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LAFJAH Mama
LABORATOIRE DE CHIMIE DES MATERIAUX - LCM
Article 07 :Année de publication 2016
Titre Preparation of mordenite zeolite with expended mesopores by hydrothermal synthesis
   
Revue, référence Journal of Advinses Chemsitry, ISSN 2321-807X Volume 12 Number 5
   
Autres auteurs Boumediéne BENSAFI *
Nadjet CHOUAT
Djamal DARI
Mama LAFJAH
Fatiha DJAFRI
Mohamed SASSI
   
Mots Clefs Mordenite synthesis mesopores N,N-dimethylaniline template
   
Résumé
   Mesostructured mordenite was hydrothermally synthesized using N,N-dimethylaniline (NNDMA) as a new organic template. The synthetized mesoporous zeolite mordenite was characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), N2 physical adsorption (BET), and Fourier transform infrared spectroscopy (FTIR). XRD and FTIR have been used to inform on the mordenite structure. SEM shows crystals with a spherical shape, and N2 physical adsorption confirms the presence of mesoporous channels by BJH method with high surface area. The results show that, in presence of NNDMA as organic template, mesoporous mordenite can be successfully synthesized.
Article 06 :Année de publication 2014
Titre TiO2 nanorods for gas phase photocatalytic applications
   
Revue, référence Catalysis Today, M. Lafjah et al. / Catalysis Today 235 (2014) 193–200
   
Autres auteurs Mama Lafjah
Asma Mayoufi
Emmanuel Schaal
Fatiha Djafri
Abdelkader Bengueddach
Nicolas Keller
Valérie Keller
   
Mots Clefs TiO2 nanorods, Gas-phase, photocatalysis, Hydrogen sulfide, degradation, Methanol degradation
   
Résumé
   ABSTRACT : Anatase TiO2 nanorod photocatalysts were prepared following a two-step procedure, consisting first in the alkaline hydrothermal treatment at 150°C for 24 h of commercial Aeroxide TiO2 P25, and a subsequentcalcination at a temperature between 350°C and 700°C. The final calcination led to the transformationof dried TiO2(B) nanotubes into pure anatase TiO2 nanorods, together with a decrease in surface areaas well as with the maintain of both one-dimensional morphology and anatase phase with the tem-perature increase. In the case of the methanol degradation, an optimum in terms of performances wasobtained for TiO2 nanorods calcined at 500°C, with a surface area of 122m2/g. This resulted from balanced physicochemical properties with increasing the temperature, with the increase in TiO2 crystallinity, ben-eficial for lowering the recombination rate, and the decrease in surface area, associated to the increasein the anatase crystallite size, that lower both adsorption capacity of TiO2 nanorods and ability to pro-duce OH• radicals. By contrast, the optimum in terms of conversion or sulfur removal rate was observedfor nanorods calcined at 380°C in the more rarely studied photocatalytic oxidation of H2S, for whichthe accumulation at the surface of sulfates as ultimate reaction products deactivates the photocatalyst.Indeed, TiO2 nanorods calcined at a lower temperature of 380°C suffered from a strongly less marked deactivation than the Aeroxide TiO2 P25 reference and nanorods calcined at lower as well as at higher temperatures. They might take advantage of a higher surface area of 219m2/g for overcoming their detri-mental lower crystallinity and thus improving their resistance to deactivation, by allowing the storageof larger amounts of poisoning sulfates.
Article 05 :Année de publication 2014
Titre TiO2 nanorods for gas phase photocatalytic applications
   
Revue, référence Catalysis Today, Catalysis Today 235 (2014) 193–200
   
Autres auteurs Mama Lafjah
Asma Mayoufi
Emmanuel Schaal
Fatiha Djafri
Abdelkader Bengueddach
Nicolas Keller
Valérie Keller
   
Mots Clefs TiO2 nanorods, Gas-phase photocatalysis, Hydrogen sulfide degradation, Methanol degradation
   
