Absence Of Methanol Research Articles

Selectivity of hydrogen peroxide decomposition towards hydroxyl radicals in catalytic wet peroxide oxidation (CWPO) over Fe/AC catalysts

Two Fe/AC catalysts prepared with different iron precursors (iron nitrate and iron pentacarbonyl) and the same AC support have been tested in H(2)O(2) decomposition in presence and absence of methanol, a known strong scavenger of hydroxyl radicals, to investigate the selectivity towards .OH formation in this reaction and their behavior in the CWPO of phenol. The catalyst prepared with iron nitrate, with the most oxidized surface and the highest Fe surface content, seems to favor a higher selectivity towards .OH formation in CWPO allowing for complete phenol conversion and a significant TOC removal, with the highest mineralization degree at 50 degrees C and atmospheric pressure. Fe/AC catalysts were more efficient in the CWPO of phenol than in methanol presence due to a better use of the oxidant since adsorbed phenol on catalyst surface minimizes inefficient H(2)O(2) decomposition to H(2)O and O(2)(g). The influence of the initial H(2)O(2) concentration on phenol oxidation with this catalyst was also studied. A theoretical stoichiometric amount of H(2)O(2) for complete oxidation of phenol was chosen as the best starting concentration since auto-scavenging reactions can be minimized and it is sufficient for oxidizing phenol and the aromatic intermediates.

Aggregation kinetics of cerium oxide nanoparticles in monovalent and divalent electrolytes

As a result of the commercial availability and use of nanoparticulate cerium oxide, CeO 2, it is extremely likely that this material will be introduced into the environment requiring knowledge of its fate, transport and bioavailability in natural aquatic systems. To this end, this work probes the physicochemical interactions that govern the aggregation kinetics of cerium oxide nanoparticles using time-resolved dynamic light scattering (TR-DLS) over a range of monovalent, Na +, and divalent, Ca 2+, electrolyte concentrations. Sets of nanoparticles were synthesized by precipitation in aqueous solutions containing varying concentrations of methanol. The point of zero charge (pzc) of these nanoparticles changes as a result of synthesis method. Those produced in the absence of methanol had pzc = 6.5. As predicted by the theories of Derjaguin–Landau–Verwey–Overbeek (DLVO), both reaction-limited and diffusion-limited aggregation were observed in each solution type. The experimental critical coagulation concentrations (CCC) at pH 11.0 was ca. 80 mM and ca. 16 mM for the monovalent (NaCl) and divalent (CaCl 2) salts, respectively. DLVO theory proved to be an adequate predictor for the interactions between cerium oxide nanoparticles albeit the derived Hamaker constant of 1.0 × 10 −20 J was somewhat smaller than experimental Hamaker constants determined for other metal oxide nanoparticles. Deviations between experimental data and DLVO theory are discussed.

The influence of increasing media methanol concentration on sophorolipid biosynthesis from glycerol-based feedstocks

Candida bombicola, a known producer of sophorolipids (SLs; glycolipid surfactants), was grown on glycerol and oleic acid with up to 1.5% (v/v) methanol in the fermentation growth media to assess the effects of methanol presence on SL synthesis and structural distribution. Increasing methanol concentrations had little effect on the growth of the organism resulting in average cell dry weights (CDW; after SL separation) of 20.8 ± 0.7 g/l between 0 and 1.5% methanol. However, increasing methanol concentrations decreased SL production by 56% (from 12.7 to 5.6 g/l at 1.5% methanol) which translated to SL yields on a cellular basis of between 0.60 g SL/g cells (in the absence of methanol) to 0.27 g SL/g cells (in the presence of 1.5% methanol). LC/MS revealed that increased methanol concentrations also resulted in larger concentrations (up to 20 mol%) of free acid SLs but had little effect on the ratios of diacetylated SL lactones synthesized with palmitic acid (4 mol%), linoleic acid (3 mol%), oleic acid (80 mol%), and stearic acid (13 mol%) as the hydrophobic moieties.

