To design and understand trace metal and carbon dioxide transformation and/or capture on surfaces to prevent their release into the atmosphere.
Long-Term Research Goals
- To determine effective multi-pollutant materials for trace metal capture and gain a thorough mechanistic understanding of material's reactivity.
- To determine global homogeneous (gas-phase) and heterogeneous (surface-gas) kinetics of trace metal oxidation mechanisms for combustion applications
- To determine membrane material compositions that achieve optimal hydrogen permeabilities for gasification applications.
- To determine membrane material compositions that achieve optimal nitrogen permeabilities for combustion applications.
- Carry out ab initio-based electronic structure calculations to determine potential energy surfaces for trace metal gas-phase reactions and use RRKM theory or transition state theory to calculate rate expressions for unimolecular and bimolecular reactions, respectively. .
- Carry out density functional theory-based electronic structure calculations to model bulk and surface structures and to benchmark the computational methodology by comparing against experimental data such as band structure, lattice constant, band gap, relaxation energies and distances, etc.
- Use ab initio thermodynamics to determine the reactivity state of a given surface based upon temperature, pressure, and gas-phase partial pressures of species in equilibrium with the surface.
- Carry out nudged elastic band calculations to determine transition energies of gas-surface reactions and carry out harmonic transition state theory to determine corresponding rate expressions.
- Carry out Bader charge analysis on surfaces to determine local acidic and basic sites with potential for trace metal or carbon dioxide reactivity.
- Carry out density of states analyses to determine gas-surface binding mechanisms.
- Carry out bench-scale combustion experiments by burning methane in air to simulate a combustion flue gas environment. Chlorine gas at ppm levels can be fed into the flame to create short-lived radicals to simulate trace metal oxidation. Sulfur and nitrogen oxides are introduced in a controlled manner to understand their influence on oxidation and reactivity.
- Use a flow reactor to study gas-phase homogeneous trace metal reactivity in combustion flue gas and use Chemkin to compare experimental trace metal concentration profiles against theoretical predictions.
- Use a packed-bed reactor to investigate sorbent and catalysts for trace metal and carbon dioxide reactivity.
- Use an entrained-flow reactor to investigate mass transfer effects on capture and/or catalysis. Entrained particles in a simulated flue gas are used to represent fly ash in the ductwork of a power plant for instance or the activated carbon injection process for mercury capture.
- Use X-ray photoemission spectroscopy to characterize surfaces before and after reaction to gain understanding of surface features responsible for reactivity.
- Use an electron ionization quadrupole mass spectrometer to directly measure all trace metal species in a simulated combustion flue gas.
- Use custom-built electron ionization etc..
Short-Term (4-year) Research Goals
- Optimize the electron ionization quadrupole mass spectrometer for effective trace metal measurement.
- Determine complete gas-phase rate expressions for mercury and selenium reactions with halogen and oxygen species at combustion conditions.
- Determine the dominant species of reactive fly ash and the sensitivity parameters associated with its reactivity enhancement toward trace metals and carbon dioxide.
- Determine the dominant mechanism responsible for activated carbon's activity toward mercury adsorption and the sensitivity parameters associated with its enhancement toward mercury, selenium, and arsenic.
- Understand the nature and mechanism associated with sulfur poisoning of selective hydrogen membranes.
- Design a membrane material selective for nitrogen with permeabilities within an order of magnitude to those of palladium for hydrogen.