Ethene hydrogenation by Rh/TiO2 under SMSI conditions

Hydrogenation of ethene has been studied at 185–230 K on a Rh/TiO₂ catalyst reduced at 473–773 K. The activity decreases on increasing the reduction temperature, even at 500 K, but it is more evident when reduction is carried out at 773 K. Oxidation and reduction recovers the activity in hydrogenation.     

Oxidation/reduction kinetics of supported Rh/Rh2O3 nanoparticles in plug flow conditions using dispersive EXAFS

The kinetics of oxidation and reduction of Al(2)O(3) supported Rh nanoparticles have been determined on a 50 millisecond timescale using energy dispersive EXAFS (EDE).     

Oscillatory behavior of rare-gas atoms in SWCNT

In this paper, we have investigated both the process of rare-gas atoms (He, Ne, Ar, Kr, Xe) injected into single-wall carbon nanotube (SWNT) and the mechanical oscillatory behavior of rare-gas atoms sliding in a SWCNT by using molecular dynamics simulations. The minimal diameters of SWCNT to encapsulate rare-gas atoms are obtained, which are from 6.246 to 7.828 A. The threshold energies to encapsulate rare-gas atoms in SWCNT are also presented, which are less than 0.15 eV/atom. The oscillatory frequencies of the encapsulated atoms in zigzag SWCNT have been studied. The oscillatory frequencies are insensitive to the initial kinetic energy, but they are sensitive to the lengths and the radius of the tube, and they decrease as the length and the radius of the tube increases.     

Some aspects of metal-support strong interactions in Rh/Al2O3 catalyst under oxidising and reducing conditions

The aim of the Letter is to elucidate the nature of metal-support interaction in the 2 wt% Rh/Al₂O₃ catalyst obtained by annealing Rh–O–Al xerogel at 1113 K in air.XPS, HRTEM, and XRD results reveal that during the Rh–O–Al xerogel annealing in air, rhodium incorporates into forming alumina, which results mostly in Rh⁴⁺/δ-Al₂O₃ solid solution formation.However, in the course of the catalyst reduction at 773 with H₂ and at 823 K with CH₄ the Rh⁴⁺/δ-Al₂O₃ solid solution transforms into Rh–Al alloy. The islands of rhodium form on the surface of the Rh–Al alloy nanocrystallites if the reduction is slow enough.     

Erythrocyte electrokinetic behavior under low ionic strength conditions

Under low ionic strength conditions, a linear approximation of the electrostatic potential within the charged polyelectrolyte layer coating the membrane bilayer leads to overestimation of the red cell electrokinetic mobility. Considering the full non linearized Poisson-Boltzmann and Navier-Stokes equations relative to the erythrocyte system, the deviation at low ionic strength between theoretical and experimental values for the cell mobility then almost disappears. A weak glycocalyx expansion may account for the remaining differences. However, this result is in contrast with previously suggested explanations involving an important stretching of the polyelectrolyte chains to interpret the “artificial” erythrocyte aggregation at low ionic strength. Under such conditions cell aggregation is probably induced by haemolysate adsorption onto the erythrocyte membrane and is unlikely to be the consequence of a strong interfacial rearrangement.     

Fragmentation behavior of DOTA complexes under different activation conditions

We have investigated the fragmentation behavior of a number of DOTA‐metal complexes under collision‐induced dissociation, infrared‐multiphoton dissociation and higher‐energy collisional dissociation activation conditions. Both, positive and negative ion mode electrospray ionization was applied. The results show that characteristic fragmentations were obtained for the metal‐complexes under the investigated conditions. All elemental compositions of fragment ions have been unambiguously identified by high resolution‐accurate mass measurements. Certain trends, for instance eliminations of carbon dioxide, alkyl and amine residues, were observed that coincide with the size of the metal and its location within the periodic table. Additionally, lanthanide, aluminium and indium species with even oxidation state or containing a radical have been detected. To further investigate the observed water capture during activation, deuterium labeling experiments have also been carried out. Copyright © 2017 John Wiley & Sons, Ltd.     