Combinatorial Search for Quaternary Methanol Tolerant Oxygen Electro‐Reduction Catalyst

AbstractA combinatorial library containing 645 different compositions was synthesised and characterised for methanol tolerant oxygen electro‐reduction reaction (ORR) catalytic performance. The library was composed of compositions involving between 1 and 4 metals among Pt, Ru, Fe, Mo and Se. In an optical screening test, Pt(50)Ru(10)Fe(20)Se(10) composition exhibited the highest ORR activity in the presence of methanol. This composition was further investigated by synthesis and characterisation of a powder version catalyst [Pt(50)Ru(10)Fe(20)Se(10)/C]. At 0.85 V [vs. reversible hydrogen electrode (RHE)] in the absence of methanol, the Pt/C catalyst exhibited higher ORR current (0.0990 mA) than the Pt(50)Ru(10)Fe(20)Se(10)/C catalyst (0.0902 mA). But much higher specific activity (12.7 μA cmpt–2) was observed in the Pt(50)Ru(10)Fe(20)Se(10)/C catalyst than for the Pt/C catalyst 6.51 μA cmpt–2). In the presence of methanol, the ORR current decreased by 0.0343 and 0.247 mA for the Pt(50)Ru(10)Fe(20)Se(10)/C and Pt/C catalysts, respectively, which proved the excellent methanol tolerance of the Pt(50)Ru(10)Fe(20)Se(10)/C catalyst.

Pt-Decorated PdFe Nanoparticles as Methanol-Tolerant Oxygen Reduction Electrocatalyst

The activity and selectivity of carbon-supported Pt-decorated PdFe nanoparticles in the oxygen reduction reaction (ORR) were investigated in the presence and absence of methanol. The Pt-decorated PdFe nanoparticles, which consist of a PdPt surface and a PdFe interior, were prepared by the galvanic reaction between PdFe/C alloy nanoparticles and PtCl4(2-) in aqueous solution. The presence of a Pt-enriched surface after the replacement reaction was independently confirmed by several microstructural characterization techniques and cyclic voltammetry. The catalyst with such heterogeneous architecture is catalytically more active than a bulk PdFePt alloy catalyst with the same overall composition. The observed enhancements in catalyst performance can be attributed to the lattice strain effect between the shell and core components. The Pt-decorated PdFe (PdFe@PdPt/C) catalyst also compares favorably with a commercial Pt/C catalyst with four times as much Pt in terms of ORR activity, cost, and methanol tolerance.

Linking performance to microbiology in biofilters treating dimethyl sulphide in the presence and absence of methanol

The performance and microbiology of two inorganic biofilters treating dimethyl sulphide (DMS) in the presence and absence of methanol was investigated. Addition of methanol was shown to result in an increase in DMS removal for methanol loadings below 90 g MeOH per cubic metre per hour with the optimal methanol loading around 10-15 g MeOH per cubic metre per hour for a DMS loading of 3.4 g DMS per cubic metre per hour, a fivefold increase in the DMS removal rate compared to the biofilter treating DMS alone. Microbial community analysis revealed that the addition of methanol led to a significant increase of up to an order of magnitude in the abundance of Hyphomicrobium spp. in the biofilter co-treating DMS and methanol compared to the biofilter treating DMS alone, whilst there was no significant difference in the abundance of Thiobacillus spp. between the two biofilters. Given the behaviour of the biofilter co-treating DMS and methanol, the magnitude of the increase in Hyphomicrobium spp. in the biofilter co-treating DMS and methanol and the ability of Hyphomicrobium spp. to use both methanol and DMS as growth substrates, it was concluded that Hyphomicrobium spp. were the microorganisms responsible for the bulk of the DMS degradation in the biofilter co-treating DMS and methanol.

