Self-Sustained Oscillations as a Method to Increase an Active Surface and Catalytic Activity of Ni and Pd

The effect of Ni and Pd surface development during catalytic self-oscillatory oxidation of C 1 –C 4 alkanes on the activity of these two metals in other catalytic reactions was studied. Scanning electron microscopy investigations revealed that the surface of bulk Ni and Pd (foil or powder) developed significantly faster during alkane oxidation in a self-oscillatory regime than under stationary conditions. Thanks to increase in available metal surface achieved during such self-oscillatory pretreatment, catalytic activity of Ni in methane dry reforming and in ethylene hydrogenation and that of Pd in total methane oxidation increased by an order of magnitude compared to the untreated metals. With time on stream, the activity dropped to some stationary level that was still significantly higher than the activity of the fresh metals. Morphological changes of Ni during the pretreatment were caused by periodic oxidation–reduction of the surface atomic layers whereas in case of Pd redox cycles were accompanied by carbon dissolution-removal. The amount of carbon dissolved in Pd during self-oscillatory oxidation of C 1 –C 4 alkanes decreased with increasing chain length, likewise the metal surface development. Supported Pd/Al 2 O 3 catalyst did not exhibit significant activity changes after the self-oscillatory pretreatment suggesting that the morphology of Pd particles remained unaltered. Graphical Abstract