Optimization of the Transesterification Reaction in Biodiesel Production and Determination of Density and Viscosity of Biodiesel/Diesel Blends at Several Temperatures

Waste frying oil has been used to optimize the production of biodiesel. Biodiesel was prepared through sodium ethoxide catalyzed methanolysis from the transesterification of recycled waste frying oil. Optimization of the transesterification reaction for biodiesel production was carried out by means of statistical analyses using ANOVA. The optimum conditions for reaction were the following: a oil methanol mole ratio of 1:9, temperature of 50 degrees C, catalyst mass fraction of 0.9 %, and reaction time of 40 min, which enabled a yield of 98.7 % determined by gas chromatography/mass spectrometry (GC/MS) analysis. The density and viscosity of biodiesel/diesel blends have been determined as a function of composition at several temperatures.

Phase analysis of seeded and doped PbMg1/3Nb2/3O3 prepared by organic solution of citrates

PbMg1/3Nb2/3O3 (PMN) prepared by organic solution of citrates was analyzed by the Rietveld method to determine the influence of seeds and dopants on the perovskite and pyrochlore phase formation. It was observed that pyrochlore phase formation increases with an increase in calcination time when no additives are included during the preparation. It was also observed that a greater amount of perovskite phase appeared in doped or seeded samples. The fraction of perovskite phase increased from 88 mol % in pure sample to ∼95 mol % in doped and seeded samples calcined at 800°C for 1 h. It is clear that the addition of dopants or seeds during PMN preparation can enhance the formation of perovskite phase.

Nucleation and crystallization of titania nanoparticles in silica titania planar waveguides: A study by low frequency Raman scattering

SiO2 (1-x) - TiO2 (x) waveguides, with the mole fraction x in the range 0.07 - 0.20 and thickness of about 0.4 μm, were deposited on silica substrates by a dip-coating technique. The thermal treatments at 700-900°C, used to fully densify the xerogels, produce nucleation of TiO2 nanocrystals even for the lowest TiO2 content. The nucleation of TiO2 nanocrystals and their growth by thermal annealing up to 1300°C were studied by waveguide Raman spectroscopy, for the SiO2 (0.8) - TiO2 (0.2) composition. By increasing the annealing temperature, the Raman spectrum evolves from that typical of the silica-titania glass to that of anatase, but brookite phase is dominant at intermediate temperatures. In the low. frequency region (5-50 cm-1) of the Raman spectra, acoustic vibrations of the nanocrystals are observed. From the measured line shapes, we can deduce the size distribution of the particles. The results are compared with those obtained from the line widths in the X-ray diffraction patterns. Nanocrystals with a mean size in the range 4-20 nm are obtained, by thermal annealing in a corresponding range of 800-1300°C.

A preliminary physicochemical, exergetic and economic study of hydrogen production utilizing glycerol

