920~800 cm-1 were selected to establish model. Calibration model was built with chemometrics methods of partial least square (PLS) and back propagation-artificial neural network (BPANN) respectively. Standard deviation of calibration(SEC) of PLS model was 0. 004, and standard deviation of prediction (SEP) was 0. 005. The accuracy of the model was validated by means of t-test (α = 0.05), and the result of t-test showed that acid number of used aviation lubricating oil could be determined quickly by FTIR spectrometry with advantages of high accuracy and nopollution. [ABSTRACT FROM AUTHOR]

The mechanism of formation and accumulation of high- and low-temperature deposits in internal combustion engine is studied. It is shown that acid number is an important index of engine oil quality, based on which the oil properties that affect the engine reliability can be predicted. [ABSTRACT FROM AUTHOR]

Fuels used for diesel engines besides their main function of energy supply act as a lubricant. In this context the most important task is lubrication of precision pairs injection equipment. In this paper lubricating properties of rapeseed oil esters and camelina esters have been compared. Dependency of the electrical resistance and friction coefficient of the lubrication surface using different types of fuel was analyzed. It was stated, that the highest electrical resistance occurs when lubrication is done with diesel fuel, whereas the friction coefficient is the lowest and it occurs at lubrication with camellia esters. [ABSTRACT FROM AUTHOR]

Due to the high oil content of the seeds, Jatropha curcas L. became a focus of interest in the last decades. In order to prepare the oil for technical applications a refining is essential. This study is concerned with the enzymatic neutralization of aqueous-extracted Jatropha oil utilizing an immobilized lipase from Rhizomucor miehei. Free fatty acids were esterified with glycerol. Factors influencing the reaction were determined applying low acidic oil (acid number 4.2 mg KOH/g oil). Stirring rate of 300 rpm is adequate. The reaction rate was highest at 60°C. Free fatty acid content was reduced continuously with reaction time between 4 and 24 h. The variation of the free fatty acid content of Jatropha oil had only marginal influence on the reaction time. The amount of glycerol added to the reaction system was found to be optimal between 0.15 and 0.25 mol/L. Three percent w/w of immobilized lipase were enough to saturate the reaction system. A strong interaction between enzyme and glycerol content is likely and will be evaluated in an experimental design. The process designed after parameter screening yields acid numbers around 0.2 mg KOH/g oil. Remaining fatty acids are easily removed during the subsequent refining steps. Practical applications: Enzymatic deacidification of Jatropha crude oil described in this study provides several advantages compared to the conventional alkaline process including lower oil losses, no wastewater generation and the avoidance of aggressive chemicals. On the basis of these benefits, an enzymatic approach holds potential to be applied industrially in the future since there is an increasing interest in more sustainable processes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Biodiesel and biolubricant from high-oleic safflower were obtained. • Quality parameters of these products were suitable. • Oxidative stability of biolubricant was short, needing antioxidant addition. • TBHQ had a positive effect and kept biolubricant properties during oxidation. Double transesterification from vegetable oils could play an important role in biodiesel and biolubricant production, with the possible implementation of biorefineries to replace refineries based on petroleum. The oxidative stability of the original sample will influence the quality of the intermediate and final products, recommending highly stable raw materials or the use of antioxidants to keep quality parameters during storage. The aim of this work was to obtain a stable biolubricant, assessing its production through a double transesterification with methanol and pentaerythritol from high-oleic safflower oil and adding antioxidants, paying attention to quality parameters. Consequently, a biorefinery that produced high-quality products was proposed. In conclusion, high biodiesel and biolubricant yields were obtained (>97 and >94%, respectively) with the following chemical conditions for the latter: FAME/alcohol ratio, 1:0.33; pressure, 260 mmHg; catalyst concentration, 1.0%; temperature, 160 °C. The oxidative stability of biodiesel complied with the standard (10.78 h) due to its high methyl oleate content (exceeding 80%), whereas this parameter was shorter for the biolubricant (2.86 h), possibly due to its molecular structure. Consequently, antioxidant addition was needed, and tert -Butylhydroquinone at low concentration (500 ppm) kept viscosity and acid number of high-oleic safflower biolubricant during oxidation conditions (up to 8 h). However, tannic acid did not keep these properties in biolubricant. In conclusion, by using the right antioxidant, all the products of the proposed biorefinery were stable during oxidizing conditions, making this biorefinery more competitive. [ABSTRACT FROM AUTHOR]

