Experimental Detection of Oxygenated Aromatics in an Anisole-Blended Flame

Abstract

Anisole serves as a pivotal constituent in the model for ligninderived biofuels. Despite considerable interest in these biofuels, their combustion processes have the potential to increase the formation of aromatic compounds, particularly oxygenated aromatics. These oxygen-containing aromatics, known for their increased toxicity compared to conventional aromatics, can significantly impact the characteristics of soot particles and exhaust gas emissions. Recent research efforts have delved into the formation of oxygenated aromatics during combustion. However, our understanding of the kinetics governing the production of these aromatics remains limited, primarily due to a scarcity of experimental data for their identification. This study addresses this gap by investigating a fuel-rich hydrocarbon flame enriched with 10% anisole at an equivalence ratio of 1.90 and atmospheric pressure. Chemical products sampled from the flame underwent analysis using one-dimensional (1D) and two-dimensional (2D) gas chromatography−mass spectrometry setups. The results facilitated the separation and identification of over 100 aromatic species, encompassing approximately 80 oxygenated variants with diverse functional groups, such as alcohols, ethers, carbonyls (aldehydes, ketones), and esters. The molecular weights of these species ranged from 94 (phenol) to 224 (9-fluorenyl acetate). Surprisingly, only a fraction of the identified species have been considered in the existing literature models. Notably, alcohol and ether functional groups emerged as the most prevalent among the detected aromatics, hinting at their crucial roles in the reaction mechanisms involving anisole. The dominant reaction paths are identified and discussed in detail, offering valuable insights for future enhancements of kinetic models pertaining to "lignin-based biofuel and oxygenated aromatics".