This work has as objective to demonstrate technical and economic viability of hydrogen production utilizing glycerol. The volume of this substance, which was initially produced by synthetic ways (from oil-derived products), has increased dramatically due mainly to biodiesel production through transesterification process which has glycerol as main residue. The surplus amount of glycerol has been generally utilized to feed poultry or as fuel in boilers, beyond other applications such as production of soaps, chemical products for food industry, explosives, and others. The difficulty to allocate this additional amount of glycerol has become it in an enormous environment problem, in contrary to the objective of biodiesel chain, which is to diminish environmental impact substituting oil and its derivatives, which release more emissions than biofuels, do not contribute to CO2-cycle and are not renewable sources. Beyond to utilize glycerol in combustion processes, this material could be utilized for hydrogen production. However, a small quantity of works (theoretical and experimental) and reports concerning this theme could be encountered. Firstly, the produced glycerol must be purified since non-reacted amounts of materials, inclusively catalysts, contribute to deactivate catalysts utilized in hydrogen production processes. The volume of non-reacted reactants and non-utilized catalysts during transesterification process could be reutilized. Various technologies of thermochemical generation of hydrogen that utilizes glycerol (and other fuels) were evaluated and the greatest performances and their conditions are encountered as soon as the most efficient technology of hydrogen production. Firstly, a physicochemical analysis must be performed. This step has as objective to evaluate the necessary amount of reactants to produce a determined volume of hydrogen and determine thermodynamic conditions (such as temperature and pressure) where the major performances of hydrogen production could be encountered. The calculations are based on the process where advance degrees are found and hence, fractions of products (especially hydrogen, however, CO2, CO, CH4 and solid carbon could be also encountered) are calculated. To produce 1 Nm3/h of gaseous hydrogen (necessary for a PEMFC - Proton Exchange Membrane Fuel Cell - containing an electric efficiency of about 40%, to generate 1 kWh), 0,558 kg/h of glycerol is necessary in global steam reforming, 0,978 kg/h of glycerol in partial oxidation and cracking processes, and 0,782 kg/h of glycerol in autothermal reforming process. The dry reforming process could not be performed to produce hydrogen utilizing glycerol, in contrary to the utilization of methane, ethanol, and other hydrocarbons. In this study, steam reforming process was preferred due mainly to higher efficiencies of production and the need of minor amount of glycerol as cited above. In the global steam reforming of glycerine, for one mole of glycerol, three moles of water are necessary to produce three moles of CO2 and seven moles of H2. The response reactions process was utilized to predict steam reforming process more accurately. In this mean, the production of solid carbon, CO, and CH4, beyond CO2 and hydrogen was predicted. However, traces of acetaldehyde (C2H2), ethylene (C2H4), ethylene glycol, acetone, and others were encountered in some experimental studies. The rates of determined products obviously depend on the adopted catalysts (and its physical and chemical properties) and thermodynamic conditions of hydrogen production. Eight reactions of steam reforming and cracking were predicted considering only the determined products. In the case of steam reforming at 600°C, the advance degree of this reactor could attain its maximum value, i.e., overall volume of reactants could be obtained whether this reaction is maintained at 1 atm. As soon as temperature of this reaction increases the advance degree also increase, in contrary to the pressure, where advance degree decrease as soon as pressure increase. The fact of temperature of reforming is relatively small, lower costs of installation could be attained, especially cheaper thermocouples and smaller amount of thermo insulators and materials for its assembling. Utilizing the response reactions process in steam reforming, the predicted volumes of products, for the production of 1 Nm3/h of H2 and thermodynamic conditions as cited previously, were 0,264 kg/h of CO (13% of molar fraction of reaction products), 0,038 kg/h of CH4 (3% of molar fraction), 0,028 kg/h of C (3% of molar fraction), and 0,623 kg/h of CO2 (20% of molar fraction). Through process of water-gas shift reactions (WGSR) an additional amount of hydrogen could be produced utilizing mainly the volumes of produced CO and CH4. The overall results (steam reforming plus WGSR) could be similar to global steam reforming. An attention must to be taking into account due to the possibility to produce an additional amount of CH4 (through methanation process) and solid carbon (through Boudouard process). The production of solid carbon must to be avoided because this reactant diminishes (filling the pores) and even deactivate active area of catalysts. To avoid solid carbon production, an additional amount of water is suggested. This method could be also utilized to diminish the volume of CO (through WGSR process) since this product is prejudicial for the activity of low temperature fuel cells (such as PEMFC). In some works, more three or even six moles of water are suggested. A net energy balance of studied hydrogen production processes (at 1 atm only) was developed. In this balance, low heat value of reactant and products and utilized energy for the process (heat supply) were cited. In the case of steam reforming utilizing response reactions, global steam reforming, and cracking processes, the maximum net energy was detected at 700°C. Partial oxidation and autothermal reforming obtained negative net energy in all cited temperatures despite to be exothermic reactions. For global steam reforming, the major value was 114 kJ/h. In the case of steam reforming, the highest value of net energy was detected in this temperature (-170 kJ/h). The major values were detected in the cracking process (up to 2586 kJ/h). The exergetic analysis has as objective, associated with physicochemical analysis, to determine conditions where reactions could be performed at higher efficiencies with lower losses. This study was performed through calculations of exergetic and rational efficiencies, and irreversibilities. In this analysis, as in the previously performed physicochemical analysis, conditions such as temperature of 600°C and pressure of 1 atm for global steam reforming process were suggested due to lower irreversibility and higher efficiencies. Subsequently, higher irreversibilities and lower efficiencies were detected in autothermal reforming, partial oxidation and cracking process. Comparing global reaction of steam reforming with more-accurate steam reforming, it was verified that efficiencies were diminished and irreversibilities were increased. These results could be altered with introduction of WGSR process. An economic analysis could be performed to evaluate the cost of generated hydrogen and determine means to diminish the costs. This analysis suggests an annual period of operation between 5000-7000 hours, interest rates of up to 20% per annum (considering Brazilian conditions), and pay-back of up to 20 years. Another considerations must to be take into account such as tariffs of utilized glycerol and electricity (to be utilized as heat source and (or) for own process as pumps, lamps, valves, and other devices), installation (estimated as US$ 15.000 for a plant of 1 Nm3/h) and maintenance cost. The adoption of emission trading schemes such as carbon credits could be performed since this is a process with potential of mitigates environment impact. Not considering credit carbons, the minor cost of calculated H2 was 0,16288 US$/kWh if glycerol is also utilized as heat sources and 0,17677 US$/kWh if electricity is utilized as heat sources. The range of considered tariff of glycerol was 0-0,1 US$/kWh (taking as basis LHV of H2) and the tariff of electricity is US$ 0,0867 US$/kWh, with demand cost of 12,49 US$/kW. The costs of electricity were obtained by Companhia Bandeirante, localized in São Paulo State. The differences among costs of hydrogen production utilizing glycerol and electricity as heat source was in a range between 0,3-5,8%. This technology in this moment is not mature. However, it allows the employment generation with the additional utilization of glycerol, especially with plants associated with biodiesel plants. The produced hydrogen and electricity could be utilized in own process, increasing its final performance.