Bagasse was subjected to a liquefaction process with polyethylene glycol/glycerol using sulfuric acid as catalyst. The effects of various liquefaction conditions, such as reaction time, liquefaction temperature, catalyst content, and liquid ratio (liquefaction solvents/bagasse), on the liquefied residue (LR) content and hydroxyl and acid numbers of liquefied products were investigated. The preferred liquefaction condition of bagasse was determined through orthogonal experiments. The results showed that the catalyst content and reaction time have a greater influence than liquid ratio and liquefaction temperature on the percentage of LR. The hydroxyl and acid numbers of the liquefied products were influenced by many factors, including liquefaction temperature, reaction time, acid content, and liquid ratio. The hydroxyl number of liquefied products decreased as the liquefaction reaction progressed, but the acid number of liquefied products increased. Based on the obtained data, the kinetics for liquefaction was modeled using the first-order reaction rate law and the apparent activation energy for the liquefaction of bagasse was estimated to be 38.30 kJ mol. [ABSTRACT FROM AUTHOR]

An approach based on the use of the postulates of nonequilibrium thermodynamics for describing oil aging process is proposed for determining the change in the quality of lube oil performance in internal combustion engine. It is shown that the basic characteristics of the oil aging process in the engine are the acid number and the solid phase content in the oil. [ABSTRACT FROM AUTHOR]

Abstract: Acid number is an important quality parameter for biodiesel and biodiesel blends and has been included in various quality standards including ASTM D 6751 and EN 14214. In this paper, a new simple and green potentiometric method based on green chemistry approaches has been developed to determine the acid number of biodiesel and biodiesel blends. This new method uses a reduced amount of titration solvent and recommends the use of a small sample size instead of large sample size as stated in the ASTM reference method D664. A time-efficient electrode cleaning procedure has been developed which completely eliminates the use of toxic solvents for cleaning the electrodes. This proposed green method significantly reduced the maximum % error from 101% to only −18% and repeatability was decreased from 290% to 100% when compared to ASTM D 664 method using the sample size of 2 g. This proposed green analytical method could be used for the determination of acid number of biodiesel and biodiesel blends in R&D as well as in industrial quality control laboratories as a simple, time-efficient, cost effective, and environmentally friendly method for acid number determination. [Copyright &y& Elsevier]

Abstract: Naphthenic acid (NA) present in crude oil leads to corrosion problems within oil refineries. The objective of this study is to reduce total acid number (TAN) from NA using a catalyst-free supercritical methanol (SC-MeOH), a process novel in this area. The reaction was carried out in an 8.8mL batch reactor fabricated from Hastelloy C-276 with respective design temperature and pressure of 500°C and 50MPa. The ability of SC-MeOH to reduce TAN was explored at temperatures from 300 to 350°C and methanol partial pressure (MPP) of 10MPa. Experimental results revealed that TAN removal was 99.77% at a temperature of 350°C, MPP of 10MPa and reaction time of 60min. The TAN removal followed first order kinetics, with Arrhenius parameters of activation energy 5.78kcal/ mol and a pre-exponential factor 1.56s−1. These results suggest that SC-MeOH is capable of reducing TAN from NA with no use of catalyst or additives. [Copyright &y& Elsevier]

