Effect of Self-Assemblies on the Dynamics of the Briggs–Rauscher Reaction

The study involves the dynamic evolution of the Briggs–Rauscher (BR) reaction in the presence of various surfactants—SDS (sodium dodecyl sulphate) as anionic, CTAB (cetyl trimethylammonium bromide) as cationic and TritonX‐100 [4‐(1,1,3,3‐(tetramethylbutyl) phenyl polyethylene glycol] as a neutral one in single as well as mixed mode conditions (SDS + TX‐100 and CTAB + TX‐100). The reaction has been monitored potentiometrically at 30 °C under CSTR conditions. These surfactants affect the reaction dynamics to an extent which depends on the nature and concentration of the surfactant and the formation of their self‐assemblies. The experimental findings indicate that the oscillatory behavior of the BR reaction in the presence of surfactants is due to the efficacy of organized surfactant assemblies to selectively distribute the key species involved in the reaction, and their interaction with the counter ions in cases of ionic micelles. The study reveals that the evolution of oscillatory behavior is a characteristic feature of the surfactant.     

Effect of Fluorine Ion on the Electrical Properties of Glasses in the Na2O–P2O5 System

The temperature–concentration dependence of the electrical conductivity of glasses in the NaPO₃–NaF system has been investigated. The regularities revealed are interpreted from the standpoint of the structural microinhomogeneity of glasses, which is due to the formation of polar structural units of the Na⁺[O^–POO_2/2], Na₂ ⁺[O^– ₂POO_1/2], Na⁺[F^–POO_2/2], and Na⁺F^– types. It is shown that the concentration dependence of the electrical conductivity is governed by the ratio between the concentrations of these structural units.     

Effect of the Synthesis Method on Co-catalysts Based on MCM-41 for the Fischer–Tropsch Reaction

In this work, cobalt catalysts based on ordered mesoporous materials of the MCM-41 type were synthesized and characterized. The synthesis of the catalysts was performed by using different methods: impregnation; incorporation of the metal in the synthesis gel and ionic exchange of the metal by the template. Different characterization techniques were used (N₂ adsorption–desorption, XRD, TPR, SEM and XPS) to study the textural and structural properties of the samples and the metal-support interaction corresponding to each method of synthesis. These samples were tested in the CO Hydrogenation (Fischer–Tropsch Synthesis) by measuring the CO conversion and the selectivity to CO₂ and some groups of hydrocarbons chains. The results show that structural and textural properties as well as the metal-support interactions are affected by the synthesis method. According to this study, catalytic performance is related to the properties of the samples, observing that the metal support interaction highly affects the activity and selectivity of the catalysts.     

Effect of the reaction conditions on the properties of poly(4,4′-diphenylether-1,3,4-oxadiazole)s

Summary Poly(4,4-diphenylether-1,3,4-oxadiazole)s have been prepared by polycondensation of 4,4-diphenylether dicarboxylic acid and hydrazine sulphate, HS, in poly(phosphoric acid), PPA, under different reaction condictions. The products were characterized by viscometry, gel permeation chromatography, ¹H-NMR spectrometry and thermogravimetric analysis. Dense membranes have been prepared and submitted to gas transport and wide angle X-ray diffraction, WAXD, experiments. The differences found in permeability and selectivity parameters, as well as in density and WAXD results, are discussed in terms of their solution viscosities and hydrazide repeat unit contents.     

PEG Modification Effect of Silica on the Suzuki–Miyaura Coupling Reaction Using Silica-immobilized Palladium Catalysts

Abstract  

The Pd phosphine complex catalysts immobilized onto polyethylene glycol (PEG)-modified silica were prepared in order to clarify the effect of the PEG modification on the Suzuki–Miyaura coupling reaction in organic solvents. For the reaction of ethyl p-bromobenzoate and phenylboronic acid in the presence of potassium carbonate in toluene, the PEG-modified silica-immobilized Pd catalysts exhibited much higher activities than the catalysts without PEG modification.     

