Magnetic pigments composed of SrxBa1-xFe12O19 were prepared using a modified Pechini method. The influence of the calcination temperature and the composition of the solid solution on the structural, colorimetric, and magnetic properties were investigated. XRD patterns showed pigments crystallizing in a magnetoplumbite-type structure after calcination above 900 degrees C. The formation of alpha-Fe2O3 as a secondary phase was also observed in some compositions. Raman and Mossbauer spectroscopy indicated the presence of Fe in different coordination sites, which strongly influenced the magnetic and colorimetric properties of the pigments. A brown colour was obtained for all the magnetic pigments, with a higher saturation when calcination was performed at 900 degrees C. A meaningful increase in saturation was attained for the sample with a Sr0.50Ba0.50Fe12O19 composition, which was related to the short-range disorder and occupancy of Fe3+ cations at different sites. The addition of Sr2+ (up to x = 0.50) to the solid solution improved the intensity of the brown colour by increasing the a* and b* colour coordinates and decreasing L*. Magnetic measurements revealed saturation magnetization values of 56.8 emu g(-1) for BaFe12O19. Upon the addition of Sr2+, an increase in the ferromagnetic behaviour was observed for barium-containing pigments, which indicates the possibility of their use as magnetic pigments in high-density recording media or paints for construction.

Maranhão state in Brazil presents a big potential for the cultivation of several oleaginous species, such as babassu, soybean, castor oil plant, etc... These vegetable oils can be transformed into biodiesel by the transesterification reaction in an alkaline medium, using methanol or ethanol. The biodiesel production from a blend of these alcohols is a way of adding the technical and economical advantages of methanol to the environmental advantages of ethanol. The optimized alcohol blend was observed to be a methanol/ethanol volume ratio of 80 % MeOH: 20 % EtOH. The ester content was of 98.70 %, a value higher than the target of the ANP, 96.5 % (m/m), and the biodiesel mass yield was of 95.32 %. This biodiesel fulfills the specifications of moisture, specific gravity, kinematic viscosity and percentages of free alcohols (methanol plus ethanol) and free glycerin.

According to the Resolution number 7 from the Brazilian National Agency of Oil, Natural Gas and Biofuels (ANP), the official methodologies for free glycerin determination in biodiesel are the ASTM D 6584, EN 14105 and EN 14106 methods. However, these procedures are limited to the analysis of free glycerin in methyl esters and they are not suitable for the analysis of esters from lauric oils. In the present work, a gas chromatographic method was developed for the determination of the amount of free glycerin in ethyl esters from lauric oils, aiming at overcoming the limitations present in the official methods. Moreover, the present method can also be used for ethanol and methanol biodiesel samples from other oily sources. Besides, a methodology that ascertains the content of free glycerin by UV-Vis spectrophotometry was also applied. Both methods were sensitive enough to determine the content of free glycerin in biodiesel, below the limit specified by the ANP, fixed at 0.02 % (200 mg/L), achieving the detection limits of 5.69 mg/L and 2.17 mg/L for the chromatographic and spectrophotometric methods, respectively.

In this study, modifications of alumina surface with of alkaline earth metal oxides were studied, using the polymeric precursor method. The modified compounds were characterized by X-ray diffraction, nitrogen adsorption-desorption and scanning electron microscopy. The catalytical properties of these new catalysts were evaluated for the transesterification reaction of babassu oil. It is observed that the transesterification reaction of babassu oil with methanol was successfully carried out using the modified alumina samples.

SrSnO3, a perovskite-type complex oxide, was synthesized by the modified Pechini method using two different precursors, tin chloride and metallic tin. The first one is already traditional in the literature and it claims about 30 days, only for the cleaning of tin citrate aiming at the elimination of the chloride. The second route was developed by our research group and saves time, taking 6 h to complete the synthesis of the resin. The results show that SrSnO3 obtained from the metallic tin show a higher short range order, leading to a band gap value higher than those reported in the literature, besides a meaningful reduction in the formation of SrCO3, as compared to the one obtained from tin chloride.

The physicochemical characterization and thermal profile of honeys produced by stingless bees are poorly known, mainly due to the high diversity of flora mellifera and to the low production that is inherent of these species. The objective of this study was to determine the physicochemical characteristics of five samples of honey from bees from the species Melipona seminigra merrillae of Amazonas State, Brazil. The thermal degradation profile of these honey samples was evaluated by thermogravimetry in order to contribute with the establishment of a quality standard of honeys produced from Brazilian stingless bees. Thus, the following analyses were performed: reducing sugars, moisture, hydroxymethylfurfural, protein, ash, pH, and acidity. The results showed that the current legislation concerning the honey of Apis mellifera is not an appropriate standard for all the properties analyzed, reinforcing the need for a honey standard including the honeys of all Brazilian bees. The honey samples displayed similar thermal degradation profiles, with the thermal process starting at room temperature and ending at a temperature next to 600 °C.

