Murad, Sohail - U of Illinois - Chicago Miller, Jeffrey - BP Research Center, Naperville, IL
GOALI: Molecular Dynamics Simulations of Membrane Assisted Phase Equilibrium in Dilute Solutions
The PI's propose to develop a direct simulation method to investigate the phase equilibrium of dilute solutions. The method is based on using a membrane to assist in attaining equilibrium between two or more phases. Direct simulation methods, although conceptually the simplest methods for studying phase equilibrium are usually difficult to implement because they require: (i) long simulation times to account for slow diffusion through the interface; (ii) large systems to account for the thickness of the interface and to have sufficiently large regions to represent the bulk phases; and (iii) are not suitable when the densities of the two phases are close to each other, since it becomes difficult to maintain two separate phases. Preliminary work using the membrane-assisted method to study the solubility of gases in liquids, has shown that many of the problems with other direct simulation methods are significantly less problematic with such direct simulation methods.
The overall goal of the proposed research is to further develop this method to study a wider range of phase equilibrium problems, especially those of direct industrial interest. They will include solubility of a wide range of gases in solvents. Selective solubility of gases in solvents has been suggested as an efficient technique for separating gases, which are otherwise difficult to separate (e.g. ethylene/ethane). In addition, the solubility of gases such as O2, N2, C2H4, C2H6, etc., in solvents such as alcohols, ethers, and hydrocarbons are of considerable interest by themselves in the chemical and petroleum industries. Apart from being of direct industrial interest, these properties are very sensitive to cross interactions between different species (e.g. polar/nonpolar) which are not well understood at both the molecular and macroscopic level. The PI's will also investigate other related problems such as the partitioning of solutes in competing solvents, which are important in pollution prevention and abatement.
This research is a collaborative project with BP America, Dow Chemical Company, and Huntsman Corporation, who have expressed a willingness to commit considerable industrial resources as an expression of their interest in the success of this project. It is the PI's intention to demonstrate the robustness of these methods for important industrial projects under this GOALI proposal, and subsequently work closely with these companies to enable them to use it for additional problems and systems of more immediate and direct industrial interest. The PI's will also develop user-friendly computer codes that will be made available to the industrial partners for developmental purposes. Finally, the industrial collaboration will allow graduate students to interact with industrial scientists, and add an important dimension to their graduate education experience.
The research carried out under this grant resulted in a new theoretical method for estimating the solubility of gases in liquids. Such information is necessary because gases dissolved in flammable liquids such as oils can lead to explosions and can be a serious fire hazard. This also makes experimental measurement of these solubility rather difficult and dangerous especially at high temperatures and pressures. Previous methods used for such predictions employed empirical model parameters which were not reliable. We developed a method to rapidly estimate these parameters using a widely available property (NMR chemical shift). This made the method developed especially efficient. The new method developed has been further developed for industrial use. We have worked with Dow Chemical Company and UOP LLC to make this work easier to use by industrial scientists. The new methods developed under this grant are more reliable than currently used methods in industry and as easy to use as previously used methods with limited reliability. In test cases examined the errors in the predictions were significantly less than those of previous methods. Research resulting from this grant was both of fundamental scientific interest as well as practical interest. This is evident from the publications resulting from this grant, which were published in many fundamental journals (e.g. Journal of Physical Chemistry) and engineering journals (Fluid Phase Equilibria). Finally under this grant we also started a collaboration with Sichuan University in Chengdu, China. The work involved looking a flow of liquids in nanochannels. Nanotechnology is expected to be the driving force of many new devices, and the work carried out under this work will help understand how liquids move in these nanochannels.
