DFT-driven multi-site microkinetic modeling of ethanol conversion to ethylene and diethyl ether on γ-Al2O3(111)

We investigate the gamma-Al2O3-catalyzed production of ethylene and diethyl ether from ethanol in a combined density functional theory (DFT) and microkinetic modeling study. DFT calculations on the gamma-Al2O3(111) surface facet demonstrate that the energetically favorable pathway for ethylene formation is an E2 mechanism (E-a = 28 kcal/mol), while ether formation takes place via a bimolecular (S(N)2) mechanism (E-a = 32 kcal/mol). The DFf-parameterized two-site mean-field microkinetic model successfully captures trends in experimentally measured reaction orders. Microkinetic analysis indicates that the S(N)2 and E2 elementary steps control the overall rate. Analytical rate expressions are derived from the full microkinetic model and fit to experimental data, capturing reaction order trends with similar success as the full model. The outcome of the fitting suggests that an additional active site may be responsible for some ethanol conversion. The success of the models demonstrates the applicability of the DFT-computed mechanisms to powdered gamma-Al2O3 catalysts. (C) 2015 Elsevier Inc. All rights reserved.