Novel Microfabricated Pd-Au/SiO2 Model Catalysts for the Hydrogenation of 1,3-Butadiene

ABSTRACTModel Pd-Au/SiO2 catalysts were prepared via a microfabrication methodology and their catalytic activity was evaluated using the hydrogenation of 1,3-butadiene as a probe reaction. The catalytic particles of the microfabricated catalyst were Pd-Au squares, ranging in composition, each approximately 4 µm in size and separated by 4 µm on a silica/silicon support. The reaction was carried out at atmospheric pressure with a hydrogen to hydrocarbon ratio of 125. The bimetallic catalysts exhibited lower apparent activation energies than the pure Pd catalyst with a minimum occurring at ˜65 at% Pd. Corresponding to the decrease in activation energy, there is an increase in the turnover frequency over the monometallic catalyst at low temperatures, i.e. room temperature. At high temperatures (above 200°C) the pure Pd catalyst has the highest conversion (0.61) and the largest pre-exponential factor (4.71×1016 cc/g Pd/s), while the 73 at% Pd catalyst has the lowest conversion (0.45) and the smallest pre-exponential factor (5.59 × 10 6 cc/g Pd/s). The bimetallic catalysts also showed a higher selectivity towards 1-butene than the monometallic catalyst; however, at lower conversions (less than 25%) the pure Pd catalyst was more selectivity towards 1-butene. AFM was used to characterize the surface morphology of each of the samples.