Molar Ratio Of Water Research Articles

Electrodeposition and characterization of metallic molybdenum from aqueous electrolytes containing high acetate concentrations

Metallic molybdenum coating was deposited from an aqueous electrolyte containing a high concentration of acetate and molybdate ions in pH of 6.8±0.2. It is complicated to deposit molybdenum from an aqueous electrolyte because of its high reactivity with oxygen. The mole ratios of water to acetate were in the range of (2.4±0.2):1. It was found that the change in bath stirring rate can result in the deposition of molybdenum oxide insisted of Mo coating. Also the morphological differences of metallic Mo and molybdenum oxide layer were investigated. In the present study, a successful attempt was made metallic Mo coating with a thickness of 3–7μm that was dependent on the DC current density.The XRD investigation indicated that the crystal structure of Mo coating was amorphous. The surface composition of deposits was ascertained by energy dispersive X-ray microanalysis (EDS) that showed the presence of high Mo content (90.7%) and low content of oxygen (9.3%). In addition, different EDS analysis was obtained from the top surface of coating and subsurface section. The surface morphology of coating was studied by scanning electron microscopy (SEM). Also, XPS analysis confirmed deposition of Mo(0) metal.

Microwave-assisted degradation of guaifenesin (GGE) to produce novel compounds in the presence of imidazolium-based ionic liquids

Thermal stabilities and degradation behaviors of guaifenesin (guaiacol glycerol ether = GGE) were studied by means of the differential scanning calorimetry and thermogravimetric (TG/DTG, in nitrogen atmosphere) analyses. To investigate the microwave-assisted pathways of guaiacol production from lignin, guaiacol glycerol ether (GGE) as a nonphenolic lignin model compound was exposed to microwave irradiation in the presence of three 1-butyl-3-methylimidazolium-based ionic liquids ([BMIm]-based ILs). GGE was subjected to microwave irradiation of 300 W in a batch reactor at a temperature of 200 °C, residence times of 5 min and air atmosphere. Based on the distribution of GGE conversion products identified by gas chromatography/mass spectrometry, the most degradation pathways of GGE were discussed. The highest yields of 2-methoxyphenol (guaiacol), 1-(2-methoxy-phenoxy)-propan-2-one, and 2-hydroxymethyl-1,4-benzodioxan were obtained using [BMIm][HSO4]. [BMIm][HSO4] was recovered and reused for three times without any loss of catalytic activity. It was found that it is possible to increase the yield of guaiacol from GGE by controlling of the different parameters such as temperature, molar ratio of water to GGE, acidity and anion effect of [BMIm]-based IL, amount of [BMIm]-based IL, microwave power and irradiation time.

Structural and Dynamical Properties of Tetraalkylammonium Bromide Aqueous Solutions: A Molecular Dynamics Simulation Study Using a Polarizable Force Field

Understanding the behavior of aqueous solutions containing tetraalkylammonium (TAA) cations is of great significance in a number of applications, including polymer membranes for fuel cells. In this work, a polarizable force field has been used to perform atomistic molecular dynamics (MD) simulations of aqueous solutions containing tetramethylammonium (TMA) or tetrabutylammonium (TBA) cations and Br counterions. Extensive MD simulations of TMA-Br/water and TBA-Br/water systems were conducted as a function of solution composition (ion pair:water molar ratios of 1:10, 1:20, 1:30, 1:63, and 1:500) at atmospheric pressure and 298 K. Our simulations demonstrate excellent agreement with available experimental data for solution densities and diffusion coefficients of different species as a function of solution composition, providing us confidence in analyzed structural and dynamic correlations. Various ion-ion and ion-water spatial distributions and the extent of cation aggregation are discussed in light of changes in the structure of cations hydration shells. The delicate balance between cation ionic core interactions with water and the hydrophobic interactions of alkyl tails leads to nontrivial self-assembly of TAA cations and the formation of an interpenetrating cationic network at higher concentrations. The ions and water dynamics are strongly coupled with the observed structural correlations and are analyzed in terms of various residence time, diffusion coefficients, and ionic conductivity.