Effect of Polysaccharides on the Properties of the Mucoadhesive Poly(Vinyl Alcohol) Multicore–Shell Microparticles

This study discusses about the effect of polysaccharides (agar, gum tragacanth, and guar gum) on the properties of the core (organogel)–shell [poly(vinyl alcohol)] microparticles. The size, swelling, and mucoadhesive properties of the poly(vinyl alcohol) microparticles were altered in the presence of the polysaccharides. Thermal analysis confirmed the presence of organogels within the microparticles. Fourier transform infrared spectroscopy confirmed the presence of the polysaccharides within the microparticles. The microparticles were biocompatible in nature. Drug release indicated that an alteration in the shell composition can be used for altering drug release. Ciprofloxacin-loaded microparticles showed sufficient antimicrobial efficiency.     

Theoretical Study of the Water–Gas Shift Reaction on a Au/Hematite Model Catalyst

Topics in Catalysis - Using the density functional theory, the mechanism of the water–gas shift reaction has been investigated employing a model catalyst formed by a Au5 cluster supported on...     

Promotion Effect of FeOx Addition on the Catalytic Activity of Supported Cu Catalysts for the Water–gas Shift Reaction

Among the supported Cu–FeO_x catalysts, Al₂O₃-supported Cu–FeO_x catalyst exhibited the highest activity for WGS reaction. The enhancement of the catalytic activity by adding FeO_x to Cu/Al₂O₃ could be interpreted by the two possibilities; one is the formation of highly dispersed Cu⁰ and the other is the participation of reduced FeO_x in WGS reaction in the presence of Cu⁰.     

Effect of the processing on the production of cordierite–mullite composite

In this study, effect of process on the production of cordierite–mullite composite was studied. For this reason two different processing methods were used in the production of cordierite–mullite composites. In first process, in situ cordierite–mullite composites were produced from cordierite and mullite layers which were formed by using aqueous tape casting method. In second one, composite was produced by addition of pre-produced mullite powders (in different weight percents, 0–30) into cordierite starting powders. The results show that the addition of pre-sintered mullite powders to the cordierite slip has more effect on densification behavior and mechanical properties of composites than layered production method.     

Effect of the acid–base composition of water on the wettability of coals of different ranks (Short Communication)

The results of the experimental studies allowed us to assume that the process characteristics determined by the wettability of coal (dust suppression, hydraulic fracturing, coal washing, etc.) may be insensitive to the acid–base composition of utilized water in a range of pH 4.6–10.     

Effect of Oxygen Pressure on Phase Equilibria in the Lu–Mn–O System

The heterogeneous equilibria attained during thermal dissociation and hydrogen reduction of LuMnO₃ and LuMn₂O₅ are investigated using the static method (vacuum circulation setup) and X-ray powder diffraction analysis of quenched solid phases. It is found that the dissociation of LuMn₂O₅ proceeds in three stages. At the low-oxygen boundary of the homogeneity region of LuMn₂O₅, this compound dissociates into LuMnO₃ and Mn₃O₄ with the liberation of oxygen. Upon reduction, LuMnO₃ dissociates with the formation of Lu₂O₃ and MnO and the liberation of oxygen. Equations for the dissociation and reduction reactions of LuMn₂O₅ and LuMnO₃ are derived, and mass balance equations for these processes are written. A fragment of the isothermal section of the phase diagram of the Lu–Mn–O system at a temperature of 900°C is constructed in the composition–oxygen pressure coordinates.     

Effect of brookite phase on the anatase–rutile transition in titania nanoparticles

Nanosized TiO₂ powders were prepared from the precipitation in the TiCl₄ precursor under various pH values. The prepared titania existed in the form of nanocrystalline anatase with some brookite, which was evidenced by X-ray diffraction analysis and Raman spectroscopy. The average crystallite sizes of the TiO₂ particles heat treated at 450 °C for 2 h are in the range of 7–9 nm. The lattice constant c of anatase increased with increasing the synthesized pH value, whereas the volume fraction of the brookite phase increased with decreasing the synthesized pH value. The beginning and ending temperatures for the anatase–rutile transformation were found to decrease with increasing the volume fraction of the brookite phase. The brookite phase in the powder is responsible for enhancing the anatase–rutile transition.     

