Effects of Na{sup +} cations on PdY catalysts
- Univ. of Pittsburgh, PA (United States). Dept. of Chemical and Petroleum Engineering
The acidity of supports affects the catalytic activity of supported Pd catalysts for methanol synthesis. In previous studies focusing on the effects of zeolite acidity, the concentrations of the zeolitic protons were varied by back-exchanging the protons with Na{sup +} cations. However, there is a lack of understanding about the effects of Na{sup +} cations on the supported Pd catalysts and their catalytic activity. This paper focuses on this issue. CO chemisorption, N2 physisorption, ethane hydrogenolysis, and methanol synthesis were used to characterize three different catalysts with varying sodium contents (Pd/HY, Pd/NaHY, Pd/NaY). Pd/NaHY and Pd/HY were prepared from NaY and NH{sub 4}Y, respectively, by ion-exchange with [Pd(NH{sub 3}){sub 4}](NO{sub 3}){sub 2}. Pd/NaY was prepared from Pd/NaHY by back-exchange of H{sup +} with Na{sup +}. Steady-state isotopic transient kinetic analysis (SSITKA) was utilized in the study of methanol synthesis as well as N{sub 2} physisorption. The amount of CO adsorption and the overall catalytic activity for methanol synthesis increased in the following order: Pd/NaY < Pd/HY < Pd/NaHY. The results from ethane hydrogenolysis on the catalysts indicate that the Na{sup +} cations did not decorate the Pd surfaces. The SSITKA results from methanol synthesis indicate that the concentration of active sites for methanol synthesis on Pd/NaHY was larger than that of either Pd/NaY or Pd/HY. The reaction results suggest that the Na+ cations influence the interaction between CO and Pd by electronic rather than structural effects.
- OSTI ID:
- 349275
- Report Number(s):
- CONF-980985--; ISBN 1-890977-15-2
- Country of Publication:
- United States
- Language:
- English
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