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Methanol Concentration (methanol + concentration)
Selected AbstractsThe Nanocrystalline Nickel with Catalytic Properties on Methanol Oxidation in Alkaline MediumFUEL CELLS, Issue 5 2009R. M. A. Tehrani Abstract The hexagonal closed packed (hcp) nanocrystalline nickel (Ni), with an average diameter of 9.7,±,2.27,nm was deposited uniformly on composite graphite (CG) by the rapid scanning (6,500,mVs,1) voltammetry technique. The hcp-nano Ni-modified CG electrode was investigated for the catalytic oxidation of methanol in alkaline medium through the formation of NiOOH. A high anodic current was obtained at peak potential of +570,mV vs Ag/AgCl. Both the scan rate and the methanol concentration affected the oxidation of methanol. The results showed that catalytic activity had increased with decrease in Ni particle diameter. It was also shown that the hcp-nano Ni/CG modified electrode was the most efficient catalyst in the oxidation of methanol. [source] Electrochemical Reduction of Oxygen on Carbon Supported Pt and Pt/Ru Fuel Cell Electrodes in Alkaline SolutionsFUEL CELLS, Issue 4 2003E.H. Yu Abstract A study of O2 reduction in 1 M NaOH solution at gas diffusion electrodes made from carbon supported Pt and Pt/Ru catalysts is reported. Two Tafel regions were observed for both the Pt and Pt/Ru electrodes. Although the same mechanism was suggested for oxygen reduction on both Pt and Pt/Ru catalysts, the O2 reduction activity was lower on Ru. Electrochemical Impedance Spectroscopy (EIS) analysis was carried out at different potentials and showed the significant contribution of diffusion on the reaction process and kinetics. The effect of methanol on O2 reduction was investigated in solutions containing various concentrations of methanol. The electrode performance deteriorated with increasing methanol concentration because of a mixed cathode potential. The methanol tolerance, i. e., the methanol concentration which polarises the O2 reduction reaction for O2 reduction, at the Pt/C electrode with a Pt loading of 1.2 mg cm,2 is 0.2 M methanol in 1 M NaOH. [source] Cell growth and Trametes versicolor laccase production in transformed Pichia pastoris cultured by solid-state or submerged fermentationsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 4 2010Marcos López Abstract BACKGROUND: Growth kinetics of Pichia pastoris and heterologous expression of Trametes versicolor laccase were compared. This is the first study of its kind between solid-state yeast cultures done on polyurethane foam (PUF) and submerged liquid fermentations (SmF). RESULTS: The maximum values of biomass were similar for SSF (solid-state fermentation) and SmF experiments when the BOD (biochemical oxygen demand) was lower than 100 g L,1. For higher BOD levels, the maximum values of biomass were 55 g L,1 (SSF) and 35 g L,1 (SmF). Micrographs of PUF preparations showed yeast growing within liquid lamellae, thinner than 100 µm, forming large horizontal aggregates. Yeast aggregates were much smaller in SmF than in SSF experiments; however, laccase expression was lower in PUF than in SmF, unless the methanol concentration was increased to 63 g L,1, which was inhibitory only to the SmF system. CONCLUSION: The results show that oxygen mass transfer is more efficient in SSF, which is related to the higher area/volume ratio compared with SmF. Induction differences may also be due to hindered diffusion of methanol within large yeast aggregates. Copyright © 2009 Society of Chemical Industry [source] Influence of technological parameters on the epoxidation of 1-butene-3-ol over titanium silicalite TS-2 catalystJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 9 2009Agnieszka Wróblewska Abstract BACKGROUND: The influence of technological parameters on the epoxidation of 1-butene-3-ol (1B3O) over titanium silicalite TS-2 catalyst has been investigated. Epoxidations were carried out using 30%(w/w) hydrogen peroxide at atmospheric pressure. The major product from the epoxidation of B3O was 1,2-epoxybutane-3-ol, with many potential applications. RESULTS: The influence of temperature (20,60 °C), 1B3O/H2O2 molar ratio (1:1,5:1), methanol concentration (5,90%(w/w)), TS-2 catalyst concentration (0.1,6.0%(w/w)) and reaction time (0.5,5.0 h) have been studied. CONCLUSION: