Vapor‐Phase Carbonylation of Dimethoxymethane over H‐Faujasite

Carbonylation gets a phase lift : The usual liquid‐phase, high‐pressure processes for carbonylating formaldehydes are avoided in a novel vapor‐phase reaction. Using an acid zeolite (Faujasite) at near‐atmospheric pressure dimethoxymethane (DMM; the dimethyl acetal of formaldehyde; see scheme) is carbonylated to produce methyl methoxyacetate (MMAc). This approach provides a new route to ethylene glycol under mild conditions.

     

An approach for analysing transportation costs and a case study

One of the important parameters in the determination of optimal transportation system is economy. Therefore, a realistic method based on the technical, economical and operational parameters of various transportation modes, namely, road, railway, and sea routes is required in the analysis of costs. This method will take into consideration the probable price escalations during the lifetime of a certain transportation system. The cost of a unit of cargo or passenger per route length should be considered since it is an indicator of economics. In this paper, an approach for transportation cost analysis based on the economic analysis of the alternative modes of cargo or passenger transportation, is presented.     

High resolution electronic absorption spectra of aniline, anilino and silicon dioxide

High resolution electronic absorption spectra of aniline and anilino free radical have been recorded in the vapor phase at room temperature by flash photolysis technique, and subsequent reactions have been investigated by kinetic spectroscopy. It was possible to follow the kinetics of the anilino radical's decay which occurred predominantly by bimolecular recombination. Decay parameters of anilino free radical were measured from the absorption bands.     

Experimental and numerical investigation of pressure drop coefficient and static pressure difference in a tangential inlet cyclone separator

The aim of this study was to investigate the pressure drop coefficient and the static pressure difference related to the natural vortex length and to evaluate the results for gas-particle applications. CFD simulations were carried out using a numerical technique which had been verified previously. Results obtained from the numerical simulations were compared with the experimental data. Analysis of the results showed that the pressure drop coefficient decreases with the increasing inlet velocity, becoming almost constant above a certain value of the inlet velocity. The reason is that the effect of viscous forces decreases at high Reynolds numbers. The pressure drop coefficient also decreases with the increasing exit pipe diameter and decreasing exit pipe length.     

Some characteristic behavior of mixed spin-1/2 and spin-1 Ising nano-tube

The magnetization of a cylindrical Ising nano-tube is investigated by the use of the effective field theory with correlations. The effects of the crystal field couplings at the surface shell to the order parameters, susceptibility, internal energy, specific heat and free energy are investigated. Some characteristic phenomena are examined in the thermal variations, depending on crystal field term. Moreover, tricritical and critical points are found on the (D/J,kT/J) plane, where D/J and kT/J are reduced crystal-field and temperature, respectively.     

p-Hertz excitation spectroscopy of an optical antenna, optical transmitter-receiver mechanism

o-Xylene sensitized biacetyl fluorescence and phosphorescence have been investigated and photosensitized fluorescence and phosphorescence lifetimes of biacetyl in the vapor phase have been determined. Attempts to detect the triplet of biacetyl by its absorption spectrum were unsuccessful, primarily due to, it is believed, the low extinction coefficients of the triplet, and the low triplet concentrations produced by the optical pumping device at room temperature.     

Speciation of Cr(III) and Cr(VI) in Environmental Samples after Solid Phase Extraction on Amberlite XAD–2000

A method for speciation of Cr(III) and Cr(VI) in real samples has been developed. Cr(VI) has been separated from Cr(III) and preconcentrated as its pyrrolidinedithiocarbamate (APDC) complex by using a column containing Amberlite XAD–2000 resin and determined by FAAS. Total chromium has also been determined by FAAS after conversion of Cr(III) to Cr(VI) by oxidation with KMnO₄. Cr(III) has been calculated by subtracting Cr(VI) from the total. The effect of pH, flow‐rate, adsorption and batch capacity and effect of various metal cations and salt anions on the sorption onto the resin were investigated. The adsorption is quantitative in the pH range of 1.5–2.5, and Cr(VI) ion was desorbed by using H₂SO₄ in acetone. The recovery of Cr(VI) was 97 ± 4 at a 95% confidence level. The highest preconcentration factor was 80 for a 200 mL sample volume. The adsorption and batch capacity of sorbent were 7.4 and 8.0 mg g^?1 Cr(VI), respectively, and loading half time was 5.0 min. The detection limit of Cr(VI) is 0.6 μg/L. The procedure has been applied to the determination and speciation of chromium in stream water, tap water, mineral spring water and spring water. Also, the proposed method was applied to total chromium preconcentration in microwave digested moss and rock samples with satisfactory results. The developed method was validated with CRM‐TMDW‐500 (Certified Reference Material Trace Metals in Drinking Water) and BCR‐CRM 144R s (Certified Reference Material Sewage Sludge, Domestic Origin) and the results obtained were in good agreement with the certified values. The relative standard deviations were below 6%.     

