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Molecular
Thermodynamics of Solvents, Monomers, and Polymers
Polymers with multiple functional groups have been found to
possess unique and useful optical, thermal, and mechanical
properties. The manufacture of these polymers requires knowledge
of their solution properties and phase behavior to optimize the
design and operation of reactors and separation units. Professor
Chapman's group uses molecular modeling techniques (including
molecular simulation and statistical mechanics) to relate
knowledge of molecular forces to the thermophysical properties
of polymer solutions and blends. The Statistical Associating
Fluid Theory (SAFT) equation of state produced from this
research is applied by numerous polymer companies throughout the
world to model phase behavior in polymer processing.
Thermodynamics and Structure of Complex Fluids in the
Interfacial Region
Prediction of the interaction of complex fluids, (e.g.,
hydrogen bonding fluids, hydrocarbons, proteins, and polymers)
with adsorbing surfaces is essential for the control of many
processes of current industrial and scientific interest. These
processes include microchannel reactors, catalysis, assembly of
nano-materials, bio-sensors, and membrane separations. Professor
Chapman’s group has developed molecular simulations and density
functional theory to predict the thermodynamic properties,
structure, and surface forces of associating and non-associating
components near hydrophobic and hydrophilic surfaces.
Mechanisms and Kinetics of Gas Hydrate Decomposition
Gas hydrates are, quite literally, self-assembled nano-structures
formed by the cooperative hydrogen bonding of water molecules to
form cages that encapsulate gas molecules. These solid
crystalline clathrate structures are significant because they
trap vast amounts of natural gas on the ocean floor (notably the
Gulf coast) and in permafrost and other geologic deposits. The
amount of carbon in gas hydrates is estimated to be more than
twice the amount of carbon in all other fossil fuel deposits.
Gas hydrates have also been proposed as potentially useful in
novel gas separation processes and in transport of natural gas.
Gas hydrates are also a problem in their proclivity to plug
subsea pipelines from offshore platforms causing economic loss
and potentially unsafe conditions. To avoid hydrate plugs, the
oil and gas industry spends about 500 millions of dollars
annually on inhibitors (e.g., methanol or glycol) or as much as
$48 MM to insulate a single subsea pipeline (Exxon).
To accurately model the decomposition and formation processes
and to optimize hydrate applications requires the mechanism and
dissociation rates of hydrates as well as heat and mass transfer
data. In addition, quantifying the effect of porous media on
hydrate decomposition kinetics is essential for the production
of natural gas from hydrates. Professor Chapman’s group combines
NMR and molecular simulation with phase equilibria and kinetic
studies to provide needed thermodynamic, transport, and kinetic
data for hydrate decomposition.
Asphaltene Precipitation and Deposition
The formation of asphaltene plugs in piping represent a
significant problem in oil production and refining. Asphaltenes
are a collection of polydisperse molecules consisting mostly of
polynuclear aromatics with varying proportions of aliphatic and
alicyclic moieties and small amounts of heteroatoms (oxygen,
sulfur, vanadium, etc.). Problems in recovery and refining
operations associated with asphaltenes are due primarily to
their molecular size and their self-aggregation. Hence, a better
understanding of asphaltene phase behavior and deposition
requires a better understanding of how molecular size and
aggregation affect phase behavior and deposition.
A similar material to asphaltenes are polynuclear aromatics
extracted from pitch. Researchers have shown that these
polynuclear aromatics for a meso-phase that can be used to spin
inexpensive, high quality carbon fibers. Professor Chapman’s
group in collaboration with George Hirasaki is modeling the
thermodynamic properties and phase behavior of asphaltenes using
the Statistical Associating Fluid Theory (SAFT).
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