Oxidation study of benzaldehyde with synchrotron photoionization and molecular beam mass spectrometry

The oxidation of benzaldehyde (A1CHO) at atmospheric pressure in a jet-stirred reactor at equivalence ratios of 0.4 and 2.0 within 475–900 K was studied. The intermediates and products were identified by synchrotron radiation photoionization and molecular beam mass spectrometry. Compared with previous studies, 29 species such as HCHO, CH3O, H2O2, ketene, furan, 2,4-cyclopentadiene-1-one (C5H4O), furfural, o-benzoquinone, 1,4-benzenediol and 1,4-cyclohex-2-enedione were newly detected. A kinetic model, involving 376 species and 2163 reactions was proposed, which reasonably predicted the experimental value. Rate-of-production analysis shows that H-abstractions reactions involving H atoms, OH, CH3, HO2 and phenoxy radicals dominate the consumption of A1CHO. The decarbonylation reactions and ring opening reactions have a certain contribution to the promotion of oxidation process. Phenoxy radicals, phenol and C5H4O are one of the most significant intermediates for A1CHO oxidation. Sensitivity analysis shows that A1CHO+OH=A1CO+H2O and H2O2(+M) =OH+OH(+M) are among the most sensitive reactions to promote the consumption of A1CHO at both conditions while the reaction A1OH+O2=A1O+HO2 has strong inhibiting effect. A1CHO is more difficult to produce benzene compared with benzyl alcohol oxidation while is easier to generate phenol at the same condition. These results will enrich the understanding the oxidation mechanism and soot formation of A1CHO as a potential aromatic fuel.