| 초록 |
A Pd-La/SiO2 catalyst, containing La2O3 as a promoter for improving the selectivity of the catalyst for ethylene production in acetylene hydrogenation, was additionally modified with Si added by a chemical vapor deposition (CVD) method. The role of the added Si species was to lower the temperature required for reducing the air-oxidized, Pd-La/SiO2 catalyst, which is necessary for the catalyst to resume the initial high ethylene selectivity. The Si-modified catalyst exhibited high ethylene selectivity when the air-oxidized catalyst was reduced at relatively low temperatures, e.g., 300oC, while the catalyst containing no Si had to be reduced at high temperatures, e.g., 500oC, to resume the initial ethylene selectivity. This was because the added Si species suppressed the La2O3 promoter particles, which were located on the Pd surface after reduction, from migrating back to the interface of the Pd particles and the SiO2 support when the catalyst was oxidized in air. The anchoring role of the Si species, which were introduced exclusively on the Pd surface by a CVD method, was confirmed as the catalyst was characterized by H2 chemisorption, infrared observation of adsorbed CO, XPS, and the temperature-programmed desorption of ethylene. |
