Sadiq M.,Chouaïb Doukkali University |
Sahibed-dine A.,Chouaïb Doukkali University |
Baalala M.,Chouaïb Doukkali University |
Nohair K.,Chouaïb Doukkali University |
And 4 more authors.
Arabian Journal of Chemistry | Year: 2011
Synthesis and physico-chemical characterization of a pure magnesium phosphate (MgP) prepared by coprecipitation, and MgP modified by introduction of cobalt-molybdenum (4-12wt.% of MoO3 with the Co/Mo ratio fixed at 0.5) have been carried out. The structural properties of these catalysts were characterized by X-ray diffraction, their textural properties were determined by N2 adsorption-desorption isotherms and the dispersion of cobalt-molybdenum was studied by XPS spectroscopy. Their acid properties have been investigated by in situ FT-IR spectroscopy of adsorbed molecules, often, 2,6-dimethylpyridine (pKa=6.7), pyridine (pKa=5.3). Co-Mo incorporation leads to a modification in the MgP acid-base properties, especially on the acid sites type and number. Thus, lower loading of cobalt-molybdenum species decreased the number of strong Lewis acid sites whereas higher loading increased it. It was found that Lewis acid sites on magnesium phosphates play an important role in the isomerization of 3,3-dimethylbut-1-ene.The 3,3-dimethylbut-1-ene (33DMB1) conversion increases with the reaction temperature from 493 to 653. K for MgP, but decreases after 573. K for MgP supported by Co-Mo. A linear relationship between both types of acid sites and conversion values was found. The deactivation of the catalysts appears at high reaction temperature (>573. K). © 2010.
Bali F.,University of Science and Technology of Oran |
Jalowiecki-Duhamel L.,Unite de Catalyse et Chimie du Solide
Green Energy and Technology | Year: 2010
The effective utilization of CO2 is gaining great attention due to its environmental relevance. As a matter of fact, synthesis of methanol from syngas (CO + H2) is very important in industry and synthesis of methanol from CO2 + H2 is one of the most economic processes. Therefore, it is important to develop new catalysts for this reaction with high activity and selectivity to methanol. Methanol synthesis is carried out at low temperature on copper-based catalysts, such as Cu/ZnO/Al2O3 and Cu/ZnO/Cr2O3 compounds, with various compositions (Klier et al., 1982). Besides, it has been shown that similar catalysts are also active for diene hydrogenation (Jalowiecki et al., 1987; 2006). Previously (Bali et al., 1995; 1996), we have shown that the Cu-Zr-O system prepared by coprecipitation is constituted after calcination of a zirconium and copper solid solution, in which Cu2+cations are inserted into the zirconia lattice, in close contact with copper oxide. The size of the latter varies from crystallized grains to small particles and/or clusters depending on experimental conditions.