Ring-cleavage Reactions of Aromatic Hydrocarbons Studied by FT-IR Spectroscopy. II. Photooxidation of o-, m-, and p-Xylenes in the NOx-Air System

Article abstract of DOI:10.1246/bcsj.58.2541

α-Dicarbonyl compounds produced in the photooxidation of o-, m-, and p-xylenes were analyzed quantitatively using long-path FT-IR spectroscopy.Glyoxal, methylglyoxal, and biacetyl were observed in the case of o-xylene, and glyoxal and methylglyoxal were observed in cases of m- and p-xylenes.Yields of glyoxal, methylglyoxal, and biacetyl were 8, 23, and 10percent (mole/mole) of o-xylene consumed, respectively.Yields of glyoxal and methylglyoxal were 13 and 42percent in the case of m-xylene, and 24 and 12percent in the case of p-xylene.These yields could be explained by the ring cleavage of 6,7-dioxabicyclo<3.2.1>octane compounds of OH-aromatics-O2 adduct.Formation of maleic anhydride was observed in the case of O-xylene and it is suggested that maleic anhydride is produced from cis-2-butenedial.Formation of 3-hexene-2,5-dione (unsaturated γ-dicarbonyl) was observed from p-xylene.The ring-cleavage process accounts for 41, 55, and 36percent of the total reaction in o-, m-, and p-xylenes, respectively.