Showing papers on "Ammonium hydroxide published in 2009"

A Soluble and Highly Conductive Ionomer for High‐Performance Hydroxide Exchange Membrane Fuel Cells

Abstract: Hydrogen proton exchange membrane fuel cells (PEMFCs) have been demonstrated to have high power density and reasonable energy density. Their commercialization, however, has been hampered by the high cost and low durability of their electrocatalysts. By switching from an acidic medium to a basic one, hydroxide (OH ) exchange membrane fuel cells (HEMFCs) have the potential to solve the problems of catalyst cost and durability while achieving high power and energy density. In a basic environment, the cathode oxygen reduction over-potential can be significantly reduced, leading to high fuel cell efficiency, and catalysts in basic medium are also more durable. In addition, the facile cathode kinetics allows nonprecious metals to be used as catalysts, thus drastically reducing the cost of the fuel cell. Further, HEMFCs can offer fuel flexibility (e.g., methanol, ethanol, ethylene glycol, etc.) because of their low overpotential for hydrocarbon fuel oxidation and reduced fuel crossover. One of the most significant problems for HEMFCs is the lack of a soluble ionomer that can be used in the catalyst layer to build an efficient three-phase boundary and thus drastically improve the utilization of the catalyst particles and reduce the internal resistance. One of the most desirable properties of an ionomer for use in the catalyst layer is high solubility in low-boiling-point water-soluble solvents such as ethanol and (nor 2-)propanol, because these solvents are easy and safe to handle and remove during the electrode preparation. The ionomer should also have high hydroxide conductivity and alkaline stability. For PEMFCs, Nafion has been the ionomer of choice because it meets these requirements. But for HEMFCs, the most commonly used material for the hydroxide exchange membrane (HEM) is a quaternary ammonium hydroxide containing polymer that has poor solubility in the aforementioned simple solvents, low hydroxide conductivity, and poor alkaline stability. For example, Tokuyama Co. very recently reported two types of soluble quaternary ammonium hydroxide containing polymers (product code: A3Ver2, soluble in tetrahydrofuran or n-propanol, and AS-4, soluble in n-propanol); however, as a result of their low hydroxide conductivity, their incorporation into the catalyst layers of HEMFCs only led to a moderate improvement in performance. In another case, Park et al. prepared an ionomer solution of the trimethylamine (TMA) and N,N,N’,N’-tetramethyl-1,6-hexanediamine (TMHDA) based polysulfone– methylene quaternary ammonium hydroxide (T/TPQAOH) in dimethylacetamide (DMAc, b.p. 166 8C). Similar to the Tokuyama results, the low hydroxide conductivity of the ionomer significantly limited the improvement in fuel cell performance, and in addition, removal of the high-boilingpoint solvent is considered difficult and unsafe in the presence of finely dispersed catalysts. Owing to the lack of a soluble highly conductive solid ionomer, aqueous solutions of KOH or NaOH have been previously used in the electrodes, where the introduction of metal cations (M) offsets the key advantages of a HEMFC over traditional liquid-electrolytebased alkaline fuel cells (AFCs). Furthermore, owing to the lack of a good ionomer as the binder, non-ionic conductive PTFE and proton-conductive Nafion ionomers were used as substitutes in the electrodes, even though these materials were known to have no hydroxide conductivity. Recently, Varcoe et al. reported a TMHDA-based polyvinylbenzylcrosslinked quaternary ammonium hydroxide (TPCQAOH) electrochemical interface to enhance HEMFC performance. Because the polymer used was not soluble in ionomer form, one could question its ability to form an efficient three-phase-boundary structure in the catalyst layer, thereby limiting performance. Moreover, the hydroxide conductivity and stability of the electrochemical interface are still of concern because it is based on quaternary ammonium hydroxide groups. Quaternary phosphonium containing polymers showed excellent solubility in methanol. The strong basicity of the tertiary phosphine suggests that quaternary phosphonium hydroxides are very strong bases. Therefore in this work, we synthesized a new quaternary phosphonium based ionomer that is soluble in low-boiling-point water-soluble solvents and is highly hydroxide conductive: tris(2,4,6-trimethoxyphenyl) polysulfone-methylene quaternary phosphonium hydroxide (TPQPOH; Scheme 1). The TPQPOH ionomer exhibits excellent solubility in pure methanol, ethanol, and n-propanol and in their aqueous solutions (50 wt% in water, see Table S1 in the Supporting Information). On the other hand, the TPQPOH is insoluble in pure water, even at 80 8C, suggesting that it can be used in the [*] Dr. S. Gu, Dr. R. Cai, T. Luo, Dr. Z. Chen, M. Sun, Y. Liu, Prof. Dr. Y. S. Yan Department of Chemical and Environmental Engineering University of California—Riverside Riverside, CA 92521 (USA) Fax: (+1)951-827-5696 E-mail: yushan.yan@ucr.edu Homepage: http://www.engr.ucr.edu/faculty/chemenv/ yushanyan.html

Characterization of fast pyrolysis bio-oils produced from pretreated pine wood.