Estimation of CO2 Absorption Capacity via Correlating Measured Electrical Conductivity in a Diethanolamine Solvent System Compared to Monoethanolamine Solvent Systems

The objective of this study was to determine the correlation equation between the CO2 absorption capacity and measured electrical conductivity in a CO2 absorption system using diethanolamine (DEA) as a solvent based on various theoretical and experimental results. In addition, the capacity and various results of the system were quantified and compared to those of the monoethanolamine (MEA) system reported in previous papers. DEA solvent at 4 M was confirmed to be the most suitable one for application in a commercial process because its mole ratio of CO2 to amine was approximately 0.5. The ionic conductivities of carbamic acid (R2NH2+) and carbamate (R2NCOO–) were estimated to be 38.46 and 20.01 S·cm2·mol–1·z–1, respectively. They were smaller than those of their corresponding ions of the MEA system. The ionic activity coefficient of the DEA system was also smaller than that of the MEA system. However, the sensitivity of the CO2 absorption capacity to electrical conductivity measured in a constant-concentration solution of the DEA system was higher than that in the MEA system. These results were basically caused by differences in molecular size, the mole ratio of water to all ions present (H2O/ions), and the density of the electron dispersion of molecules between the MEA system and the DEA system.

Crystal structure of catena-poly[silver(I)-μ-l-valinato-κ2N:O

The reaction of Ag2O with l-valine (l-Hval, C5H11NO2) in a 1:2 molar ratio in water, followed by vapour diffusion, afforded a coordination polymer of the title compound, [Ag(C5H10NO2)] n , with N-Ag-O repeat units, which is classified as a type III silver(I) complex with amino acid ligands. The asymmetric unit consists of two independent units of [Ag(l-val)]. In the crystal, the polymeric chains run along [101], and neighbouring chains are linked via a weak Ag⋯Ag inter-action and N-H⋯O hydrogen bonds. The title complex exhibited anti-microbial activity against selected bacteria (Escherichia coli, Bacillus subtilis, Staphylococcous aureus and Psedomonas aeruginosa).

Fabrication and Microstructure of Ru Core Silica Shell Structure Particles by a Reverse Micelle and Sol-Gel Processing

The Ru core SiO2 shell nano size particles have been synthesized within reverse micelle via metal alkoxide hydrolysis and condensation. The size of the particles and the thickness of the coating can be controlled by manipulating the relative rates of the hydrolysis and condensation reactions of tetraethoxysilane (TEOS) within the micro-emulsion. The average size of synthesized Ru core SiO2 shell particles was about in the size range of 15-40 nm. The average size and distribution of the synthesized Ru core SiO2 shell particles increased and narrow with R value increased. Otherwise, the average size and distribution of the synthesized Ru core SiO2 shell particles decreased and narrow with H value increased. TEM studies of particle formation indicate that the reaction process in the complex system containing reverse micelles and TEOS is governed by a diffusion-controlled process. The effects of synthesis parameters, such as the molar ratio of water to TEOS, and the molar ratio of water to surfactant, are discussed.

Fabrication and Microstructure Tuning of a Pyrimidine-Bridged Organoalkoxysilane Membrane for CO2 Separation

A novel pyrimidine-bridged organoalkoxysilane membrane was developed from 4,6-bis(3-(triethoxysilyl)-1-propoxy)-1,3-pyrimidine (BTPP) via a sol–gel process. Self-catalyzed and HCl-catalyzed BTPP sols with different water molar ratios were prepared for membrane formation to tailor the microstructure of the BTPP membranes. A higher water molar ratio for the HCl-catalyzed sols led to the formation of a silica network with improved porosity and a well-connected structure. Gas adsorption measurements indicated that BTPP xerogels tended to show a dense silica network due to an organic-rich hybrid structure, and these also showed a higher level of CO2/N2 selectivity due to the presence of pyrimidine groups that could conduct special interactions with CO2. Single-gas permeation testing was performed at different permeation temperatures using gases with different kinetic diameters: He (2.6 A), H2 (2.89 A), CO2 (3.3 A), N2 (3.64 A), CH4 (3.8 A), and SF6 (5.5 A). The BTPP membranes showed a sharp kinetic diameter de...