In this study honey samples produced by Melipona (Michmelia) seminigra merrillae, collected in seven counties distributed in the central and southern region of Amazonas state in Brazil, were analysed for their botanical origin, content and profile of phenolic compounds, and antioxidant and antimicrobial activities. Twenty-two pollen types were identified. The total phenolic content ranged from 17 to 66 mg GAE/g of extract; the highest contents were found in honeys produced from pollen types such as Clidemia and Myrcia. The antioxidant activity was higher in the samples that contained higher quantities of phenolic compounds. In relation to the antibacterial activity, samples CAD3, CAD4 and SAD3 presented the best results. Fourteen phenolic compounds were determined. Among them, we identified the flavonoid taxifolin, which has not previously been described in honeys from stingless bees, and we report the identification of catechol in Brazilian honey samples for the first time.

In this work La1-xCaxCoO3 (x = 0-0.4) pigments were synthesized by the polymeric precursor method with heat treatments at 700, 800 and 900 degrees C for 4 h. The powders were characterized by colorimety, UV-vis spectroscopy and powder X-ray diffraction (XRD). The X-ray diffraction patterns showed the presence of a single phase perovskite, changing its structure from rhombohedral to cubic, when calcium was added to the lattice. All of the pigments had a black colour with a strong absorption over the whole of the visible spectrum as a consequence of the different oxidation states of cobalt and the high short-range disorder. The substitution of Ca2+ for La3+ did not influence the pigment colour but decreased its final cost. (C) 2013 Elsevier Ltd. All rights reserved.

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.

Taking into account the importance of natural antioxidants in the preservation of oils and fats, the present study evaluated the antioxidant action of five plant extracts in the control of soybean oil stability, by means of the accelerated techniques Rancimat and PDSC. These plants are rosemary ( Rosmarinus officinalis L. ) , chamomile ( Matricaria recutita L.), coriander ( Coriandrum sativum L.), fennel ( Foeniculum vulgare ), and senna ( Cassia angustifolia Vahl). The plant extracts and also the synthetic antioxidant BHT were added to the samples of crude soybean oil at the concentration of 1,000 mg kg −1 . The values of total phenolic contents ranged from 8.7 ± 0.4 to 63.0 ± 2.3 mg GAE g −1 extract and a strong positive correlation was observed between the total phenolic contents and the overall antioxidant activity of the plant extracts. Such high values indicate a good protection of the analyzed soybean oil, moreover for the Rosemary extract that was superior to the remaining extracts. In the Rancimat technique the rosemary extract was more effective than the synthetic BHT antioxidant. The OIT values of Rosemary extract and the BHT antioxidant were equivalent, and the former, showed the highest phenolic contents among the extracts, for all the performed tests, confirming that it is a powerful natural source of antioxidants.

Currently, biodiesel, a biofuel obtained from vegetable oils or animal fats, is becoming increasingly important in power generation. The properties of biodiesel are tied to the chemical composition of the oil or fat from which it was obtained. Esters prepared with saturated fatty acids have a high cloud point, high viscosity, while the unsaturated esters are less viscous and more easily oxidized. In this sense, the present study aimed to evaluate the oxidative stability as well as the hydrodynamic properties of quaternary mixtures of soybean (SBO), cotton (CTO), jatropha curcas (JCO) and babassu oils (BBO). The samples M4O (12.50 JCO:25.00 SBO:12.50 CTO:50.00 BBO, w/w%) and SBO showed the best kinematic viscosities, while the samples M1O (16.67 JCO:33.33 SBO:33.33 CTO:16.67 BBO, w/w%) and CTO showed the best pour point and fluidity point. The oxidation induction time (OIT) was measured using pressure differential scanning calorimetry (PDSC) and also Rancimat and Petro-Oxy apparatuses. The replacement of the studied individual oils by their quaternary mixtures was shown to improve the deficiencies of the individual oils. Among the individual oils, BBO displayed the highest and CTO the lowest OIT values. As for the mixtures, the best and the worst OIT were M4O and M1O, respectively. When the oxidative stability and cold flow properties were analyzed together, the sample that showed the best performance of them all was M3O (14.29 JCO:42.86 SBO:14.29 CTO:28.56 BBO, w/w%). (C) 2011 Elsevier Ltd. All rights reserved.

