Thermodynamic study of the solubility of sodium naproxen in some ethanol + water mixtures

By using the van't Hoff and Gibbs equations the apparent thermodynamic functions Gibbs energy, enthalpy, and entropy of solution for sodium naproxen in ethanol + water cosolvent mixtures, were evaluated from solubility data determined at temperatures from (278.15 to 308.15) K. The drug solubility was greatest in neat water and lowest in neat ethanol at all the temperatures studied. By means of non-linear enthalpy-entropy compensation analysis, it follows that the dissolution process of this drug in ethanol-rich mixtures is entropy-driven, whereas, in water-rich mixtures the process is enthalpy-driven.

Periculum novi systematis mineralogici secundum theoriam electro-chemicam

Painovuosi nimekkeestä.

Electrocatalytic oxidation of methanol by the [Ru3O(OAc)6(py)2(CH3OH)]3+cluster: improving the metal-ligand electron transfer by accessing the higher oxidation states of a multicentered system

The [Ru3O(Ac)6(py)2(CH3OH)]+ cluster provides an effective electrocatalytic species for the oxidation of methanol under mild conditions. This complex exhibits characteristic electrochemical waves at -1.02, 0.15 and 1.18 V, associated with the Ru3III,II,II/Ru3III,III,II/Ru 3III,III,III /Ru3IV,III,III successive redox couples, respectively. Above 1.7 V, formation of two RuIV centers enhances the 2-electron oxidation of the methanol ligand yielding formaldehyde, in agreement with the theoretical evolution of the HOMO levels as a function of the oxidation states. This work illustrates an important strategy to improve the efficiency of the oxidation catalysis, by using a multicentered redox catalyst and accessing its multiple higher oxidation states.

Diesel/biodiesel soot oxidation with ceo2 and ceo2-zro2-modified cordierites: a facile way of accounting for their catalytic ability in fuel combustion processes

CeO2 and mixed CeO2-ZrO2 nanopowders were synthesized and efficiently deposited onto cordierite substrates, with the evaluation of their morphologic and structural properties through XRD, SEM, and FTIR. The modified substrates were employed as outer heterogeneous catalysts for reducing the soot originated from the diesel and diesel/biodiesel blends incomplete combustion. Their activity was evaluated in a diesel stationary motor, and a comparative analysis of the soot emission was carried out through diffuse reflectance spectroscopy. The analyses have shown that the catalyst-impregnated cordierite samples are very efficient for soot oxidation, being capable of reducing the soot emission in more than 60%.

Degradação eletroquímica da vinhaça usando eletrodo de diamante dopado com boro

The degradation of vinasses in aqueous solution from ethanol industry has been investigated by electrochemical oxidation using a boron doped diamond electrode (BDD). Samples of vinasses were electrolyzed in medium of (0.1 mol L-1) Na2SO4 solutions at controlled potentials of +2.4, +3.0 and +4.0 V (vs. Ag/AgCl) and exhibited considerable reduction of total organic carbon. The cyclic voltammetry studies indicate that the vinasses are oxidized irreversibly over the BDD at 2.0 V (vs. Ag/AgCl) in diffusion controlled process. From the experimental results it is clear that the BDD electrode can be a valuable tool to the electrochemical degradation of vinasses in practical applications

Thermodynamic study of the solubility of triclocarban in ethanol + propylene glycol mixtures

By using the van't Hoff and Gibbs equations the apparent thermodynamic functions Gibbs energy, enthalpy, and entropy of solution for triclocarban in ethanol + propylene glycol mixtures were evaluated from solubility data determined at temperatures from (293.15 to 313.15) K. The drug solubility was greatest in the mixture with 0.60 in mass fraction of ethanol and lowest in neat propylene glycol at almost all the temperatures studied. Non-linear enthalpy-entropy compensation is found indicating apparently different mechanisms of the solution process according to the mixtures composition.

Kinetics of oxidation of biodiesel from soybean oil mixed with TBHQ: determination of storage time

Synthetic antioxidants are an alternative to prevent or retard the degradation of biofuels made from vegetable oils. In this study, it was evaluated the oxidative stability of B100 soybean oil biodiesel, in the presence of tercbutylhydroquinone (TBHQ). The results showed that the induction period, that precedes the seeding process, was delayed in the presence of the antioxidant. Moreover, the obtained results suggest that the B100 biodiesel containing TBHQ can present a storage time at 25 ºC, three times longer than the estimated time for the pure B100.

Biomimetic oxidation of carbamazepine with hydrogen peroxide catalyzed by a manganese porphyrin

This laboratory project is planned for an undergraduate chemistry laboratory in which students prepare a manganese porphyrin able to mimic the oxidative metabolism of carbamazepine, one of the most frequently prescribed drugs in the treatment of epilepsy. The in vitro oxidation of carbamazepine results in the formation of the corresponding 10,11-epoxide, the main in vivo metabolite. The reaction is catalyzed by manganese porphyrin in the presence of H2O2, an environmentally-friendly oxidant. Through this project students will develop their skills in organic synthesis, coordination chemistry, chromatographic techniques such as TLC and HPLC, UV-visible spectrophotometry, and NMR spectroscopy.

