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Ḩajjah, Yemen

Berenblyum A.S.,Lomonosov Moscow University of Fine Chemical Technology | Al-Wadhaf H.A.,Hajjah University | Katsman E.A.,Lomonosov Moscow University of Fine Chemical Technology | Shamsiev R.S.,Lomonosov Moscow University of Fine Chemical Technology | Koroleva A.A.,Lomonosov Moscow University of Fine Chemical Technology
Petroleum Chemistry | Year: 2014

The reduction reaction of Pd(II) diacetate, a precursor in nanocatalyst synthesis, with molecular hydrogen on silica gel has been studied. A kinetic model involving the autocatalytic mechanism of Pd(II) reduction to Pd(0) and adequately describing the experimental data has been proposed. Similarities and dissimilarities in the mechanism of this process on silica gel and carbon have been revealed. On the basis of quantum-chemical simulation data, it has been suggested that the differences are due to both a high bond energy of the precursor with the support and modifications in geometry of various Pd(II) diacetate species adsorbed on the surface. The controllable reduction of the precursor makes it possible to manufacture materials with a metal particle size of 1.7-2.8 nm according to transmission electron microscopy data. The materials catalyze the reaction of phenylacetylene hydrogenation to styrene with a high activity and selectivity at 25°C and 1 atm of hydrogen. © 2014 Pleiades Publishing, Ltd. Source

Sattar A.A.,Ain Shams University | El-Sayed H.M.,Ain Shams University | Alsuqia I.,Hajjah University
Journal of Magnetism and Magnetic Materials | Year: 2015

CoFe2O4/NiFe2O4 core/shell magnetic nanocomposite was synthesized by using hydrothermal method.The analysis of XRD indicated the coexistence of CoFe2O4, NiFe2O4as core/shell composite. The core/shell structure of the composite sample has been confirmed by HR-TEM images, EDX and FT-IR measurements. The size of obtained core/shell nanoparticles was 17 nm in core diameter and about 3 nm in shell thickness. The magnetization measurements showed that both the coercive field and the saturation magnetization of the resulting core/shell nanocomposite were slightly decreased compared to those of the CoFe2O4 core but the thermal stability is of the magnetization parameter was enhanced. Furthermore, superparamagnetic phase is established at temperatures higher than the room temperature. The results were discussed in terms of the surface pinning and the magnetic interaction at the interface between the core and shell. © 2015 Elsevier B.V.All rights reserved. Source

Benmoussa H.,Gabes University | Elfalleh W.,Gabes University | Farhat A.,Gabes University | Servili M.,University of Perugia | And 2 more authors.
JAOCS, Journal of the American Oil Chemists' Society | Year: 2016

Olive oil with rosemary leaves by microwave assisted infusion (MAI) as an alternative to conventional infusion (CI) was evaluated. Microwave heating was applied to the mixture in order to accelerate diffusion of the rosemary volatile compounds into the olive oil. The volatile components of the aromatized oils were quantified by HS-SPME/GC–MS, as well as several quality indexes such as free fatty acids (FFA), peroxide value (PV), specific coefficients of extinction, chlorophyll and carotenoid content, and color assessment. Fatty acid profiles of the oils aromatized by MAI were compared to those produced by CI. Results showed that the infusion time is reduced from 12 h to 10 min when utilizing MAI in place of CI. MAI treatment caused a slight increase in FFA levels, and specific extinction coefficient indices (K232 and K270). PV during MAI remained unchanged for the first 3 min, after which there was an observable increase. All physico-chemical values were found to be well below the maximum permitted limits. The MAI treatment reduced chlorophyll and carotenoid levels during the final step of aromatization, thus affecting final color. The MAI aromatized oil was characterized by its clear green color (L*, a*, b* parameters). Fatty acid analysis showed that MAI slightly changed the fatty acid composition of the olive oil. This study indicates that MAI appears to be a viable and rapid method to flavor olive oil with rosemary leaves. © 2016, AOCS. Source

Gadallah A.-S.,Cairo University | Alhijry I.A.,Mansoura University | Alhijry I.A.,Hajjah University | Abdelkader H.I.,Mansoura University | Abou Kana M.T.H.,Cairo University
Optics and Laser Technology | Year: 2015

Abstract The influence of [Ag NPs: PM567] complex formation on optical properties of parent PM567 laser dye in 2-hydroxyethyl methacrylate (homomonomer, homopolymer) and 2-hydroxyethyl methacrylate/methyl methacrylate (comonomer, copolymer) hosts was studied at room temperature. The silver nanoparticles were synthesized by chemical reduction method. Its size and concentration was determined by high resolution transmission electron microscope and UV/VIS absorption spectroscopy. The experimental results showed that the optical properties of dye were remarkably enhanced with optimum concentrations of NPs and dye. The effect of different nanoparticle concentrations on the optical properties of complex based not only on NPs and dye concentrations, but also on nature of milieu. Whereas, [1 × 10-4 mol/L PM567:40% C Ag NPs] and [1 × 10-3 mol/L PM567:40% C Ag NPs] were the optimum complexes in case of monomer and polymer hosts respectively. Also, at optimum concentration of PM567 dye in polymeric samples (1 × 10-3 mol/L), the gain values of dye in HEMA were 1.9 and 2.4 with respect to absence and presence of Ag NPs. While in HEMA/MMA copolymer, the gain values were 1.8 and 2.45 respectively. In a deeper study, [1 × 10-3 mol/L: 40% C Ag NPs] complex in HEMA/MMA copolymer host had preferable ASE Slope efficiencies and photostabilities, compared with complex in HEMA homopolymer host. © 2015 Elsevier Ltd. Source

The selective hydrogenation of phenylacetylene (PhA) into styrene (St) in the presence of a palladium nanocatalyst has been investigated. Salient features of this reaction have been revealed, such as independence of the PhA hydrogenation and St hydrogenation (after exhaustion of PhA) rates from the PhA and St concentrations, respectively; their nearly first-order dependence on the hydrogen pressure; and the first order in catalyst loading. The experimental results obtained according to a special plan have been processed using computer programs for various reaction mechanisms. It has been found that adequate description is achieved for the only scheme involving the adsorption one to two PhA and/or St molecules and one to two hydrogen molecules on the active site of the same type. The presence of one hydrogen molecule on the active site leads to the hydrogenation of PhA to St or St to ethylbenzene (EB). In the presence of two adsorbed hydrogen molecules, PhA is selectively hydrogenated to St and nonselectively hydrogenated directly to EB. It has been shown that the nature of the selectivity of the palladium catalyst is determined by the thermodynamics of competitive adsorption of PhA and St. The activation energies of the individual steps of the process have been determined. © 2014 Pleiades Publishing, Ltd. Source

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