Selective production of hydrogen by steam reforming of glycerol over Ni/Fly ash catalyst

Hydrogen was produced with high selectivity by steam reforming of glycerol over a novel fly ash based catalyst. The catalysts were prepared by impregnating fly ash with varying amounts of nickel and were characterized suitably by XRD, FESEM, EDS, BET and TPR techniques. The catalyst containing 7.5wt% Ni on fly ash gave highest hydrogen yield in the glycerol steam reforming reaction. A complete process development was carried out with the best catalyst by varying three important process parameters, namely temperature, glycerol to water molar ratio and space-time. A maximum yield of 5.8mol of hydrogen per mole of glycerol fed was produced at 550°C with steam to glycerol molar ratio of 12 and a space-time of 8.4kg cat h/kmol of glycerol fed with 98.6% conversion of glycerol. Two kinetic models (power-law type and LHHW type) were developed from the experimental data obtained under reaction conditions free from mass transfer limitations. The activation energy of the glycerol reforming reaction as determined from both the models was 30.0kJ/mol.

Crystallisation of a salt hydrate with a complex solid form landscape

Different approaches were utilized to assess the thermodynamic stability relationship between four distinct hemihydrates of sitagliptin L-tartrate (SLT). These phases are true polymorphs, having the same chemical composition and molar ratio of water, but different arrangement in the crystal lattice. The general approaches (Burger and Ramberger rules) have only limited applicability, but indicated a monotropic relationship between Phase 1 and Phase 2. The crystallisation and transformation behaviour of the polymorphs was strongly influenced by the solvent composition. As the stability thereof was found to be solvent-dependent, the application of the van't Hoff plot or the solvent-mediated transformation did not unambiguously reveal the relative stability of the forms. Experiments were carried out in an endeavour to determine the most suitable concentration trajectory for cooling crystallisation of the selected candidate and prevent concomitant crystallisation. The application of in situ monitoring techniques, such as FTIR-ATR and FBRM, offered great potential for process optimization and control.

Hierarchical porous photoanode based on acid boric catalyzed sol for dye sensitized solar cells

The hierarchical porous photoanode of the dye sensitized solar cell (DSSC) is synthesized through non-aqueous sol-gel method based on H3BO3 as an acid catalyst and the efficiencies of the fabricated DSSC based on these photoanodes are compared. The sol parameters of 0.17M, water mole ratio of 4.5, acid mole ratio of 0.45, and solvent type of ethanol are introduced as optimum parameters for photoanode formation without any detectable cracks. The optimized hierarchical photoanode mainly contains anatase phase with slight shift toward higher angles, confirming the doping of boron into titania structure. Moreover, the porous structure involves two ranges of average pore sizes of 20 and 635nm. The diffuse reflectance spectroscopy (DRS) shows the proper scattering and blueshift in band gap. The paste parameters of solid:liquid, TiO2:ethyl cellulose, and terpineol:ethanol equal to 11:89, 3.5:7.5, and 25:64, respectively, are assigned as optimized parameters for this novel paste. The photovoltaic properties of short circuit current density, open circuit voltage, fill factor, and efficiency of 5.89mA/cm2, 703mV, 0.7, and 2.91% are obtained for the optimized sample, respectively. The relatively higher short circuit current of the main sample compared to other samples is mainly due to higher dye adsorption in this sample corresponding to its higher surface area and presumably higher charge transfer confirmed by low RS and Rct in electrochemical impedance spectroscopy data. Boric acid as a catalyst in titania sol not only forms hierarchical porous structure, but also dopes the titania lattice, which results in appreciated performance in this device.