Solution thermodynamics of methocarbamol in some ethanol + water mixtures

Apparent thermodynamic functions, Gibbs energy, enthalpy and entropy of solution and mixing, for methocarbamol in ethanol + water mixtures, were evaluated from solubility data determined at temperatures from 293.15 K to 313.15 K and from calorimetric values of drug fusion. The drug solubility was greatest in the mixtures with 0.70 or 0.80 mass fraction of ethanol and lowest in neat water across all temperatures studied. Non-linear enthalpy-entropy compensation was found for the dissolution processes. Accordingly, solution enthalpy drives the respective processes in almost all the solvent systems analyzed.

Treated domestic sewage: kinetics of Escherichia coli and total coliform inactivation by oxidation with hydrogen peroxide

Hydrogen peroxide has been used for decades in developed countries as an oxidizing agent in the treatment of water, domestic sewage and industrial effluents. This study evaluated the influence of the concentration of H2O2 and pH on the inactivation of Escherichia coli cells and the disinfection of sewage treated. The results showed that the inactivation rate increased with pH and H2O2. The presence of other contaminants dissolved in the effluent is probably the cause of these differences, because E. coli inactivation in synthetic wastewater was found to be much faster than in the real treated domestic sewage.

Estudo da oxidação parcial do etanol em catalisadores de Rh por DRIFTS

The partial oxidation of ethanol on γ-Al2O3, CeO2, ZrO2 and Ce xZr1-xO2 supported rhodium catalysts was investigated by Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS). The catalysts were characterized by temperature-programmed reduction (TPR) and cyclohexane dehydrogenation. DRIFTS studies on the partial oxidation of ethanol showed that ethanol is adsorbed dissociatively, through O-H bond breaking, with the formation of ethoxy species, followed by successive dehydrogenation to acetaldehyde and acetyl species. Further oxidation to acetate and carbonate species lead to the formation of CO, CH4 and H2 by decomposition. The presence of CeO2 in the catalysts favored the oxidation steps due to its oxygen storage capacity.

Use of sorghum straw (Sorghum bicolor) for second generation ethanol production: pretreatment and enzymatic hydrolysis

Agronomic biomass yields of forage sorghum BRS 655 presented similar results to other energy crops, producing 9 to 12.6 tons/ha (dry mass) of sorghum straw. The objective of this study was to evaluate the lignocellulosic part of this cultivar in terms of its potential in the different unit processes in the production of cellulosic ethanol, measuring the effects of pretreatment and enzymatic hydrolysis. Three types of pre-treatments for two reaction times were conducted to evaluate the characteristics of the pulp for subsequent saccharification. The pulp pretreated by alkali, and by acid followed by delignification, attained hydrolysis rates of over 90%.

Advances in ethanol reforming for the production of hydrogen

Catalytic steam reforming of ethanol (SRE) is a promising route for the production of renewable hydrogen (H2). This article reviews the influence of doping supported-catalysts used in SRE on the conversion of ethanol, selectivity for H2, and stability during long reaction periods. In addition, promising new technologies such as membrane reactors and electrochemical reforming for performing SRE are presented.

Nanocompósitos entre nanotubos de carbono e nanopartículas de platina: preparação, caracterização e aplicação em eletro-oxidação de álcoois

The synthesis and characterization of different platinum nanoparticle/carbon nanotube nanocomposite samples are described along with the application of these nanocomposites as electrocatalysts for alcohol oxidation. Samples were prepared by a biphasic system in which platinum nanoparticles (Pt-NPs) are synthesized in situ in contact with a carbon nanotube (CNT) dispersion. Variables including platinum precursor/CNT ratio, previous chemical treatment of carbon nanotubes, and presence or absence of a capping agent were evaluated and correlated with the characteristic of the synthesized materials. Samples were characterized by Raman spectroscopy, X-ray diffraction, thermogravimetric analysis and transmission electron microscopy. Glassy carbon electrodes were modified by the nanocomposite samples and evaluated as electrocatalysts for alcohol oxidation. Current densities of 56.1 and 79.8/104.7 mA cm-2 were determined for the oxidation of methanol and ethanol, respectively.

Influence of chloride-mediated oxidation on the electrochemical degradation of the direct black 22 dye using boron-doped diamond and β-PbO2 anodes

The Direct Black 22 dye was electrooxidized at 30 mA cm-2 in a flow cell using a BDD or β-PbO2 anode, varying pH (3, 7, 11), temperature (10, 25, 45 °C), and [NaCl] (0 or 1.5 g L-1). In the presence of NaCl, decolorization rates were similar for all conditions investigated, but much higher than predicted through a theoretical model assuming mass-transport control; similar behavior was observed for COD removal (at pH 7, 25 °C), independently of the anode. With no NaCl, COD removals were also higher than predicted with a theoretical model, which suggests the existence of distinct dye degradation pathways.