40 research outputs found
An alternative application to the portuguese agro-industrial residue : wheat straw
The effects of alkaline treatments of the wheat straw with sodium hydroxide were investigated. The optimal condition for extraction of hemicelluloses was found to be with 0.50 mol/l sodium hydroxide at 55 °C for 2 h. This resulted in the release of 17.3% of hemicellulose (% dry starting material), corresponding to the dissolution of 49.3% of the original hemicellulose. The yields were determined by gravimetric analysis and expressed as a proportion of the starting material. Chemical composition and physico-chemical properties of the samples of hemicelluloses were elucidated by a combination of sugar analyses, Fourier transform infrared (FTIR), and thermal analysis. The results showed that the treatments were very effective on the extraction of hemicelluloses from wheat straw and that the extraction intensity (expressed in terms of alkali concentration) had a great influence on the yield and chemical features of the hemicelluloses. The FTIR analysis revealed typical signal pattern for the hemicellulosic fraction in the 1,200â1,000 cmâ1 region. Bands between 1,166 and 1,000 cmâ1 are typical of xylans.Conselho Nacional de
Desenvolvimento CientĂfico e TecnolĂłgico (CNPq)Fundação de Amparo a Pesquisa do Estado de SĂŁo Paulo/Brazil (FAPESP)Fundação para a CiĂȘncia e a Tecnologia (FCT) - SFRH/BPD/26156/2005, SFRH/BPD/26108/200
Pulp Chamber Heating: An In Vitro Study Evaluating Different Light Sources and Resin Composite Layers
Impacto da temperatura da superfĂcie do mar na simulação da Zona de ConvergĂȘncia do AtlĂąntico Sul
O olhar dos conselheiros de saĂșde sobre os relatĂłrios de prestação de contas no municĂpio de Natal (Rio Grande do Norte), Brasil
Interchangeable Biomass Fuels for Paper-Based Microfluidic Fuel Cells: Finding Their Power Density Limits
Paper batteries are self-pumping emerging tools for powering portable analytical systems. These disposable energy converters must be low-cost and must achieve enough energy to power electronic devices. The drawback is to reach high energy keeping the low cost. Here, for the first time, we report a paper-based microfluidic fuel cell (P”FC) equipped with Pt/C on carbon paper (CP) anode and a metal-free CP cathode fed by biomass-derived fuels to deliver high power. The cells were engineered in mixed media configuration, where methanol, ethanol, ethylene glycol, or glycerol is electro-oxidized in an alkaline medium while Na2S2O8 is reduced in an acidic medium. This strategy allows for optimizing each half-cell reaction independently. The colaminar channel of the cellulose paper was chemically investigated by mapping the composition, which reveals a majority of elements from the catholyte and anolyte on each respective side, and a mixture of both at the interface, assuring the existing colaminar system. Moreover, the colaminar flow was investigated by investigating the flow rate considering recorded videos for the first time. All P”FC shows 150-200 s to build the stable colaminar flow, which matches the time to reach a stable open circuit voltage. The flow rate is similar for different concentrations of methanol and ethanol, but it decreases with the increase in ethylene glycol and glycerol concentrations, suggesting longer residence time for the reactants. The cells perform differently for the different concentrations, and their limiting power densities are composed of a balance among anode poisoning, residence time, and viscosity of the liquids. The sustainable P”FCs can be interchangeably fed by the four biomass-derived fuels to deliver ~2.2-3.9 mW cm-2. This allows choosing the proper fuel due to their availability. The unprecedented P”FC fed by ethylene glycol delivered 6.76 mW cm-2, which is the benchmark output power for a paper battery fed by alcohol
Room temperature selective conversion of aniline to azoxybenzene over an amorphous niobium oxyhydroxide supported on ?-FeOOH.
In this work, catalysts for the oxidation of aniline into azoxybenzene were prepared by combining ?-FeOOH
nanoparticles with 0, 2.5, 5, and 10 wt.% niobium oxyhydroxides by a simple co-precipitation method. The
niobium oxyhydroxide actively changed the chemical and textural properties of ?-FeOOH, as verified by XRD,
M?ssbauer spectroscopy, N2 adsorption-desorption measurements, and TEM images. Therefore, the catalytic
performance of ?-FeOOH to convert aniline into azoxybenzene in the presence of hydrogen peroxide was significantly improved. The catalytic activity and selectivity changed with the Nb content in the composite. The
effect of different reaction parameters like solvent type, H2O2 volume, and reaction time has been studied in
detail. The catalyst with 10 wt.% Nb was the most efficient among the evaluated catalysts, showing 100%
conversion of aniline with 80.2% selectivity to azoxybenzene when propanol was used as solvent at 25 ?C.
Moreover, the catalyst 10 wt.% Nb exhibited good stability and could be reused for various cycles without
significant loss of catalytic activity