Theoretical Study of the Thermal Decomposition of the 5-Methyl-2-furanylmethyl Radical

2012-06-28T00:00:00Z (GMT) by Baptiste Sirjean René Fournet
The thermal decomposition of the 5-methyl-2-furanylmethyl radical (R<sub>1</sub>), the most important primary radical formed during the combustion and thermal decomposition of 2,5-dimethylfuran (a promising next-generation biofuel), was studied using CBS-QB3 calculations and master equation (ME)/RRKM modeling. Because very little information is available in the literature, the detailed potential energy surface (PES) was investigated thoroughly. Only the main pathways, having a kinetic influence on the decomposition of R<sub>1</sub>, were retained in the final ME/RRKM model. Among all the channels studied, the ring-opening of the 5-methyl-2-furanylmethyl radical, followed by ring enlargement to form cyclohexadienone molecules is predicted to be the easiest decomposition channel of R<sub>1</sub>. The C<sub>6</sub> cyclic species formed can undergo unimolecular reactions to yield phenol and to a lesser extent cyclopentadiene and CO. Our calculations predict that these species are important products formed during the pyrolysis of 2,5-dimethylfuran (DMF). Other channels involved in the decomposition of R<sub>1</sub> lead directly to the formation of linear and cyclic unsaturated C<sub>5</sub> species and constitute an additional source of cyclopentadiene and CO. High-pressure limit rate constants were computed as well as thermochemical properties for important species. ME/RRKM analysis was performed to probe the influence of pressure on the rate coefficients and pressure dependent rate coefficients were proposed for pressures and temperatures ranging, respectively, from 10<sup>–2</sup> bar to 10 bar and 1000 to 2000 K.