The aim of the study was to establish the differences between chemical parameters of shelf life of unpackaged beef tenderloin and beef tenderloin packed in vacuum. Beef tenderloin used in the experiment, derived from 3 Simmental young cattle of average weight of 400 kg, which were slaughtered in an industrial slaughterhouse. Dynamics of sample testing was: day 1 (after packaging), day 7, 14, 21 and 28. During storage, the packaged and unpackaged beef was tested in respect to chemical parameters that would indicate the hydrolytic and oxidative changes. The aw value, pH, acid number, TBA(Tiobarbituric acid) and TVB-N (Total volatile basic nitrogen) values were examined. The highest aw values were measured on day 21 of testing, in samples of packaged tenderloin from the first and third cycle, while the lowest aw value was recorded on day 21 in samples of packed tenderloin from the second test cycle. All of the samples showed a decrease in pH during the first 7 days, after which the pH value increased and in 14 day it was similar in packaged and unpackaged meat samples. During the investigated study period, acid value showed a permanent and rapid increase in the unpackaged meat in relation to sluggish increase, which was registered in the packaged meat. Based on the content of malondialdehyde (MAL) the vacuum packed beef tenderloin, in all three cycles, on day 1 of the test showed no presence of secondary oxidation products. In the first two cycles of testing, from the 7 to 21 days, the amount of MAL increased, and in the third cycle, on day 7 and 14 of the test, the significant increase in the MAL content was determined, while on day 21 and 28 of the test, its content significantly decreased. The quantity of TVB-N, on day 1 of the test, in all three cycles of the tested samples of packaged and unpackaged beef tenderloin, was similar, but on day 14 of testing, the content of TVB-N in unpackaged tenderloin was higher compared to the vacuum packaged tenderloin, what indicated to a faster protein degradation in unpackaged meat compared to the vacuum packaged meat. When the results obtained for the chemical parameters from the all three cycles are taken into accounts, it can be concluded that the shelf life of the unpacked beef was 14 days and for vacuum packed tenderloin 21 days. [ABSTRACT FROM AUTHOR]

Abstract: A new method is proposed for determining the acid number (AN) of biodiesel using coulometric titration with potentiometric detection, basically employing a potentiostat/galvanostat and an electrochemical cell containing a platinum electrode, a silver electrode, and a combination pH electrode. The method involves a sequential application of a constant current between the platinum (cathode) and silver (anode) electrodes, followed by measuring the potential of the combination pH electrode, using an isopropanol/water mixture as solvent and LiCl as the supporting electrolyte. A preliminary evaluation of the new method, using acetic acid for doping a biodiesel sample, showed an average recovery of 100.1%. Compared to a volumetric titration-based method for determining the AN of several biodiesel samples (ranging from about 0.18 to 0.95mgg−1), the new method produced statistically similar results with better repeatability. Compared to other works reported in the literature, the new method presented an average repeatability up to 3.2 times better and employed a sample size up to 20 times smaller. [Copyright &y& Elsevier]

Abstract: A new method is proposed to determine the acid number (AN) of ethanol fuel using coulometric titration with potentiometric detection. The method employs a potentiostat/galvanostat and an electrochemical cell containing a three-electrode system (Pt working electrode, Ag auxiliary electrode and Ag/AgCl reference electrode) and a glass pH electrode. It involves applying a constant current through the sample (formation of hydroxyl ions), which contains LiCl as supporting electrolyte, and acquiring the potential of the pH electrode. A preliminary evaluation of the method showed that carbon dioxide and metallic cations contribute significantly to the AN, whereas the addition of LiCl has two opposite effects: it increases the AN at low concentrations (unwanted reduction reactions) and decreases the AN due to the removal of some carbon dioxide (increase of polarity). The method was compared to a volumetric/potentiometric titration-based method to determine the AN of different ethanol samples, producing similar average results for the hydrated samples and lower standard deviations between replicates. [Copyright &y& Elsevier]

Abstract: Structural characterization of corn stalk (CS) factions including whole stalk, ear husk, leaf blade, stem bark and stem pith was conducted. Different fractions were liquefied by solvolysis liquefaction method. Acid number, hydroxyl number and insoluble residues ratios (IRR) of liquefied products from CS factions were monitored. Results showed chemical compositions of CS fractions had remarkable difference. Cellulose, hemicellulose and lignin accounted for 36.9–41.43%, 21.77–37.3% and 3.38–7.52% of the raw material, respectively. Acid numbers increased with increasing time from 30 to 90min, whereas hydroxyl numbers decreased gradually, IRR decreased and then increased. However, properties of liquefied products differed remarkably. Higher acid number, higher hydroxyl number, and lower IRR were detected from ear husk liquefied products. This is coincident with the higher content of hemicelluloses in ear husk. This work proved that whole utilization process is unsatisfactory in solvolysis liquefaction and different fractions of CS should be given themselves optimum applications. [Copyright &y& Elsevier]

