Marilena Meira

Determination of the oxidation stability of biodiesel and oils by spectrofluorimetry and multivariate calibration.

Oxidation stability is an important quality parameter for biodiesel. In general, the methods used to evaluate the oxidation stability of oils and biodiesels are time-consuming. This work reports the use of spectrofluorimetry, a fast analytical technique, associated with multivariate data analysis as a powerful analytical tool to prediction of the oxidation stability. The prediction of the oxidation stability showed a good agreement with the results obtained by the EN14112 reference method Rancimat. The models presented high correlation (0.99276 and 0.97951) between real and predicted values. The R(2) values of 0.98557 and 0.95943 indicated the accuracy of the models to predict the oxidation stability of soy oil and soy biodiesel, respectively. The residual distribution does not follow a trend with respect to the predicted variables indicating the good quality of the fits.

Identificação de adulteração de biocombustível por adição de óleo residual ao diesel por espectrofluorimetria total 3D e análise das componentes principais

Total spectrofluorimetry associated to Principal Components Analysis (PCA) were used to classify into different groups the samples of diesel oil, biodiesel, vegetal oil and residual oil, as well as, to identify addition of non-transesterified residual vegetable oil, instead of biodiesel, to the diesel oil. Using this method, the samples of diesel oil, mixtures of biodiesel in diesel and mixtures of residual oil in diesel were separated into well-defined groups.

Constituintes químicos de Ipomoea subincana Meisn. (Convolvulaceae)

The chloroform extract of aerial parts of Ipomoea subincana was submitted to different chromatographic procedures which afforded methyl caffeate, ethyl caffeate, methyl 3,4-dimethoxycinnamate, lupeol, a-amyrin, b-amyrin, 3-b-O-b-D-glycopiranosyl-sitosterol, b-sitosterol, stigmasterol, scopoletin, aromadendrane-4b,10a-diol, n-docosyl-cis-p-coumarate and n-icosyl-trans-p-coumarate, vanilin, cinamic acid and vanillic acid. However, from the ethyl acetate extract besides quercetin and 3-O-b-D-glycopiranosyl-quercetin were isolated methyl 4-O-E-feruloyl-5-O-E-caffeoyl-quinate, methyl 3,5-di-O-E-caffeoyl-quinate and methyl 4-O-E-caffeoyl-quinate. The structures of the compounds were established on the basis of spectral data.

Triterpenos e ferulatos de alquila de Maprounea guianensis

This work describes the phytochemical study of hexane extracts from the stem of Maprounea guianensis. Besides 3-oxo-21a-H-hop-22(29)-en (moretenone), b-sitosterol, lupenone and lupeol, a mixture of dodecosyl, tetracosyl, hexacosyl, octacosyl and triacontyl ferulates was also isolated, as well as 3-b-acetoxy-lup-20(29)-en-28-oic acid, 3b-O-trans-p-coumaroyl-lup-20(29)-en-28-oic acid and 3b-O-trans-p-coumaroyl-urs-12-en-28-oic acid. The structures of these compounds were established by spectroscopic analysis.

Development of a spectrofluorimetry-based device for determining the acetylene content in the oils of power transformers.

Power transformers are essential for a functioning electrical system and therefore require special attention by maintenance programs because a fault can harm both the company and society. The temperature inside a power transformer and the dissolved gases, which are primarily composed of acetylene, are the two main parameters monitored when detecting faults. This paper describes the development of a device for analyzing the acetylene content in insulating oil using spectrofluorimetry. Using this device introduces a new methodology for the maintaining and operating power transformers. The prototype is currently operating in a substation. The results presented by this system were satisfactory; when compared to chromatographic data, the errors did not exceed 15%. This prototype may be used to confirm the quality of an insulating oil sample to detect faults in power transformers.

Validation of LED spectrofluorimeter for determination of both biodiesel and nontransesterified residual cooking oil in diesel samples

This paper presents the results of the validation of a LED spectrofluorimeter patented for the analysis of biodiesel in diesel and non-transesterified residual cooking oil (RCO) in diesel. Detection limit, quantification limit and sensitivity were determined from the regression lines. The spectrofluorimeter validated in this study was adequate for quantifying the amount of biodiesel in diesel in the range from 2% to 45% (B02-B45) with an R-squared value of 0.9962 and a detection limit of 3%. For the analysis of non-transesterified RCO in diesel, the linear range was from 2% to 20% with an R-squared value of 0.9872 and a detection limit of 2%. The accuracy of the equipment for the analysis of biodiesel in diesel and non-transesterified RCO in diesel was evaluated using Students t-test for paired data. With 95% confidence level there was no significant difference between the actual values and those determined by the equipment.

