Theoretical Investigation on the Reaction Kinetics of OH with Furfural.

Abstract

Furfural is a typical representative molecule of furan compounds and an important intermediate species in the oxidation of furan derivatives. The rate constant of furfural with OH is calculated for the first time using a high-level quantum chemistry method combined with the Rice-Ramsperger-Kassel-Marcus theory/master equation method. The M06-2X/jun-cc-pVTZ method was used to construct the potential energy surface of the reaction path. The preliminary reactions can occur through three different pathways: H-abstraction from the furan ring, H-abstraction from the side chain, and a preliminary OH-addition. The pathways via the OH-addition mechanism of the furfural + OH system were superior to H-abstraction in the temperature range of 298-400 K. When the temperature exceeds 400 K, the H-abstraction will be faster. Moreover, with the increase of pressure, the competition of the pathway via the OH-addition mechanism in the low-temperature region will gradually weaken. Under low-temperature conditions, INT1 and INT4 are the main intermediate species. The formation of bimolecular products, the 2-furanol (P7) + aldehyde group and the (3E)-4-hydroxybuta-1,3-diene-1-one (P8) + aldehyde group at C(2) and C(5) sites, are the main reaction pathways via the OH-addition mechanism. The formation of (2-furanyl)(oxy) methyl (P4) + H₂O (i.e., R4) always dominates for the four H-abstraction reactions. For the initial H-abstraction reaction, there is no pressure dependence, but for the preliminary OH-addition reaction, there is a significant positive pressure dependence. This work not only provides the necessary rate constants for modeling development but also provides theoretical guidance for the practical application of furan-based fuel.