Experimental and kinetic study of oxidative steam reforming of ethanol over fresh and spent bimetallic catalysts

摘要

Two bimetallic catalysts (Pt-Co and Ni-Co), supported on a CeO2-SiO2 mixed oxide and prepared by wet impregnation, were tested for oxidative steam reforming of ethanol in a fixed bed and compared with a previously investigated Pt-Ni sample. The Ni-Co catalyst displayed an improved performance compared to the Pt-Co one, in terms of both activity and stability: a mean conversion below 80% was reached over the noble metal-based catalyst after 70 h of time-on-stream at 500 degrees C while the same value, with a higher H-2 yield, was recorded over the Ni-Co sample after 260 h. A kinetic investigation was also performed and the model assuring the best agreement with experimental data involved ethanol decomposition, methane oxidation, methane steam reforming and water gas shift reactions. The activation energies (E-a) of the above reactions over the Ni-Co catalyst were shown to be lower than those measured for the noble-metal based sample, demonstrating that a higher activity can be reached by combining nickel and cobalt: for example, in the case of methane reforming, E-a = 77.1 kJ.mol(-1) was predicted against a value of 231.7 kJ.mol(-1) found for the Pt-Co sample. A further kinetic study was performed over the spent catalysts and the extent of deactivation was found to be more pronounced over the Pt-Co/CeO2-SiO2 catalyst.