Kinetics of the Tetrahydrofurfuryl Alcohol + •OH Reaction from Ab Initio RRKM-Master Equation Calculations

Abstract

The kinetics of the reaction between tetrahydrofurfuryl alcohol (THFA) – a potential biofuel and •OH radicals, were investigated using high-level ab initio calculations combined with Rice-Ramsperger-Kassel-Marcus/master equation (RRKM/ME) modeling over temperatures of 200-2000 K and pressures from 0.76 to 76,000 Torr, including corrections for hindered internal rotation and Eckart tunneling. A comprehensive potential energy surface for all hydrogen-abstraction pathways was constructed at the CCSD(T)/cc-pVTZ//M06-2X/aug-cc-pVTZ level. The ring oxygen atom induces a nonuniform electron density distribution, lowering C-H bond dissociation energies at the Cα positions and favoring hydrogen abstraction at these sites. The global rate coefficient exhibits slight pressure dependence at low temperatures due to pre-reactive complex stabilization, while pressure effects vanish above ~800 K. The overall rate coefficient displays a characteristic U-shaped Arrhenius behavior and can be represented at 760 Torr by 7.23×102×T-5.25×exp(-269.7 K/T) + 7.40×10-23×T3.26×exp(543.0 K/T) (cm3/molecule/s). Below 500 K, the 2-(hydroxymethyl) tetrahydrofuran-2-yl radical (P4) + H2O and hydroxy(tetrahydrofuran-2-yl)methyl radical (P5) + H2O channels dominate, while above 700 K the 5-(hydroxymethyl)tetrahydrofuran-3-yl radical (P2) + H2O channel becomes predominant, reflecting the increasing importance of entropic effects at elevated temperatures. The calculated rate constants are consistent with those reported for the related 2-methyltetrahydrofuran + •OH system, supporting the reliability of the present kinetic model.