Theoretical investigation on the carbon sources and orientations of the aldehyde group of furfural in the pyrolysis of glucose

• The possible pathways leading to the formation of furfural from glucose were investigated using DFT methods.
• The kinetically feasible pathways that lead to the formation of FF was proposed.
• The possible carbon sources and orientations of aldehyde group of FF were investigated.
• Several reactions for the elimination of hydroxylmethyl group were investigated.

ionFurfural (FF) is a valuable and characteristic product of glucose pyrolysis, but little attention has been focused on its formation mechanism. In this study, density functional theory (DFT) methods were employed to investigate the possible pathways leading to the formation of FF from glucose. The results indicate that the pyrolysis of hydroxymethyl furfural (HMF) to FF is hardly to occur duo to the high activation energy (86.3 kcal/mol) required. The dominant FF formation pathway is Path-B2 which involves the 3-deoxy-glucose (3-DG) intermediate with overall energy barrier of 87.2 kcal/mol. The major proportions of FF are derived from C1–C5 of glucose and the aldehyde group in FF formed at C1 is dominant over that at C5. FF involving the C2–C6 of glucose, which include two orientations (C2 and C6) of the aldehyde group only account for a minor proportion.