Carbon-Supported Pt – TiO2 as a Methanol-Tolerant Oxygen-Reduction Catalyst for DMFCs

Carbon-supported catalysts with varying at. wt ratios of Pt to Ti, namely, 1:1, 2:1, and 3:1, are prepared by the sol–gel method. The electrocatalytic activity of the catalysts toward oxygen reduction reaction (ORR), both in the presence and absence of methanol, is evaluated for application in direct methanol fuel cells (DMFCs). The optimum at. wt ratio of Pt to Ti in is established by fuel cell polarization, linear sweep voltammetry, and cyclic voltammetry studies. heat-treated at with Pt and Ti in an at. wt ratio of 2:1 shows enhanced methanol tolerance, while maintaining high catalytic activity toward ORR. The DMFC with a cathode catalyst exhibits an enhanced peak power density of in contrast to the achieved from the DMFC with carbon-supported Pt catalyst while operating under identical conditions. Complementary data on the influence of on the crystallinity of Pt, surface morphology, and particle size, surface oxidation states of individual constituents, and bulk and surface compositions are also obtained by powder X-ray diffraction, scanning and transmission electron microscopy, X-ray photoelectron spectroscopy, energy dispersive analysis by X-ray, and inductively coupled plasma optical emission spectrometry.

Study on thermal stability of tertiary pyridine resin

The fundamental properties of tertiary pyridine resin (TPR) and its mixtures with methanol/HCl and HNO3 were investigated in order to evaluate the thermal stability of TPR and to determine the conditions necessary to avoid runaway reactions. Based on experimental DSC results, it was found that TPR with HCl was thermally stable, but strong decomposition was possible with TPR in the presence of HNO3. From the results of heating tests on the gram scale, TPR with HNO3 reacted violently under high temperature regardless of HNO3 concentration and presence or absence of methanol. However, it was considered that the violent exothermic reaction could be controlled by heating temperature.

Spectroscopic study of the properties of surface compounds in methanol conversions on Cu/γ-Al2O3

The reactions of methanol on the (10% Cu)/γ-Al2O3 surface were studied by the spectrokinetic method (simultaneous measurements of the conversion rates of surface compounds and the product formation rates). Bridging and linear methoxy groups result from the interaction of methanol with surface hydroxyl groups. Formate and aldehyde-like complexes form by the oxidative conversion of the linear methoxy groups. Hydrogen forms via the recombination of hydrogen atoms on copper clusters, and the hydrogen atoms result from interconversions of surface compounds. The source of CO2 in the gas phase is the formate complex, and the source of CO is the aldehyde complex. In the absence of methanol in the gas phase, dimethyl ether forms by the interaction between two bridging methoxy groups. When present in the gas phase, methanol reacts with methoxy groups on the surface. The roles of oxygen and water vapor in the conversions of surface compounds are discussed.

Promotional effect of upper Ru oxides as methanol tolerant electrocatalyst for the oxygen reduction reaction

The role of Ru on the oxygen reduction reaction in the presence of methanol has been investigated. To this end a series of carbon supported Pt based electrocatalysts containing Ru and Co have been prepared and thoroughly characterized. The catalytic performance on the oxygen reduction reaction (ORR) both in the presence and in the absence of methanol by linear sweep voltammetry on rotating disk electrode has been studied. In spite of its documented ability towards methanol and CO oxidation, when Ru-containing catalysts are subjected to excursions to potentials more positive than 0.8 V vs. NHE they develop a certain tolerance to the presence of methanol. This feature is attributed to the formation of upper oxide Ru species that impede the methanol oxidation reaction to occur under the typical reaction conditions of the oxygen reduction process, i.e. potentials more positive than 0.7 V vs. NHE and oxygen saturated atmospheres. The evolution of Ru species with the applied potential has been investigated by XPS, identifying the presence of upper oxidized Ru phases.