The mechanism of dephosphorylation of bis(2,4-dinitrophenyl) phosphate in mixed micelles of cationic surfactants and lauryl hydroxamic acid

(Figure Presented) Mixed micelles of cetyltrimethylammonium bromide (CTABr) or dodecyltrimethylammonium bromide (DTABr) and the α-nucleophile, lauryl hydroxamic acid (LHA) accelerate dephosphorylation of bis(2,4-dinitrophenyl) phosphate (BDNPP) over the pH range 4-10. With a 0.1 mole fraction of LHA in DTABr or CTABr, dephosphorylation of BDNPP is approximately 10 4-fold faster than its spontaneous hydrolysis, and monoanionic LHA - is the reactive species. The results are consistent with a mechanism involving concurrent nucleophilic attack by hydroxamate ion (i) on the aromatic carbon, giving an intermediate that decomposes to undecylamine and 2,4-dinitrophenol, and (ii) at phosphorus, giving an unstable intermediate that undergoes a Lossen rearrangement yielding a series of derivatives including N,N-dialkylurea, undecylamine, undecyl isocyanate, and carbamyl hydroxamate. © 2009 American Chemical Society.

Prognostic factors associated with time to hCG remission in patients with low-risk postmolar gestational trophoblastic neoplasia

Objective The purpose of this study was to identify the clinical factors associated with time to hCG remission among women with low-risk postmolar GTN. Methods This study included a non-concurrent cohort of 328 patients diagnosed with low-risk postmolar GTN according to FIGO 2002 criteria. Associations of time to hCG remission with history of prior mole, molar histology, time to persistence, use of D&C at persistence, presence of metastatic disease, FIGO score, hCG values at persistence, type of first line therapy and use of multiagent chemotherapy were investigated with both univariate and multivariate analyses. Results Overall median time to remission was 46 days. Ten percent of the patients required multi-agent chemotherapy to achieve hCG remission. Multivariate analysis incorporating the variables significant on univariate analysis confirmed that complete molar histology (HR 1.45), metastatic disease (HR 1.66), use of multi-agent therapy (HR 2.00) and FIGO score (HR 1.82) were associated with longer time to remission. There was a linear relationship between FIGO score and time to hCG remission. Each 1-point increment in FIGO score was associated with an average 17-day increase in hCG remission time (95% CI: 12.5-21.6). Conclusions Complete mole histology prior to GTN, presence of metastatic disease, use of multi-agent therapy and higher FIGO score were independent factors associated with longer time to hCG remission in low-risk GTN. Identifying the prognostic factors associated with time to remission and effective counseling may help improve treatment planning and reduce anxiety in patients and their families. © 2013 Elsevier Inc. All rights reserved.

Caracterização físico-química e rendimento da moagem úmida de quatro híbridos de milho

Pós-graduação em Engenharia e Ciência de Alimentos - IBILCE

Atividade biológica de gel dentifrício e enxagüatório bucal contendo extratos vegetais

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Avaliação da densidade mineral óssea do rádio e ulna de gatos por meio da técnica de densiometria óptica em imagem radiográfica e sua correlação com o peso, porcentagem de cinzas e níveis de cálcio e fósforo da amostra do tecido da região estudada

Pós-graduação em Medicina Veterinária - FMVZ

Cationização de amidos de tuberosas tropicais para fabricação de papéis

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Parâmetros genéticos de características de carcaça e de qualidade da carne de aves oriundas de cruzamento recíproco

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Uma análise da dinâmica do pêndulo eletromecânico utilizando a teoria de pertubações

Pós-graduação em Matemática - IBILCE

Rendimentos de carcaça e de cortes comerciais de bulbalinos Murrah castrados abatidos com diferentes períodos de confinamento

Pós-graduação em Zootecnia - FMVZ

Avaliação da reparação de feridas cutâneas e ósseas realizadas por técnicas convencionais e com laser de Er, Cr:YSGG: estudo em ratos

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Alterações do perfil médio facial no tratamento da má oclusão de classe II, divisão 1 de Angle com aparelho extrabucal de Kloehn

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)