Catalysis Center for Energy Innovation

Overview of Multiscale Modeling Approach

Dion VlachosUniv. of Delaware

Catalysis Center for Energy Innovation

Mathematical and computational methods developed

Bottom-up modelingProcess design

Coarse-grainingTop-down modelingCatalyst design

Bottom-up and Top-down Modeling:Process Design and Catalyst Screening

Reviews: Chem. Eng. J. 90, 3 (2002); Chem. Eng. Sci. 59, 5559 (2004); Adv. Chem. Eng. 30, 1 (2005)

Catalysis Center for Energy Innovation

The 30,000 Miles AirviewSignificant progress made on method development and testing

Field is maturing

Focus has been on prototype problems

Complex systems have by-and-large not been studied

Perspecive: Vlachos, AIChE J. 58(5), 1314 (2012)

Catalysis Center for Energy Innovation

Hierarchy Enables Rapid Screening of Chemistry, Fuels, and Catalysts

Quantum:ab initio, DFT, TST,

CPMD, QM/MM MD

Continuum: MF-ODEs

Discrete: KMC

Ideal: PFR, CSTR, etc.

Computational Fluid Dynamics

(CFD)

Length

Mesoscopic:PDEs

Discrete:CG-KMC

Pseudo-homogeneous:Transport correlations

Quantum-based correlations:

BEPs, GA, LSRs

Catalyst scale:Reaction rate

Reactor scale:Performance

Electronic scale:Parameter estimation

Accuracy, cost

Review: Salciccioli et al., Chem. Eng. Sci. 66, 4319 (2011)

Catalysis Center for Energy Innovation

Toward High-throughput Computing:Metal and Metal-like Catalysis

Thermochemistry via GA & LSRsReaction barriers and pre-exps via BEPsPerform MKM

DFT-based, semi-empirical, or hierarchical (screen with semi-empirical and refine via DFT)

Error analysis; Assessment of model predictions

Brønsted Evans Polanyi (BEP)

Microkinetic Model

(MKM)

Salciccioli et al., J. Phys. Chem. C , 114, 20155 (2010); J. Phys. Chem. C, 116, 1873 (2012)Sutton and Vlachos, ACS Catal. 2, 1624 (2012); J. Catal. 297, 202 (2013)

Linear Scaling Relations (LSRs)

Group Additivity (GA)

Catalysis Center for Energy Innovation

• Instead of simulating dynamics, KMC focuses on rare events• Simulates reactions much faster than Molecular Dynamics• Incorporates spatial information contrary to micro-kinetic models

The Kinetic Monte Carlo Approach

CO(gas) + OH COOH

reactants

products

Potential Energy Surface

Metal surface

transitionstate

‡

B

E‡k TB

rxnrxn

k T Qk e

h Q

Stamatakis and Vlachos, J. Chem. Phys. 134, 214115 (2011); http://www.dion.che.udel.edu/downloads.php