A.S. Silva

Desidratação da polpa de tamarindo pelo método de camada de espuma

The foam-mat drying process was studied for the tamarind pulp at 50, 60, 70 and 80oC and the temperature effect on the tamarind powder were evaluated as regards to ascorbic acid content, total titratable acidity and colour, expressed by luminosity (L*) and hue (ho). For the representation of the drying process three models for thin-layer were applied and the criterion of evaluation used were the coefficient of determination (R2) and root mean square error (DQM). According to the results the temperature is a determinant parameter in the drying process, and the Midilli and Kucuk model was the best one to represent the behavior of the drying curves. The best results for ascorbic acid content, titritable acidity and colour were obtained at the temperatures of 60 and 70 oC.

DRYING KINETICS OF CORIANDER (Coriandrum sativum) LEAF AND STEM CINÉTICAS DE SECADO DE HOJA Y TALLO DE CILANTRO (Coriandrum sativum)

Abstract The drying kinetics of coriander leaves and stems, with or without blanching, was studied at several temperatures (50, 60, 70, and 80°C) at constant air velocity (1.5 m s−1) in a fixed-bed dryer. Three drying models, Henderson and Pabis, Midilli et al., and the Logarithmic, were fitted to the experimental data. According to the results obtained, it was verified that the increase in the temperature of drying air, increases the drying rate of the coriander leaf and stem. Blanching used as a pre-treatment favors the increase in the drying rate of the stem. The Midilli et al. drying model was found to satisfactorily describe the air-drying curves of coriander leaves and stems. Resumen La cinética del secado de las hojas y tallos de cilantro, con o sin escaldado, se estudió a diferentes temperaturas (50, 60, 70 y 80°C) con velocidad constante del aire (1,5 m s−1) en un secador de lecho fijo. Tres modelos matemáticos: Pabis y Henderson, Midilli et al., y el logarítmico, se ajustaron a los datos experimentales. De acuerdo a los resultados obtenidos, se comprobó que el aumento de la temperatura del aire de secado, aumentó la velocidad de secado de la hoja y tallo de cilantro. El escaldado utilizado como pre-tratamiento, favorece el aumento en la velocidad de secado del tallo. El modelo matemático de Midilli et al. presentó mejor ajuste para los datos experimetales. Palabras clave: Pretratamiento, Coriandrum sativum, escaldado, deshidratacíon

Característica higroscópica e termodinâmica do coentro desidratado

The determination of adsorption isotherms of moisture is an essential factor in the projects and studies of systems for drying, processing, storage, packaging and shelf-time prediction of food products. The adsorption isotherms are obtained by means of variation of moisture content in terms of equilibrium water activity at a constant temperature, and its prediction is performed by the application of mathematical models to experimental data. Through the adsorption isotherms it can be calculated some thermodynamic properties such as isosteric heat of adsorption, which is used in the analysis, development of case study of food and moisture-solid interactions. Thus, this work aimed to study the behavior of adsorption isotherms of leaves and stems of dehydrate coriander, evaluate the model that represents the behavior of the curves and determine the isosteric heat of adsorption. The experimental data were fitted by nonlinear regression, the GAB, Oswin, Smith, BET, Halsey and Peleg models had been used. The models which best represented the behavior of the adsorption curves of the leaf and stem were from Smith and Peleg. The isosteric heat of adsorption obtained from dried leaf is larger than the stem.

Evaluation of Catalyst Ni0.4Cu0.1Zn0.5Fe2O4 on Methyl Esterification of Free Fatty Acid Present in Cottonseed Oil

This study aimed to assess the performance of the solid catalyst Ni0.4Cu0.1Zn0.5Fe2O4, synthesized by combustion reaction, over the methyl esterification reaction of the fatty acids present in cottonseed oil. The catalyst was characterized by XRD, FTIR pyridine absorption, Raman spectroscopy, and SEM. The reactions were conducted at 140 and 180°C with molar ratios of 1:3, 1:6 and 1:9, with 2% of catalyst and reaction time of 2 h. The XRD results showed that the single phase ferrite was obtained with surface area of 87 m2/g and with mesoporous characteristic. It was observed from the FTIR pyridine absorption only the presence of Lewis acid sites. The Raman spectra confirm the presence of the inverse spinel phase. The results indicated that at 180°C and molar ratio of 1:9, the conversion of free fatty acids was about 87%.

