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).