The Effect of Nanoparticles on the Mass Transfer in Liquid–Liquid Extraction

This article investigates the effect of nanoparticles on mass transfer in the liquid–liquid extraction for the chemical system of n-butanol–succinic acid–water. For this purpose, nanofluids containing various concentrations of ZnO, carbon nanotubes (CNT), and TiO₂ nanoparticles in water, as base fluid, were prepared. To examine the flow mode effect on mass transfer rate, different fluid modes including dropping and jetting were employed in the process. Results show that mass transfer rate enhancement depends on the kinds and the concentration of nanoparticles and the modes of flow. It was observed that after adding nanoparticles, the mass transfer rate significantly increases up to two-fold for ZnO nanoparticles. Furthermore, the results indicate that under the circumstances in which the mass flow rate is high enough, the effect of nanoparticles on the mass transfer phenomenon is too slight.     

Effect of chromium on the kinetics of the contact melting and the graphite-to-diamond transformation in the Co–Fe–C system

We have studied the effect of chromium concentration in alloys of the Co–Fe system on their interaction with graphite at p, T parameters of thermodynamic stability of diamond. It has been found that addition of chromium to the alloys stabilizes the Me₃C-type carbide, as a result, the structure of a layer of a contact melting at the alloy–graphite interface is identical to a horizontal section of the metastable phase diagram of the Fe–C system. It is shown that addition of chromium to the Co–Fe–C system lowers the eutectic melting temperature by 80–100 K. In this case, the coefficient of carbon diffusion in the melt increases by ∼20–30%. An increased surface activity of a Cr-containing melt with respect to graphite is noted, which is the reason of intensive intrusion of the melt deep into a graphite layer along the grain boundaries. As a result, the number of nucleating diamond crystals and the degree of the graphite→diamond transformation increases.     

Effect of emulsifier on poly(urea–formaldehyde) microencapsulation of tetrachloroethylene

Microcapsules containing tetrachloroethylene as an internal phase were prepared by in situ polymerization of urea–formaldehyde (UF) without prepolymerization. The effects of different emulsifiers on the process of microencapsulation and morphology of microcapsules were investigated. The results show that the emulsifier gum arabic (GA) can effectively slow down the deposition rate of resin onto the oil/water interface, which can lead to smooth and compact surface of microcapsules. The surface activity of GA was also enhanced by complex formation of gum arabic and sodium dodecyl benzene sulfonate. The microcapsules represent good thermal and barrier property as a result of the formation of capsule wall with compact microstructure.     

Effect of the operation parameters on the Fischer–Tropsch synthesis in fluidized bed reactors

For the Fischer–Tropsch synthesis (FTS), this paper presents a numerical investigation in a 3D fluidized bed reactor. The effect of the operation parameters such as bed temperature, superficial gas velocities, particle size and bed heights is discussed. A 3D-CFD model coupled with FTS chemical kinetics was set up. The computational results are compared with experimental data in terms of the components production rates, etc. The analysis shows that the bed heights, the bed temperature, the superficial gas velocities and particle sizes affect the C_5 + selectivity and the reaction rates. Product yields are dependent on the operating conditions especially the temperature.     

Study on the reactivity of ultrafine cerium–molybdenum oxide particles in the absence of molecular oxygen

The cracking, hydrocracking and hydrodesulfurization activities of gallium–aluminum mixed oxide catalysts, with fluoride added as promoter, were investigated. The addition of fluoride to the Ni–Mo catalyst supported on the mixed oxides leads to a significant enhancement in the cracking (no metals) and the hydrocracking (Ni–Mo) reactions of the catalysts, respectively. This enhancement of activity is attributed to the promotional effect of fluoride and the presence of gallium in the support, which leads to catalysts that are more resistant to deactivation. The results of the hydrodesulfurization experiments are not so encouraging. The activity of the catalysts was depressed by the addition of fluoride and with increasing gallium oxide content of the support. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of test parameters in the exposure of Ca–Mg–Al–silicate on yttria stabilized zirconia

Jet engine components need protective coatings to function against both high-temperature and environmental effects. Ingested calcium–magnesium–aluminosilicates (CMAS) dust particulates are extremely detrimental to the life of the coatings. However, many methods exist to investigate the infiltration of CMAS into these coatings with each method exploring a different aspect of the degradation process. To probe the overlap in these methods, this study focuses on the effect of grain size, areal density, and aspect ratio on the infiltration of CMAS into yttria stabilized zirconia. The infiltration depths ranged from 6 up to 85 µm depending on the test conditions.