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Mechanistic insights into aqueous phase propanol dehydration in H‐ZSM‐5 zeolite
Author(s) -
Mei Donghai,
Lercher Johannes A.
Publication year - 2017
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.15517
Subject(s) - chemistry , propanol , zeolite , aqueous solution , protonation , dehydration , molecule , 1 propanol , hydrogen bond , molecular dynamics , methanol , computational chemistry , catalysis , organic chemistry , ion , biochemistry
Aqueous phase dehydration of 1‐propanol over H‐ZSM‐5 zeolite was investigated using density functional theory (DFT) calculations. The water molecules in the zeolite pores prefer to aggregate via the hydrogen bonding network and be protonated at the Brønsted acidic sites (BAS). Two typical configurations, i.e., dispersed and clustered, of water molecules were identified by ab initio molecular dynamics simulations of the mimicking aqueous phase H‐ZSM‐5 unit cell with 20 water molecules per unit cell. DFT calculated Gibbs free energies suggest that the dimeric propanol–propanol, the propanol–water, and the trimeric propanol–propanol–water complexes are formed at high propanol concentrations in aqueous phase, which provide a kinetically feasible dehydration reaction channel of 1‐propanol to propene. The calculation results indicate that the propanol dehydration via the unimolecular mechanism becomes kinetically discouraged due to the enhanced stability of the protonated dimeric propanol and the protonated water cluster acting as the BAS site for alcohol dehydration. © 2016 American Institute of Chemical Engineers AIChE J , 63: 172–184, 2017