Effect of third-phase properties on benzyl-n-butyl ether synthesis in phase transfer catalytic system

The production of benzyl-n-butyl ether from benzyl chloride and n-butanol is studied in phase transfer catalytic system. A third phase is formed when polyethylene glycol (PEG) and dodecane are used as the phase transfer catalyst (PTC) and an organic solvent, respectively. The production rate at the three-phase system is higher by seven times than that at the two-phase system. The ether production rate and its selectivity are dependent on the initial concentration of n-butanol. These are affected by the properties of the third phase, especially the concentrations of n-butanol and water in the third phase.

n-Butanol reacts with benzyl chloride and potassium hydroxide simultaneously. The reaction between n-butanol and potassium hydroxide occurs in the aqueous phase. Then, the selectivity of ether on a basis of initial n-butanol is below 0.6 in a stirred tank batch reactor. The selectivity is much improved at 0.9 by using a static triphase batch reactor in which the organic and aqueous phases are separated by the third phase. The interphase mass transfer can be accelerated by ultrasonic device.     

Evaluation of protein adsorption on hydrogenated amorphous carbon films by surface plasmon resonance phenomenon

To develop an anti-thrombogenic coating, hydrogenated amorphous carbon (a-C:H) and related films were studied in terms of their protein adsorption during the initial process in thrombogenesis by surface plasmon resonance (SPR) phenomenon using a multilayer device consisting of an a-C:H layer on Au. Two a-C:H films with different hydrogen contents, a nitrogenated a-C:H (a-C:N:H) and a fluorinated amorphous carbon (a-C:F) film were prepared on the Au layer in the multilayer device. Human serum albumin (HSA) in a phosphor buffer (PB) was used as a protein. Na₂HPO₄·12H₂O, NaH₂PO₄·2H₂O and deionized water were mixed to coordinate PB. From the attenuation of reflected light, the SPR angle was determined to the angle at minimum reflection intensity. The observed behavior of the SPR angle indicated that HSA was adsorbed on all films. The SPR angle was analyzed to estimate the multilayer index of the HSA-adsorbed layer on each film. The HSA adsorption ability of both a-C:H and a-C:N:H films was similar, and the absorption ability of the a-C:F film was lower than that of the other films. Hence, the surface polarization dominates the adsorption ability of HSA on a-C:H films and related film.     

Effect of oxidizing agents on selenate formation in a wet FGD

In a coal combustion process, a considerable amount of selenium is captured in the wet FGD, where it is oxidized from selenite to selenate , which is difficult to remove. Diethyl-p-phenylene-diammonium (DPD) absorptiometric analysis and ion chromatography identified peroxodisulfate ion as the dominant oxidizing agent in the FGD liquor. Selenite was easily oxidized to selenate in the presence of and the oxidation was accelerated as the temperature increased. Addition of Mn²⁺ ion was found to be effective in controlling selenate formation. When Mn²⁺ ion was added, oxidized not selenite to selenate but rather Mn²⁺ to MnO₂, which captured some dissolved selenite.     

Properties of Mn-doped p-type InxGa1-xAsyP1-y grown by liquid-phase epitaxy

Epitaxial layers of p-type In_xGa_1-xAs_yP_1-y doped with Mn were grown by liquid-phase epitaxy on (111)-B oriented InP substrates at a growth temperature of 635°C. The doping characteristics and electrical and luminescent properties were studied and compared with those in Zn-doped epilayers. The distribution coefficient of Mn was about 0.1–0.3. The p-type epilayers with hole concentration of up to 3 × 10¹⁸ cm^?3 could be easily obtained by Mn doping. The activation energy of the Mn acceptor was about 40 meV. Mn doping yielded a broad photoluminescent emission spectrum which probably arises from d-shell interaction of the Mn as well as strong phonon coupling. From electron beam-induced current measurements in p-n heterojunctions utilizing Mn, a value of L_n = 2 μm was obtained for the minority carrier diffusion length of electrons in the p-type region.     

REVIEW

The exponential growth of research activities in nanotechnologies, as well the rapidly increasing utilization of microscale technologies in societal applications, is affecting directly the development and implementation of corresponding numerical methodologies in many scientific and technological areas, including heat transfer. Of particular interest are length scales at which the continuum approach ceases to be valid. Molecular Dynamics (MD) simulation is a very promising, general method to study such scales, allowing for the direct simulation of the motion and interaction of particles (atoms or molecules). This paper reviews recent works on molecular dynamics in heat transfer, focusing on, but not limited to, challenging interfacial and phase change phenomena to demonstrate the advantages, potential, and the current limitations of this methodology.     