Résumé
   ABSTRACT : Anatase TiO2 nanorod photocatalysts were prepared following a two-step procedure, consisting first in the alkaline hydrothermal treatment at 150°C for 24 h of commercial Aeroxide TiO2 P25, and a subsequentcalcination at a temperature between 350°C and 700°C. The final calcination led to the transformationof dried TiO2(B) nanotubes into pure anatase TiO2 nanorods, together with a decrease in surface areaas well as with the maintain of both one-dimensional morphology and anatase phase with the tem-perature increase. In the case of the methanol degradation, an optimum in terms of performances wasobtained for TiO2 nanorods calcined at 500°C, with a surface area of 122m2/g. This resulted from balanced physicochemical properties with increasing the temperature, with the increase in TiO2 crystallinity, ben-eficial for lowering the recombination rate, and the decrease in surface area, associated to the increasein the anatase crystallite size, that lower both adsorption capacity of TiO2 nanorods and ability to pro-duce OH• radicals. By contrast, the optimum in terms of conversion or sulfur removal rate was observedfor nanorods calcined at 380°C in the more rarely studied photocatalytic oxidation of H2S, for whichthe accumulation at the surface of sulfates as ultimate reaction products deactivates the photocatalyst.Indeed, TiO2 nanorods calcined at a lower temperature of 380°C suffered from a strongly less marked deactivation than the Aeroxide TiO2 P25 reference and nanorods calcined at lower as well as at higher temperatures. They might take advantage of a higher surface area of 219m2/g for overcoming their detri-mental lower crystallinity and thus improving their resistance to deactivation, by allowing the storageof larger amounts of poisoning sulfates.
Article 04 :Année de publication 2008
Titre Synthèse de la zéolithe aluminotitanosilicate de type BEA par la méthode d'imprégnation par voie humide
   
Revue, référence Annales de Chimie - Science des Matériaux, Ann. Chim. Sci. Mat., 2008, 33 (1), pp.17-26
   
Autres auteurs MANSOUR Riad
DJAFRI Fatiha
BENGUEDDACH Abelkader
KADIRI Mokhtaria
   
Mots Clefs Titanium , Beta zéolite , titanoaluminosilicates, impregnation, Wet method
   
Résumé
   Les zéolithes sont des aluminosilicates microporeux parfaitement cristallins, utilisées principalement comme catalyseurs, échangeurs d’ions et adsorbants. La plus importante des propriétés des zéolithes reste l’activité catalytique (acide ou redox). L’incorporation du titane (Ti) dans la matrice silicate de la zéolithe Bêta, de structure topologique type BEA, lui confère un pouvoir catalytique redox important. La préparation des zéolithes titanoaluminosilicates à large pores a été effectuée selon la méthode d’imprégnation par voie humide, où nous avons apporté une modification au niveau de la préparation du xérogel. Les produits de synthèse sont caractérisés par différentes techniques d’analyse : DRX, IR-TF, adsorption d’azote à 77K (BET), analyse chimique (ICP) et par microscopie électronique à balayage (MEB). La diffraction des rayons X a permis d’identifier les phases zéolithiques présentes dans le solide avec une bonne cristallinité, la spectroscopie infra-rouge confirme l’incorporation du titane dans le réseau zéolithique par une raie d’absorption à 960 cm-1, la microscopie électronique à balayage a révélé que les cristaux sont sous forme sphéroïde avec un diamètre entre 0,4 et 0,5 µm, l’analyse élémentaire nous a permis de déterminer la quantité de titane incorporée dans la zéolithe et les isothermes d’adsorption sont bien de type I avec une surface spécifique estimée à environ 600 m2g-1 .
Article 03 :Année de publication 2007
Titre A new method for synthesis of BEA type boro-titanosilicate catalysts: dry cogel impregnation method
   
Revue, référence Bulletin of the Catalysis Society of India, Bulletin of the Catalysis Society of India ,6, (2007), 34-41.
   
Autres auteurs M. Lafjah
R. Mansour
M. Kadiri
A. Djafri
A.Bengueddach
   
Mots Clefs Isomorphous subtitution, Ti-Beta, sol-gel process, dry gel method, wetness. boro-titanosilicate,
   
