Comparative Study of the Physico-Chemical Properties of Nanocrystalline CuO–ZnO–Al2O3 Prepared from Different Precursors: Hydrogen Production by Vaporeforming of Bioethanol

The physico-chemical and catalytic properties of CuO–ZnO–Al2O3, synthesised by sol–gel process (SG), impregnation method (IMP) and a combination of both preparative procedures (ISG), were comparatively studied. Samples were characterised with thermogravimetric-differential thermal analysis (TG–DTA), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS) techniques and oxygen chemisorption. XPS study was not consistent with the bulk findings and revealed the presence of Cu2+, Cu+ and/or Cu0 species at the catalysts surface. Surface analysis revealed also that copper enrichment occurred mainly at the surface of SG and IMP solids. The reducibility of the mixed oxides catalysts was always modified with respect to that of pure copper oxides phases and the reduction of CuO was markedly affected by the presence of ZnO–Al2O3. Temperature programmed reduction (H2-TPR) analysis showed that the temperature corresponding to maximum reduction rate of copper oxide was ca. 256 °C for IMP sample and ca. 296 °C for both SG and ISG solids. These latter showing a high resistance to reduction suggest a strong interaction of copper species with ZnO–Al2O3, limiting thus copper particles sintering. CuO particle size was found to be ca. 20 nm for both SG and ISG solids and ca. 40 nm for IMP catalysts. Besides, at 300 °C SG and ISG samples showed superior amount of reversible O2 uptake with respect to IMP solids. Catalytic activity of CuO–ZnO–Al2O3 was measured with bio-ethanol steam reforming reaction. SG catalysts exhibited both high selectivity to hydrogen and high stability with time on stream than IMP and ISG catalysts. This was attributed both to the particles size of copper species, their amount on the catalytic surface and to their strong interaction with ZnO–Al2O3

Comparative Study of the Physico-Chemical Properties of Nanocrystalline CuO-ZnO-Al2O3 Prepared from Different Precursors: Hydrogen Production by Vaporeforming of Bioethanol

Kaddouri, A. Mazzocchia, C.The physico-chemical and catalytic properties of CuO-ZnO-Al2O3, synthesised by sol-gel process (SG), impregnation method (IMP) and a combination of both preparative procedures (ISG), were comparatively studied. Samples were characterised with thermogravimetric-differential thermal analysis (TG-DTA), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS) techniques and oxygen chemisorption. XPS study was not consistent with the bulk findings and revealed the presence of Cu2+, Cu+ and/or Cu-0 species at the catalysts surface. Surface analysis revealed also that copper enrichment occurred mainly at the surface of SG and IMP solids. The reducibility of the mixed oxides catalysts was always modified with respect to that of pure copper oxides phases and the reduction of CuO was markedly affected by the presence of ZnO-Al2O3. Temperature programmed reduction (H-2-TPR) analysis showed that the temperature corresponding to maximum reduction rate of copper oxide was ca. 256 A degrees C for IMP sample and ca. 296 A degrees C for both SG and ISG solids. These latter showing a high resistance to reduction suggest a strong interaction of copper species with ZnO-Al2O3, limiting thus copper particles sintering. CuO particle size was found to be ca. 20 nm for both SG and ISG solids and ca. 40 nm for IMP catalysts. Besides, at 300 A degrees C SG and ISG samples showed superior amount of reversible O-2 uptake with respect to IMP solids. Catalytic activity of CuO-ZnO-Al2O3 was measured with bio-ethanol steam reforming reaction. SG catalysts exhibited both high selectivity to hydrogen and high stability with time on stream than IMP and ISG catalysts. This was attributed both to the particles size of copper species, their amount on the catalytic surface and to their strong interaction with ZnO-Al2O3

Use of ozonized oxygen in heterogeneous catalysis. Effect on the apparent activation energy

The catalytic oxidation of lower olefins has been studied. The effect of ozonized oxygen has been examined. The results show that the apparent activation energy decreases. The industrial importance of the phenomenon is pointed out

Solubility of sodium formate in aqueous hydroxide solutions

Measurements were made of the solubility of sodium formate at 21, 60, and 120 °C In aqueous solutions of sodium hydroxide. The concentratlon of sodium hydroxide ranges from 0 to 40% w/w. The results are combined wlth data of binary systems to give a semiquantltatlve description of the total phase diagram HCOONa-NaOH-H2O

Structural characterisation of hightemperature K-exchanged sodalite

The exchange reaction of Na-sodalite with KCl was studied by means of hightemperature X-ray powder diffraction, ex-situ and in-situ, up to 800 \ub0C. The powder data were fully refined with the Rietveld method and showed that a substantial amount of K enters the structure in the same crystallographic position of Na, causing some Cl ions to be displaced from their position. The paper shows that sodalite is a potentially good matrix for trapping alkaline metal ions from the electrorefining process of nuclear waste and proposes a method to quickly estimate the amount of K in the structure