Selective hydrogenation of acetylene in the presence of ethylene on K+-β-zeolite supported Pd and PdAg catalysts Original Research Article

The selective hydrogenation of acetylene in the presence of ethylene has been studied on K+ exchanged β-zeolite supported Pd and PdAg catalysts. Results from batch reactor studies with Fourier transform infrared spectroscopy (FTIR) have shown that the K+-β-zeolite support is more selective than the Al2O3 or Na+-β-zeolite supports toward the hydrogenation of acetylene. The rate and equilibrium constants for Pd/K+-β-zeolite and PdAg/K+-β-zeolite were determined using a Langmuir–Hinshelwood model. The selectivity of the PdAg bimetallic catalyst is twice of that of the Pd catalyst. Results from flow reactor studies show that the PdAg/K+-β-zeolite catalyst has higher selectivity but lower activity toward acetylene hydrogenation than the Pd/K+-β-zeolite catalyst. The selectivity to the undesirable ethane by-product is inhibited on the bimetallic catalyst. Extended X-ray absorption fine structure (EXAFS) studies and transmission electron microscope (TEM) analysis confirm the formation of Pd–Ag bimetallic bonds in the PdAg/K+-β-zeolite catalyst.