We have studied the effect of the biodegradable polymer TPA (Thermal Polyaspartate Anion) on the acidity of diesel fuel and its blends with biodiesel. We determine the effectiveness of the polymer based on the acid number of the polymer/fuel composition. The results show that the acid number is significantly reduced when the polymer is added, i.e., the quality of the fuel is improved. [ABSTRACT FROM AUTHOR]

The acidity of low and high free fatty acid containing feedstock varieties and biodiesel production intermediary products were tested using a variety of standard methods by the use of manual and automatic titration apparatus. The objective was to select the optimal test method for intermediary products in biodiesel processing and to optimize the selected technique by reducing the extent of bias. We found that there are two major reasons for variations in electrode potential readings. Colloid chemistry has an impact on the initial phase of titration by breakage and reformulation of the partially disperse system. Electric and magnetic fields in the titration beaker were the main reasons for sensitive fluctuations in electrode potentials in the potential range of interest for acid number readings. Refluxing the analyte with the diluting solvent proved to be an efficient technique to offset the influence of colloid processes. Addition of a filter electrolyte to the titration solvent allowed the filter fluctuations to be related to changes in uniformity of electric and magnetic fields in the titration beaker. Addition of filter electrolyte improved signal reliability than shading the external noises by wrapping the titration beaker in aluminium foil. Mathematical interpretation of potential readings revealed the extent of improvement in electrode potential fluctuation by the techniques employed. Both the aqueous and non-aqueous titration are suitable for accurate testing the acid number of biodiesel feedstock and intermediary products. [ABSTRACT FROM AUTHOR]

Due to an increase in the commercial use of biodiesel and biodiesel blends, both ASTM D 6751 and EN 14214 include the acid number (AN) as an important quality parameter. It was found that determination of AN of biodiesel and biodiesel blends using the ASTM D 974 results in large values of repeatability (up to 73.41%) and larger percentage error (up to 42.88%). Therefore, ASTM D 974 has been modified using a lower concentration of base (0.02 M KOH instead of 0.1 M KOH) as well as reducing the amount of toxic titration solvent from 100 mL to only 10 mL. This makes the modified ASTM D 974 as a green analytical method which uses a reduced amount of toxic solvent. This modified method significantly reduced the maximum percentage error from 42.88 to 5.92%. The application of this modified ASTM D 974 for the determination of AN of biodiesel and biodiesel blends was studied. The accuracy of this modified ASTM D 974 for biodiesel (B100) was measured to be within 3.51% over the AN range of 0.313-0.525 mg KOH/g and maximum repeatability was decreased from 8.37 to 2.75% within this AN range which is far below the ASTM D 974 stated repeatability specifications. For B20, B10, B5, B2, and B1, the most accurate values were measured at AN values of 0.177, 0.067, 0.072, 0.126, and 0.096 mg KOH/g, respectively. Excellent linearity values of R for calculated and experimentally determined AN were obtained. The difference between the experimental and the calculated AN for all biodiesel and biodiesel blend samples was within ± 0.018 mg KOH/g. This extensive study has demonstrated that this modified ASTM D 974 is a reliable method for the determination of AN and could be used for establishing the specifications of AN for biodiesel and biodiesel blends ranging from B1 to B20 in quality standards. [ABSTRACT FROM AUTHOR]

Abstract: This paper evaluates analytical methods based on near infrared (NIR) and middle infrared (MIR) spectroscopy and multivariate calibration to monitor the stability of biodiesel. There was a focus on three parameters: oxidative stability index, acid number and water content. Ethylic and methylic biodiesel from different feedstocks were used in experiments of accelerated aging, in order to take into account the wide variety of oilseeds and feedstocks available in Brazil. Partial least squares (PLS) and multiple linear regression (MLR) models were developed. Different pre-processing techniques and spectral variable/regions selection algorithms were evaluated. For MLR models, the successive projection algorithm (SPA) was employed. Interval PLS (iPLS) and selection of variables taking into account the significant regression coefficients were used for PLS models. Results showed that both near and middle infrared regions, and all variable selection methods tested were efficient for predicting these three important quality parameters of B100, the root mean squares error of prediction (RMSEP) values being comparable to the reproducibility of the corresponding standard method for each property investigated. [Copyright &y& Elsevier]

