Journal
JOURNAL OF PHYSICAL CHEMISTRY C
Volume 124, Issue 52, Pages 28437-28447Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.jpcc.0c05585
Keywords
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Funding
- U.S. Department of Energy (DOE), Office of Energy Efficiency and Renewable Energy (EERE), Bioenergy Technologies Office (BETO), at the Pacific Northwest National Laboratory (PNNL)
- U.S. DOE [DE-AC05-76RL01830]
- DOE's Office of Biological and Environmental Research [DE-AC02-76SF00515]
- U.S. DOE, Office of EERE, BETO [DE-AC05-00OR22725]
- UT-Battelle, LLC
- U.S. DOE, Office of Science, Office of Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division, Catalysis Science Program
- Chemical Catalysis for Bioenergy Consortium (ChemCatBio), a member of the Energy Materials Network (EMN)
- ChemCatBio, a member of EMN
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Ethanol is an important C-2 platform molecule for producing value-added chemicals and distillate hydrocarbon fuels (e.g., jet and diesel). Among these, catalytic upgrading of ethanol to butenes can generate valuable commodity chemicals (e.g., 1-butene) and provide C-4 olefin intermediates that can be further upgraded to jet/diesel fuels. Two-dimensional (2D) zeolites offer hierarchical mesoporous structures, leading to improved mass transport and reduced diffusion length, which can help to address the coking challenges faced by ethanol conversion to hydrocarbons over three-dimensional (3D) zeolites. In this study, we investigate the acidcatalyzed conversion of ethanol to 1-butene over the Bronsted acid sites (BAS) in 2D-pillared MFI zeolite (2D-PMFI) using ab initio molecular dynamics (AIMD) simulations, in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and calorimetric measurements. A detailed thermodynamic analysis, using quasi-harmonic approximation (QHA), on the Gibbs free-energy pathway of ethanol conversion shows that the consideration of entropy is critical to accurately capture the detailed thermodynamic profiles. Employing the Blue Moon ensemble method, the formation of framework-bound butoxide from ethoxy and ethene is found to be the likely rate- determining step (RDS), proceeding via a stepwise mechanism. The reactivity of 2D-PMFI can be further tuned by manipulating RDS through careful control of the number of BAS and operating temperatures. The calculated vibrational density of states (VDOS) validate the structural models of adsorbed ethanol by comparing with the experimental DRIFTS measurements. Overall, our study provides mechanistic insights into ethanol upgrading over the 2D-PMFI and shows the importance of evaluating entropic effects in such a confined system.
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