Abstract: The pretreatment of biomass prior to the fast pyrolysis process has been shown to alter the structure and chemical composition of biomass feed stocks leading to a change in the mechanism of biomass thermal decomposition. Pretreatment of feed stocks prior to fast pyrolysis provides an opportunity to produce bio-oils with varied chemical composition and physical properties. This provides the potential to vary bio-oil chemical and physical properties for specific applications. To determine the influence of biomass pretreatments on bio-oil produced during fast pyrolysis, we applied six chemical pretreatments: dilute phosphoric acid, dilute sulfuric acid, sodium hydroxide, calcium hydroxide, ammonium hydroxide, and hydrogen peroxide. Bio-oils were produced from untreated and pretreated 10-year old pine wood feed stocks in an auger reactor at 450 °C. The bio-oils’ physical properties of pH, water content, acid value, density, viscosity, and heating value were measured. Mean molecular weights and polydispersity were determined by gel permeation chromatography. Chemical characteristics of the bio-oils were determined by gas chromatography–mass spectrometry and Fourier transform infrared techniques. Results showed that the physical and chemical characteristics of the bio-oils produced from pretreated pine wood feed stocks were influenced by the biomass pretreatments applied. These physical and chemical changes are compared and discussed in detail in the paper.

Calcium Niobate Nanosheets Prepared by the Polymerized Complex Method as Catalytic Materials for Photochemical Hydrogen Evolution

Abstract: The Dion-Jacobson phase niobate perovskite, KCa2Nb3O10, was prepared by the polymerized complex (PC) method. The corresponding proton-exchanged material, HCa2Nb3O10, was then exfoliated by reaction with tetra(n-butyl)ammonium hydroxide (TBA+OH−), yielding unilamellar colloidal nanosheets whose lateral dimensions increased with the final calcination temperature in the PC synthesis. By restacking the TBA+-stabilized nanosheets with hydrochloric acid, aggregates of HCa2Nb3O10 nanosheets were obtained and tested as photocatalytic materials. The rate of H2 production from aqueous methanol solution under band gap irradiation (λ > 300 nm) was dependent on the calcination temperature. The best materials, prepared by the PC method at the intermediate calcination temperature of 1273 K, had higher activity than those made by a conventional solid state reaction. In contrast, the rate of visible-light hydrogen evolution (λ = 450 ± 20 nm) from aqueous ethylenediaminetetraacetic acid (EDTA) solution with materials sensi...

Reduction of silver nitrate by polyaniline nanotubes to produce silver-polyaniline composites

Abstract: Polyaniline (PANI) nanotubes were prepared by oxidation of aniline in 0.4 M acetic acid. They were subsequently used as a reductant of silver nitrate in 1 M nitric acid, water or 1 M ammonium hydroxide at various molar ratios of silver nitrate to PANI. The resulting PANI-silver composites contained silver nanoparticles of 40–60 nm size along with macroscopic silver flakes. Under these experimental conditions, silver was always produced outside the PANI nanotubes. Changes in the molecular structure of PANI were analyzed by FTIR spectroscopy. Silver content in the composites was determined as a residue by thermogravimetric analysis, and confirmed by density measurements. The highest conductivity of a composite, 68.5 S cm−1, was obtained at the nitrate to PANI molar ratio of 0.67 in water. Also, the best reaction yield was obtained in water. Reductions performed in an acidic medium gave products with conductivity of 10−4–10−2 S cm−1, whereas the reaction in alkaline solution yielded non-conducting products.

Wet clean compositions for CoWP and porous dielectrics

Abstract: The present invention is a formulation for wet clean removal of post etch and ash residue from a semiconductor substrate having a CoWP feature, comprising; Deionized water; Organic acid; Amine and/or quaternary ammonium hydroxide; wherein the formulation is compatible with the CoWP feature and either (a) the molar ratio of amine and/or quaternary ammonium hydroxide to organic acid provides a pH in the range of 7-14; or (b) the formulation includes a corrosion inhibitor. A method of using the formulation is also described.

