Hans-Heinrich Carstensen
Research Associate Professor
Research Description
Modeling of complex chemical reaction processes
has become an important engineering tool for process optimization. Obviously,
reliable predictions depend on the availability of accurate chemical
kinetic mechanisms. In the recent past the demand for increasingly accurate
and comprehensive kinetic models have led to mechanisms containing hundreds
of species and thousands of reactions. Since experimentally available
thermodynamic and kinetic information cover just a tiny fraction of
the input data needed to generate such large mechanisms, alternative
resources have to be exploited. Fortunately, electronic structure methods
have matured to a point that they produce thermodynamic and kinetic
information of small molecules (up to 10 non-hydrogen atoms) with accuracies
comparable to experiment. Furthermore, it is possible to generalize
thermochemical properties in terms of group additivity and rate estimation
rules. This provides the framework to apply results obtained for small
model compounds to species that are too large for high-level electronic
structure methods.
In my research I calculate molecular properties of gas phase species preferably
with the CBS-QB3 model chemistry. The electronic energy, geometry (rotational
constants), frequencies and hindered rotor information are used to predict heats
of formation, entropies and heat capacities of the stationary points of the potential
energy surface of interest (reactants, products and transition states) by means
of statistical mechanics. This information in turn serves as input for transition
state theory, which yields high-pressure rate constants. A large number of rate
constants found in typical reaction mechanisms are not just temperature but also
pressure dependent. We use Quantum Rice Ramsperger Kassel (QRRK) theory in conjunction
with the modified strong collision approach to analyze these pressure dependent
reactions and to extract apparent rate constants.
selected Publications
“Rate Constant Rules for the Automated Generation of Gas-Phase Reaction Mechanisms” Hans-Heinrich Carstensen and Anthony M. Dean, J. Phys. Chem. A, 113, 367-380 (2009).
“The Kinetics of Pressure-Dependent Reactions” in Comprehensive Chemical Kinetics, 42, 105–187 (2007), Hans-Heinrich Carstensen and Anthony M. Dean
“Detailed Kinetic Modeling of C2H5 + O2”, J. Phys. Chem A., 109, 2264-2281 (2005), H.-H. Carstensen, C. K. Naik, and A.M. Dean