Cobalt promoted Ni/MgAl2O4 catalyst in lean methane catalytic oxidation

In the present research, magnesium aluminate spinel was prepared as catalyst support using a novel, facile, and efficient mechanochemical method. The Co-promoted catalysts with 20 wt.% of Ni were fabricated using an impregnation route and the samples were analyzed by the X-ray diffraction (XRD), N₂ adsorption/desorption (BET), temperature-programmed reduction and desorption (H₂-TPR and O₂-TPD), and field emission scanning electron microscopy (FESEM) tests. The results confirmed that all samples have a mesoporous structure with a high specific surface area and the presence of cobalt caused complete CH₄ oxidation at low temperatures, and no side reactions were observed. The results indicated that the 3%Co-20%Ni/MgAl₂O₄ catalyst was the optimal sample among the prepared catalysts, owing to the improvement of reduction features and oxygen mobility. The 50 and 90% of methane conversion was obtained at 530 and 600 °C, respectively. Also, the influence of calcination temperature, GHSV, and feed ratio was determined on the catalytic activity. The obtained outcomes revealed that the calcination temperature has a significant effect on the textural properties and catalytic efficiency. The sample calcined at 700 °C showed the weakest performance, which was related to the sintering of particles at high temperatures. The catalytic stability showed that the 3%Co-20%Ni/MgAl₂O₄ has acceptable stability during 600 min time of reaction.

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Some necessary and sufficient conditions for Hypercyclicity Criterion

We give necessary and sufficient conditions for an operator on a separable Hilbert space to satisfy the hypercyclicity criterion. This paper is a part of the second author’s Doctoral thesis, written at Shiraz University under the direction of the first author.     

Poly(N‐Bromobenzene‐1,3‐Disulfonylamide), N,N,N′,N′‐Tetrabromobenzene‐1,3‐Disulfonylamide and DABCO‐Bromine Complex: As Novel Reagents for the Oxidative Coupling of Thiols to Disulfides

An efficient method for the oxidative coupling of thiols to their corresponding disulfides by new reagents poly(N‐bromobenzene‐1,3‐disulfonylamide) PBBS , N,N,N′,N′‐tetrabromobenzene‐1,3‐disulfonylamide TBBDA and DABCO‐bromine complex is described. The reaction was applicable to a variety of thiols with high chemoselectivity.     

Supercritical carbon dioxide extraction of Mentha pulegium L. essential oil

The dependence of Mentha pulegium L. (pennyroyal) essential oil composition, obtained by supercritical carbon dioxide (SC-CO₂), with the following parameters: pressure, temperature, extraction time (dynamic), and modifier (methanol) was studied. The results were also compared with those obtained by conventional hydrodistillation method in laboratory conditions. Regarding the percentages of menthone (30.3%) and pulegone (52.0%), the optimum SFE results were obtained at the following experimental conditions: pressure=100 atm, T=35 °C, dynamic time=10 min, and V_modifier=0 μl. The results of hydrodistillation showed that the major components of M. pulegium L. were pulegone (37.8%), menthone (20.3%), and piperitenone (6.8%). The evaluation of the composition of each extract was performed by gas chromatography-mass spectrometry.     

Normal subgroup based power graph of finite groups

Ricerche di Matematica - Let G be a finite group and $$N \unlhd G$$ . The normal subgroup based power graph of G, $$\Gamma _N(G)$$ , is an undirected graph with vertex set $$(G{\setminus }N) \cup...     

Using a new solvation model for thermodynamic study on the interaction of nickel with human growth hormone

Thermodynamics of the interaction between Ni²⁺ and human growth hormone (hGH) were determined at 27 °C in Nail solution by isothermal titration calorimetry. A new method to predict protein penetration and the effect of metal ions on the stability of proteins is introduced. The new solvation model was used to reproduce the enthalpies of Ni²⁺-hGH interaction over the whole range of Ni²⁺ concentrations. The solvation parameters recovered from the new equation, attributed to the structural change of hGH and its biological activity.     

Kinetic study of triphenylphosphine addition to para‐benzoquinone

Kinetics of the addition reaction of triphenylphosphine to para‐benzoquinone in 1,2‐dichloroethane as solvent was studied. Initial rate method was used to determine the order of the reaction with respect to the reactants. Pseudo‐first‐order method was also used to calculate the rate constant. This reaction was monitored by UV‐vis spectrophotometry at 520 nm by variable time method. On the basis of the obtained results, the Arrhenius equation of this reaction was obtained: The activation parameters, E_a, ΔH^#, ΔG^#, and ΔS^# at 300 K were 5.701, 6.294, 19.958 kcal mol^?1 and ?45.853 cal mol^?1 K^?1, respectively. This reaction is first and second order with respect to triphenylphosphine and para‐benzoquinone, respectively. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36:472–479, 2004     

Chromium Trioxide Supported onto Wet Silica Gel: Rapid Oxidation of Alcohols to Carbonyl Compounds Under Microwave Irradiation in Solventless System

In an environmentally benign system, alcohols are rapidly oxidized to carbonyl compounds using CrO 3 supported onto wet silica gel as an oxidant under microwave irradiation.