- Gas-phase reactions:
- Combustion of alternative and traditional fuels
- Thermo-chemical conversion of biomass
- Gas-surface reactions
1. Impact of alternative fuels on combustion kinetics
The goal of this research is to develop detailed chemical models which will be used to quantitatively characterize the impact of alternative fuels on combustion kinetics. We have been interested in Fischer-Tropsch fuels and biologically-derived diesels, especially at low temperatures (< 1000 K) where the fuel ignition behavior plays a role.
To understand the low-temperature oxidation chemistry of fuels, a systematic study on smaller systems (referred to as surrogate molecules, having similar chemical functional groups to those found in real fuel molecules) will be carried out using accurate electronic structure calculations and statistical mechanics methods. Specifically, this project will target reactions between surrogate radicals and molecular oxygen, which are crucial in low-temperature oxidation and auto-ignition processes. The improved understanding obtained from these surrogates will be generalized in terms of rate estimation rules, allowing us to effectively construct improved detailed kinetic models for real fuel molecules. Such models will then be used to quantitatively characterize the impact of alternative fuels as replacements or supplements for crude-oil-derived fuels on emissions as well as performance of conventional engines/turbines.
Approaches: Electronic structure calculations, Statistical Mechanics, Reaction Class Transition State Theory (RC-TST), Pressure-dependent Analysis, and Reactor/Flame simulation.
Subjects: biodiesel, alcohol (ethanol, butanol, ...)
2. Thermochemical conversion of biomass
The goal of this research is to construct detailed kinetic mechanisms for modeling/simulation of biomass thermochemical conversion processes, including gasification and pyrolysis, to increase overall conversion efficiency and decrease capital and operating costs. Currently, we focus our efforts on the pyrolysis process, and in particular on molecular weight growth which leads to coke formation.
The initial step of biomass thermal conversion involves the primary decomposition of the lignocellulosic matrix, one of the main components of which is lignin. In terms of molecular structure, lignin contains single-aromatic rings that might serve as starting places for molecular weight growth. Therefore, understanding how lignin breaks under pyrolysis conditions can help us in finding better ways to reduce the tar formation route by either reducing the rate of molecular weight growth or by selectively reducing the concentration of tar once formed. Selected model compounds, which represent the bonds and interlinkages commonly found in lignin, will be studied using accurate electronic structure calculations and statistical mechanics methods. This simplifies the effort by dealing with smaller systems that can be studied in more detail, and results can later be applied and extended to larger, more complex and real systems.
Approaches: Electronic structure calculations, Statistical Mechanics and Pressure-dependent Analysis.
Subjects: lignin components
3. Computational Design of Novel Catalysts/Materials
The purpose of this research is to design better catalysts/materials for complex chemical/physical processes using first-principles density functional theory (DFT) methods. With a statistical mechanics tool currently developed for gas-surface reactions in the group, micro-kinetic mechanisms for such processes will be constructed in an attempt to bridge fundamental chemistry/physics and surface reaction engineering.
DFT methods are employed to study adsorption/desorption as well as conversion of the species involved in the processes. Calculation results will allow us to evaluate mechanisms on the
surface considered and their applications, energetically. To give a more complete picture, the micro-kinetic mechanisms will be constructed by means of statistical mechanics. These micro-kinetic mechanisms, once validated, will be used to effectively model the applications in real operational conditions.
Approaches: Periodic Calculations, Statistical Mechanics
Subjects: ZnO-based catalysts/materials
4. Code development
Computational tools have been developed in order to assist the efforts above. Specifically, the following codes have been developed in our group:
- MWMC (MultiWell-MultiChannel)
- SurfKin (Surface Kinetics)
Approaches: C/C++, Fortran.
- Thermochemical Conversion of Biomass