Methionine bound to Pd/γ-Al2O3 catalysts studied by solid-state (13)C NMR
Robert L Johnson1, Thomas J Schwartz2, James A Dumesic2
1Department of Chemistry, Iowa State University, Ames, IA 50011, United States.
Solid State Nuclear Magnetic Resonance
|October 1, 2015
Summary
Solid-state NMR reveals how methionine binds to and breaks down on palladium catalysts. This method identifies key species responsible for catalyst inhibition, aiding in surface characterization.
Area of Science:
- Catalysis
- Surface Chemistry
- Spectroscopy
Background:
- Methionine (Met) is an amino acid relevant to catalytic processes.
- Understanding Met interaction with catalysts is crucial for optimizing reactions.
- Palladium (Pd) on gamma-alumina (γ-Al2O3) is a common catalytic material.
Purpose of the Study:
- To investigate the chemisorption and breakdown of methionine on Pd/γ-Al2O3 catalysts.
- To utilize solid-state NMR as a probe for catalyst surface interactions.
- To characterize species responsible for catalyst inhibition.
Main Methods:
- Solid-state magic-angle spinning NMR spectroscopy.
- (13)C-enriched methionine used for enhanced signal detection.
- Analysis of chemical shift changes and spectral features.
Main Results:
- Methionine preferentially binds to Pd nanoparticles over γ-Al2O3.
- SCH3 groups are immobilized on Pd, while NCH groups show motion on small Pd particles.
- Catalyst inhibition is linked to a specific breakdown product (SCH3 signal at 22ppm) formed via C-S bond cleavage in reducing environments.
Conclusions:
- Solid-state NMR is a sensitive technique for probing catalyst surfaces.
- The study elucidates methionine's binding and breakdown pathways on Pd/γ-Al2O3.
- NMR characterization can identify catalyst inhibitors before and after reactions.
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