Oxidative steam reforming of ethanol in a fluidized bed over CeO2-SiO2 supported catalysts: effect of catalytic formulation

Pt-Ni/CeO2-SiO2, K-Pt-Ni/CeO2-SiO2 and Pt-Co/CeO2-SiO2 catalysts, prepared by wet impregnation, were reduced in situ and tested for the oxidative steam reforming of ethanol in a fluidized bed reactor at 500 °C, H2O/C2H5OH ratio of 4 and O2/C2H5OH ratio of 0.5. The results of physiochemical characterization revealed high surface area for all the catalysts, due to their deposition on silica, and considerable reducibility. However, K-addition to the Ni-based sample worsened the catalytic performance: during stability tests, a quite high carbon formation was observed upon potassium doping. Moreover, the K-containing catalyst displayed a not negligible by-products selectivity (i.e. acetaldehyde). On the other hand, Ni substitution by cobalt resulted in significantly lower ethanol conversions and hydrogen yields after 220 h of time-on-stream (TOS). However, all the catalysts at different times reached a plateau condition with no more deactivation. The best results were observed for the Pt-Ni/CeO2-SiO2 catalyst, which displayed a stable performance after 300 h of test, with a reduction in ethanol conversion of only 20%. Carbon formation was measured during the test, demonstrating that coke selectivity progressively decreased with TOS, until observing a net rate of coke formation equal to zero.