The epoxidation process is most effective if conducted at a temperature of 20 °C, 1B3O/H2O2 molar ratio 1:1, methanol concentration (used as the solvent) 80%(w/w), catalyst concentration 5%(w/w) and reaction time 5 h. Copyright © 2009 Society of Chemical Industry [source] Epoxidation of allyl alcohol with hydrogen peroxide over titanium silicalite TS-2 catalystJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 7 2007Agnieszka Wróblewska Abstract The influence of the technological parameters on the course of the epoxidation of allyl alcohol with 30% H2O2 in the presence of titanium silicalite TS-2 catalyst and methanol as a solvent was studied. The process was performed in an autoclave at the autogenic pressure. The influence of temperature in the range 20,120 °C, molar ratio of allyl alcohol/H2O2 (1:1,10:1), methanol concentration in the reaction mixture (10,80% w/w), catalyst TS-2 concentration (0.1,2.0% w/w) and reaction time (1,8 h) were investigated. The functions describing the process were: selectivity of transformation to glycidocidol in relation to allyl alcohol consumed, selectivity of transformation to organic compounds in relation to hydrogen peroxide consumed, conversions of allyl alcohol and hydrogen peroxide. Copyright © 2007 Society of Chemical Industry [source] Effect of solvent concentration on the extraction kinetics and diffusivity of Cyclosporin A in the fungus Tolypocladium inflatumBIOTECHNOLOGY & BIOENGINEERING, Issue 1 2007May Ly Abstract The kinetics of solid-liquid extraction and extraction yields of the immunosuppressant drug Cyclosporin A (CyA) from the mycelia of Tolypocladium inflatum were examined in this study. A 2 L stirred, baffled vessel was used to extract CyA from wet mycelia mass. Three different organic solvents were used, namely, methanol, acetone, and isopropanol at different concentrations in aqueous mixtures at room temperature. It was found that the best solvent was acetone at 50% v/v concentration achieving 100% extraction of CyA from the mycelia of T. inflatum. Although acetone proved to be the better solvent for CyA extraction, further studies were performed using methanol. A linear relationship was found between extraction yield of CyA and methanol concentration with 100% CyA extraction at 90% v/v methanol. The partition coefficients of CyA between the solid mycelia phase and the aqueous solvent phase were found to decrease exponentially with increasing methanol concentration. A liquid extraction model was developed based on the diffusion equation to correlate the kinetic data of CyA extraction from the solid mycelia of T. inflatum. Non-linear regression analysis of experimental data was used with the diffusion equation in order to calculate the effective diffusivities of CyA in the mycelia of T. inflatum. For all three organic solvents used, the effective diffusivities of CyA were found to be between 4.41,×,10,15 and 6.18,×,10,14 m2/s. This is the first time CyA effective diffusivities in T. inflatum are reported in the literature. Biotechnol. Bioeng. 2007;96: 67,79. © 2006 Wiley Periodicals, Inc. [source] Optimization of the expression of recombinant human activin A in the yeast Pichia pastorisBIOTECHNOLOGY PROGRESS, Issue 2 2010Dale Fredericks Abstract We report a new procedure to express recombinant human activin A using the methanolic yeast, Pichia pastoris. Optimization of culture procedures has involved comprehensive examination of the effects of culture vessel shape, volume of broth in the induction and expression cultures, methanol concentration, culturing temperature, and pH of the expression cultures. After this optimization, as well as modification of the native cleavage sites, a laboratory scale procedure has been established which routinely produced 2,10 mg/L amounts of this vital growth factor in the highly efficient, eukaryotic yeast system. This system avoids the need to produce this protein and similar TGF-, proteins in mammalian cell lines which, in addition to being costly, produce many native binding partners of these cystine knot proteins, a factor which can dramatically affect yields of the target protein. © 2010 American Institute of Chemical Engineers Biotechnol. Prog., 2010 [source] Mechanism Exploration during Lipase-Mediated Methanolysis of Renewable Oils for Biodiesel