Optimization of platinum dispersion in Pt–PEM electrodes: application to the electrooxidation of ethanol

Nafion® can be used as a solid polymer electrolyte in a PEM fuel cell. Direct platinization of the membrane was realized by chemical reduction of a platinum compound. The platinization procedure was modified to enhance the roughness factor and thus to improve the electrocatalytic activity towards ethanol electrooxidation. The Pt–PEM electrodes were characterized by TEM, atomic absorption analysis, cyclic voltammetry and their polarization curves for ethanol electrooxidation.     

The anodic behaviour of iron in ethanol—water solutions in the presence and absence of NaClO4 as the supporting electrolyte

The anodic behaviour of iron in ethanol—water solutions and the effect of NaClO₄ have been investigated on the basis of potentiostatic polarization curves and electrochemical impedance plots. The influence of the water content in ethanol (6–80 vol.%) on the anodic polarization curves without a supporting electrolyte is to increase the anodic current density monotonically with potential. Furthermore, for a given potential, the current density is higher when the water content is increased. In the presence of NaClO₄ the polarization curves shift towards more high current in the low anodic potential range. Thus, addition of NaClO₄ not only increases the conductivity of ethanol solutions in its role as a supporting electrolyte, but it also modifies the electrochemical process significantly.     

Physiochemical insight into the solution behavior of cationic gemini surfactant in water and ethanol–water systems

Surfactants in water and both alcohol-water mixed solutions are used extensively in a host of industrial applications. This work presents the solution behavior and micellar transition of a cationic gemini surfactant (GS): N,N′-dihexadecyl-N,N,N′,N′-tetramethyl-N,N′-ethanediyl-diammonium dibromide (16-2-16) in water and mixed water-ethanol media. Phase behavior for 16-2-16 in the ethanol–water system was investigated at ambient temperature. The rheological data obtained for these systems at varying alcohol concentrations showed that the system viscosity (η) decreased with as the ethanol concentration increased. Small-angle neutron scattering (SANS) was used to probe the structural details of the cationic micelles as a function of ethanol concentration and temperature. The scattering data inferred a structural transition from unilamellar vesicles (ULV) through rod-like micelles to ellipsoidal micelles occurs that is dependent on the solvent composition and temperature indicating the behavior of ethanol molecules as a cosolvent in the process of micelle breaking. The plausible physicochemical interactions in the 16-2-16-ethanol mixed system were further investigated using a computational simulation study employing density functional theory (DFT)/B3LYP (Gauss View 5.0.9) utilizing a 3-21G basis set.     

Experimental-stochastic investigation of the combustion cyclic variability in HSDI diesel engine using ethanol–diesel fuel blends

An experimental investigation is conducted to evaluate the combustion characteristics of a fully instrumented, high-speed, direct injection (HSDI), standard ‘Hydra’ diesel engine, at various loads when using ethanol–diesel fuel blends up to 15% by vol. ethanol. In each test, combustion chamber and fuel injection pressure diagrams of many consecutive cycles were obtained using a specially developed, high-speed, data acquisition and processing system. Following a performance and exhaust emissions investigation and a heat release analysis of the measured cylinder pressure diagrams reported by the authors, the present work focuses on the cycle-by-cycle combustion variation (cyclic variability) as reflected in the pressure indicator diagrams, by analyzing for the maximum pressure, maximum pressure rate, (gross) indicated mean effective pressure, and dynamic injection timing and ignition delay. These parameters were analyzed using stochastic analysis techniques for averages, standard deviations, coefficients of variation, probability density functions, auto-correlations, power spectra and cross-correlation coefficients. Thus, any cause and effect relationship between cyclic pressure variations and the injection system or the kind of fuel used can be revealed, given the concern for the low cetane number of ethanol blends promoting cyclic variability that can lead to degraded performance and emissions characteristics.     

Dynamics of the heterogeneous catalytic oxidation of ethanol—II. Qualitative modelling of dynamic features

In recent years heterogeneous catalytic reaction systems have been shown to produce a complex dynamic behavior. For example the heterogeneous catalytic oxidation of ethanol on palladium was found to exhibit multistability as well as relaxation oscillations (Jaeger., 1986, Ber. Bunsenges. phys. Chem.90, 1075–1079; 1990, Chem. Engng Sci.45, 947–953). The reaction provides the clear experimental identification of a global Hopf bifurcation and so-called overlapping states near the transition point. In this paper a dynamic model will be developed which is based on these experimental facts. The model describes all instabilities observed and predicts the corresponding transitions in agreement with the observations.     

