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

The selective hydrogenation of acetylene in the presence of ethylene has been studied on K+ exchanged beta-zeolite supported Pd and PdAg catalysts. Results from batch reactor studies with Fourier transform infrared spectroscopy (FTIR) have shown that the K+-beta-zeolite support is more selective than the Al2O3 or Na+-beta-zeolite supports toward the hydrogenation of acetylene. The rate and equilibrium constants for Pd/K+-beta-zeolite and PdAg/K+-beta-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+-beta-zeolite catalyst has higher selectivity but lower activity toward acetylene hydrogenation than the Pd/K+-beta-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+-beta-zeolite catalyst. (C) 2007 Elsevier B.V. All rights reserved.