Properties of surface compounds in methanol conversion on γ-Al2O3: Data of in situ IR spectroscopy

In situ IR spectroscopic studies show that a formate, an aldehyde-like complex, and bridging and linear methoxy groups exist on the alumina surface involved in methanol conversion. In the absence of methanol in the gas phase, the interaction between two bridging methoxy groups yields dimethyl ether in the gas phase. When methanol is present in the gas phase, it interacts with methoxy groups on the surface. This reaction makes the main contribution to the formation of dimethyl ether. The linear methoxy group undergoes conversion via several routes. The main route is desorption with methanol formation in the gas phase, and no more than 10% of the linear methoxy groups are converted into formate and aldehyde, which are CO2 sources in the gas phase. In the absence of methanol in the gas phase, the conversion rate of the methoxy groups is independent of the presence of water and oxygen. A scheme of the surface reactions is suggested to explain the conversion of the methoxy groups.

Properties of nanostructures obtained by anodization of aluminum in phosphoric acid at moderate potentials

The influence of the process duration, anodizing potential and methanol addition on the structural features of porous anodic alumina formed in a 0.3 M H3PO4 solutions by twostep self-organized anodizing was investigated for potentials ranging from 100 to 170 V. The structural features of porous structures including pore diameter and interpore distance were evaluated from FE-SEM top-view images for samples anodized in the presence and absence of methanol. For the highest studied anodizing time and methanol volume fraction, an excellent agreement between experimental values of the interpore distance and theoretical predictions was observed. The pore arrangement regularity was analyzed for various electrolyte compositions and anodizing potentials. It was found that the regularity ratio of porous alumina increases linearly with increasing anodizing potential and time. The addition of methanol improves the quality of nanostructures and especially better uniformity of pore sizes is observed in the presence of the highest studied methanol content.

Electrocatalytic activity, methanol tolerance and stability of perfluoroalkyl-substituted mononuclear, and ball-type dinuclear cobalt phthalocyanines for oxygen reduction in acidic medium

Electrocatalytic activity, methanol tolerance and stability of three phthalocyanine (Pc) complexes (a heptadecafluorononyl-substituted mononuclear CoPc 1, a pentaerythritol-bridged ball-type dinuclear Co2Pc2 2 and a heptadecafluorodecyl-substituted, pentaerythritol-bridged ball-type dinuclear Co2Pc2 3) and the performance of dual catalysts of 2/Pt and 3/Pt, dispersed on a high surface area carbon substrate, Vulcan XC-72 (VC) and Nafion (Nf), towards oxygen reduction (OR) were investigated and compared by surface cyclic voltammetry, rotating disk electrode, rotating ring-disk electrode and chronoamperometry experiments in acidic medium. The VC/Nf/3 modified glassy carbon electrode showed much higher catalytic performance, compared to VC/Nf/2 and VC/Nf/1 modified ones. The long term stability of the VC/Nf/3 catalyst in acidic medium was better than that of VC/Nf/2. It was found that the VC/Nf/1, VC/Nf/2 and VC/Nf/3 catalysts are nearly insensitive to the presence of methanol. In the presence of 1 M methanol in the electrolyte, the catalytic performances of 2- and 3-based catalysts were much better than that of the Pt-based one. Thus, it was shown that the VC/Nf/2-Pt and VC/Nf/3-Pt dual catalysts can be good alternatives to VC/Nf/Pt as cathode catalysts in direct methanol fuel cells. Moreover, in the absence of methanol, the mixing of 3 with Pt resulted in the enhancement of catalytic activity for OR, when compared to 3 and even Pt in the high overpotentials region.

Introduction of methanol in the formation of polyaniline nanotubes in an acid-free aqueous solution through a self-curling process

This study reports the synthesis of polyaniline (PANI) nanotubes with the introduction of methanol in aqueous solutions. SEM images indicate that well-dispersed PANI nanotubes are produced when the concentration of methanol increases up to 1M. On the other hand, polymers primarily form irregular agglomerates when only monomers and oxidant are used in the absence of methanol. Transmission electron microscopy (TEM) reveals that the resulting nanotubes have an outer diameter of about 200nm and an inner diameter of 0–50nm. Fourier transform infrared (FT-IR) spectra indicate that the intermediate samples obtained at a reaction time of around 60min have a structure consisting of a head of phenazine-like units and a tail of para-linked aniline units. Ultraviolet–visible (UV–vis) spectra indicate that emeraldine salt polyaniline (ES-PANI) appears in sequence as the reaction time reaches 75min. At the time interval of 60–75min, the self-curling behavior of the PANI intermediates first appears at 60min, and PANI nanotubes can be observed starting at 75min. This is the first study to observe this self-curling process and propose that it explains the formation of PANI nanotubes. Noteworthily, the nanotubes transform into irregular agglomerates after a de-doping process.

