Properties of Pd/SiO ₂ catalyst doubly promoted with la oxide and Si for acetylene hydrogenation

Pd/SiO ₂ for acetylene hydrogenation was doubly promoted with La oxide and Si, the latter being selectively deposited on Pd instead of on SiO ₂. La oxide promoted the ethylene selectivity of the catalyst due to its strong interaction with Pd after the catalyst had been reduced at high temperature, e.g., 500 °C, and Si prevented the migration of La oxide in the catalyst when the reduced catalyst was exposed to air. Consequently, the doubly promoted catalyst showed high ethylene selectivity comparable to that of 500 °C-reduced Pd-La/SiO ₂ even when the catalyst had been oxidized and subsequently reduced at low temperature, e.g., 300 °C.