The most widely used process for producing biodiesel is the transesterification reaction using alkaline catalysts, due to their high reaction rates and appreciable conversion rates. Low cost catalysts (alkali, alkaline earth and transition metal hydroxides) are often used. In this work, the catalytic activity of sodium hydroxide (NaOH) in the synthesis of Jatropha curcas ethanol biodiesel was studied. Ethoxide ions, recently prepared (BINaOH) and stored under refrigeration for 12 (B12NaOH) and 24 (B24NaOH) hours were used in transesterification reactions. Each of these reactions was also conducted by means of newly produced ethoxide ions (BINaOH). The yields of each reaction condition were calculated as B12NaOH - 86.7%, B24NaOH - 99.3%, and BINaOH - 82.8%. It can be concluded that the transesterification reaction of J. curcas oil is not only adversely affected by hydroxyl ions (hydrolysis reaction) but also positively affected by ethoxide ions. The properties of flow and oxidative stability of biodiesel samples produced in each of the transesterification reaction conditions were analyzed as well. (C) 2011 Elsevier Ltd. All rights reserved.

The restriction to the use of synthetic antioxidants has fostered the research on natural antioxidants, taking into account that the prolonged usage of these substances can harm seriously the human being provoking degenerative diseases. In the present study, the antioxidant effect of the ethanolic rosemary (Rosmarinus officinalis L.) extract on the oxidative stability of edible vegetable oils was investigated by means of the pressurized differential scanning calorimetry (PDSC) and oven test techniques. The rosemary extract, at the concentration of 2,000 mg kg−1, as well as the synthetic antioxidant tert-butylhydroquinone (TBHQ) at the concentrations of 100 and 200 mg kg−1 were added to samples of sunflower oil, corn oil, and soybean oil. The fatty acid profiles of the vegetable oils were determined by gas chromatography–mass spectrometry confirming the elevated contents of unsaturated fatty acids. The thermogravimetric analysis showed that the rosemary extract is stable at the frying temperature of the oils. The results of the oxidative stability demonstrated that the extract of Rosmarinus officinalis displayed a more effective protective action in the PDSC technique, when compared with the synthetic antioxidant TBHQ, indicating that it is a promising source of natural antioxidants for edible vegetable oils.

Physicochemical and thermal analyses were undertaken to evaluate the influence of the temperature on the oxidation of sea fish oil once its polyunsaturated fatty acids deteriorate rapidly. Fish oil displayed four decomposition steps in synthetic air atmosphere and only one step in nitrogen atmosphere. The first step started at 189 and 222 °C for oxidizing and inert atmospheres, respectively. An OIT value of 53 min was measured at 100 °C. After the degradation process the peroxide index and the iodine index reduced from 35.38 to 9.85 meq × 1000 g−1 and from 139.79 to 120.19 gI2 × 100 g−1, respectively. An increase of the free fatty acids amount from 0.07 to 0.17% was observed while viscosity increased from 57.2 to 58.0 cP. Absorption at 272 nm also increased. The thermogravimetric and spectroscopic techniques are reproducible and versatile being an option for characterization of edible oil oxidation.

The vegetal species Pimenta dioica Lindl, popularly known as Jamaican pepper, is a 6–15 m tall tree, which belongs to the Mirtaceae family. Its fruits have an essential oil of great economic value in the international market, due to its high level of eugenol (its major compound), which is largely used in chemical and pharmaceutical industries. In this work, the extraction of the essential oil from the fruits of Pimenta dioica Lindl was carried out by the hydrodistillation method, using a modified Clevenger system. It was observed that the volume of the extracted oil reaches a maximum at 4 h, with a yield of 2.7% (m/m). The essential oil was characterized by physico-chemical analyses, such as density, refraction index, ethanol solubility, color, and appearance, besides UV–vis and infrared spectroscopy and gas chromatography/mass spectrometry. Thus, eugenol was confirmed as the major component of the essential oil of Pimenta dioica Lindl (77%). The technique of differential scanning calorimetry (DSC) was used for the determination of boiling point of the sample of essential oil from the fruits of Pimenta dioica (L.).

Chromium and cobalt oxides are widely used in the manufacture of industrial pigments. In this work, the Co(Co2−xCrx)O4 powders with different chromium concentrations (x=0, 0.25 and 1) were synthesized by the polymeric precursor method, heat treatment between 600 and 1000°C. These powders were characterized by X-ray diffraction, infrared spectroscopy, colorimetry, UV–vis absorption and X-ray photoelectron spectroscopies. Even with the addition of chromium, the XRD patterns revealed that all powders crystallize in a single spinel cubic structure. The spinels with higher cobalt amount, Co(CoCr)O4 and Co(Co1.75Cr0.25)O4, displayed a dark color, without the Co3+ reduction observed in Co3O4 between 900 and 950°C. The spinel with higher chromium amount, CoCr2O4, was green. The colors were directly related to the occupation of tetrahedral and octahedral sites by the chromophores, as well as to the different oxidation states of chromium and cobalt. The different optical band gap values estimated from UV–vis spectra suggested the existence of intermediary energy levels within the band gap. X-ray photoelectron spectroscopy confirmed an increasing presence of Co(III) and a decreasing amount of Cr(VI) with cobalt enrichment.