Kinetics and thermodynamics of the adsorption of some dyestuffs and p-nitrophenol by chitosan and MCM-chitosan from aqueous solution

The effect of initial concentration, temperature, and shaking rate on the adsorption of three dyestuffs [orange II (O-II), crystal violet (CV), and reactive blue 5 (RB5)] and an ideal adsorbate, p-nitrophenol (PNP), by chitosan (Sigma C-3646) and the effect of temperature on the adsorption of O-II and CV by monocarboxymethylated chitosan (MCM-chitosan) were investigated. Kinetic data obtained for the adsorption of each dyestuff and PNP by chitosan and of O-II and CV by MCM-chitosan at different temperatures were applied to the Lagergren equation, and adsorption rate constants (k(ads)) at these temperatures were determined. These rate constants related to the adsorption of O-II and RB5 by chitosan and of O-II by MCM-chitosan were applied to the Arrhenius equation, and activation energies (E(a)) were determined. In addition, the isotherms for adsorption, at different temperatures, of each dyestuff and PNP by chitosan and of O-II and CV by MCM-chitosan were also determined. These isothermal data were applied to linear forms of isotherm equations that they fit, and isotherm constants were calculated. Because the isotherm curves obtained for the adsorption of O-II and CV by chitosan and of CV by MCM-chitosan fit the Langmuir adsorption isotherm, b constants were applied to thermodynamic equations, and thermodynamic parameters (delta G, delta H, and delta S) were calculated. Lastly, chitosan and MCM-chitosan were compared with respect to the ability to take up the dyestuffs and PNP.     

Simulation and micro-fabrication of optically switchable split ring resonators

The effect of conductivity variation as a proposed method for the investigation of photoconductive switching properties of split ring resonators (SRRs) is simulated. Three different systems that are applicable under certain fabrication and/or optical excitation conditions are described. The simulated transmission spectrum indicates that for a large range of dark conductivity values, complete switching of the SRR resonance is possible. One of the simulated systems, involving split ring resonators on Si substrate, was fabricated and characterized. The transmission spectrum of that system was measured, with the Si in its high-resistivity state, and a −60 dB dip between 108 and 115 GHz, due to SRRs magnetic resonance, was observed.     

Experimental and theoretical investigation of the drilling of alumina ceramic using Nd:YAG pulsed laser

Alumina ceramics have found wide range of applications from semiconductors, communication technologies, medical devices, automotive to aerospace industries. Processing of alumina ceramics is rather difficult due to its high degree of brittleness, hardness, low thermal diffusivity and conductivity. Rapid improvements in laser technologies in recent years make the laser among the most convenient processing tools for difficult-to-machine materials such as hardened metals, ceramics and composites. This is particularly evident as lasers have become an inexpensive and controllable alternative to conventional hole drilling methods. This paper reports theoretical and experimental results of drilling the alumina ceramic with thicknesses of 5 mm and 10.5 mm using milisecond pulsed Nd:YAG laser. Effects of the laser peak power, pulse duration, repetition rate and focal plane position have been determined using optical and Scanning Electron Microscopy (SEM) images taken from cross-sections of the drilled alumina ceramic samples. In addition to dimensional analysis of the samples, microstructural investigations have also been examined. It has been observed that, the depth of the crater can be controlled as a function of the peak power and the pulse duration for a single laser pulse application without any defect. Crater depth can be increased by increasing the number of laser pulses with some defects. In addition to experimental work, conditions have been simulated using ANYS FLUENT package providing results, which are in good agreement with the experimental results.