Abstract: The aim of this work is to study the transesterification of vegetable oil with a high acid number at unchanged reaction conditions. Rapeseed oil was used as the raw material and its acid number was changed by the addition of oleic acid (from 0.89 to 12.25mgKOH/g). Methanol was used for transesterification (molar ratio of oil to methanol 1:6) and potassium hydroxide was used as a catalyst. After the reaction time, the residue of the catalyst was neutralised by gaseous carbon dioxide and the methanol excess was removed. After the separation of two phases, each of them was analyzed (in the ester phase: yield, content of methyl ester and acid number; in the glycerol phase: yield, density, viscosity, content of glycerol, soaps, methyl ester, potassium carbonate and hydrogen carbonate). The obtained data was compared with theoretical material balances and the effect on the saponification of oil was discussed. The results show that the yield of methyl ester (biodiesel) is significantly affected by a higher acid number, as well as enhanced soap formation. On the other hand, the conversion of the oil and acid number of the ester phase remain at constant values in studied borders. [Copyright &y& Elsevier]

Abstract: A series of laboratory depletion experiments are conducted at reservoir temperatures with three different live crude oils, as well as mineral oils. These tests examine the role of oil composition on the heavy-oil solution gas drive process. The morphology of gas bubbles, pore pressure, critical gas saturation and oil recovery is compared. Core-level depletion indicates that oil composition plays a role in determining metastability of dispersed gas bubbles in foamy oil. Generally, systems that exhibit effluent gas bubbles on the order of the size of pores tend to recover more oil, all other factors being equal. The concentration of organic acid and base groups as well as asphaltene content of crude oil is measured to characterize each crude-oil sample and develop an understanding of the influence of oil chemistry. Results suggest that significant asphaltene content as well as substantial acid number (the amount of potassium hydroxide in milligrams that is needed to neutralize the acid groups in one gram of crude oil) and base number (the amount of potassium hydroxide in milligrams needed to neutralize the acid titrant for one gram of crude oil) are indicators of whether oil is foamy. The partitioning of acid and base groups between the asphaltene fraction and deasphalted oil is also studied. Organic acid and base groups are clearly present in the asphaltene fraction. The role of such functional groups on oil foam stability is investigated by measuring the lifetime of single foam films formed from crude oil and asphaltene solutions. Transparent micromodels etched with a sandstone pore network and containing gas dispersed within the oil are also used to investigate the correlation of acid number, base number, and asphaltene content on gas-bubble coalescence. The results show that a high concentration of asphaltene that exhibits acid and base functional groups tends to increase foamability and film lifetime of gas/crude-oil dispersions. The deasphalted fraction is not foamy despite possessing significant acid and base number. We conclude that acid and base groups within asphaltene, and their interaction at the gas–oil interface, are a source of interfacial stability. [Copyright &y& Elsevier]

Abstract: The effect of γ-irradiation (4 and 9kGy) and packaging on the lipolytic and oxidative processes in lipid fraction of Bulgarian fermented salami during storage at 5°C was evaluated (1st, 15th and 30th days). No significant differences were observed in the amounts of total lipids (TL), total phospholipids (TPL) and acid number (AN) within the vacuum packed samples of salami treated with 4 and 9kGy during storage. The changes in thiobarbituric acid reactive substances (TBARS) depended mainly on the irradiation dose applied and did not exceed 1.37mg/kg in all groups. The most intensive lipolytic and oxidative processes and the lowest sensory assessment were found in the non-packed irradiated (9kGy) samples. [Copyright &y& Elsevier]

In this article, the corrosion tests are studied for the high acidic crude oil, desalted crude oil, fractions of crude oil, atmospheric residual oil, crude oil of removing acid, viscosity-decreased residual oil, and fractions of viscosity-decreased residual oil. At the same time, the microanalysis of the test samples is performed, that is to say the surface configuration and surface componential of the test samples are observed and analyzed. Through the research of corrosion rules for the high-acidic crude oil, the selecting of equipment materials and the anti-corrosion scheme can be ensured while refining this kind of the high-acidic crude oil. [ABSTRACT FROM AUTHOR]

