Search results for "Calcination"
showing 10 items of 112 documents
A calcined clay fixed bed adsorption studies for the removal of heavy metals from aqueous solutions
2021
Abstract A natural clay material from southern Tunisia was used as a low cost sorbent in a column-wise removal of metal pollutants. This is fundamentally important for a sustainable wastewater treatment strategy. This work has been performed within the framework of a project aiming to the valorization of natural geomaterials, from Tunisia, in several environmental applications. Column adsorption experiments were carried out for a better production of cleaner effluents and further understanding of the main mechanisms involved in the removal process, through a dynamic methodology, that would allow an industrial scale treatment. A calcined clay sample was used as an adsorbent for the removal o…
CoOx catalysts supported on alumina and alumina-baria: influence of the support on the cobalt species and their activity in NO reduction by C3H6 in l…
2003
Abstract CoO x catalysts (Co 1 and 3 wt.%) were prepared by incipient-wetness impregnation of the supports, Al 2 O 3 and Al 2 O 3 (80 wt.%)-BaO (20 wt.%), and calcined at 500 and 800 °C. The samples were characterized by X-ray diffraction (XRD) and BET techniques. H 2 -temperature programmed reduction (TPR) and UV-Vis diffuse reflectance spectroscopy (DRS) spectra were recorded with the aim to identify the different Co species formed. The presence of Co 2+ species tetrahedrally and octahedrally coordinated appears strongly influenced by the nature of the support and the cobalt content. Co 3 O 4 particles were detected after calcination at 500 °C, a successive treatment at 800 °C promotes th…
A study of the behaviour of Pt supported on CeO2–ZrO2/Al2O3–BaO as NO storage–reduction catalyst for the treatment of lean burn engine emissions
2002
Abstract The behaviour of a Pt(1 wt.%) supported on CeO2–ZrO2(20 wt.%)/Al2O3(64 wt.%)–BaO(16 wt.%) as a novel NOx storage–reduction catalyst is studied by reactivity tests and DRIFT experiments and compared with that of Pt(1%)–BaO(15 wt.%) on alumina. The former catalyst, designed as a hydrothermally stable sample, is composed of an alumina modified with Ba ions and an overlayer of ceria-zirconia. The results pointed out that during the calcination barium ions migrates over the surface of the catalyst which thus show a good NOx storage–reduction behaviour comparable with that of Pt–BaO on alumina, although Ba ions result much better dispersed.
Thermal stability, structural properties and catalytic activity of Pd catalysts supported on Al2O3–CeO2–BaO mixed oxides prepared by sol–gel method
2003
Abstract Al2O3–CeO2–BaO oxides with constant Al/Ba mass ratio and increasing cerium content were prepared, using the sol–gel procedure, and calcined at 1000 °C for 5 h. The influence of barium oxide on the thermal stability and on the morphological and structural properties of the corresponding supports, in terms of increasing surface area of alumina and ceria dispersion, was studied. The corresponding Pd (1 wt.%) catalysts were prepared by a stepwise impregnation method with a solution of palladium acetylacetonate in benzene. Palladium was introduced in two sequential steps by impregnation 0.5 wt.% of Pd each time. The structural and textural properties of the materials were studied by X-r…
Mesoporous SBA-15 silica modified with cerium oxide: Effect of ceria loading on support modification
2010
Abstract The present work investigates the effect of ceria loading on silica SBA-15. Five CeO2/SBA-15 samples with CeO2 content equal to 5, 10, 15, 20 and 30 wt% were prepared by wetness-impregnation of the support with cerium nitrate hexahydrate, as precursor, dissolved in ethanol. After drying at room temperature, the resulting samples were calcined at 400 °C for 2h. Characterizations by BET surface area and pore-size distribution, XRD, NH3-TPD and H2-TPR were performed.
The catalytic performance of mesoporous cerium oxides prepared through a nanocasting route for the total oxidation of naphthalene
2010
Cerium oxides have been prepared by nanocasting of a mesoporous siliceous KIT-6. Through this synthesis method a partially ordered mesoporous structure, as demonstrated by several characterization techniques (N2 adsorption, XRD and HRTEM) has been obtained. Accordingly, very high surface areas have been achieved (up to 163 m2/g), despite using high calcination temperatures (550 °C). We have demonstrated that the aging temperature of the siliceous template is of outstanding importance, as this parameter is directly responsible for both the pore size and the surface area of the catalysts. In addition, whilst a low preparation temperature (40 °C) makes the further removal of the silica templat…
From Spherical Mesopores to Worm-Shaped Mesopores : Morphology Transition in Titania–Polystyrene-b-poly(ethylene oxide) Composite Films with Increasi…
2013
A morphology transition from spherical mesopores to worm-shaped mesopores within titania block copolymer composite thin films has been observed by varying the sol–gel reaction time from 40 min to 48 h in the four-component templating system of polystyrene-$\mathit{b}$-poly(ethylene oxide) (PS-$\mathit{b}$-PEO), 1,4-dioxane, concentrated HCl, and titanium tetraisopropoxide (TTIP) with a PS-$\mathit{b}$-PEO mass concentration of 0.25 wt.-%. The impact of the sol–gel reaction time on the local structure, long-range lateral structure, and vertical structure of the as-prepared, calcined, and UV-degraded thin films as well as the structural changes in solution have been systematically investigate…
Green synthesis of Pd@graphene nanocomposite: Catalyst for the selective oxidation of alcohols
2016
Abstract Due to their excellent physicochemical properties and synergistic effect, graphene metallic NPs based nanocomposites have gained significant attention in various technological fields including catalysis. Here we demonstrate a single pot, facile and environmental friendly synthesis of catalytically active palladium(Pd)@graphene nanocomposites (SP-HRG-Pd) by the simultaneous reduction of graphene oxide (GRO) and PdCl 2 using Salvadora persica L. (miswak) root extract (RE) as bioreductant. The synthesis of SP-HRG-Pd was confirmed by various spectroscopic and microscopic techniques, including ultraviolet–visible (UV–vis), Fourier-transform infrared (FT-IR), Raman and X-ray photoelectro…
The role of molybdenum in Mo-doped V–Mg–O catalysts during the oxidative dehydrogenation of n-butane
1999
Abstract A detailed study on the influence of the addition of molybdenum ions on the catalytic behaviour of a selective vanadium–magnesium mixed oxide catalyst in the oxidation of n-butane has been performed. The catalysts have been prepared by impregnation of a calcined V–Mg–O mixed oxides (23.8 wt% of V2O5) with an aqueous solution of ammonium heptamolybdate, and then calcined, and further characterised by several physico-chemical techniques, i.e. SBET, XRD, FTIR, FT-Raman, XPS, H2-TPR. MgMoO4, in addition to Mg3V2O8 and MgO, have been detected in all the Mo-doped samples. The incorporation of molybdenum modifies not only the number of V5+-species on the catalyst surface and the reducibil…
Characterization of [Cu]-MCM-41 by XPS and CO or NO adsorption heat measurements
2002
We report the characterization of copper doped MCM-41 prepared by original direct synthesis by XPS and adsorption calorimetry of CO and NO, which are selective molecular probes for Cu(I) and Cu(II) respectively. Investigation of the nature of the copper ions in this particular calcined Cu-MCM-41 by NO adsorption calorimetry shows that two types of energetically distinct adsorption sites exist, meaning the presence of two populations of Cu(II) species differently coordinated to the silica surface in quasi-equimolar concentration, as ascertained by XPS data. A small amount of Cu(I) was also detected, probably stemming from a partial reduction upon the successive vacuum treatments. The respect…