Phase Change-Driven Negative Activation Energies in Pd/Carbon-Based/Organic Getter Hydrogenation Reactions
Long N Dinh1, Hom N Sharma1, Sarah M Matt1
1Lawrence Livermore National Laboratory, 7000 East Ave, Livermore, California 94550-9234, United States.
The Journal of Physical Chemistry. A
|September 23, 2020
Summary
This study investigated the hydrogenation of 1,4-diphenylbutadiyne (DPB) using palladium catalysts. Researchers observed a rare negative activation energy barrier, explained by phase changes and hydrogen transport.
Area of Science:
- Chemical Engineering
- Catalysis Science
- Materials Science
Background:
- Investigated the hydrogenation of 1,4-diphenylbutadiyne (DPB) blended with carbon-supported palladium (Pd/C).
- Explored reaction kinetics under isothermal-isobaric conditions (1333 Pa H2, 291-315 K).
Purpose of the Study:
- To model the performance of the DPB-catalysis/support system.
- To understand the influence of temperature and H2 partial pressure on the reaction.
- To elucidate the molecular-level energetics using first-principles density functional theory (DFT).
Main Methods:
- Isothermal-isobaric hydrogenation experiments.
- Constant rate of H2 input experimentation.
- First-principles density functional theory (DFT) calculations.
Main Results:
- Observed alternating zones of positive and negative activation energy barriers during DPB hydrogenation.
- Explained the negative activation energy phenomenon by phase changes and H2 transport.
- Provided kinetic data for modeling catalyst performance.
Conclusions:
- The study demonstrates a rarely encountered chemical process exhibiting a negative activation energy barrier.
- Phase changes and hydrogen transport are key factors influencing the observed kinetics.
- DFT calculations offered insights into the energetics of DPB hydrogenation.
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