Facile Synthesis of Carbon-Supported IrxSey Chalcogenide Nanoparticles and Their Electrocatalytic Activity for the Oxygen Reduction Reaction

Vulcan XC-72R carbon-supported IrxSey chalcogenide catalysts with different Se/Ir atomic composition were synthesized via a microwave-assisted polyol process using H2IrCl6 and Na2SeO3 as the Ir and Se precursors. IrxSey chalcogenide catalysts were characterized by powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). The data were discussed with respect to the Se-free carbon-supported Ir nanoparticles prepared by the same microwave-assisted polyol process. The XRD results revealed that IrxSey chalcogenide catalysts showed characteristic reflections of cubic metallic iridium, and the average particle size increased with the increase of Se content in the chalcogenide catalysts. TEM images indicated that IrxSey chalcogenide catalysts were well dispersed on the surface of the carbon support with a narrow particle size distribution when y/x ≤ 1/3. When y = x, because of the particle agglomeration, we were not able to build particle size distribution and calculate the average particle size for Ir50Se50/C catalyst. Cyclic voltammogram (CV), rotating disk electrode (RDE) and single-cell measurements were conducted to evaluate the electrocatalytic activity of IrxSey chalcogenide catalysts. The CV results suggested that Se covered some surface area of Ir particles, and also, the surface properties of Ir particles were changed after Se modification. The RDE measurements were carried out with the absence/presence of methanol. In the absence of methanol, IrxSey/C catalysts showed a comparable oxygen reduction reaction (ORR) activity with Pt/C catalyst. However, in the presence of methanol, IrxSey/C catalysts showed a better ORR activity than Pt/C catalyst. The performance of the membrane electrode assembly (MEA) prepared with the most active Ir85Se15/C as the cathode catalyst in a single proton exchange membrane fuel cell (PEMFC) was also tested and achieved a maximum power density of 500 mW cm-2 at the current density of 1500 mA cm-2.

Novel synthesis of a highly active carbon-supported Ru 85Se 15 chalcogenide catalyst for the oxygen reduction reaction

A carbon-supported Ru 85Se 15 chalcogenide catalyst was synthesized via a microwave-assisted polyol process using RuCl 3 and Na 2SeO 3 as the Ru and Se precursors. The Ru 85Se 15 chalcogenide catalyst was characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and inductively-coupled plasma-atomic emission spectroscopy (ICP-AES). The XRD pattern for Ru 85Se 15/C clearly exhibited the characteristic reflections of metallic ruthenium. The TEM image indicated that the Ru 85Se 15 chalcogenide catalyst was well dispersed on the surface of the carbon support with a narrow particle size distribution. Rotating disk electrode (RDE) and single-cell measurements were carried out to evaluate the electrocatalytic activity of the Ru 85Se 15 chalcogenide catalyst. The oxygen reduction reaction (ORR) activity of the Ru 85Se 15/C catalyst was compared with the commercial Pt/C catalyst with the absence/presence of methanol. In the absence of methanol, the Ru 85Se 15/C catalyst showed a comparable ORR activity with the Pt/C catalyst. However, in the presence of methanol, the Ru 85Se 15/C catalyst showed a better ORR activity than the Pt/C catalyst. The performance of the membrane electrode assembly (MEA) prepared with Ru 85Se 15/C as the cathode catalyst in a single proton exchange membrane fuel cell (PEMFC) showed the maximum power density of 400 mW cm −2 at the current density of 1300 mA cm −2.