Optimization hydrogen production over visible light-driven titania-supported bimetallic photocatalyst from water photosplitting in tandem photoelectrochemical cell

Solar hydrogen production was investigated over a Cu-Ni doped TiO2 photocatalyst from water photosplitting in a tandem photoelectrochemical cell, which was made up by connecting a modified photoelectrochemical cell to dye solar cell in a series. A mathematical representation for preparation parameters for hydrogen production was successfully generated. Optimization of hydrogen production was conducted with varying preparation parameters of Cu-Ni doped TiO2 photocatalyst including molar ratios of water, acetic acid and Cu to titanium tetraisopropoxide. The optimum preparation parameters of photocatalyst was obtained at molar ratios of water, acetic acid and Cu to titanium tetraisopropoxide of 32, 4.9, and 5.9, respectively. Physical and photoelectrochemical characterization revealed that low content of water and Cu decreased the charge transfer resistance and charge carrier recombination rate on Cu-Ni/TiO2 surface. This is attributed to the better crystallinity and less degree of agglomeration which led to obtain optimum particle size at this condition. Maximum hydrogen production rate of 2.12 mL/cm2. h was achieved under the optimum condition using the tandem photoelectrochemical cell in the aqueous KOH and glycerol solution under visible light irradiation (λ > 400 nm).

Synthesis and Characterization of CoMn<sub>2</sub>O<sub>4</sub> Nanopowders by a Reverse Micelle Processing

CoMn2O4 nanoparticles were synthesized by reverse micelle processing from the mixed precursor (consisting of Co (NO3)2 ·6H2O and MnCl2·4H2O). The CoMn2O4 was prepared by mixing the aqueous solution at a molar ratio of Co : Mn = 1 : 2. The synthesized powders were calcined at 600°C for 2h. The average size and distribution of synthesized powders were in the range of 10-20nm and narrow, respectively. The average size of the synthesized powders increased with increasing water to surfactant molar ratio. The XRD diffraction patterns show that the phase of CoMn2O4 was spinel (JCPDS no.77-0471). The synthesized and calcined powders were characterized by thermogravimetry-differential scanning calorimeter (TG-DSC), X-ray diffraction analysis (XRD) and transmission electron microscopy (TEM). The magnetic property of the powder was measured by Vibrating Sample Magneto-meter (VSM) at 298K. The effect of synthesis parameter, such as the molar ratio of water to surfactant, is discussed.

Comparative analysis of single-step and two-step biodiesel production using supercritical methanol on laboratory-scale

Single-step supercritical transesterification and two-step biodiesel production process consisting of oil hydrolysis and subsequent supercritical methyl esterification were studied and compared. For this purpose, comparative experiments were conducted in a laboratory-scale batch reactor and optimal reaction conditions (temperature, pressure, molar ratio and time) were determined. Results indicate that in comparison to a single-step transesterification, methyl esterification (second step of the two-step process) produces higher biodiesel yields (95wt% vs. 91wt%) at lower temperatures (270°C vs. 350°C), pressures (8MPa vs. 12MPa) and methanol to oil molar ratios (1:20 vs. 1:42). This can be explained by the fact that the reaction system consisting of free fatty acid (FFA) and methanol achieves supercritical condition at milder reaction conditions. Furthermore, the dissolved FFA increases the acidity of supercritical methanol and acts as an acid catalyst that increases the reaction rate. There is a direct correlation between FFA content of the product obtained in hydrolysis and biodiesel yields in methyl esterification. Therefore, the reaction parameters of hydrolysis were optimized to yield the highest FFA content at 12MPa, 250°C and 1:20 oil to water molar ratio. Results of direct material and energy costs comparison suggest that the process based on the two-step reaction has the potential to be cost-competitive with the process based on single-step supercritical transesterification. Higher biodiesel yields, similar or lower energy and methanol consumption per unit of biodiesel, and higher market value of the glycerol obtained in the two-step process explain this observation.

