69 research outputs found
Influence of acid–base properties of cobalt–molybdenum catalysts supported on magnesium orthophosphates in isomerization of 3,3-dimethylbut-1-ene
AbstractSynthesis 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 653K for MgP, but decreases after 573K 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 (>573K)
DTA/TGA characterization of ZrXCe1-XO2 catalysts and study of their reactivity in soot oxidation
International audienc
High resolution NMR unraveling Cu substitution of Mg in hydrotalcitesethanol reactivity
cited By 1International audienc
Catalytic properties of beta zeolite exchanged with Pd and Fe for toluene total oxidation
Siberia: 'Private' house Lake BaikalColorVolume 137, Page 1
«Les cyclodextrines : nouveaux promoteurs pour la préparation de catalyseurs cobalt supportés sur zircone»
National audienc
Impact of cyclodextrins on the structure and performances of zirconia-supported cobalt catalysts for the oxidation of VOC»
International audienceno abstrac
Total oxidation of formaldehyde over MnOx-CeO2 Catalysts : the effect of acid treatment
The effect of acid treatment in mixed MnOx 12CeO2 samples has
been investigated in the catalytic total oxidation of formaldehyde. The acid
treatment has no effect on the textural and redox properties of the materials when
Mn is stabilized in a MnOx 12CeO2 solid solution (Mn content below 50%).
However, these properties were found to be highly altered by acid treatment
when the solubility limit of Mn in the ceria was exceeded (Mn content above
50%). This enabled access to the primary porosity and oxidized the manganese
species to a higher oxidation state via a Mn dismutation reaction. As a result, the
catalytic activity of pure manganese oxide, after chemical activation, in the
oxidation of formaldehyde is greatly improved\ue0d5at 100 \ub0C, the conversion of
formaldehyde is increased by a factor of 5 and the corresponding intrinsic
reaction rate by 1.4. Combined in situ surface analysis unambiguously identified
formate species as a result of formaldehyde oxidation at room temperature on the
chemically activated pure MnOx. The evolution of various surface species was
monitored by increasing the temperature and in situ FTIR, and XPS results provided direct evidence of the desorption of
monodentate formate species into formaldehyde and the oxidation of bidentate-bridging formate species. Changes in the average
oxidation state of surface manganese confirmed the participation of oxygen from MnOx in the formation of formate species at
room temperature and their transformation into CO2 and H2O when increasing the temperature
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