Over the past 20 years, Fourier transform infrared (FTIR) spectroscopy has evolved to become an important tool for quantitative analysis, and its application to edible oil analysis has been an active area of research. This paper reviews the evolutionary development of methodology for FTIR analysis of edible oils in our laboratory, focusing on strategies and techniques used to quantitate a variety of common edible oil quality control parameters, such as free fatty acid content, iodine value, saponification number, peroxide value, solid fat index, trans content, moisture content, anisidine value, etc., as well as conceptual, instrumental, and software/automation innovations originating in related work on lubricant analysis. In our initial development of FTIR methods for edible oil analysis, the calibration approaches employed were mainly based on partial-least-squares regression using either molecular model systems or process samples. Subsequently, the concept of signal transduction was developed as a means of facilitating the routine implementation of some of these FTIR methods and was also considered for the analytically related lubricant sector. However, the viscosity, complexity, and matrix variability of in-service lubricants required new approaches, while the high sample volumes common to the field made automation a prerequisite. These issues were addressed through the use of signal transduction in combination with dilution as well as extraction techniques to facilitate automation while maintaining quantitation. A related concept, termed spectral reconstitution, was initially developed to speed up the qualitative condition monitoring of in-service lubricants. Spectral reconstitution was subsequently successfully applied to trans analysis in edible oils and was shown to provide a generalized means for high-volume FTIR transmission analysis of viscous oils. This technique has since been adapted to quantitative peroxide value and free fatty acid analysis, allowing for throughputs of up to 120 samples per hour. These developments represent the integration of analytical methodologies for the edible oil and lubricant sectors, with potential for extension to the fuel sector as triacylglycerols become a feedstock for biodiesel. [ABSTRACT FROM AUTHOR]

Acid catalyzed ageing of oil impregnated kraft paper has been studied experimentally. Five different carboxylic acids (formic, acetic, laevulinic, stearic and naphtenic acid) have been added to mineral oil to arrive at a neutralization value of 0,4 mg KOH/g. Thereafter, kraft paper of two different humidities has been allowed to equilibrate with the oil. The results show that the lower the molecular weight of the carboxylic acids is the more is absorbed by the paper. Furthermore, a clear synergy for the paper ageing rates between moisture and the lower molecular weight acids is found, while for the higher molecular weight acids almost no effects were found. It is concluded that present techniques for measuring acidity of oils do not reflect these detailed conditions. It is suggested to introduce a new measuring technique for neutralization value where water rinsing is used to identify the content of low molecular weight, water soluble acids. [ABSTRACT FROM AUTHOR]

Abstract: In this work, low-density polyethylene (LDPE) plastic which is a mager product within plastics and formed a high amount of waste was chosen as a material to be worked. LDPE was both decomposed thermally and catalytic in a continuous reactor via as an oxidative media. Catalytic and thermal processes were investigated at the temperature range of 400–500°C and raw material feeding at a rate of 0.7gmin−1. As a result of degradation, the maximum liquid yield, acid and peroxid numbers of liquid products in thermal and catalytic oxidative media at 400°C temperature and 600mLmin−1 air flow rate conditions have determined as 102%, 28, 52 and 75%, 16 and 43, respectively. In addition, the molecular weight of liquid products were determined by GC/MS system and found that oxygenic compounds for thermal and catalytic oxidative pyrolysis aproximately 50 and 27%, respectively. [Copyright &y& Elsevier]

Coating resin manufacturing requires knowledge of the extent of reaction during resin synthesis so the appropriate actions can be taken (addition of the next reactant, reaction termination, etc.). This article reports the results from experiments conducted to survey the utility of dielectric spectroscopy (DES) as a real-time, in-situ technique to monitor the extent of reaction during synthesis of three low molecular weight resins that are representative of components used in coatings formulations. The resins made were based on very different chemistries: (1) a 100% solids polyacrylate functional oligomer from the Michael reaction between a polyacrylate monomer and an acetoacetate ester; (2) an acrylate fimctional monomer from the reaction between an epoxy ester and acrylic acid; and (3) a solvent-based isocyanate-terminated polyurethane prepolymer from the reaction between a mixture of diols and excess diisocyanate. In all three cases, very good to excellent correlations were found between continuous real-time DES output and the values of characteristic QC parameters (viscosity, acid number, epoxy equivalent weight, % NCO, ATR-FTIR peak heights for reactants and products, and GPC data) determined by off-line analysis of samples taken periodically during the reactions. [ABSTRACT FROM AUTHOR]

