Abstract
Computer simulation has been increasingly used in recent years as a powerful tool to better understand a wide range of phenomena in physical science and chemical engineering. However, its potential and credibility can only be realized when the predictions of the computer simulations can be reconciled with carefully collected experimental data. In this talk, the speaker will present a number of examples in science and engineering to show how important the computer simulation can help scientists and engineers to understand better the microscopic mechanisms to reveal the underlying physics of the observed phenomena. Most important is the application of this tool which allows people to challenge or validate the classical theories which stand unchallenged in the literature for a very long time. The speaker will take an example of the Cohan theory developed in 1938 to explain the mechanisms of hysteresis in adsorption in pores with two open ends, in which he attributed adsorption and desorption follow different equilibrium paths of different curvatures of the interface separating the gas-like phase and the adsorbed phase. This theory has a number of deficiencies: (i) it can’t describe the critical hysteresis temperature, (ii) it can’t explain the capillary condensation in pores of channel shape which led Brunauer et al. to develop incorrect theory for adsorption in channels, and (iii) it can’t describe hysteresis in pores with one end closed to the bulk gas surroundings. The speaker's detailed computer simulation with various schemes developed in his research group shows these deficiencies of the Cohan theory: (i) they can explain the critical hysteresis temperature (and critical hysteresis pore size) with the new concept of “instant” thermal undulation of the interface separating the gas phase and the adsorbed phase within the pore, (ii) they can explain the condensation in a channel pore (such as activated carbon pores) with the new concept of “instant” liquid embryo with extremely short life time, (iii) they can explain hysteresis in a closed end pore with the new concept of continuing restructuring of the adsorbed phase with the progress of adsorption, and (iv) they show that the equilibrium paths as postulated by Cohan are not “equilibrium”, but rather metastable states of either metastable absorbed film or metastable liquid condensate (this is done with the new Mid Density Scheme developed in the speaker's research group). Another example the speaker wants to present is the problem of adsorption of associating fluids (water and methanol) in carbon materials to show the potential of the computer simulation in better understanding how these fluids adsorb, in a mechanism that is not possible with any classical theories. The experimental data of water on graphitized thermal carbon black obtained by Kiselev and co-workers in 1968 has stood unchallenged for nearly 50 years, and it was reconciled for the first time with the computer simulation carried out in the speaker's research group, and this has shed a much greater insight into the importance of functional group on the carbon surface. A final example is the unusual heat of adsorption (in the form of a spike in the plot of the isosteric heat versus loading) for adsorption of gases on homogeneous graphite surface, observed by Rouquerol et al. in 1977. This is once again reconciled with the research group's detailed computer simulations with a kinetic Monte Carlo scheme and a Bin-Monte Carlo scheme, developed in the group, and through the microscopic analysis of their simulation results they derive the underlying physics of the unusual heat surge observed by Rouquerol’s group in France.
About the speaker
Prof Duong D Do received his PhD at the University of Queensland in 1980. He was research fellow at the California Institute of Technology from 1980 to 1981. He returned to the University of Queensland in 1981, where he is currently Professor of Chemical Engineering.
Prof Do's research is evolved around the development and application of molecular simulation tools to understand the fundamentals of adsorption and desorption of gaseous mixtures on crystalline and amorphous surfaces and in confined spaces of pores of various topologies. His recent research is focused on the development of kinetic Monte Carlo and Bin-Monte Carlo simulations and the microscopic understanding of hysteresis in gaseous mixtures in ordered mesoporous solids, and the development of a new algorithm to determine the equilibrium phase transition in complex pores. He is on editorial board of a number of journals including Adsorption, Adsorption Science and Technology, Journal of Non-Equilibrium Thermodynamics and Frontiers of Chemical Engineering.
Prof Do received numerous awards including the Commonwealth Research Award, Union Carbide prize, Esso Award of Excellence in Chemical Engineering, UQ's Excellence in Teaching Award and Q-Index Top 10 Researchers. He is a Member of the American Institute of Chemical Engineers and the International Adsorption Society.
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