Oxidative degradation and corrosiveness of biodiesel

Abstract Biodiesel fuels are attracting increasing attention worldwide as an environmentally friendly fuel. Despite the numerous advantages of biodiesel compared with diesel, some studies indicate that biodiesel is more susceptible to oxidation and therefore more corrosive to metals. The research indicates that stainless steel, cast iron, galvanized steel, carbon steel, and aluminum materials are relatively compatible with pure biodiesel, whereas copper, bronze, brass, lead, tin, zinc, and iron are incompatible, decreasing the stability of biodiesel and increasing its corrosiveness. The use of synthetic antioxidant additives for biodiesel is a necessity to minimize its susceptibility to oxidation. The efficiency of a given antioxidant depends on the feedstock used for biodiesel production. In general, the effectiveness of order of antioxidants was pyrogallol>propyl gallate>Ethanox4760E>N,N′-di-sec-butyl-p-phenylenediamine>2,2′-methylene-bis-(4-methyl-6-ter-butylphenol)>2-tert-butyl-4-hydroxyanisole and 3-tert-butyl-4-hydroxyanisole>2-(1,1-dimethylethyl)-1,4-benzenediol [tert-butylhydroquinone (TBHQ)]∼2,6-bis(1,1-dimethylethyl)-4-methylphenol>2,5-di-tert-butyl-hydroquinone>α-tocopherol. There are few studies showing the effect of inhibitors on the corrosion of metals in biodiesel. Antioxidant compounds may also act as a corrosion inhibitor, but the mechanism of action of these corrosion inhibitors is the formation of a persistent adsorbed monolayer film at the metal/solution interface. For example, the antioxidant TBHQ used in biodiesel retarded the corrosion process in copper, carbon steel, and galvanized steel, acting as a corrosion inhibitor through the formation of a protective film layer.

Prediction of properties of biodiesel-diesel blends using spectrofluorimetry and multivariate calibration

AbstractRegressions based on fluorescence spectroscopy were developed to provide relatively inexpensive and rapid measurements of the concentration, viscosity, and specific gravity of biodiesel-diesel blends. The methods involved obtaining a mathematical model from spectrofluorimetric data and data from a given property (concentration, dynamic viscosity, or specific gravity) using partial least squares (PLS) regression, which was then applied as a model for predicting properties of interest. The predicted concentrations, dynamic viscosities, and specific gravities of the biodiesel-diesel blends were compared with actual values and agreed reasonably well with the obtained results. The models showed high correlation between real and predicted values. The R-square values near 1 indicated excellent model accuracy for predicting concentrations, specific gravities, and dynamic viscosities of biodiesel-diesel blends. The residual distribution did not follow a trend with respect to the predicted variables, indicating an excellent fit to the data.

Separation and Identification of Functional Groups of Molecules Responsible for Fluorescence of Biodiesel Using FTIR Spectroscopy and Principal Component Analysis

In order to separate and identify functional groups of molecules responsible for fluorescence compounds present in biodiesel, a column chromatography coupled with infrared spectroscopy and multivariate analysis was performed. A biodiesel sample was packed in a chromatographic column and the fractions obtained were used to perform the analyses. Before undergoing the separation process, the biodiesel sample was analyzed by light emitting diode (LED)-induced fluorescence and compared its spectrum with β-carotene and soybean oil patterns. The low cost and speed of analysis suggest that this technique can be used in the separation of biodiesel substances. The fluorescence emission spectra allowed identifying molecules such as β-carotene, in which the spectrum of its pattern exhibited fluorescence within a region ranging from 500 to 700 nm and chlorophyll molecules. When soybean oil is excited at around 405 nm, it features a fluorescent emission band within the region of 670 nm, which reveals the presence of chlorophyll. Infrared spectroscopy coupled with principal component analysis allowed to discriminate the fractions and to identify the functional groups of compounds present in the sample.

PROSPECÇÃO TECNOLÓGICA EM PROCESSOS DE PURIFICAÇÃO DE BIODIESEL

Um dos problemas associados a producao do biodiesel e a geracao de efluentes resultantes do processo da lavagem deste combustivel com agua. Considerando os problemas ambientais advindos deste processo a busca por novos processos de purificacao vem se tornando uma necessidade para a continuidade do biodiesel na matriz energetica. Desta forma, este trabalho teve como objetivo fazer um levantamento do estado da arte em termos de artigos e patentes abordando metodos alternativos de purificacao por via seca para a remocao de residuos de glicerol, monoglicerideos e diglicerideos ate os limites exigidos pela legislacao. Foram encontrados 319 documentos de patentes na base de dados do Espacenet relacionados a processos de purificacao de biodiesel. No entanto, apenas 25 patentes estao relacionadas a processos alternativos. Segundo a literatura consultada a purificacao por via seca pode substituir com vantagens o metodo tradicional, levando em consideracao a rapidez, a reducao de efluentes gerados e qualidade do produto dentro das normas internacionais.