Synergistic bimetallic Ru–Pt catalysts for the low-temperature aqueous phase reforming of ethanol

Aqueous phase reforming (APR) of ethanol has been studied over a series of Ru and Pt catalysts supported on carbon and titania, with different metal loadings and particle sizes. This study proposed that, on both metals, ethanol is first dehydrogenated to acetaldehyde, which subsequently undergoes C C cleavage followed by different paths, depending on the catalyst used. For instance, although monometallic Pt has high selectivity toward H₂ via dehydrogenation, it has a low efficiency for C C cleavage, lowering the overall H₂ yield. Large Ru particles produce CH₄ through methanation, which is undesirable because it consumes H₂. Small Ru particles have lower activity but higher selectivity toward H₂ rather than CH₄. On these small particles, CO blocks low-coordination sites, inhibiting methanation. The combination of the two metals in bimetallic Ru–Pt catalysts results in improved performance, benefiting from the desirable properties of each Ru and Pt, without the negative effects of either. © 2018 American Institute of Chemical Engineers AIChE J, 65: 151–160, 2019     

Advantages of Preozonation in the Upgrading of the Mont Valérien Plant in France

The Mont Valérien plant supplies water to the western suburbs of Paris. Raw water comes from the River Seine downstream from the city. The old plant comprised two treatment lines: a slow sand filtration line built 80 years ago and a rapid settling and filtration line built in 1960. The process for the upgraded plant was determined after an in-depth study including industrial-scale experiments and laboratory tests.

The new treatment line includes the following: preozonation, oagulationflocculation and settling in a sludge-blanket type settling tank (PULSATOR), rapid gravity sand filtration, ozonation, and granular activated carbon filtration.

Results from laboratory tests used for the design are presented: ozonation rate, advantages for the quality of the treated water, expected reagejit savings, etc.     

Effect of ethanol addition in gasoline and gasoline–surrogate on soot formation in turbulent spray flames

The effect of ethanol on soot formation has been studied in turbulent spray flames of gasoline/ethanol and gasoline–surrogate/ethanol mixtures containing 10%, 20% and 30% of alcohol in volume. A hybrid burner specially designed to stabilize different liquid fuels flames with identical hydrodynamic conditions has been used. Spatially resolved measurements of soot volume fraction and of soot precursors concentration have been carried out by coupling Laser-Induced Incandescence (LII) at 1064 nm and Laser-Induced Fluorescence (LIF) at 532 nm. Significant reductions of the concentrations of soot and soot precursors have been observed when adding ethanol to gasoline. A similar behaviour has been obtained with a gasoline–surrogate which has been found to reproduce well the sooting propensity of the unleaded gasoline used in this work. The analysis of the correlation existing between the peak soot volume fraction measured in flames and the Threshold Soot Index (TSI) of the different mixtures tested in this work revealed that the effect of ethanol was not only a dilution one but that the oxygen contained in the alcohol also influence the soot formation. Finally, the comparison of the LII fluence curves and time decays obtained in gasoline/ethanol mixtures showed that soot particles oxidized faster when ethanol is added to the base fuel.     

Mineral content in fishes in the lower course of the itapecuru river in the state of Maranhão,Brazil

Concentrations of calcium, iron, potassium, magnesium, phosphorus, zinc, copper, selenium and nickel were determined in the muscle tissue of seven species of fish (Plagioscion squamosissimus, Geophagus surinamensis, Prochilodus lacustres, Curimata sp., Schizodon dissimilis, Ageneiosus ucayalensis and Hypostomus plecostomus) collected from the lower course of the Itapecuru River in the state of Maranhão, Brazil. The samples were digested in a nitricperchloric solution and analyzed using an inductively coupled plasma atomic emission spectrometer, with the construction of specific calibration curves for each element. The highest concentrations of constituent minerals were found for phosphorus, potassium, nickel and magnesium (399.83, 144.60, 90.20 and 29.49 mg 100 g^?1, respectively) in G. surinamensi, P. lacustres and Curimata sp. The lowest concentrations were found for copper, zinc, iron and selenium (0.12, 0.51, 1.05 and 8.31 mg 100 g^?1, respectively) in Curimata sp., S. dissimilis, A. ucayalensis and P. squamosissimus. The concentrations of all minerals can be considered low and are below the maximum limit established by Brazilian legislation for the human ingestion of fish meat. A comparison of the seven species of fish investigated revealed no statistically significant differences regarding the concentrations of minerals, suggesting that size and different dietary habits do not exert an influence on absorption. The low concentrations of metals, such as Fe, Cu, Zn and Ni, may be related to the environmental conditions of the mouth of the river, which receives ocean inputs that produce particular tide cycles with a strong dispersion capacity, thereby diminishing residence time in the water column and reducing the availability of these metals to species of fish.     