Crystal structure of 2-methyl-1H-imidazol-3-ium hydrogen oxalate dihydrate.

Single crystals of the title mol-ecular salt, C4H7N2 (+)·HC2O4 (-)·2H2O, were isolated from the reaction of 2-methyl-1H-imidazole and oxalic acid in a 1:1 molar ratio in water. In the crystal, the cations and anions are positioned alternately along an infinite [010] ribbon and linked together through bifurcated N-H⋯(O,O) hydrogen bonds. The water mol-ecules of crystallization link the chains into (10-1) bilayers, with the methyl groups of the cations organized in an isotactic manner.

Reverse worm-like micelles formed by an equi-charged mixture of cationic gemini surfactant and anionic single-chain surfactant in cyclohexane

An equi-charged mixture of cationic gemini surfactant, C,C′-bis(sodium dodecyldimethylammonium bromide)-p-benzenedimethylene (12-Ph-12), and anionic surfactant, sodium laurate (SL), can be dissolved in cyclohexane to form reverse worm-like micelles. The samples, with their different surfactant concentrations and water contents, were studied using rheological measurements. The minimum value of W 0, the molar ratio of water to total surfactants, was 9 for the equally charged system of 12-Ph-12 (200 mmol L−1)/SL. The maximum value of zero-shear viscosity (η 0) of this system was 1858 Pa s−1 at W 0 = 14. Upon increasing the 12-Ph-12 concentration to 300 mmol L−1, η 0 increased rapidly to 2200 Pa s−1. The dynamic rheology showed the typical visco-elastic response of a thread-like micelle solution at 12-Ph-12 (200 mmol L−1) and W 0 = 10, with a relaxation time (τ R) of 0.11 s. At W 0 = 14, a characteristic of a surfactant gel was shown, where the elastic modulus (G′) and the viscous modulus (G″) were independent of frequency. Non-linear visco-elasticity showed a strain-softening response at high strains.

Water Nanocluster Formation in the Ionic Liquid 1-Butyl-3-methylimidazolium Tetrafluoroborate ([C4mim][BF4])-D2O Mixtures.

The microstructure of mixtures of deuterated water in the ionic liquid [C4mim][BF4] is investigated by small-angle neutron scattering (SANS) measurement. In the salt-rich region, water dissolves in the ionic liquid up to 0.7 mole fraction, whereupon distinct, nanometer-sized water clusters are observed. These water nanoclusters increase in size with increasing water addition while the mole ratio of water dissolved into the ionic liquid nanostructure increases from 2 to 4. These results provide direct confirmation for recent simulations as well insight into the source of nonidealities in some thermophysical and transport properties (e.g., density and viscosity) of salt-rich aqueous mixtures reported in the literature.

Structure, dielectric property and impedance spectroscopy of La2/3Cu3Ti4O12 ceramics by sol–gel method

La2/3Cu3Ti4O12 (LCTO) precursor powders were synthesized by the sol–gel method. Effect of sol conditions and sintering process on microstructure and dielectric properties of LCTO powders or ceramics were investigated systematically. The optimum sol conditions for the synthesis of precursor powders were as follows: the Ti4+ concentration of 1.00 mol/L, the molar ratio of water and titanium of 5.6:1 and the sol pH of 1.0, respectively. After sintered at 1105 °C for 15 h, the LCTO ceramics exhibited more homogeneous microstructure, much higher dielectric constant (ca 09–1.6 × 104) and lower dielectric loss (ca 0.057). The higher dielectric constant of the LCTO ceramics might be due to the internal barrier layer capacitor effect. The LCTO ceramics showed two kinds of conductivity activation energy for grain boundary conductivity from complex impedance analysis. The transition temperature of two activation energy values occured between 170 and 210 °C. The temperature range of 170–210 °C was critical pseudocritical region of the dielectric constant, dielectric loss and activation energy. Furthermore, it was concluded that the grain boundary play an important role for electrical properties.