Effect of solvents on the particle morphology of nanostructured ZnO

Abstract: Nanostructured ZnO thin films have been prepared by simple sol-gel dip coating technique. Zinc acetate, ammonium hydroxide, sodium hydroxide and ethanol are used as precursors. As prepared nanostructured films are annealed at 500 °C and characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive analysis of X-rays (EDAX). The shapes of the particles are found spherical in nature having particle sizes in the range of 30 nm. With the change of solvent from ammonium hydroxide to sodium hydroxide, particle shapes have been changed from spherical to nanowires having average diameter of 60 nm.

Improvement to the esterification procedure used in solid phase peptide synthesis

Abstract: A new procedure of esterificalion of N-protected amino acids to chloromethyl polymers using tetramethyl ammonium hydroxide as a base has been developed. Elemental nitrogen and amino acid analysis of the polymers are in good agreement.

Sol−Gel Synthesis and Characterization of Co−Mo/Silica Catalysts for Single-Walled Carbon Nanotube Production

Abstract: A series of silica-supported Co−Mo samples prepared by the sol−gel method has been compared as catalysts for the synthesis of single-walled carbon nanotubes (SWNT) The concentration ratio of ammonium hydroxide to the silica precursor tetraethoxysilane (TEOS) has an important effect on the resulting morphology of the silica support and, consequently, on the nature of the Co−Mo catalytic species In turn, these morphology changes have significant effects on carbon yield, quality, and type of the single-walled carbon nanotubes obtained by the disproportionation of CO at 750 °C In addition, a catalyst with an open microscale structure has been prepared by using carbon fibers as burnable sacrificial templates This open structure results in several-fold enhanced carbon yield, while keeping the same nanotube quality as those obtained on conventional powder catalysts

Chromic slag wet method detoxifcation and resource comprehensive utilization new technique

Abstract: A new harmless comprehensive utilization technique for wet processing chromic slag comprises steps as follows: ball milling chromic slag to 80-200 meshes, adding water to prepare slurry, immersing the slurry in hydrochloric acid solution, regulating the pH to 5-6, performing solid-liquid separation with filter press, in the immersion liquid after separation, the hexavalent chrome is reduced to trivalent chromium, adding sodium hudroxide aqueous solution, regulating the pH to 4-6, roughly preparing chromic hydroxide, adding sulfuric acid into filtrate, regulating the pH to 5-6, removing the calcium coprecipitated with magnesium in the rest filtrate, preparing the 2-water calcium sulphate whisker, adding alkali to the filtrate after filter-pressing to regulate the pH to 9-12 to synthesize super-fine magnesium hydroxide powder; the solution after filter-pressing is concentrated to prepare sodium chloride. The main contents of extracts within the chromic slag treated by wet processing all can meet primary, secondary or even accredited national or ministerial standard. The technique can thoroughly detoxicate Cr in chromic slag and can prepare nine products, includiing chromic hydroxide, magnesium hydroxide, ammonium hydroxide, silicon dioxide, magnetic ferrous ferricoxide, 2-water calcium sulphate, corundum intermediate, sodium chloride, and tailings-chromite; and the extracts after processing chromic slag have high quality.

Pilot-Scale Fermentation of Aqueous-Ammonia-Soaked Switchgrass

Abstract: Aqueous-ammonia-steeped switchgrass was subject to simultaneous saccharification and fermentation (SSF) in two pilot-scale bioreactors (50- and 350-L working volume). Switchgrass was pretreated by soaking in ammonium hydroxide (30%) with solid to liquid ratio of 5 L ammonium hydroxide per kilogram dry switchgrass for 5 days in 75-L steeping vessels without agitation at ambient temperatures (15 to 33 degrees C). SSF of the pretreated biomass was carried out using Saccharomyces cerevisiae (D(5)A) at approximately 2% glucan and 77 filter paper units per gram cellulose enzyme loading (Spezyme CP). The 50-L fermentation was carried out aseptically, whereas the 350-L fermentation was semiaseptic. The percentage of maximum theoretical ethanol yields achieved was 73% in the 50-L reactor and 52-74% in the 350-L reactor due to the difference in asepsis. The 350-L fermentation was contaminated by acid-producing bacteria (lactic and acetic acid concentrations approaching 10 g/L), and this resulted in lower ethanol production. Despite this problem, the pilot-scale SSF of aqueous-ammonia-pretreated switchgrass has shown promising results similar to laboratory-scale experiments. This work demonstrates challenges in pilot-scale fermentations with material handling, aseptic conditions, and bacterial contamination for cellulosic fermentations to biofuels.