Ionic liquid effects on mass transfer efficiency in extractive distillation of water–ethanol mixtures

The relatively high viscosities of ionic liquids could reduce the mass transfer efficiency of the extractive distillation process. The rate-based model was adopted to analyze this phenomenon since it predicted the performance of an extractive distillation pilot plant using ionic liquids as solvent. For the water–ethanol separation, three ionic liquids: 1-ethyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium acetate and 1-ethyl-3-methylimidazolium dicyanamide and the organic solvent ethylene glycol were used for the analysis. Simulations were conducted for sieve trays and Mellapak^® 250Y. The results indicate that relatively high viscosities affect the mass transfer efficiency. However, the improvements in relative volatilities obtained from the ionic liquids help to overcome this effect. However, with high solvent viscosities (>65 mPa s at T = 353.15 K) it was not possible to overcome the reductions. Additionally, at higher distillate rates high relative volatilities yielded negative effects on mass transfer efficiency because of a decrease in vapor velocity.     

Formation of gas hydrates in the systems methane–water–ROH (ROH=ethanol,n-propanol,i-propanol,i-butanol)

Numerical data on the decomposition curves of gas hydrates formed by methane and aqueous solutions of ethanol (with the concentration up to 24 mol%), isopropanol (concentration: up to 42 mol%), n-propanol (concentration: up to 32 mol%) and isobutanol (up to the saturated aqueous solution) are presented. Investigations were carried out within the pressure range 1–16 MPa. It has been found that hydrate formation occurs in a specific manner for each of these systems and no general regularities are observed. Ethanol acts as an inhibitor of hydrate formation; however, for a given molar concentration the decrease in the temperature of hydrate formation is smaller for ethanol than for methanol. Isopropanol and n-propanol form double hydrates with methane; decomposition temperatures of these hydrates differ insignificantly from each other and from the decomposition temperature of the hydrate of pure methane. Finally, decomposition temperatures of the hydrates formed by aqueous isobutanol solutions are lower in comparison with the hydrate formed by pure methane.     

Thermodynamic parameters of amitriptyline hydrochloride–additives at cloud point: effects of the ethanol–water mixed media

Abstract

Addition of organic solvents is known to change the properties of amphiphiles through modification of bulk phase. Amitriptyline hydrochloride (AMT) is a tricyclic amphiphilic drug which is usually used as an antidepressant. In drug delivery, the cloud point (CP) of the drug is an important parameter. This article discusses the effects of ethanol–water (EtOH–WR) compositions on the energetic parameters, such as changes in Gibbs energy of clouding (Δ_sG⁰), enthalpy of clouding (Δ_sH⁰), and entropy of clouding (TΔ_sS⁰) of AMT-additive systems. Monovalent alkali halide salts, cationic conventional surfactants, and gemini surfactants were used as additives in the EtOH–WR mixed media whose compositions were varied between 0 and 15% (w/w). The Δ_sG⁰ values are positive for all the additives and the values decrease with the rise in mole fractions of the additives. The Δ_sH⁰ and TΔ_sS⁰ were noted to be positive except for KF in 15% EtOH–WR mixed media.     

Role of the Initial Formation of the Iron Nano-Particles in the Multi-Walled Carbon Nanotubes Growth Process

Careful preparation of the iron nano-particle catalyst for carbon nanotubes (CNTs) fabrication has crucial importance for initial growth of multi-wall carbon-nanotubes (MWCNTs). Thin iron layer was thermally deposited in a high vacuum onto the surface of the SiO2/Si wafer at about 300 K. The sample was heated up to 700℃ in a hydrogen atmosphere, and then the sample was heated once again at750℃ in ethylene atmosphere. After hydrogen treatment continuous Fe layer was changed into many well separated Fe nano-peaks. AFM, SEM and HR-TEM studies of deposited MWCNTs allow us to propose a growth mechanism for long, straight MWCNTs.     