Inclusion of high-quality vegetable oils is of great importance for a scientifically balanced diet. Hence, there is a need for analytical techniques that can be used in the control of the purity and authenticity of such oils. Therefore, three reversed-phase HPLC methods were devised for the qualitative and quantitative measurement of fatty acids. These methods were applied to various vegetable oils and are an alternative to often-used gas chromatographic techniques. In the first step, the vegetable oil is hydrolysed, then the free fatty acids obtained are analysed by HPLC without any further derivatization. Omission of the hydrolysis step allows the determination of the amount of free fatty acids in the oils with the proposed methods. The iodine value and the acid number can be calculated from the chromatographic data. [ABSTRACT FROM AUTHOR]

Increasing environmental demands influence the requirements for devices and materials used in the power industry. One example is a power transformer and an electro-insulating liquid used in it. In order to meet these requirements, electro-insulating liquids should be characterized by, inter alia, high biodegradability and good fire properties. One of such liquids is natural ester. However, its oxidation stability is low in comparison to mineral oil and demands improvement, which can be achieved by the addition of an antioxidant. The authors of this work used fullerene nanoparticles for that purpose. Pure natural ester samples were prepared, and samples with two concentrations of fullerene, 250 mg/L and 500 mg/L in natural ester. All these samples were aged in a thermal oxidation process. Thereafter, the aging properties of all the samples were compared to assess the oxidation stability of modified liquids. Moreover, the electrical properties of prepared insulating liquids were investigated to assess if fullerene deteriorates these properties after aging process. Based on the obtained results, it was proved that the aging process slowed down in the case of both fullerene concentrations in ester. The acid number of natural ester modified using fullerene was lower than in the case of pure liquid. [ABSTRACT FROM AUTHOR]

A correlation is established experimentally between the content of oxidation products determined by IR spectroscopy and the acid number of lubricating oils used in gas-pumping units. A new express method is proposed fro determining acid number. [ABSTRACT FROM AUTHOR]

Production of alternative fuels, such as biodiesel, from transesterification of vegetable oil driven by heterogeneous catalysts is a promising alternative to fossil diesel. However, achieving a successful substitution for a new renewable fuel depends on several quality parameters. 1H NMR spectroscopy was used to determine the amount of methyl esters, free glycerin and acid number in the transesterification of soybean oil with methanol in the presence of hydrotalcite-type catalyst to produce biodiesel. Reaction parameters, such as temperature and time, were used to evaluate soybean oil methyl esters rate conversion. Temperatures of 100 to 180 °C and times of 20 to 240 min were tested on a 1 : 12 molar ratio soybean oil/methanol reaction. At 180 °C/240 min conditions, a rate of 94.5 wt% of methyl esters was obtained, where free glycerin and free fatty acids were not detected. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A visual and green titrimetric method is proposed for the determination of the acid number of oils and fats. The sample is dissolved in a water-ethanol mixture (1:1 v/v) and titrated with a 0.02 mol L aqueous NaOH solution. Phenolphthalein is used as acid-basic indicator. Oils of canola, sunflower, linseed, castor, corn and soy as well as swine lard, a total of twelve real samples, were analyzed. The results obtained were compared with those from the application of the AOCS Cd 3d-63 method, through a statistical linear regression procedure at the 95 % confidence level and no evidence for systematic differences between the two sets of results was observed. The mean RSD (relative standard deviation ) for the proposed procedure is 4.8 %, whereas that of the official method was found to be 5.4 %. [ABSTRACT FROM AUTHOR]

Abstract: A green and simple visual method is proposed for the determination of the acid number of biodiesel. The method was compared with that of the AOCS Cd 3d-63. The sample is dissolved in a 1:1 (v/v) ethanol:water mixture and phenolphthalein is added. This method replaces the use of the 1:1 (v/v) toluene:isopropanol mixture as solvent. The titration is performed with a 0.02molL−1 NaOH solution in water, avoiding the 0.1molL−1 KOH solution in isopropanol. A statistical comparison using the Student’s t and the Snedecor F tests showed that the proposed green method offers equivalent results to AOCS Cd 3d-63, with a little better precision. [Copyright &y& Elsevier]