Production in a tert -Butanol SystemBIOTECHNOLOGY PROGRESS, Issue 5 2007Wei Du tert -Butanol has been developed as a novel reaction medium for lipase-mediated methanolysis of renewable oils for biodiesel production, in which lipase could maintain high catalytic activity, although the logP value of tert -butanol was just about 0.35. The related mechanism exploration has been carried out, and it has been proposed first in this manuscript that in the biodiesel production system, log Penvironment (log Penvironment = xmethanol log Pmethanol + xoils log Poils + xsolvent log Psolvent) including reactants and organic solvent should be taken into account to consider the effect of the whole environment on lipase activity instead of just considering the effect of the organic solvent itself. Further study showed that the operational stability of the lipase could be improved significantly in this system and there was no loss in lipase activity even after its being continuously used for 200 batches. The phase diagrams of the ternary-components tert -butanol/methanol/rapeseed oils were plotted further, and it was found that the methanol tolerance was the saturated methanol concentration in the system. It was demonstrated first here that the improved stability of the lipase was due to the elimination of negative effects caused by methanol and byproduct glycerol in the tert -butanol system. [source] Performance Tests and Pressure Drop Measurements in the Anode Flowfield of a ,DMFCFUEL CELLS, Issue 4 2010S.-S. Hsieh Abstract Cell performance tests and measurements of the pressure drops in the anode flow channels of a custom-made microdirect methanol fuel cell (,DMFC) are conducted and studied for different methanol concentrations (0.5,2,M), flow rates (10,20,sccm) and operating temperatures (40,80,°C). The anode flowfields consist of three channel/four pass flow channels with widths of 500,2000,,m and a total length of 300,400,mm. Moreover, flow characteristics of the CO2 gas bubbles and methanol solution in the anode flow channels are identified and analysed for CO2 fraction through visualisation. Finally, an optimal channel size for the present ,DMFC is obtained. [source] Effect of anode current collector on the performance of passive direct methanol fuel cellsINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 8 2009Qin-Zhi Lai Abstract The effect of anode current collector on the performance of passive direct methanol fuel cell (DMFC) was investigated in this paper. The results revealed that the anode of passive DMFC with perforated current collector was poor at removing the produced CO2 bubbles that blocked the access of fuel to the active sites and thus degraded the cell performance. Moreover, the performances of the passive DMFCs with different parallel current collectors and different methanol concentrations at different temperatures were also tested and compared. The results indicated that the anode parallel current collector with a larger open ratio exhibited the best performance at higher temperatures and lower methanol solution concentrations due to enhanced mass transfer of methanol from the methanol solution reservoir to the gas diffusion layer. However, the passive DMFC with a smaller open ratio of the parallel current collector exhibited the best performance at lower temperatures and higher methanol solution concentrations due to the lower methanol crossover rate. Copyright © 2009 John Wiley & Sons, Ltd. [source] A semi-empirical cell voltage model for polymer electrolyte/methanol systems: Applicability of the group contribution methodJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2008Ji Yun Seong Abstract A new group contribution model is established to describe the cell voltage of a direct methanol fuel cell as a function of the current density. The model equation is validated with experimental data over a wide range of methanol concentrations and temperatures. The proposed model focuses on very unfavorable conditions for cell operation, that is, low methanol solution concentrations and relatively low cell temperatures. The proposed group contribution method includes a methanol crossover effect that plays a major role in determining the cell voltage of a direct methanol fuel cell. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] | |||||||||||||