Analysis on the Causes of Death in Elderly Population in Xiamen During the Period of 2002～ 2009

目的 了解厦门市老年人口死亡特征,评价老年人口主要死因的影响程度及变化趋势.方法 应用死亡率、标化死亡率、死因构成及死因顺位、老年保健效益指数(GEI)等统计指标,对2002-2009年厦门市60岁以上老年人口死因资料进行分析.结果 2002-2009年间老年人口死亡总数为42 435人,占全部死亡人数的72.43%,平均死亡率为31.11‰.死亡率男性高于女性,城乡差异无统计学意义.主要死因为恶性肿瘤、脑血管病、心脏病、呼吸系统疾病、损伤与中毒等,前五位死因占总死亡的84.68%,全死因中慢性非传染性疾病的死亡占总死亡的90.59%.主要疾病的GEI顺位为恶性肿瘤、意外伤害、传染病、呼吸系统疾病和心脑血管疾病,大多数死因的GEI高于0.5,女性普遍高于男性.与1987-1997年统计结果比较,死亡率呈下降趋势,各主要疾病的GEI也有所下降.结论 厦门市老年人口主要死因是恶性肿瘤、心脑血管疾病和呼吸系统疾病等慢性疾病,是影响老年人寿命的最主要原因,应当作为老年医疗卫生工作的重点,并引起全社会的关注.     

Dynamics of Phase Transitions in the SHS of a 3Cu–Al Powder Mixture in the Regime of Thermal Explosion

The paper reports results of dynamic xray photography of selfpropagating hightemperature synthesis of a 3Cu–Al powder mixture in the regime of thermal explosion. The stages of formation of the final product are considered, beginning with the heating of the starting mixture and interaction of its components and ending with phase transitions during cooling of the product — intermetallides Cu₉Al₄ and Cu₃Al, which are the main components of Cu based tribotechnical materials. It is shown that upon heating in the temperature range of 550 – 590°C, the intensity of diffraction lines of Al drops to the background level. The exothermicreaction of synthesis of the intermetallide is initiated at a temperature of 610 – 630°C. In the period of sharp increase in temperature to 1040°C, the presence of the starting copper and the newly formed hightemperature phase with the Cu₉Al₄ tructure are detected simultaneously in the combustion wave. When cooled to 300$°C, the material contains two cubic phases — Cu₉Al₄ and an solid solution of Al in Cu. Further cooling is accompanied by formation and increase of peaks of the Cu₃Al phase with an orthorhombic lattice. The phase composition of aluminum bronze produced by SHS with combustion in the regime of thermal explosion is not in equilibrium.     

Identification of the pathway of α-oxidation of cerebronic acid in peroxisomes

Cerebronic acid (2-hydroxytetracosanoic acid), an α-hydroxy very long-chain fatty acid (VLCFA) and a component of cerebrosides and sulfatides, is unique to nervous tissues. Studies were carried out to identify the pathway and the subcellular site involved in the oxidation of cerebronic acid. The results from these studies revealed that cerebronic acid was catabolized by α-oxidation to CO₂ and tricosanoic acid (23:0). Studies with subcellular fractions indicated that cerebronic acid was α-oxidized in fractions having particulate bound catalase and enzyme systems for the β-oxidation of VLCFA (e.g., lignoceric acid), suggesting peroxisomes as the subcellular organelle responsible for α-oxidation of cerebronic acid. Etomoxir, an inhibitor of mitochondrial fatty acid oxidation, had no effect on cerebronic acid α-oxidation. Further, cerebronic acid oxidation was found to be dependent on the presence of NAD⁺ but not FAD, NADPH, ATP, Mg²⁺, or CoASH. Intraorganellar localization studies indicated that the enzyme system for the α-oxidation of cerebronic acid was associated with the peroxisomal limiting membranes. Studies on cultured fibroblasts from normal subjects and patients with peroxisomal disorders indicated an impairment of α-oxidation of cerebronic acid in cell lines that lack peroxisomes [e.g., Zellweger syndrome (ZS)]. On the other hand, α-oxidation of cerebronic acid was found to be normal in cell lines from X-linked adrenoleukodystrophy, adult Refsum disease, and rhizomelic chondrodysplasia punctata. Our results clearly demonstrate that α-oxidation of α-hydroxy VLCFA (cerebronic acid) is a peroxisomal function and that this oxidation is impaired in ZS. Furthermore, this α-oxidation enzyme system is distinct from the one for the α-oxidation of β-carbon branched-chain fatty acids (e.g., phytanic acid).     

