Computational prediction of ?/?-selectivities in the pyrolysis of oxygen substituted phenethyl phenyl ethers
- ORNL
Lignin is a potential renewable source of oxygenated chemicals and liquid fuels, its reaction pathways are often studied using model compounds. Phenethyl phenyl ether (PPE; PhCH2CH2OPh)) is the simplest model for the most common -O-4 linkage in lignin. Previously, we developed a computational scheme to calculate the / -product selectivity in the pyrolysis of PPE by systematically exploiting error cancellation in the computation of relative rate constants. The / -selectivity is defined as the selectivity between the competitive hydrogen abstraction reaction paths on the - and -carbon of PPE. We use density functional theory and employ transition state theory where we include diagonal anharmonic correction in the vibrational partition functions for low frequency modes for which a semi-classical expression is used. In this work we investigate the effect of oxygen substituents (hydroxy, methoxy) in the para-position on the phenethyl-ring of PPE on the / -selectivities. The total / -selectivity increases when substituents are introduced and is larger for the methoxy than the hydroxy substituent. The strongest effect of the substituents is observed for the -pathway of the hydrogen abstraction by the phenoxyl chain carrying radical for which the rate increases. For the -pathway and the abstraction by the R-benzyl radical (R=OH,OCH3) the rate decreases with the introduction of the substituents. These findings are compared with results from recent experimental studies.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). National Center for Computational Sciences (NCCS)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- DE-AC05-00OR22725
- OSTI ID:
- 978790
- Journal Information:
- Journal of Physical Chemistry A, Vol. 112, Issue 22
- Country of Publication:
- United States
- Language:
- English
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