Thermal decomposition kinetics of furfural and furfuryl alcohol

The thermal decomposition of furfural and furfuryl alcohol plays a crucial role in shaping their combustion characteristics and assessing their viability as biofuels. Despite their importance, significant discrepancies remain in the literature regarding their decomposition pathways and reaction kinetics. Understanding these processes is essential for accurately modeling their behavior in combustion systems and optimizing their use in sustainable energy applications. This study presents the first direct measurements of the decomposition of furfural and furfuryl alcohol in a shock tube at temperatures ranging from 1264 to 1694 K and pressures ranging from 0.88 to 1.24 bar. We monitored the reaction progress by tracking the time-resolved decay of furfural (k1) and furfuryl alcohol (k2) using deep UV absorption diagnostics at 213 nm and 222 nm, respectively. The determined rate coefficients exhibit Arrhenius behavior and may be described as (unit: s–1, uncertainty: ±20 %):k1=3.84×1013e(−33677T)(1288−1694K)k2=2.22×1011e(−25305T)(1264−1621K)At 1400 K, the thermal decomposition of furfuryl alcohol proceeds 2.3 times faster than that of furfural, with an activation energy lower by 16.6 kcal mol⁻¹. However, at higher temperatures, both reactions exhibit reduced structural dependence, converging to similar rates by 1600 K. Our measurements help resolve discrepancies in previously reported rate coefficients, which vary by two orders of magnitude. Furthermore, this study offers a comprehensive comparison of the thermal decomposition kinetics of five-membered cyclic compounds, underscoring the impact of ring architecture and side-chain substituents. The measured rate coefficients improve prediction accuracy and provide valuable validation targets for existing models, shedding light on deficiencies in the current literature.