Thermal behavior pattern of tributyl phosphate under adiabatic conditions

Violent decomposition of Tributyl Phosphate (TBP), a widely employed extractant in the Plutonium Uranium Extraction process of nuclear fueling reprocessing plants in the presence of Nitric acid at temperatures in excess of 130 °C is a matter of concern in serious accidents including in the Savannah River (USA) and Tomsk (Russia). The thermal behavior of TBP under adiabatic conditions employing the world’s benchmark adiabatic calorimeter, the Accelerating Rate Calorimeter is examined. TBP shows multiple self heating exothermic activities with the onset of primary exotherm at 250 °C. The exothermic activity is accompanied by considerable pressure rise. The thermal decomposition of TBP is found to follow first order Arrhenius kinetic model. TBP loses about 70% of its chemical moieties as volatile matter during the exothermic decomposition. Spectroscopic methods are used to elucidate the degradation pathway.     

Evaluating shape memory behavior of polymer under deep-drawing conditions

Thermoplastic polyurethanes (TPU) are a popular family of shape memory polymers (SMP) due to their excellent abrasion & weather resistant, and mechanical strength. However, conventional processing operations or their combination with other polymers by adhesion or blending can affect their unique shape memory behavior. Currently, there are no effective methods to study and quantify the shape memory behavior of SMP based polymer laminates as they would respond to deep drawing operations. In this paper, a new method was introduced to effectively quantify the recovery behavior of TPU based polymer laminates undergoing simultaneous stretching and bending operations at different processing temperatures. The results presented show the value of developing a shape recovery characterization method that resembles the stresses of thermoforming to properly assess formability of shape memory polymers used in laminate constructions.     

Electrochemical behavior of Pd–Rh alloys

Pd–Rh alloys were prepared by electrochemical codeposition. Bulk compositions of the alloys were determined by the energy dispersive X-ray analysis method, while surface compositions were determined from the potential of the surface oxide reduction peak. Cyclic voltammograms, recorded in 0.5 M H₂SO₄ for Pd–Rh alloys of different bulk and surface compositions, are intermediate between curves characteristic of Pd and Rh. The influence of potential cycling on electrochemical properties and surface morphologies of the alloys was studied. Due to electrochemical dissolution of metals, both alloy surface and bulk become enriched with Pd. Carbon oxides were adsorbed at a constant potential from the range of hydrogen adsorption. The presence of adsorbed CO₂ causes remarkable diminution of hydrogen adsorption but it does not significantly influence hydrogen insertion into the alloy bulk. On the other hand, in the presence of adsorbed CO, both hydrogen absorption and adsorption are strongly suppressed. Oxidative removal of the adsorbates results in a characteristic voltammetric peak, whose potential increases with the decrease in Rh surface content. Electron per site (eps) values calculated for the oxidation of the adsorbates change with alloy surface composition, more for CO₂ than CO adsorption, indicating the variation of the structure and composition of CO₂ and CO adsorption products. The course of the dependence of eps values on surface composition suggests that the products of CO₂ and CO adsorption on Pd–Rh alloys are similar but not totally identical.     

Phase behavior of polymer blends under equilibrium and nonequilibrium conditions

This contribution embraces two topics related to phase behavior of polymer blends under equilibrium and nonequilibrium. 1. Polymer blends can undergo different phase changes as liquid-liquid phase transition and crystallization. Coupling of demixing and crystallization may occur at the kinetic stage. This is illustrated by blends of poly(ϵ-caprolactone)(PCL) and poly(styrene-co-acrylonitrile)(SAN). 2. Extension of studies to blend systems under flow is necessary for the better understanding of structure formation in polymer blends outside equilibrium. Polymer molecules will be oriented and stretched when subjected to flow. This may result in flow-induced phenomena. Effects of flow on the phase behavior have been studied only for a few blends, as yet. The primary observation was flow-induced miscibility. Apparent shifts of the phase transition temperatures will be discussed qualitatively in terms of a decoupled mode theory.     