Anisotropic silicon etchant composition

Abstract: An etchant composition contains (a) an alkaline compound mixture of an organic alkaline compound and inorganic alkaline compound and (b) a silicon-containing compound. The organic alkaline compound is composed of one or more ingredients from quaternary ammonium hydroxide and ethylenediamine. The inorganic alkaline compound is composed of one or more ingredients from sodium hydroxide, potassium hydroxide, ammonia and hydrazine. The silicon-containing inorganic compound is composed of one or more ingredients from metal silicon, fumed silica, colloidal silica, silica gel, silica sol, diatomaceous earth, acid clay and activated clay, and the silicon-containing organic compound is composed of one or more ingredients from quaternary ammonium salts of alkyl silicate and quaternary ammonium salts of alkyl silicic acid.

Photoresist cleaning agent

Abstract: The invention discloses a photoresist cleaning agent, which comprises quaternary ammonium hydroxide, water, alkyl diol aryl-ether, dimethyl sulfoxide, and the corrosion inhibitor of a polycarboxylic acid type, wherein, the carbon atom number of alkyl diol in the alkyl diol aryl-ether is 3-18. The photoresist cleaning agent of the invention can effectively remove photoresist (light blockage) or other etching residues on metal, metal alloy or dielectric substrates, and meanwhile, has much lower corrosion on such metal materials as aluminum, copper, and the like, and on such non-metal materials as silica, and the like, thus having good application prospect in a microelectronics field, such as cleaning a semiconductor wafer, etc.

Analysis of nerve agent degradation products in high-conductivity matrices by transient ITP preconcentration and CZE separation coupled to ESI-MS.

Abstract: Preconcentration of nerve agent degradation products (alkyl methylphosphonic acids) contained in high-conductivity matrices was performed using transient ITP to enhance sensitivity of CE-ESI-MS. The separation conditions of the five studied alkyl methylphosphonic acids in CE-MS were first optimized. The presence of methanol in the separation medium was required to obtain a good separation of the analytes under counter-EOF conditions. Preconcentration by ITP was induced by the BGE acting as leading electrolyte (LE) while the terminating electrolyte (TE) was loaded before the sample because of the counter-EOF conditions. Different leading ions (formate or acetate) and LE concentrations were tested. The best results for the analysis of soil extracts fortified with the analytes were obtained with an LE composed of 30 mM CH 3 COONH 4 adjusted to pH 8.8 with ammonium hydroxide in (35:65 v/v) MeOH/H 2 O mixture. The TE consisted of 200 mM glycine adjusted to pH 10.0 with ammonium hydroxide in the same solvent mixture. The loading length of the TE zone was optimized. The initial pH of the TE, which determined the initial mobility of the terminating ion, appeared to markedly influence the resolution and the sensitivity. This transient ITP-CZE-MS method was then adapted for the analysis of rat urine samples fortified with the analytes, which required the use of a more concentrated LE (50 mM). LODs between 4 and 70 ng/ mL in soil extract, and between 5 and 75 ng/mL in rat urine were reached from extracted ion electropherograms.

Titanium oxide sol manufacturing method

Abstract: There is provided a method for efficiently producing an anatase-type titanium oxide sol in an extremely advantageous dispersion state. The method comprises mixing a titanium alkoxide, an organic acid, and a quaternary ammonium hydroxide with water in a molar ratio of the organic acid of 0.4 to 4.0 relative to 1 sol of a titanium atom of the titanium alkoxide and in a molar ratio of the quaternary ammonium hydroxide of 0,8 to 1.9 relative to 1 mol of the organic acid to prepare an aqueous mixed solution having a concentration in terms of TiO2 of (3.5 to 10% by mass, heating the aqueous mixed solution to 50 to 100°C to remove an alcohol; and subjecting the resulting titanium-containing aqueous solution to a hydrothermal treatment at 110 to 170°C .

Controlling the Size and Surface Morphology of Carboxylated Polystyrene Latex Particles by Ammonium Hydroxide in Emulsifier-free Polymerization

Abstract: In emulsifier-free, emulsion polymerization with ionizable comonomer, the ionization of the comonomer is critical in determining the size of the final polymeric particles at sub-micrometer scale. In this study, polystyrene latex beads with carboxylates on the surface were synthesized using acrylic acid as a comonomer. Specifically, ammonium hydroxide was added to the emulsifier-free polymerization system to promote the ionization of acrylic acid by increasing pH. Smaller polystyrene latex particles were produced by increasing the ammonium hydroxide concentration in the reaction system, due to the enhanced stability promoted by the ionization of acrylic acid during the nucleation step. In addition, the surface morphology of the polystyrene latex particles was controlled by the concentration of acrylic acid, the dissociation of which was influenced by the ammonium hydroxide concentration.