Influence of Cesium in Pt/NaCsβ on the Physico-Chemical and Catalytic Properties of the Pt Clusters in the Aromatization ofn-Hexane

Various Pt/NaCsβ catalysts with decreasing Na/Cs ratios and a Pt/KL sample taken as a reference catalyst for aromatization ofn-hexane, have been prepared by exchange of NaCsβ and KL zeolites in a Pt tetraammine solution then calcination and reduction. The increase of the Cs content in the NaCsβ zeolitic support results in a decrease of the cyclohexane adsorption and Pt exchange capacities. The Pt/Csβ and Pt/KL samples show similar behaviors which strongly differ from those of the Na-containing Pt/NaCsβ samples in terms of (i) reducibility of the Pt ions after calcination, (ii) shape of the FTIR spectra of CO adsorbed on the Pt clusters after reduction, and (iii) catalytic activity of these clusters in the conversion ofn-hexane. In particular, the selectivity to aromatization is much higher on the Pt/Csβ and Pt/KL catalysts than on the Na-containing Pt/NaCsβ ones. The reasons for the specific behaviors of the Pt/Csβ and Pt/KL samples are discussed.     

Stereochemistry of the hydroperoxides formed during autoxidation of CLA methyl ester in the presence of α-tocopherol

The initial steps in the autoxidation of CLA methyl ester are poorly understood. The aim of this study was to determine the stereochemistry of the hydroperoxides formed during autoxidation of CLA methyl ester in the presence of a good hydrogen atom donor. For this purpose, 9-cis, 11-trans CLA methyl ester was autoxidized in the presence of α-tocopherol under atmospheric oxygen at 40°C in the dark. The CLA methyl ester hydroperoxides were isolated, reduced to the corresponding hydroxy derivatives, and separated by HPLC. The stereochemistry of seven hydroxy-CLA methyl esters was investigated. The position of the hydroxy group was determined by GC-MS. The geometry as well as the position of the double bonds in the alkyl chain was determined by NMR. In addition, the ¹³C NMR spectra of six hydroxy-CLA methyl esters were assigned using COSY, gradient heteronuclear multiple bond correlation, gradient heteronuclear single quantum correlation, and total correlation spectroscopy experiments. The autoxidation of 9-cis, 11-trans CLA methyl ester in the presence of a good hydrogen atom donor is stereoselective in favor of one geometric isomer, namely the 13-(R,S)-hydroperoxy-9-cis, 11-trans-octadecadienoic acid methyl ester. Three types of conjugated diene hydroperoxides are formed as primary hydroperoxides: trans,trans hydroperoxides (12-OOH-8t,10t and 9-OOH-10t,12t), a cis,trans hydroperoxide with the trans double bond adjacent to the hydroperoxide-bearing carbon atom (13-OOH-9c,11t), and a new type of cis,trans lipid hydroperoxide with the cis double bond adjacent to the hydroperoxide-bearing carbon atom (8-OOH-9c,11t). In addition, three nonkinetic hydroperoxides (13-OOH-9t,11t, 8-OOH-9t,11t, and 9-OOH-10t,12c) are formed. This study supports the theory that CLA methyl ester autoxidizes at least partly through an autocatalytic free radical reaction. The complexity of the hydroperoxide mixture is due to formation of two different pentadienyl radicals. Moreover, the stereoslectivity in favor of one geometric isomer can be explained by the selectivity of the two previous steps: the preferential formation of a W-conformer of the pentadienyl radical over the Z-conformer, and regioselectivity of the oxygen addition to the pentadienyl radical.     

Effects of the structure of CeCu catalysts on the catalytic combustion of toluene in air

CeCu composite oxide catalysts were prepared by a hard-template method (CeCu-HT) and a complex method (CeCu-CA). The prepared CeCu composite oxide catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and Brunauer–Emmett–Teller (BET) analyses. The catalytic properties of the prepared CeCu composite oxide catalysts were also investigated by the catalytic combustion of toluene in air. XRD results showed that the synthesized CeCu composite oxide catalysts had different phase components and crystallinities but similar CeO₂CuO solid solution phases. Low-angle XRD, TEM, and BET results indicated that the prepared CeCu-HT catalyst had a developed ordered mesoporous structure and a large specific surface area of 206.1 m² g^?1. Toluene catalytic combustion results indicated that the CeCu-HT catalyst had higher toluene catalytic combustion activity in air than the CeCu-CA catalyst. The minimum reaction temperature at which toluene conversion exceeded 90% for toluene catalytic combustion on the CeCu-HT catalyst was 225 °C. The toluene catalytic combustion conversion on the CeCu-HT catalyst at 240 °C exceeded 99.3% with decreased toluene concentration in air to below 70 ppm. On the other hand, the toluene catalytic combustion conversion on the CeCu-CA catalyst was only 92% even when the reaction temperature reached 280 °C. The differences between the toluene catalytic combustion performances of the CeCu composite oxide catalysts prepared by different methods can be attributed to their discrepant compositions and structures.