Catalytic Combustion Chemistry Studied with Cluster-Ion Spectroscopy
Abstract
To provide fundamental data relevant to Air Force needs in catalytic combustion, we investigate the reactions of metal ions with small hydrocarbon molecules in the gas phase. Laser spectroscopy experiments, complemented by theory, explore the structures and energetics of hydrocarbon molecules interacting with metal catalytic sites. These studies reveal molecular details of reaction intermediates for hydrocarbon cracking or metathesis reactions and possible structures of soot nucleation centers. Cation-molecular complexes of metals such as Al, V, Zn, Ga, Fe, and Pt with hydrocarbons such as acetylene, ethylene, ethane, propylene or benzene are produced with laser vaporization in a supersonic molecular beam. Complexes having a specific composition are characterized with mass spectrometry and infrared or UV-visible laser photodissociation spectroscopy, complemented by computational chemistry. These model studies probe the structures of these complexes, and how they vary with the electronic structure of the metal. These experiments also determine the relative reactivity of different metals, and whether electrostatic cation-molecular (e.g., cation-pi) complexes form, as opposed to carbides or other metal-inserted products. UV-visible laser spectroscopy reveals excited states and energetic thresholds for bond breaking. Additional experiments combine photodissociation with photofragment imaging methods to investigate metal-molecular bond energies. Computational studies identify the structural arrangements of metal and hydrocarbons, the energetics of bonding, the electronic spin state, and the characteristic spectral patterns for each structural arrangement, allowing unambiguous identification of reaction intermediates and products. The structural and energetic information for different metals and reactions provides new insights into the mechanisms of catalytic combustion.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Mar 14, 2024
- Source ID
- FA95502310686
Entities
People
- Michael A Duncan
Organizations
- Air Force Office of Scientific Research
- The University of Georgia
- United States Air Force