Multielemental determination of GEOTRACES key trace metals in seawater by ICPMS after preconcentration using an ethylenediaminetriacetic acid chelating resin

GEOTRACES is an international research project on marine biogeochemical cycles of trace elements and their isotopes. GEOTRACES key trace metals in seawater are Al (8-1000 ng/kg), Mn (4-300 ng/kg), Fe (1-100 ng/kg), Cu (30-300 ng/kg), Zn (3-600 ng/kg), and Cd (0.1-100 ng/kg), of which global oceanic distribution will be determined on a number of research cruises. This work introduces a novel method of solid-phase extraction to determine Al, Mn, Fe, Co, Ni, Cu, Zn, Cd, and Pb in seawater by adjusting the pH of the sample to 6 and carrying out a single preconcentration step. The trace metals were collected from approximately 120 mL of seawater using a column of a chelating resin containing the ethylenediaminetriacetic acid functional group and eluted with approximately 15 mL of 1 M HNO3. Mn and Fe in the eluate were measured by inductively coupled plasma mass spectrometry (ICPMS) using the dynamic reaction cell mode, and the other metals were measured using the standard mode. Using this procedure, the trace metals were collected quantitatively, while >99.9% of alkali and alkaline earth metals in seawater were removed. The procedural blank was <7% of the mean concentration in deep ocean waters, except 16% for Pb. The overall detection limit was <14% of the mean concentration in deep ocean waters. The RSD was <9%. Our values for the trace metals in the certified reference materials of seawater NASS-5 and nearshore seawater CASS-4 agreed with the certified values (except that there is no certified value for Al). This method was also successfully applied to the reference materials of open-ocean seawater produced by the SAFe program. Our Fe concentrations were 5.9 +/- 0.7 ng/kg for surface water (S1) and 50.4 +/- 2.9 ng/kg for deep water (D2), which are in agreement with the interlaboratory averages of 5.4 +/- 2.4 and 50.8 +/- 9.5 ng/L, respectively. The data for other metals were oceanographically consistent.     

Theory of film condensation on shock-tube endwall behind reflected shock wave (Part II: Theoretical basis for determination of condensation coefficient)

This paper is concerned with the theoretical basis for the determination of the condensation coefficient of vapor by means of a shock tube. Film condensation on the shock-tube endwall behind a reflected shock wave is analyzed on the basis of the first author's gas-dynamics theory. It is clarified that there exists a transition phenomenon during the growth of a liquid film, that is, the liquid film grows in proportion to time immediately after the reflection of the shock wave, and after a transition time, it grows in proportion to the square root of time. The transition phenomenon between these growths is caused by the change in heat conduction characteristics at the endwall. The reason why the condensation coefficient must be determined before the transition is clarified. © 1997 Scripta Technica, Inc. Heat Trans Jpn Res 25(3): 166–177, 1996     

Atomic origins of the high catalytic activity of nanoporous gold

Distinct from inert bulk gold, nanoparticulate gold has been found to possess remarkable catalytic activity towards oxidation reactions. The catalytic performance of nanoparticulate gold strongly depends on size and support, and catalytic activity usually cannot be observed at characteristic sizes larger than 5 nm. Interestingly, significant catalytic activity can be retained in dealloyed nanoporous gold (NPG) even when its feature lengths are larger than 30 nm. Here we report atomic insights of the NPG catalysis, characterized by spherical-aberration-corrected transmission electron microscopy (TEM) and environmental TEM. A high density of atomic steps and kinks is observed on the curved surfaces of NPG, comparable to 3-5 nm nanoparticles, which are stabilized by hyperboloid-like gold ligaments. In situ TEM observations provide compelling evidence that the surface defects are active sites for the catalytic oxidation of CO and residual Ag stabilizes the atomic steps by suppressing {111} faceting kinetics.     

Preparation of aminoalkyl celluloses and their adsorption and desorption of heavy metal ions

Aminoalkyl celluloses (AmACs) were prepared from 6-chlorodeoxycellulose and aliphatic diamines H₂N(CH₂)_mNH₂ (m = 2, 4, 6, 8). Their adsorption and desorption of divalent heavy metal ions such as Cu²⁺, Mn²⁺, Co²⁺, Ni²⁺ and their mixtures were also investigated in detail. Adsorption of metal ions on AmACs was remarkably affected by the pH of the solution, the metal ion and its initial concentration, and also the number of methylene units in the diamines. No adsorption of metal ions occurred on AmACs in strongly acidic solutions. However, metal ions were adsorbed rapidly on AmACs from weakly acidic solutions and the amount of adsorption increased with increasing pH. The effectiveness of AmACs as adsorbents decreased with increasing length of the methylene moiety, and AmACs from ethylenediamine (m = 2) was most effective. The adsorption of metal ions on AmACs was in the order Cu²⁺ > Ni²⁺ > Co²⁺ > Mn²⁺. Accordingly, their behavior followed the Irving-Williams series and Cu²⁺ ions were preferentially adsorbed from solutions containing metal ion mixtures. The adsorbed ions were easily desorbed from the AmACs by stirring in 0.1 M HCl.     

Effects of Boron, Carbon, and Iron Content on the Stacking Fault Formation during Synthesis of β-SiC Particles in the System SiO2-C-H2

Through the systematic addition of B, C, and Fe, additive effects on the stacking fault formation and the morphology of the particles formed during reaction synthesis of β-SiC were investigated in the present study. The whisker content of the synthesized product and the formation mechanism of whiskers were closely related to the stacking fault density. The addition of B inhibited whisker formation probably because of isotropic imperfection and the suppression of surface diffusion. Increase in the reduction force by using an active carbon source and also adding excess carbon led to an increase in stacking fault density through enhanced whisker formation. In the presence of Fe, the synthesized β-SiC whiskers appeared to possess only a small amount of stacking faults. The growth mechanism was different with Fe; i.e., isotropic growth occurred via a dissolution-precipitation reaction through a liquid phase in the Fe-Si system.