Mg-V-Al mixed oxides with mesoporous properties using layered double hydroxides as precursors: catalytic behavior for the process of ethylbenzene dehydrogenation to styrene under a carbon dioxide flow

A new catalyst for the process of ethylbenzene dehydrogenation to styrene under a CO2 atmosphere was obtained using vanadium-substituted layered double hydroxides as precursors. After calcination, vanadium-substituted hydrotalcite-like samples gave mixed oxides with a high surface area and strong mesoporous characteristics; the XRD analysis indicates the formation Of Mg3V2O8 and Mg2Al2O4 in bulk while the XPS results point to the presence of a mixture of V5+ and V3+ ions on the surface. Catalytic tests show that the styrene yield and selectivity increase when the vanadium content of the sample increases. The higher catalytic activity is attributed to the formation of V5+ on the surface that is promoted by the presence of CO2 as a cofeed gas. The FTIR adsorption of pyridine shows that aluminum contributes to Lewis-type acidity of the catalyst and is important for establishing features of the catalyst deactivation process. (C) 2003 Elsevier Inc. All rights reserved.