Use of methanol and oxygen in promoting the destruction of deca-chlorobiphenyl in supercritical water

The destruction of the well-known PCB, deca-chlorobiphenyl (10-CB), by oxidation and methanolysis in supercritical water (SCW), has been studied in a micro-reactor hydrothermal diamond-anvil cell (DAC, 50 nL) and in larger batch reactors (6 mL). The DAC was coupled to optical and infrared microscopes. In the DAC experiments, 10-CB proved to be stable under pyrolytic conditions, whereas in water, it was hydrolyzed and actually dissolved at temperatures above 475 °C. When partial oxygen was added to the 10-CB/water system, the solubility of 10-CB increased slightly as compared to the pure water experiments, and 10-CB was further decomposed by oxidation. The addition of methanol resulted in further decomposition by methanolysis, as confirmed by FT–IR spectroscopy, and lowered the dissolution temperature to 419 °C. Both oxygen and methanol (25 vol.%) were then used to destroy 10-CB in batch reactors, in which the supercritical water experiments permitted a detailed study of the reaction products of the 10-CB destruction. In the absence of methanol, more than 12 intermediate products were detected by GC–MS, and 99.2% of the 10-CB was destroyed in the presence of 225% excess oxygen at 450 °C within 20 min. When methanol was used in the absence of any excess oxygen, a destruction rate of 100% was achieved at 450 °C within 10 min and only three intermediate products were detected. The enhanced destruction of 10-CB in the presence of methanol is attributed to the homogenous reaction conditions employed and the generation of free radicals.

Stabilities and Conformational Transitions of Various Proteases in the Presence of an Organic Solvent

The half-life of the activity of the PST-01 protease that was secreted by organic solvent-tolerant Pseudomonas aeruginosa PST-01 was very long in the presence of methanol as compared to that in the absence of methanol. The conformational transitions of the PST-01 protease, alpha-chymotrypsin, thermolysin, and subtilisin in the presence and absence of methanol were monitored by measuring the CD spectra. The conformational stabilities of the PST-01 protease and subtilisin in the presence of methanol were higher than those in the absence of methanol. This resulted in high stability of these proteases in the presence of methanol. Furthermore, it was suggested that the organic solvent stabilities of enzymes were closely related to the secondary structure by monitoring the conformational transitions of polyamino acids, which form the particular conformations, in the presence and absence of methanol.

Detection of Reaction Products at DMFC Cathodes by ATR-IR Spectroscopy and Mass Spectrometry

Voltammetric curves and polarization data for air/oxygen cathodes of a commercial Pt catalyst in a sulfuric acid solution containing methanol clearly showed the effect of forming mixed potentials, namely significant cathodic shifts of the operating voltages from the values in the absence of methanol. Organic species of carbonyl groups were detected by attenuated total reflection infrared (ATR-IR) spectroscopy implemented for monitoring the methanol crossover products at a catalyst layer of highly dispersed Pt under various simulated conditions of operating air cathodes. The results indicated that complete oxidation of methanol was more favorable at elevated temperatures and a higher oxygen partial pressure. A real time mass spectrometry identified the organic species in the cathode exhaust of an operating single-cell direct methanol fuel cell (DMFC) to be intact methanol and partial oxidation products, i.e., formaldehyde and formic acid. Depending on the DMFC operating condition, the concentration level of harmful organic gas reached several hundred parts per million as estimated from the interference-corrected mass spectrometric data.

Palladium-Catalyzed Cyclopentenone Formation by Carbonylative Cycloaddition of Allylic Tosylates and Alkynes

Carbonylative cycloaddition of allyl tosylates and alkynes proceeded in the presence of palladium catalysts to afford a range of cyclopentenones. In the presence of methanol, five-component coupling reactions gave methyl cyclopentenyl acetates, whereas in the absence of methanol, (cyclopentenoylmethylidene)furanones were formed from six components. Allyl tosylate was found to be essential for these reactions, as allyl acetate and allyl bromide proved to be ineffective.