Oscillatory behavior during the oxygen oxidation of ascorbic acid

The oscillatory phenomenon was observed in aqueous solution during the oxidation of ascorbic acid by oxygen. Even though the exact number and amplitude of the oscillations could not be exactly duplicated for each and every run, such factors as temperature, concentration of ascorbic acid, cupric ions, and pH affecting the oscillatory behavior were studied, and those regions where oscillations occurred were delineated. A mechanism consistent with the oscillatory behavior is proposed and discussed.     

Investigation of shear thinning behavior and microstructures of MWCNT/epoxy and CNF/epoxy suspensions under steady shear conditions

This report investigates the steady-state viscosities of multiwall carbon nanotube (MWCNT)/epoxy and carbon nanofiber (CNF)/epoxy suspensions with varying filler concentrations under different shear rates at various temperatures. In situ observation of filler networks suggests the build-up of shear induced MWCNT and CNF agglomerates at low shear rates, which correlates with the measured shear thinning behavior. The agglomeration process in MWCNT/epoxy suspensions is enhanced at lower shear rates in the case of higher temperatures, whereas, at high shear rates, both nano-fillers show good dispersion. Shear thinning behavior is observed for both types of fillers, and shear thinning exponential parameters are evaluated as a function of filler content. The shear thinning exponent increases in conjunction with increase in filler content, but it is found to saturate at a specific value, independently of filler material. Finally, the micromechanical elasticity-based analogy model is applied to the prediction of steady state shear viscosity of suspensions at higher shear rates with the assumption of complete dispersion and alignment of individual nano-fillers in suspensions. The predicted viscosities and the experimental data at higher shear rates are compared. The results conclude that fairly good agreement can be seen for the cases of CNF/epoxy suspensions at lower temperatures, whereas MWCNT/epoxy suspensions and CNF/epoxy suspensions at higher temperatures show discrepancy between the prediction and the experimental data.     

Dual behavior of alcohols in iodine-catalyzed esterification under solvent-free reaction conditions

The dual behavior phenomenon of alcohols in iodine-catalyzed esterification under solvent-free reaction conditions (SFRCs) is described; the governing factor is the stability of the carbonium ion generated from the alcohol; high concentration reaction conditions (HCRCs) or dilute solutions are much less suitable. In the case of benzylic alcohols, loss of optical activity was noted, whereas alkyl alcohols furnished a product with retention of stereochemistry.     

Investigation of agricultural residues pyrolysis behavior under inert and oxidative conditions

Three samples of biomass including rice straw, corn straw and corncob were analyzed by using TG–MS analyzer. The relevance of the oxidizing versus inert atmosphere to the conversion of Chinese typical agricultural residues are discussed and analyzed. Firstly the effect of oxygen concentration on three biomass conversion pathway is discussed. Secondly the releasing temperature and quantities of major non-condensable gases and tar components are analyzed, and finally the kinetic parameters is calculated and compared.The results show that the oxygen concentration and fuel type play an important role in biomass conversion pathway. All the detected non-condensable gases are favored by oxidative conditions for three samples. With the increase of oxygen concentration, all the condensable gases except H₂ are released over narrower temperature ranges under oxidizing conditions. All the tar components mainly evolve within 300–700 °C, with the increase of oxygen concentration, these major tar components show different features: except that benzene and phenol quickly decreases, other tar components basically changes moderately. The Coats and Redfern integral method is used for kinetic modeling, and Malek method is adopted to select the proper mechanism function. Most of experimental data can be simulated by F1 mechanism model. For the first temperature range of all samples, the values of the activation energy and of the reaction order are lower compared to the case of inert pyrolysis.     