Hidrólise de celulose por catalisadores mesoestruturados NiO-MCM-41 e MoO3-MCM-41

This study was carried out to synthesize, characterize and evaluate the application of mesoestruturated catalysts MCM-41, 5%MoO3-MCM-41 and 5%NiO-MCM-41 in the hydrolysis of microcrystalline cellulose. XRD results indicate that the phase of mesoporous MCM-41 was obtained and that the introduction of metal oxides did not affect this mesoporous phase. About the heterogeneous hydrolysis reaction, it was observed that the increase in temperature results in a higher concentration of glucose and the catalyst 5%MoO3-MCM-41 provides the highest concentrations of glucose.

Evaluation of the Processing Conditions in the Transesterification for Biodiesel Production Using the Nanomagnetic Catalyst Ni0.5Zn0.5Fe2O4

Magnetic catalysts are easily removed from the reaction process, thereby reducing the wastewater generation. Therefore, the study proposes to evaluate the performance of the nanomagnetic catalyst Ni0.5Zn0.5Fe2O4 in the transesterification reaction of the soybean oil to produce biodiesel, varying processing conditions (temperature, molar ratio of oil:alcohol and catalyst amount) on the catalytic reaction. The catalyst was synthesized by combustion reaction and characterized by XRD, BET, magnetic measurements and gas chromatography. The results revealed the inverse spinel phase formation, type B(AB)2O4, with isotherm profile classified as type V with hysteresis loop of type 3 (H3), and surface area of 48.39 m2g-1. The magnetic hysteresis curve showed a characteristic behavior of soft magnetic material with saturation magnetization value of 55 emu/g. Chromatographic analysis confirmed that the magnetic nanoparticles are catalytically active and that the processing conditions directly influence the conversion into esters.

Preparação e caracterização de catalisadores ácidos de zircônia sulfatada para aplicação na esterificação do óleo de algodão

This work aimed to produce zirconia by combustion synthesis, to analyze the structure and morphology comparatively with a commercial monoclinic ZrO2, as well as, to investigate the sulfation, aiming to obtain acid catalysts for its use in the esterification of cotton oil for biodiesel. The samples were characterized by X-ray diffraction, scanning electron microscopy (SEM), specific surface area by BET method, infrared spectroscopy (FTIR), thermal analysis (TG/DrTG/DTA), granulometric distribution, pH and chromatography. The synthesized sample evidenced the formation of the monoclinic phase with traces of the orthorhombic phase, while in the commercial sample only the monoclinic phase was observed. In the sulfation process, traces of the tetragonal phase, typical of sulfated zirconia, were observed with the presence of the monoclinic phase in the two samples. With the impregnation of the sulfate ion on the surface of the samples, an increase in the particle size was observed, as seen in the characterization of BET, granulometric distribution and SEM, which also indicated a homogeneous morphology consisting of fine particles of approximately spherical shape for both samples. The chromatography indicated conversion of 65.5 and 91.8% in methyl esters to the synthesized and commercial SO4 2-/ZrO2, respectively. The results indicated that the sulfation increased the acidity, which was evidenced by the decrease in the pH, ranging from 5.12 to 2.65, which contributed significantly to the increase of the conversion, indicating that the SO4 2-/ZrO2 is a promising catalyst in the esterification.

Synthesis of the Magnetic Nanoferrites of Spinel Type and Use in Esterification Reaction for Biodiesel Obtaining

Nanotechnology has been important in improving of the properties of the materials used in the manufacture of magnetic devices, electromagnetic radiation absorbers, cell telephony, pigments and lately in catalysis in transesterification and esterification reactions to biodiesel obtaining. The objective of this work was to synthesize and characterize magnetic materials of spinel type compound of CuFe2O4, CoFe2O4, MnFe2O4, NiFe2O4 and FeFe2O4 and to check the catalytic effect on the methyl esterification reaction of soybean oil. The samples were obtained by combustion reaction and characterized by XRD, FTIR, BET and SEM. The results analysis revealed for nanoferrites the spinel phase formation and higher specific area to the sample CoFe2O4. Generally the samples presented in irregular agglomerates form. All samples were catalytically active in the esterification reaction, with the highest conversion obtained by the sample MnFe2O4 with 57%.

