Selective hydrogenation on zeolite-supported bimetallic catalysts
Date
2005
Authors
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Publisher
University of Delaware
Abstract
New catalysts have been developed by combining Pd-based bimetallic catalysts and zeolite supports to achieve higher selectivity for the selective hydrogenation of acetylene in a stream containing excess ethylene at relatively low temperatures (300-339K). Low-temperature hydrogenation offers the opportunity of using competitive adsorption to achieve preferential hydrogenation of acetylene. Previous work for this has found that bimetallic catalysts favor low temperature hydrogenation. Results from many other groups have also shown that Pd is a good catalyst for the selective hydrogenation of alkynes in excess ethylene. Therefore the strategy of the present work was to modify Pd catalysts and embed bimetallic particles in an environment that is highly selective for acetylene hydrogenation. ☐ Cation-π interaction offers the potential for selective adsorption of acetylene. We used the ion-exchanged zeolite for the support of the bimetallic catalysts. The zeolite structure should have multiple dimensions and contain large pores, in order to house the bimetallic particles inside the pores. In this work, we focus on β-type zeolites. ☐ Flow reactor studies using GC, batch reactor studies using FTIR, and TPR evaluation have been utilized for this project. It was found that the Pd-Ag bimetallic catalyst had a much higher selectivity for acetylene hydrogenation in excess ethylene than either Pd or Ag, while the Pd-Ni bimetallic catalyst behaved similarly to the Pd catalyst. Modeling of reactions in FTIR also showed that there was a small difference in the rate constant and equilibrium constant of Pd/β-zeolite and Pd-Ni/β-zeolite. The zeolite support also exhibited enhanced activity for the low temperature hydrogenation of acetylene.