Pt-CeO[sub 2] contact and its effect on CO hydrogenation selectivity

The CO[sub 2]/CH[sub 4] ratio during methanation on Pt was found to be very sensitive to the proximity of Pt and CeO[sub 2]. On 0.6 wt% Pt/Al[sub 2]O[sub 3], the CO[sub 2]/CH[sub 4] ratio was [approx]0.09 suggesting that most of the O from CO ends up as H[sub 2]O in the product stream. In contrast, on 0.6 wt% Pt/CeO[sub 2] the CO[sub 2]/CH[sub 4] ratio ranged from 0.8-1.0. The selectivity to CO[sub 2] was not a result of the sequential water-gas shift reaction nor was it caused by a surface reduction of CeO[sub 2] by CO. The highest selectivity to CO[sub 2] is observed on catalysts with the smallest Pt particle sizes, providing further evidence that Pt-CeO[sub 2] contact influences the selectivity toward CO[sub 2] formation. In this study, the authors have also investigated whether the CO[sub 2]/CH[sub 4] ratio could be used as a probe of Pt-CeO[sub 2] contact in Pt/CeO[sub 2]-Al[sub 2]O[sub 3] catalysts. 15 refs., 8 figs., 3 tabs.