Résumé
   A combination of two methods of zeolites synthesis has been employed for the preparation of boro-titanosilicate zeotype catalysts with BEA structure. Hence, the large-pore beta zeolite-like materials containing Ti and B atoms have been synthesized following a method based on the wetness impregnation technique, accordingly, amorphous SiO2-TiO2-B2O3-TEA2O solids have been impregnated with a template solution using tetraethylammonium hydroxide(TEAOH) as a structure-directing agent however, the amorphous powders have been prepared according to the general procedure of dry gel converson method. It was observed that the properties of the [Ti]-BEA catalysts samples are found to be strongly dependent on the method used to prepare the amorphous cogel. Furthemore, the crystallization process was carried out under hydrothermal conditions. It was observed that the properties of the [B,Ti]-BEA samples are found to be strongly dependent on the method used to prepare the amorphous cogel. X-ray diffraction patterns show the BEA stuture type of the obtained materials and FT-IR spectroscopy analysis of the samples indicates that titanium atoms are located mainly in the tetrahedral framework position and that boron atoms has two kinds of coordination namely tetragonal and trigonal one.It should be noted that the [B,Ti]-BEA samples prepared by the new method(DCI : Dry Cogel Impregnation) exhibit better cristallinity and more important microporous volume as well as different morphology and crystal size compared to the conventional wetness impregnation method.
Article 02 :Année de publication 2007
Titre Basic dye removal from aqueous solutions by dodecylsulfate- and dodecyl benzene sulfonate-intercalated hydrotalcite
   
Revue, référence Journal of Hazardous Materials, Journal of Hazardous Materials 153 (2008) 911–918
   
Autres auteurs Mohamed Bouraada a
Mama Lafjah a
Mohand Said Ouali a
* Louis Charles de Menorval b
   
Mots Clefs Surfactant-intercalated hydrotalcite, Sorption isotherm, Kinetics, Basic dye, Surfactants
   
Résumé
   Dodecylsulfate- and dodecyl benzene sulfonate-hydrotalcites were prepared by calcination–rehydratation method. The surfactants intercalation in the interlayer space of hydrotalcite were checked by PXRD and FTIR spectroscopy where the resulting materials were found to be similar to those reported in the literature and were used to remove a basic dye (safranine) from aqueous solutions. The sorption kinetics data fitted the pseudo second order model. The isotherms were established and the parameters calculated. The sorption data fitted the Langmuir model with good values of the determination coefficient. The thermodynamic parameters calculated from Van’t Hoff plots gave a low value of _G◦ (<−20 kJ mol−1) indicating a spontaneous physisorption process. Two regeneration cycles were processed by acetone extraction leading to the same removal capacity of the obtained materials as the original surfactant-intercalated hydrotalcites. The UV–vis spectra of the recovered extracts were similar to the spectrum of safranine, which means that the dye was recovered without any modification.
Article 01 :Année de publication 2006
Titre Synthesis of Borosilicate Zeotypes by Steam-assisted Conversion Method
   
Revue, référence Journal of the Korean Chemical Society, Journal of the Korean Chemical Society 2007, Vol. 51, No.2 pp. 178-185 Printed in the Republic of Korea
   
Autres auteurs R. Mansour*
M. Lafjah
F. Djafri
A. Bengueddach
   
Mots Clefs Borosilicate, Structure Directing Agent, MFI, MEL, Pentasil, Intergrowth, Dry Gel Method, Steam-assisted Method
   
Résumé
   Intermediate pentasil borosilicate zeolite-like materials have been crystallized by a novel method named steam-assisted conversion, which involves vapor-phase transport of water. Indeed, amorphous powders obtained by drying Na2O.SiO2.B2O3.TBA2O gels of various compositions using different boron sources are transformed into crystalline borosilicate zeolite belonging to pentasil family structure by contact with vapors of water under hydrothermal conditions. Using a variant of this method, a new material which has an intermediate structure of MFI/MEL in the ratio 90:10 was crystallized. The results show that steam and sufficiently high pH in the reacting hydrous solid are necessary for the crystallization to proceed. Characterization of the products shows some specific structural aspects which may have its unique catalytic properties. X-ray diffraction patterns of these microporous crystalline borosilicates are subjected to investigation, then, it is shown that the product structure has good crystallinity and is interpreted in terms of regular stacking of pentasil layers correlated by inversion centers (MFI structure) but interrupted by faults consisting of mirror-related layers (MEL structure). The products are also characterized by nitrogen adsorption at 77 K that shows higher microporous volume (0.160 cc/g) than that of pure MFI phase (0.119 cc/g). The obtained materials revealed high surface area (~600 m2/g). The infrared spectrum reveals the presence of an absorption band at 900.75 cm-1 indicating the incorporation of boron in tetrahedral sites in the silicate matrix of the crystalline phase.



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