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Talk Abstract
Multiscale Models For Chemical Reactors

Dionisios G. Vlachos
Department of Chemical Engineering
University of Massachusetts

vlachos@snail.ecs.umass.edu

Joint work with S. Raimondeau, P. Aghalayam, V. Nikolakis, G. Bonilla, and M. Tsapatsis.

The desire to construct reactor models from first principles is well established. Such systems exhibit multiple length and time scales, ranging from 1 Angstrom to 1 meter and from picoseconds to seconds or minutes, respectively. While the fluid phase can be described by a set of PDEs, spatial inhomogeneities at interfaces render continuum models inadequate. Application of ab initio or molecular models over the entire spectrum of scales is currently impractical. Thus an approach based on domain decomposition of hybrid (deterministic and stochastic) models has been developed [1].

In this talk we will discuss two classes of multiscale algorithms suitable for reactor scale design and control, namely fully coupled and uncoupled. In the former case, models at various scales are solved simultaneously. In the latter case, information obtained at each smaller scale is used as input into a more coarse scale model. Criteria for use of each class of algorithms will first be presented. Two applications will next be presented.

The first one involves use of complex surface chemistry in catalytic reactors. In particular, simulations on catalytic oxidation of CO on Pt will be presented, where the hierarchy of density functional theory, semi-empirical chemistry simulations based on the Bond-Order Conservation approach, Monte Carlo simulations, and reactor scale models is exploited [2].

The second one deals with materials deposition [3]. New results from thin inorganic films of zeolites will be discussed and compared to experiments [4, 5].

References

1. D. G. Vlachos, AIChE J., 43, (11), 3031 (1997).

2. S. Raimondeau, P. Aghalayam, M. A. Katsoulakis and D. G. Vlachos, in Foundations of molecular modeling and simulation (Colorado, 2000), pp. submitted.

3. D. G. Vlachos, Appl. Phys. Lett., 74, (19), 2797 (1999).

4. V. Nikolakis, E. Kokkoli, M. Tirrell, M. Tsapatsis and D. G. Vlachos, Chemistry of Materials, 12, (3), 845 (2000).

5. G. Bonilla, D. G. Vlachos and M. Tsapatsis, Microporous and Mesoporous Materials, in preparation (2000).


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