Ferroudja Bali and Louise Jalowiecki-Duhamel
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.
After activation in H2, the solid solution is maintained and Cu2+cations are partially reduced. The solids obtained are able to store hydrogen and are active toward isoprene hydrogenation reaction. Besides, some Cu- and Ni-based mixed oxides have already been found to be good hydrogenation catalysts related to their ability to store hydrogen (Wrobel et al., 1993). An active site modeling has been proposed based on the presence of coordinatively unsaturated sites (CUS) (Siegel, 1973), in agreement with some previous results reported by Siegel, considering that the most important parameter involved in the constitution of an active site is the number of coordinative unsaturations, whatever the nature of the cation (Jalowiecki et al., 1987). The purpose of this work was to synthesize a new catalyst based on copper which will be active in methanol synthesis and to understand its working during the catalytic process. Zirconia has been chosen as a support, because several studies have reported the interest of a Cu-Zr-O system for this
I. Dincer et al. (eds.), Global Warming, Green Energy and Technology,
DOI 10.1007/978-1-4419-1017-2_19, © Springer Science+Business Media, LLC 2010
reaction. We report on CO2 hydrogenation activity and selectivity of zirconium-copper oxides. Some physico-chemical characterizations are performed in order to explain the results obtained. Finally, we propose a modeling of the active site based on some results previously reported on Cu- or Ni- based mixed oxide catalysts (Wrobel et al., 1993).
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