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.     

Rapid and efficient synthesis of 2-imidazolines and bis-imidazolines under ultrasonic irradiation

Rapid and efficient preparation of 2-imidazolines and bis-imidazolines by reaction of ethylenediamine with nitriles in the presence of catalytic amounts of sulfur under ultrasonic irradiation is reported. The advantages of this system are short reaction times, high yields and the ability to carry out large scale reactions.     

Aromatic poly(sulfone sulfide amide imide)s as new types of soluble thermally stable polymers

A new diamine monomer containing flexible sulfone, sulfide, and amide units was prepared via three steps. Nucleophilic chloro displacement reaction of 4‐aminothiophenol with 4‐nitrobenzoyl chloride in the presence of propylene oxide afforded N‐(4‐mercapto‐phenyl)‐4‐nitrobenzamide and subsequent reduction of the nitro intermediate led to 4‐amino‐N‐(4‐mercapto‐phenyl)benzamide. Two moles of this amino thiophenol compound was reacted with bis‐(4‐chloro phenyl)sulfone to provide a novel diamine monomer. The diamine was reacted with aromatic dianhydrides to form polyimides via a two‐step polycondensation method, formation of poly(amic acid)s, followed by chemical imidization. The resulting polymers were characterized and their physical properties including thermal behavior, thermal stability, solubility and inherent viscosity were studied. Copyright © 2007 John Wiley & Sons, Ltd.     

Synthesis and characterization of novel heat resistant poly(amide imide)s

A series of new poly(amide imide)s was prepared from new diacid containing sulfone, ether, amide and imide groups with various aromatic diamines. The diacid was synthesized via four steps, starting from reaction of 4-aminophenol with 4-nitrobenzoyl chloride in the presence of propylene oxide afforded N-(4-hydroxy phenyl)-4-nitrobenzamide. In the second step, reduction of nitro group resulted in preparation of 4-amino-N-(4-hydroxy phenyl) benzamide. In the next step for the preparation of diamine, the reaction of 4-amino-N-(4-hydroxy phenyl) benzamide with bis-(4-chlorophenyl) sulfone in the presence of K₂CO₃ was achieved. The prepared sulfone ether amide diamine was reacted with two moles of trimellitic anhydride to synthesize related sulfone ether amide imide diacid. The precursors and final monomer were characterized by FT-IR, H-NMR and elemental analysis. Direct polycondensation reaction of the sulfone ether amide imide diacid with different diamines in the presence of triphenyl phosphite afforded five different poly (sulfone ether amide imide amide)s. The obtained polymers were fully characterized and their physical properties including thermal behavior, thermal stability, solubility, and inherent viscosity were studied.     

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.     

Efficient regio- and stereoselective ring opening of epoxides with alcohols, acetic acid and water catalyzed by ammonium decatungstocerate(IV)

Epoxides can be cleaved in a regio- and stereoselective manner under neutral conditions with alcohols and acetic acid in the presence of catalytic amounts of decatungstocerate(IV) ion, ([CeW₁₀O₃₆]⁸⁻), affording the corresponding β-alkoxy and β-acetoxy alcohols in high yields. In water, ring opening of epoxides occurs with this catalyst to produce the corresponding diols in good yields.     

Soluble, thermally stable poly(ester amide)s derived from terephthalic acid bis(carboxydiphenyl methyl)ester and different diamines

Terephthalic acid bis(carboxydiphenyl methyl)ester (TBE) as a new monomer for the preparation of polyamides was synthesized through the nucleophilic substitution reaction of benzilic acid with terephthaloyl chloride. This diester-diacid (TBE) was characterized using conventional spectroscopic methods. Polycondensation reactions of TBE with different aromatic and semi-aromatic diamines via Yamazaki method resulted different poly(ester amide)s. All the polymers were characterized and their physical and thermal properties were studied.