JOURNAL of the Tunisian Chemical Society

serving the Research, the Education and the Industry

Reaction of amines on N-(1-carbomethoxy-2-benzimidazol) imidates : Synthesis of [1,2-a]benzimidazo-1,3,5-triazin-4-ones

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The action of ethylchloroformate on iminoesters, derived from 2-aminobenzimidazole, leads to the formation of imidates N-(1-carbo-ethoxy-2-benzimidazoyl) 2 . Treatment of theses compounds by primary amines yields to [1,2-a]benzimidazo-1,3,5-triazin-4-one 3.

R. Abderrahim, B. Hajjem, B. Baccar

Pages 367-372

Influence of some parameters on the synthesis of type A, X and Y zeolythes

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Type A, X and Y zeolites have been synthesized from sodic silicoaluminate gels. The influence of the composition of the gel, reaction temperature, alkalinity and aging time on the kinetics of formation and nature and quality of the product has been investigated. High yields of crystals, above 90%, have been obtained.

F. Hamidi, A. Bengueddach, Z. Derriche, F. Fajula, F. Di Renzo

Pages 373-383

Effect of addition of Cr3+ and Eu3+ ions on the reductibility of Ni2+ in X zelithes and on the properties of metallic phase

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The presence of promoter ions in the Ni2+ /zeolithe X system has a great influence on nickel reductibility and formed metallic phases. The addition of Eu3+ ions allowed, after reduction of Ni2+, to the formation of a highly dispersed metallic state of nickel (d ≤ 12 Å). A similar dispersion can be obtained by using Cr3+ but with particle size superior to 20 Å. A comparative study of the reactivity of Ni°-Eu-zeolithe X and Ni°-Cr-zeolithe X systems showed a particular behaviour of nickel particles with diameter equal to or less than 12 Å. The chemisorption and catalytic properties of these particles are attenuated due to the formation of "hydrogen species" strongly chemisorbed on the nickel surface. These species inhibit the contact between sites and molecules to adsorb.

S. Djemel, A. Ghorbel

Pages 385-397

Kinetics of decomposition of diammonium phosphate

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The aim of this work is to make a detailed study of kinetics of the grain's drying of diammonium phosphate (DAP) disposed in a fixed bed in order to determine the mechanisms restricting the thermal decomposition process. The decomposition rate is measured by a microbalance in an TGA apparatus. The solid sample formed by a pile of spherical grains of DAP is hanging on the scale and subject to a constant flux of heat.

M. Baguenne, A. Bellagi

Pages 399-409

Synthesis and characterization of silica gels obtained from Tunisian sand

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Silica gels were obtained by alkaline attack of Tunisian sand. The influence of several pysico-chemical parameters such as temperature, pH, molar ratio K2O/SiO2 size particles and reaction time able to act on the transformations sand-sol and sol-gel was studied. The aerogels obtained by hypercritical drying showed a 5000 m2/g specific area.

J. Bouaziz, B. Elleuch, R. El Gharbi

Pages 411-419

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