Polymers with Tethered Anionic and Cationic Groups as Membranes for Fuel Cells

Abstract: Summary: Ionic clustering, water binding, and ion conductivity were studied in polymers functionalized with sulfonic acid and quaternary ammonium hydroxide groups. Small-angle x-ray scattering showed that no clustering occurred in the quaternary ammonium containing anion exchange membranes, while evidence of ionic clusters was present in both sulfonated poly(phenylene) and in Nafion, a poly(perfluorosulfonic acid). Interestingly, the water self-diffusion coefficients of the anion exchange membranes were generally greater than those observed for the sulfonated poly(phenylene)s, and moreover, the water self diffusion coefficients in anion exchange membranes were not a strong function of diffusion time. The water binding behavior lead to increased normalized conductivity in anion exchange membranes as compared to proton exchange membranes at the highest ion exchange capacities.

Silver–copper electrodeposition from ammonium hydroxide solution: influence of EDTA and HEDTA

Abstract: The influence of EDTA (ethylenediaminetetraacetic acid, disodium salt) or HEDTA (N-(2-hydroxyethyl)ethylenediaminetriacetic acid, trisodium salt) on silver–copper electrodeposition from ammonium hydroxide solution was investigated. Voltammetric studies showed that silver was deposited at potentials more negative than +0.100 V, while the copper(II) ion was reduced to copper(I) ion and metallic copper at potentials more negative than +0.100 and −0.375 V, respectively. Chronoamperometry, scanning electron microscopy and energy-dispersive X-ray spectroscopy (EDS) indicated that, for deposits obtained at −0.450 V, increasing either the silver content in the silver–copper deposit or the charge density of deposition led to dendritic growth. Moreover, dendritic growth decreased when either the EDTA or HEDTA concentration increased. EDS analysis of the deposits obtained at −0.200 V showed codeposition of copper with silver, which was attributed to Cu(I) ion disproportionation to Cu(0) and Cu(II). Moreover, the silver–copper deposits obtained at −0.200 V, from a solution containing EDTA or HEDTA, were non-dendritic in spite of the high silver content. The presence of EDTA and HEDTA improved the silver–copper morphology. X-ray diffraction analysis indicated that the silver–copper electrodeposit was a supersaturated solid solution.

X-ray diffraction studies on the thermal decomposition mechanism of nickel hydroxide.

Abstract: Nickel hydroxide samples were prepared by using sodium hydroxide and ammonium hydroxide as precipitating agents. The powder X-ray diffraction pattern shows that the degrees of crystallinity in these samples are quite different. The thermal decomposition mechanism of these two nickel hydroxide samples has been determined using powder X-ray diffraction and thermogravimetric analysis. We observe that the transformation of nickel hydroxide to nickel oxide in the crystalline sample is via a two-phase mixture, whereas in a poorly ordered sample, it is through a single phase. This indicates that the decomposition mechanism mainly depends on the preparative conditions and the nature of the sample.

Cleaning solution for photoresist

Abstract: The present invention provides a cleaning solution for photoresist. The cleaning solution includes quaternary ammonium hydroxide, water, alkyl glycol aryl ether, dimethyl sulfoxide, and polycarboxylic acid corrosion inhibitor. The cleaning solution can remove photoresists and other etching residues on metals, alloys and dielectric materials, etc. Meanwhile, the cleaning solution has a low corrosiveness toward metals such as Al, Cu, and nonmetallic materials such as SiO2. The cleaning solution will be well applied in microelectronics industry field such as semiconductor chip cleaning.

An improved process for the preparation of montelukast sodium and its intermediates

Abstract: The present invention relates to a process for the preparation of montelukast sodium (formula I) and formula.4. The invention concerns the coupling of thiol derivative, Methyl I - (mercaptomethyl)cyclopropane acetate with mesylate of formula 4 compound using alkyl substituted ammonium hydroxide base, alkali amides and purification of Montelukast acid by crystallization in suitable organic solvents. The invention further concerns to provide an improved process of montelukast intermediates having good yield and quality.

Method for synthesizing ZSM-5 molecular sieve

Abstract: The invention is a ZSM-5 molecular sieve synthesizing method, belonging to inorganic chemical synthesis technical field. And it prepares the ZSM-5 molecular sieve by preparing guiding agent and reacting mixed solution, hydrothermal crystallization, and routine filtering, washing, drying and baking, where the guiding agent uses tetrapropyl ammonium bromide or tetrapropyl ammonium hydroxide as the first organic alkali template and the reacting mixed solution uses annular molecular amine- hexamethylene imine or piperidine or their mixture as the second organic alkali template; and it has advantages of omitting ion exchange procedure, short process, low producing cost, not discharging ammonium- and nitrogen- containing waste water, not polluting environment, etc.