Pyrolysis behavior of pectin under the conditions that simulate cigarette smoking

In this paper, the formation mechanism of pyrolysis gases released during the pyrolysis of pectin under the conditions that simulate cigarette smouldering was investigated by thermogravimetric analysis coupled to Fourier transform infrared spectrometer (TG-FTIR). Moreover, the combustion behavior of pyrolysis gases was studied by micro-scale combustion calorimetry (MCC). TG-FTIR results illustrated that the composition of the gaseous products was mainly composed of CO₂, H₂O, CO, methanol, methane and carbonyl compounds. MCC results demonstrated that the combustion of pectin was mainly determined by the prolysis gases formed in the temperature range of 200-300 °C. Flash pyrolysis experiment in combination with high performance liquid chromatography (FPy-HPLC) was used to study the pyrolytic formation of eight carbonyl compounds (i.e. formaldehyde, acetaldehyde, acetone, acrolein, propionaldehyde, crotonaldehyde, methyl ethyl ketone and butyraldehyde) during the pyrolysis of pectin under the pyrolysis conditions of cigarette puffing. Results demonstrated that pyrolysis temperature influenced the formation of acetaldehyde, acrolein, propionaldehyde and butyraldehyde greatly, while nitrogen flow affected the generation of formaldehyde, acetone, crotonaldehyde and methyl ethyl ketone deeply.     

Deformation behavior of thin,compliant layers under tensile loading conditions

In this article, a connection is made between the behavior of thin layers of Newtonian liquids under tensile loading conditions and the behavior of highly deformable elastic or viscoelastic solids, which are more commonly used as adhesives. The behavior of Newtonian liquids is understood in the most quantitative detail and serves as a starting point for understanding the origins of fingering and cavitation instabilities that appear when the tensile deformation rates applied to these layers are sufficiently large. Similar instabilities appear in solid systems and can be attributed to common features of the stress distribution for incompressible liquids and solids. A unifying treatment is presented that can be used to understand the overall deformation behavior and adhesive performance of a wide variety of solid and liquid systems that are typically applied as thin layers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4023–4043, 2004     

Oscillatory regime of titanium anodization under voltage control

Regular current oscillations during anodization of titanium in potentiostatic conditions were postulated in the literature but never documented experimentally. We here report emergence of such oscillatory anodization on Ti submitted previously to the activation procedure. Activation consisted in remaining the specimen under open circuit conditions in the electrolyte containing fluoride ions. The sign of the activation end point was fast drop of the electrode potential to negative values, well below the potential of the cathodic hydrogen evolution. At the active state titanium exposed to the electrolyte its surface free of oxides and subsequent anodization occurred on the bare metal and not on the metal covered with native oxide.Oscillations were observed in 1 M H₂SO₄ in the voltage range from 6 to 30 V in both voltage scan and step experiments. Their amplitude, shape and spectral character changed with anodization voltage. Electrolyte mixing had no influence on oscillations suggesting no role played by the transport in the electrolyte bulk. At elevated temperature oscillations were more regular and similar was the influence of mixture of H₂SO_4aq with ethylene glycol. The latter introduced however strong ohmic voltage drop in the electrolyte this causing the change of the shape and periods of oscillations.     

Pt／YSZ固体电解质界面的电化学动力学研究

用循环伏安，线性扫描等电化学方法研究Ｐｔ／ＹＳＺ固体电解质界面的电化学行为，发现氧在Ｐｔ上的电化学吸附过程是Ｔｅｍｋｉｎ吸附过程，吸附量随时间对数增加，吸附氧的阴极还原是不可逆的过程，通过研究获得吸附氧阴极还原过电荷传递系数，Ｔｅｍｋｉｎ系数等重要参数。     

On the anomalous behavior of thiodiglycol under conditions of the vinylation reaction

Conclusions The interaction of thiodiglycol with acetylene under the usual vinylation conditions is accompanied by an anomalous reaction, leading to vinyl ethers of monothioethylene glycol.