Avaliação catalítica dos espinélios ZnAl2O4 e ZnAl1,9Eu0,1O4 na transesterificação metílica do óleo de soja

Este estudo objetivou avaliar o efeito da dopagem de europio na estrutura e na morfologia do espinelio ZnAl1,9Eu0,1O4 e seu desempenho como catalisador na transesterificacao metilica do oleo de soja. Os pos do espinelio ZnAl1,9Eu0,1O4 foram sintetizados por meio da reacao de combustao e caracterizados por difracao de raios X (DRX), espectroscopia de absorcao optica na regiao do infravermelho com transformada de Fourier (FTIR), microscopia eletronica de varredura e analise termogravimetrica. As reacoes de transesterificacao foram conduzidas a 160 e 180 oC, razao molar oleo/alcool 1:15, 2% de catalisador e tempo de reacao 3 h. Os resultados das caracterizacoes por DRX e FTIR indicaram a fase espinelio do aluminato e duas bandas de absorcao entre 450 e 700 cm-1, caracteristicas da estrutura de espinelio. Os resultados das reacoes de transesterificacao mostraram que a dopagem de ZnAl2O4 com 0,1 mol de europio favoreceu um aumento na conversao catalitica de 15,8% para 68,7%, indicando que os ions europio tornam o catalisador mais ativo. Aumentando a temperatura da reacao de 120 para 180 oC promoveu um aumento consideravel na conversao catalitica de 18,4 para 68,7%, utilizando o catalisador dopado com europio. A conversao do catalisador reutilizado ZnAl1,9Eu0,1O4 mostrou uma reducao em cerca de 31% quando foi utilizado pela terceira vez.

Study of Nanoferrites Ni0,5Zn0,5Fe2O4 and Ni0,1Cu0,4Zn0,5Fe2O4 as Catalysts in the Methyl Transesterification of Soybean Oil

Research with emphasis on substitution of energy sources used in worldwide for renewable energy undoubtedly indicates that the use of biodiesel would be an option to increase the income in rural areas, reduction in oil derivatives spending and also new opportunities for job creation. Soon, in purpose to contribute with the research growth, this research proposes to evaluate the new catalysts performance as nanoferrites Ni0,5Zn0,5Fe2O4 (pure) and Ni0,1Cu0,4Zn0,5Fe2O4 (doped with 0.4 mol of Cu2+) in transesterification reactions of soybean oil methyl. For both samples were synthesized by chemical method in the stoichiometry of the combustion reaction, using urea as a fuel source and a resistance heating coil. During synthesis were measured time and combustion temperature. Later they were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), textural analysis (BET) and subjected to catalytic tests bench. The reaction conditions used in the transesterification were: 10 g of oil, 2 h reaction time, molar ratio of 1:20 oil and alcohol, 4% (w/w) of catalyst and reaction temperature of 160°C. Finally, the reaction product was characterized for conversion into methyl esters by gas chromatography. Results has shown only the presence of the inverse spinel phase, characteristic of Ni-Zn ferrite for both samples, with crystallite size of 26 and 29 nm, respectively. The thermogravimetric analysis has shown that samples are thermally stable, with a weight loss of 4.9 and 3.7%, respectively. The surface area and particle size were 48.89 m2g-1 and 23 nm, and 18.06 m2g-1 and 62 nm, respectively. The conversion results obtained by the transesterification reaction were 13 and 50% Ni0,5Zn0,5Fe2O4 and Ni0,1Cu0,4Zn0,5Fe2O4, respectively, indicating that sample with presence of copper was 26% more effectively, thus being one promising catalyst for the transesterification reaction, which aims to obtain biodiesel.