Production of hydrogen from bioethanol in Cu–Ni/NbxOy catalysts obtained by different preparation methods

Ethanol steam reforming for hydrogen production was evaluated using Cu–Ni/NbxOy catalyst prepared by ion exchange (IE), wet impregnation (WI) and co-precipitation (CP). The catalysts were characterized by textural analysis, chemisorption of H2 and N2O for metallic area determination, XDR (calcined and in situ reduced samples), TPR-H2, TPD-NH3, MET/EDX e TPO-O2. Differences in crystal structure and metal-support interaction have altered the reducibility of the catalysts, besides metal surface area and crystallite size of Cu and Ni. The catalytic tests, using ethanol:water molar ratio of 1:10, temperature of 450 and 500 °C, demonstrated high H2 yield and stability, except for the IE catalyst at 500 °C, which favored the ethylene formation by ethanol dehydration. The main route for H2 obtainment in all cases was ethanol decomposition. The temperature increasing up to 500 °C favored the by-product CH4 reforming. The weakest metal-support interaction on WI catalyst provided the fully reduced metal phase, however, support characteristics achieved by this preparation method led to the filamentous coke formation. TEM images showed that different crystalline structures of the support modified the mechanism of the reaction and consequently the type of coke deposited on the surface. The CP catalyst showed low coke deposition and no metal sintering, stoichiometric H2/CO2 ratio, less than 5% of CH4, and no CO, which makes it the best candidate for hydrogen production by ethanol steam reforming.

Reverse vesicles formed by polypentadeca- and polyeicosa-oxyethylene mono n-hexadecylethers in cyclohexane

The self-assembly of polypentadeca- and polyeicosa-oxyethylene mono n-hexadecylethers (C16E15 and C16E20) in cyclohexane has been studied using small-angle X-ray scattering (SAXS), rheology measurements and polarised-microscopy (POM) observations. Both surfactants can dissolve in cyclohexane, which benefited from their low cohesive energy. A trace amount of water was used to help the formation of reverse aggregates. The SAXS measurements and POM observations all evinced the formation of reverse vesicles in the solutions. The solution viscosity showed the dependence on both water content, represented as the mole ratio of water to surfactant W0, and surfactant concentration Cs. The samples at Cs = 200 mmol L−1 and W0 = 15–20 had a visco-elastic response with elastic behaviour at high frequencies (G′ dominating over G″) and slightly viscous behaviour at low frequencies (G″ exceeding G′) which resulted in a crossover of G′ and G″ at below 0.1 rad s−1. The elastic plateau modulus G′P increased with increasing W0 or Cs. The effect of temperature on the rheological properties was examined. The value of flow activation energy, Ea, of C16E20 was lower than that of C16E15, which suggested that the former may be more likely to form reverse vesicles than the latter. The elastic plateau modulus G′P showed temperature dependence, which was explained in terms of the hydrogen bonding interactions between the water and the POE.

Response surface optimization of biodiesel production using immobilized Rhizopus oryzae cells

ABSTRACTBiodiesel (fatty acid methyl or ethyl esters), a clean alternative fuel, has attracted considerable attention as it is a renewable, biodegradable and non-toxic fuel and can generally be used as a substitute for diesel. The present study, biodiesel production from jatropha oil and karanja oil was studied with immobilized Rhizopus oryzae MTCC (262) cells. Prior to the optimization experiments, single point optimization studies were conducted to select the alkyl source (methanol), organic solvent (n-hexane), optimum solvent quantity (20% w/w of oil) and bead size (0.24 cm) using R. oryzae cells. Effect of reaction time (42 h) and optimum agitation speed (150 rpm) on percentage biodiesel yield were studied. Response surface optimization experiments were carried out for optimizing the operating conditions namely reaction temperature, reaction time, added water content, catalyst concentration and molar ratio of alcohol to oil. Maximum biodiesel yields of 80.5% and 78.3% for jatropha oil and karanja oil.