Solid Particle Distribution in Centrifugal Impeller Contactors

The recently developed centrifugal impeller is examined to investigate the solid–liquid mixing in a mechanically agitated contactor. Using the sample withdrawal method, the effects of impeller geometrical parameters, impeller rotational speed (200–700 rpm), solid particle size (500–1100 µm), and solid loading (2–10 vol%) on the degree of homogeneity are studied. The axial and the radial solid concentration profiles and the minimum impeller speed for the complete homogenization are also determined. In comparison with a widely used propeller impeller, considerably higher homogeneity values in lower impeller speeds are obtained (90% homogeneity against 16% homogeneity at 200 rpm at the same conditions). Having also lower power consumption makes this a superior impeller in solid–liquid mixing processes especially in shear-sensitive systems.      

Reaction parameters influence on the catalytic performance of copper-silica aerogel in the methanol steam reforming

Steam reforming of methanol was carried out on the copper-silica aerogel catalyst.The effects of reaction temperature,feed rate,water to methanol molar ratio and carrier gas flowrate on the H_2 production rate and CO selectivity were investigated.M ethanol conversion was increased considerably in the range of about 240-300,after which it increased at a slightly lower rate.The used feed flowrate,steam to methanol molar ratio and carrier gas flowwere 1.2-9.0 m L/h,1.2-5.0 and 20-80 m L/min,respectively.Reducing the feed flowrate increased the H_2 production rate.It was found that an increase in the water to methanol ratio and decreasing the carrier gas flowrate slightly increases the H2production rate.Increasing the water to methanol ratio causes the lowest temperature in which CO formation was observed to rise,so that for the ratio of 5.0 no CO formation was detected in temperatures lower than 375℃.In all conditions,by approaching the complete conversion,increasing the main product concentration,increasing the temperature and contact time,and decreasing the steam to methanol ratio,the CO selectivity was increased.These results suggested that CO was formed as a secondary product through reverse water-gas shift reaction and did not participate in the methanol steam reforming reaction mechanism.     

Green synthesis and investigation of antioxidant ability new pyrazines containing pyrrolo[2,1-a]isoquinolines derivatives

In this study, a new, easy and high yield procedure is investigated for the generation of pyrazine containing pyrrolo[2,1-a]isoquinoline derivatives using multicomponent reaction of phthalaldehyde or its derivatives, primary amines, α-haloalketones, electron deficient acetylenic compounds, ammonium acetate and KF/Clinoptilolite nanoparticles (KF/CP NPs) as catalyst in water at room temperature. The reactions of 2-hydroxy phthalaldehyde, primary amines, α-haloketones, electron deficient acetylenic compounds, and ammonium acetate in the presence of KF/CP NPs as catalyst in water at room temperature produce pyrazine derivatives in good yields. Also, in this work, antioxidant ability was studied for a number of prepared compounds employing the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and power of compounds for reducing of ferric ion experiments and evaluating results with synthetic antioxidants (TBHQ and BHT). Comfortable, simple, fast and fresh procedure is the advantages of this study.     

DNA oxidation by peroxo-chromium(v) species: oxidation of guanosine to guanidinohydantoin

Reactions of peroxo-chromium(v) complexes with DNA afforded mainly guanine oxidation yielding, a four-electron oxidation product, guanidinohydantoin, and exhibited extensive base labile strand scission.     

Modified piecewise linear DEA model

Recently, Cook and Zhu have proposed the Piecewise Linear Data Envelopment Analysis (PL-DEA) model, a situation in which a generalization of the DEA methodology which incorporates piecewise linear functions of factors is considered. Standard DEA models provide an efficiency score and targets for an inefficient unit, but the PL-DEA model fails to produce acceptable targets. Thus, this issue has been considered in the piecewise linear CCR model, in which a non-increasing set of multipliers describe the weight function. Also, the piecewise linear CCR model has been enhanced by introducing two MIP models for a two-stage procedure in order to set targets precisely. Furthermore as it follows, the above-mentioned models are compared with each other and an example is provided for the sake of lucidity.     

Investigation of the anchoring silane coupling reagent effect in porphyrin sensitized mesoporous V-TiO2 on the photodegradation efficiency of methyl orange under visible light irradiation

In order to efficient utilization of visible light in the photodegradation reaction, mesoporous vanadium doped TiO₂ (V-TiO₂) particles sensitized by tetrakis(4-carboxyphenyl)porphyrin (TCPP) dyes were synthesized, and characterized. For investigation of the anchoring coupling between porphyrin and TiO₂ surface, two photocatalyst containing ester-like linkage (TCPP–V-TiO₂) and amide-like linkage (TCPP–NH₂–V-TiO₂) were compared in the photodegradation of methyl orange (MO) aqueous solution. It was found that the photocatalytic activity of the TCPP–V-TiO₂ was higher than TCPP–NH₂–V-TiO₂ (95 % compared to 62 %). Importantly, TCPP–V-TiO₂ was particularly stable in the visible light photocatalytic activity after six cycles.     

Behaviour of nematic liquid crystals doped with ferroelectric nanoparticles in the presence of an electric field

A planar nematic liquid crystal cell (NLC) doped with spherical ferroelectric nanoparticles is considered. Polarisation of the nanoparticles are assumed to be along the NLC molecules parallel and antiparallel to the director with equal probability. The NLC molecules anchoring to the cell walls are considered to be strong, while soft anchoring at the nanoparticles surface is supposed. Behaviour of the NLC molecules and nanoparticles in the presence of a perpendicular electric field to the NLC cell is theoretically investigated. The electric field of the nanoparticles is taken into account in the calculations. Freedericksz transition (FT) threshold field in the presence of nanoparticles is found. Then, the director and particles reorientations for the electric fields larger than the threshold field are studied. Measuring the onset of the nanoparticles reorientation is proposed as a new method for the FT threshold measurement.