2014-03-05
10:15 at HCI J 574

Molecular Thermodynamics for Chemical Process and Product Design

Ioannis G. Economou

Texas A+M University at Qatar, Chemical Engineering Program, Doha, Qatar and National Center for Scientific Research “Demokritos”, Aghia Paraskevi, Greece

The accurate knowledge of physical properties and phase equilibria of complex fluids is a critical factor towards the design and optimization of chemical processes and novel products. Experimental measurements are often limited by temperature and pressure conditions, toxicity, flammability or instability of one or more of the components, cost, etc. Thermodynamic models with strong physical basis provide the means to understand and quantify interactions and phenomena at the molecular and mesoscopic level and eventually predict macroscopic properties of interest. The unprecedented increase of computing power at relatively low price in recent decades has allowed the development of predictive methods that span the entire range of length and time scales, from sub-atomic quantum mechanical calculations up to macroscopic equations of state. In this presentation, we will discuss molecular simulation methods that are used widely for chemical process and product design. Molecular Dynamics (MD) allows the accurate study of a physical system as it evolves over time and the calculation of macroscopic properties as statistical averages. In this respect, one can calculate both equilibrium thermodynamic properties and time-dependent transport and dynamic properties. We will discuss a few examples from our recent research, mainly associated with the oil & gas industry. In the first example, we use MD to predict the diffusivity of gases (carbon monoxide, hydrogen and water) in heavy n-alkanes at elevated temperature and pressure. Predictions are subsequently used for the design of a Fischer-Tropsch process known as Gas-To-Liquid that allows formation of high value hydrocarbons from natural gas. The second example is driven by the need to develop efficient technologies for CO2 capture and sequestration, which are critical for the control of greenhouse gas concentration in the atmosphere. Here, we use MD simulations to predict the diffusivity of CO2 in H2O at various temperatures and pressures. In all cases, the use of a realistic and accurate force-field for the calculation of intermolecular interactions plays a critical role. Finally, we will present recent work on the development of a statistical mechanics-based equation of state for the prediction of complex mixture phase equilibria. Representative examples for the case of highly polar mixtures will be discussed. In all cases, comparison against experimental data will be presented.